# Source code for apsw.shell

    #!/usr/bin/env python3

    # This supports Python 3.6 onwards
    # Python 3.6 doesn't let us do from __future__ import annotations
    # so we can't do correct typing.

    # mypy: ignore-errors

    import sys
    import apsw
    import shlex
    import os
    import io
    import inspect
    import csv
    import re
    import textwrap
    import time
    import codecs
    import base64
    import argparse
    import contextlib
    import traceback
    import code

    from typing import TextIO, Optional

    class Shell:
        """Implements a SQLite shell

        :param stdin: Where to read input from (default sys.stdin)
        :param stdout: Where to send output (default sys.stdout)
        :param stderr: Where to send errors (default sys.stderr)
        :param encoding: Default encoding for files opened/created by the
          Shell.  If you want stdin/out/err to use a particular encoding
          then you need to provide them `already configured <http://docs.python.org/library/codecs.html#codecs.open>`__ that way.
        :param args: This should be program arguments only (ie if
          passing in sys.argv do not include sys.argv[0] which is the
          program name.  You can also pass in None and then call
          :meth:`process_args` if you want to catch any errors
          in handling the arguments yourself.
        :param db: A existing :class:`~apsw.Connection` you wish to use

        The commands and behaviour are modelled after the `interactive
        shell <https://sqlite.org/sqlite.html>`__ that is part of
        SQLite.

        You can inherit from this class to embed in your own code and user
        interface.

        Errors and diagnostics are only ever sent to error output
        (self.stderr) and never to the regular output (self.stdout).  This
        means using shell output is always easy and consistent.

        Shell commands begin with a dot (eg .help).  They are implemented
        as a method named after the command (eg command_help).  The method
        is passed one parameter which is the list of arguments to the
        command.

        Output modes are implemented by functions named after the mode (eg
        output_column).

        When you request help the help information is automatically
        generated from the docstrings for the command and output
        functions.

        You should not use a Shell object concurrently from multiple
        threads.  It is one huge set of state information which would
        become inconsistent if used simultaneously, and then give baffling
        errors.  It is safe to call methods one at a time from different
        threads.  ie it doesn't care what thread calls methods as long as
        you don't call more than one concurrently.
        """

        class Error(Exception):
            """Class raised on errors.  The expectation is that the error
            will be displayed by the shell as text so there are no
            specific subclasses as the distinctions between different
            types of errors doesn't matter."""
            pass

        def __init__(self,
                     stdin: Optional[TextIO] = None,
                     stdout=None,
                     stderr=None,
                     encoding: str = "utf8",
                     args=None,
                     db=None):
            """Create instance, set defaults and do argument processing."""
            # The parameter doc has to be in main class doc as sphinx
            # ignores any described here
            self.exceptions = False
            self.history_file = "~/.sqlite_history"
            self.bindings = {}
            self._db = None
            self.dbfilename = None
            if db:
                self.db = db, db.filename
            else:
                self.db = None, None
            # keep a reference around allowing switching connections
            self.db_references = set()
            self.prompt = "sqlite> "
            self.moreprompt = "    ..> "
            self.separator = "|"
            self.bail = False
            self.changes = False
            self.echo = False
            self.timer = False
            self.header = False
            self.nullvalue = ""
            self.output = self.output_list
            self._output_table = self._fmt_sql_identifier("table")
            self.widths = []
            # do we truncate output in list mode?
            self.truncate = True
            # a stack of previous outputs
            self._output_stack = []

            # other stuff
            self.set_encoding(encoding)
            self.stdin = stdin or sys.stdin
            self._original_stdout = self.stdout = stdout or sys.stdout
            self.stderr = stderr or sys.stderr

            # default to box output
            if self._using_a_terminal() and hasattr(self, "output_box"):
                self.output = self.output_box
                self.box_options = {
                    "quote": False,
                    "string_sanitize": 1,
                    "null": "NULL",
                    "truncate": 4096,
                    "text_width": self._terminal_width(32),
                    "use_unicode": True
                }

            # we don't become interactive until the command line args are
            # successfully parsed and acted upon
            self.interactive = None
            # current colouring object
            self.command_colour()  # set to default
            self._using_readline = False
            self._input_stack = []
            self.input_line_number = 0
            self._calculate_output_modes()
            self.push_input()
            self.push_output()
            self._input_descriptions = []

            if args:
                try:
                    self.process_args(args)
                except Exception:
                    if len(self._input_descriptions):
                        self._input_descriptions.append("Processing command line arguments")
                    self.handle_exception()
                    raise

            if self.interactive is None:
                self.interactive = self._using_a_terminal()

        def _using_a_terminal(self):
            return getattr(self.stdin, "isatty", None) and self.stdin.isatty() and getattr(self.stdout, "isatty",
                                                                                           None) and self.stdout.isatty()

        def _ensure_db(self):
            "The database isn't opened until first use.  This function ensures it is now open."
            if not self._db:
                if not self.dbfilename:
                    self.dbfilename = ":memory:"
                self._db = apsw.Connection(self.dbfilename,
                                           flags=apsw.SQLITE_OPEN_URI | apsw.SQLITE_OPEN_READWRITE
                                           | apsw.SQLITE_OPEN_CREATE)
            return self._db

        def _set_db(self, newv):
            "Sets the open database (or None) and filename"
            (db, dbfilename) = newv
            if self._db:
                self._db.close(True)
                self._db = None
            self._db = db
            self.dbfilename = dbfilename

        db = property(_ensure_db, _set_db, None, "The current :class:`~apsw.Connection`")

        def process_args(self, args):
            """Process command line options specified in args.  It is safe to
            call this multiple times.  We try to be compatible with SQLite shell
            argument parsing.

            :param args: A list of string options.  Do not include the
               program as args[0]

            :returns: A tuple of (databasefilename, initfiles,
               sqlncommands).  This is provided for informational purposes
               only - they have already been acted upon.  An example use
               is that the SQLite shell does not enter the main interactive
               loop if any sql/commands were provided.

            The first non-option is the database file name.  Each
            remaining non-option is treated as a complete input (ie it
            isn't joined with others looking for a trailing semi-colon).

            The SQLite shell uses single dash in front of options.  We
            allow both single and double dashes.  When an unrecognized
            argument is encountered then
            :meth:`process_unknown_args` is called.
            """
            # we don't use optparse as we need to use single dashes for
            # options - all hand parsed
            if not args:
                return None, [], []

            # are options still valid?
            options = True
            # have we seen the database name?
            havedbname = False
            # List of init files to read
            inits = []
            # List of sql/dot commands
            sqls = []

            while args:
                if not options or not args[0].startswith("-"):
                    options = False
                    if not havedbname:
                        # grab new database
                        self.db = None, args[0]
                        havedbname = True
                    else:
                        sqls.append(args[0])
                    args = args[1:]
                    continue

                # remove initial single or double dash
                args[0] = args[0][1:]
                if args[0].startswith("-"):
                    args[0] = args[0][1:]

                if args[0] == "init":
                    if len(args) < 2:
                        raise self.Error("You need to specify a filename after -init")
                    inits.append(args[1])
                    args = args[2:]
                    continue

                if args[0] == "header" or args[0] == "noheader":
                    self.header = args[0] == "header"
                    args = args[1:]
                    continue

                if args[0] in ("echo", "bail", "interactive"):
                    setattr(self, args[0], True)
                    args = args[1:]
                    continue

                if args[0] == "batch":
                    self.interactive = False
                    args = args[1:]
                    continue

                if args[0] in ("separator", "nullvalue", "encoding"):
                    if len(args) < 2:
                        raise self.Error("You need to specify a value after -" + args[0])
                    getattr(self, "command_" + args[0])([args[1]])
                    args = args[2:]
                    continue

                if args[0] == "version":
                    self.write(self.stdout, apsw.sqlitelibversion() + "\n")
                    # A pretty gnarly thing to do
                    sys.exit(0)

                if args[0] == "help":
                    self.write(self.stderr, self.usage())
                    sys.exit(0)

                if args[0] in ("no-colour", "no-color", "nocolour", "nocolor"):
                    self.colour_scheme = "off"
                    self._out_colour()
                    args = args[1:]
                    continue

                # only remaining known args are output modes
                if getattr(self, "output_" + args[0], None):
                    self.command_mode(args[:1])
                    args = args[1:]
                    continue

                newargs = self.process_unknown_args(args)
                if newargs is None:
                    raise self.Error("Unrecognized argument '" + args[0] + "'")
                args = newargs

            for f in inits:
                self.command_read([f])

            for s in sqls:
                self.process_complete_line(s)

            return self.dbfilename, inits, sqls

        def process_unknown_args(self, args):
            """This is called when :meth:`process_args` encounters an
            argument it doesn't understand.  Override this method if you
            want to be able to understand additional command line arguments.

            :param args: A list of the remaining arguments.  The initial one will
               have had the leading dashes removed (eg if it was --foo on the command
               line then args[0] will be "foo"
            :returns: None if you don't recognize the argument either.  Otherwise
               return the list of remaining arguments after you have processed
               yours.
            """
            return None

        def usage(self):
            "Returns the usage message.  Make sure it is newline terminated"

            msg = """
    Usage: python3 -m apsw [OPTIONS] FILENAME [SQL|CMD] [SQL|CMD]...
    FILENAME is the name of a SQLite database. A new database is
    created if the file does not exist. If omitted or an empty
    string then an in-memory database is created.
    OPTIONS include:

       -init filename       read/process named file
       -echo                print commands before execution
       -[no]header          turn headers on or off
       -bail                stop after hitting the first error
       -interactive         force interactive I/O
       -batch               force batch I/O
       -column              set output mode to 'column'
       -csv                 set output mode to 'csv'
       -html                set output mode to 'html'
       -line                set output mode to 'line'
       -list                set output mode to 'list'
       -python              set output mode to 'python'
       -separator 'x'       set output field separator (|)
       -nullvalue 'text'    set text string for NULL values
       -version             show SQLite version
       -encoding 'name'     the encoding to use for files
                            opened via .import, .read & .output
       -nocolour            disables interactive colour output
    """
            return msg.lstrip()

        ###
        ### Value formatting routines.  They take a value and return a
        ### text formatting of them.  Mostly used by the various output's
        ### but also by random other pieces of code.
        ###

        # bytes that are ok in C strings - no need for quoting
        _printable = [
            ord(x) for x in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789~!@#$%^&*()`_-+={}[]:;,.<>/?|"
        ]

        def _fmt_c_string(self, v):
            "Format as a C string including surrounding double quotes"
            if isinstance(v, str):
                op = ['"']
                for c in v:
                    if c == "\\":
                        op.append("\\\\")
                    elif c == "\r":
                        op.append("\\r")
                    elif c == "\n":
                        op.append("\\n")
                    elif c == "\t":
                        op.append("\\t")
                    elif ord(c) not in self._printable:
                        op.append("\\" + c)
                    else:
                        op.append(c)
                op.append('"')
                return "".join(op)
            elif v is None:
                return '"' + self.nullvalue + '"'
            elif isinstance(v, bytes):
                o = lambda x: x
                fromc = chr
                res = ['"']
                for c in v:
                    if o(c) in self._printable:
                        res.append(fromc(c))
                    else:
                        res.append("\\x%02X" % (o(c), ))
                res.append('"')
                return "".join(res)
            else:
                # number of some kind
                return '"%s"' % (v, )

        def _fmt_html_col(self, v):
            "Format as HTML (mainly escaping &/</>"
            return self._fmt_text_col(v).\
               replace("&", "&amp;"). \
               replace(">", "&gt;"). \
               replace("<", "&lt;"). \
               replace("'", "&apos;"). \
               replace('"', "&quot;")

        def _fmt_json_value(self, v):
            "Format a value."
            if isinstance(v, str):
                # we assume utf8 so only some characters need to be escaed
                op = ['"']
                for c in v:
                    if c == "\\":
                        op.append("\\\\")
                    elif c == "\r":
                        op.append("\\r")
                    elif c == "\n":
                        op.append("\\n")
                    elif c == "\t":
                        op.append("\\t")
                    elif c == "/":
                        op.append("\\/")
                    elif c == '"':
                        op.append("\\" + c)
                    elif c == "\\b":
                        op.append("\\b")
                    elif c == "\\f":
                        op.append("\\f")
                    else:
                        # It isn't clear when \u sequences *must* be used.
                        # Assuming not needed due to utf8 output which
                        # corresponds to what rfc4627 implies.
                        op.append(c)
                op.append('"')
                return "".join(op)
            elif v is None:
                return 'null'
            elif isinstance(v, bytes):
                o = base64.encodebytes(v).decode("ascii")
                if o[-1] == "\n":
                    o = o[:-1]
                return '"' + o + '"'
            else:
                # number of some kind
                return str(v)

        def _fmt_python(self, v):
            "Format as python literal"
            if v is None:
                return "None"
            elif isinstance(v, str):
                return repr(v)
            elif isinstance(v, bytes):
                res = ['b"']
                for i in v:
                    if i in self._printable:
                        res.append(chr(i))
                    else:
                        res.append("\\x%02X" % (i, ))
                res.append('"')
                return "".join(res)
            else:
                return "%s" % (v, )

        def _fmt_sql_identifier(self, v):
            "Return the identifier quoted in SQL syntax if needed (eg table and column names)"
            if not len(v):  # yes sqlite does allow zero length identifiers
                return '""'
            nonalnum = re.sub("[A-Za-z_0-9]+", "", v)
            if len(nonalnum) == 0:
                if v.upper() not in self._sqlite_reserved:
                    # Ok providing it doesn't start with a digit
                    if v[0] not in "0123456789":
                        return v
            # double quote it unless there are any double quotes in it
            if '"' in nonalnum:
                return "[%s]" % (v, )
            return '"%s"' % (v, )

        def _fmt_text_col(self, v):
            "Regular text formatting"
            if v is None:
                return self.nullvalue
            elif isinstance(v, str):
                return v
            elif isinstance(v, bytes):
                # sqlite gives back raw bytes!
                return "<Binary data>"
            else:
                return "%s" % (v, )

        ###
        ### The various output routines.  They are always called with the
        ### header irrespective of the setting allowing for some per query
        ### setup. (see output_column for example).  The doc strings are
        ### used to generate help.
        ###

        def output_column(self, header, line):
            """
            Items left aligned in space padded columns.  They are
            truncated if they do not fit. If the width hasn't been
            specified for a column then 10 is used unless the column name
            (header) is longer in which case that width is used.  Use the
            .width command to change column sizes.
            """
            # as an optimization we calculate self._actualwidths which is
            # reset for each query
            if header:

                def gw(n):
                    if n < len(self.widths) and self.widths[n] != 0:
                        return self.widths[n]
                    # if width is not present or 0 then autosize
                    text = self._fmt_text_col(line[n])
                    return max(len(text), 10)

                widths = [gw(i) for i in range(len(line))]

                if self.truncate:
                    self._actualwidths = ["%" + ("-%d.%ds", "%d.%ds")[w < 0] % (abs(w), abs(w)) for w in widths]
                else:
                    self._actualwidths = ["%" + ("-%ds", "%ds")[w < 0] % (abs(w), ) for w in widths]

                if self.header:
                    # output the headers
                    c = self.colour
                    cols = [
                        c.header + (self._actualwidths[i] % (self._fmt_text_col(line[i]), )) + c.header_
                        for i in range(len(line))
                    ]
                    # sqlite shell uses two spaces between columns
                    self.write(self.stdout, "  ".join(cols) + "\n")
                    if c is self._colours["off"]:
                        self.output_column(False, ["-" * abs(widths[i]) for i in range(len(widths))])
                return
            cols = [
                self.colour.colour_value(line[i], self._actualwidths[i] % (self._fmt_text_col(line[i]), ))
                for i in range(len(line))
            ]
            # sqlite shell uses two spaces between columns
            self.write(self.stdout, "  ".join(cols) + "\n")

        output_columns = output_column

        def output_csv(self, header, line):
            """
            Items in csv format (comma separated).  Use tabs mode for tab
            separated.  You can use the .separator command to use a
            different one after switching mode.  A separator of comma uses
            double quotes for quoting while other separators do not do any
            quoting.  The Python csv library used for this only supports
            single character separators.
            """

            # we use self._csv for the work, setup when header is
            # supplied. _csv is a tuple of a StringIO and the csv.writer
            # instance.

            fixdata = lambda x: x

            if header:
                s = io.StringIO()
                kwargs = {}
                if self.separator == ",":
                    kwargs["dialect"] = "excel"
                elif self.separator == "\t":
                    kwargs["dialect"] = "excel-tab"
                else:
                    kwargs["quoting"] = csv.QUOTE_NONE
                    kwargs["delimiter"] = fixdata(self.separator)
                    kwargs["doublequote"] = False
                    # csv module is bug ridden junk - I already say no
                    # quoting so it still looks for the quotechar and then
                    # gets upset that it can't be quoted.  Which bit of no
                    # quoting was ambiguous?
                    kwargs["quotechar"] = "\x00"

                writer = csv.writer(s, **kwargs)
                self._csv = (s, writer)
                if self.header:
                    self.output_csv(None, line)
                return

            if header is None:
                c = self.colour
                line = [c.header + fixdata(self._fmt_text_col(l)) + c.header_ for l in line]
            else:
                fmt = lambda x: self.colour.colour_value(x, fixdata(self._fmt_text_col(x)))
                line = [fmt(l) for l in line]
            self._csv[1].writerow(line)
            t = self._csv[0].getvalue()
            # csv lib always does DOS eol
            assert (t.endswith("\r\n"))
            t = t[:-2]
            # should not be other eol irregularities
            assert (not t.endswith("\r") and not t.endswith("\n"))
            self.write(self.stdout, t + "\n")
            self._csv[0].truncate(0)
            self._csv[0].seek(0)

        def output_html(self, header, line):
            "HTML table style"
            if header:
                if not self.header:
                    return
                fmt = lambda x: self.colour.header + self._fmt_html_col(x) + self.colour.header_
            else:
                fmt = lambda x: self.colour.colour_value(x, self._fmt_html_col(x))
            line = [fmt(l) for l in line]
            out = ["<TR>"]
            for l in line:
                out.append(("<TD>", "<TH>")[header])
                out.append(l)
                out.append(("</TD>\n", "</TH>\n")[header])
            out.append("</TR>\n")
            self.write(self.stdout, "".join(out))

        def output_insert(self, header, line):
            """
            Lines as SQL insert statements.  The table name is "table"
            unless you specified a different one as the second parameter
            to the .mode command.
            """
            if header:
                return
            fmt = lambda x: self.colour.colour_value(x, apsw.format_sql_value(x))
            out = "INSERT INTO " + self._output_table + " VALUES(" + ",".join([fmt(l) for l in line]) + ");\n"
            self.write(self.stdout, out)

        def output_json(self, header, line):
            """
            Each line as a JSON object with a trailing comma.  Blobs are
            output as base64 encoded strings.  You should be using UTF8
            output encoding.
            """
            if header:
                self._output_json_cols = line
                return
            fmt = lambda x: self.colour.colour_value(x, self._fmt_json_value(x))
            out = ["%s: %s" % (self._fmt_json_value(k), fmt(line[i])) for i, k in enumerate(self._output_json_cols)]
            self.write(self.stdout, "{ " + ", ".join(out) + "},\n")

        def output_line(self, header, line):
            """
            One value per line in the form 'column = value' with a blank
            line between rows.
            """
            if header:
                w = 5
                for l in line:
                    if len(l) > w:
                        w = len(l)
                self._line_info = (w, line)
                return
            fmt = lambda x: self.colour.colour_value(x, self._fmt_text_col(x))
            w = self._line_info[0]
            for i in range(len(line)):
                self.write(self.stdout, "%*s = %s\n" % (w, self._line_info[1][i], fmt(line[i])))
            self.write(self.stdout, "\n")

        output_lines = output_line

        def output_list(self, header, line):
            "All items on one line with separator"
            if header:
                if not self.header:
                    return
                c = self.colour
                fmt = lambda x: c.header + x + c.header_
            else:
                fmt = lambda x: self.colour.colour_value(x, self._fmt_text_col(x))
            self.write(self.stdout, self.separator.join([fmt(x) for x in line]) + "\n")

        def output_python(self, header, line):
            "Tuples in Python source form for each row"
            if header:
                if not self.header:
                    return
                c = self.colour
                fmt = lambda x: c.header + self._fmt_python(x) + c.header_
            else:
                fmt = lambda x: self.colour.colour_value(x, self._fmt_python(x))
            self.write(self.stdout, '(' + ", ".join([fmt(l) for l in line]) + "),\n")

        def output_tcl(self, header, line):
            "Outputs TCL/C style strings using current separator"
            # In theory you could paste the output into your source ...
            if header:
                if not self.header:
                    return
                c = self.colour
                fmt = lambda x: c.header + self._fmt_c_string(x) + c.header_
            else:
                fmt = lambda x: self.colour.colour_value(x, self._fmt_c_string(x))
            self.write(self.stdout, self.separator.join([fmt(l) for l in line]) + "\n")

        _fqt_kwargs = None

        def output_box(self, column_names, rows):
            "Outputs using line drawing and auto sizing columns"
            if self._fqt_kwargs is None:
                # figure out default args
                sig = inspect.signature(apsw.ext.format_query_table)
                self._fqt_kwargs = {
                    k: v.default
                    for k, v in sig.parameters.items()
                    if v.default is not inspect.Signature.empty and k not in {"db", "query", "bindings"}
                }
            kwargs = self._fqt_kwargs.copy()
            kwargs.update(self.box_options)
            if kwargs["text_width"] < 1:
                kwargs["text_width"] = self._terminal_width(32)

            kwargs.update({"colour": self.colour != self._colours["off"]})

            self.stdout.write(apsw.ext.format_query_table._format_table(column_names, rows, **kwargs))

        output_box.all_at_once = True

        def output_table(self):
            "Outputs using ascii line drawing and strongly sanitized text"
            # this function isn't actually called - output_box is used
            1 / 0

        def output_qbox(self):
            "Outputs using line drawing and auto sizing columns quoting values"
            # this function isn't actually called - output_box is used
            1 / 0

        def _output_summary(self, summary):
            # internal routine to output a summary line or two
            self.write(self.stdout, self.colour.summary + summary + self.colour.summary_)

        ###
        ### Various routines
        ###

        def cmdloop(self, intro=None, transient=None):
            """Runs the main interactive command loop.

            :param intro: Initial text banner to display instead of the
               default.  Make sure you newline terminate it.
            :param transient: Additional message about being connected to
              a transient in memory database
            """
            if intro is None:
                intro = f"""
    SQLite version { apsw.sqlitelibversion() } (APSW { apsw.apswversion() })
    Enter ".help" for instructions
    """
                intro = intro.lstrip()
            if self.interactive and intro:
                c = self.colour
                self.write(self.stdout, c.intro + intro + c.intro_)
                if not self.dbfilename:
                    transient = transient or "Connected to a transient in-memory database.\n"
                    self.write(self.stdout, c.transient + transient + c.transient_)

            using_readline = False
            try:
                if self.interactive and self.stdin is sys.stdin:
                    import readline
                    old_completer = readline.get_completer()
                    readline.set_completer(self.complete)
                    readline.parse_and_bind("tab: complete")
                    using_readline = True
                    try:
                        readline.read_history_file(os.path.expanduser(self.history_file))
                    except IOError:
                        pass
            except ImportError:
                pass

            try:
                while True:
                    self._input_descriptions = []
                    if using_readline:
                        # we drop completion cache because it contains
                        # table and column names which could have changed
                        # with last executed SQL
                        self._completion_cache = None
                        self._using_readline = True
                    try:
                        command = self.getcompleteline()
                        if command is None:  # EOF
                            if self.interactive:
                                self.write(self.stdout, "\n")
                            return
                        self.process_complete_line(command)
                    except:
                        self._append_input_description()
                        try:
                            self.handle_exception()
                        except UnicodeDecodeError:
                            self.handle_exception()
            finally:
                if using_readline:
                    readline.set_completer(old_completer)
                    readline.set_history_length(256)
                    readline.write_history_file(os.path.expanduser(self.history_file))

        def handle_exception(self):
            """Handles the current exception, printing a message to stderr as appropriate.
            It will reraise the exception if necessary (eg if bail is true)"""
            eclass, eval, etb = sys.exc_info()

            if isinstance(eval, SystemExit):
                eval._handle_exception_saw_this = True
                raise

            if not getattr(eval, "_handle_exception_saw_this", False):
                self._out_colour()
                self.write(self.stderr, self.colour.error)

                if isinstance(eval, KeyboardInterrupt):
                    self.handle_interrupt()
                    text = "Interrupted"
                else:
                    text = str(eval)

                if not text.endswith("\n"):
                    text = text + "\n"

                if len(self._input_descriptions):
                    for i in range(len(self._input_descriptions)):
                        if i == 0:
                            pref = "At "
                        else:
                            pref = " " * i + "From "
                        self.write(self.stderr, pref + self._input_descriptions[i] + "\n")

                self.write(self.stderr, text)
                if self.exceptions:
                    stack = []
                    while etb:
                        stack.append(etb.tb_frame)
                        etb = etb.tb_next

                    for frame in stack:
                        self.write(
                            self.stderr, "\nFrame %s in %s at line %d\n" %
                            (frame.f_code.co_name, frame.f_code.co_filename, frame.f_lineno))
                        vars = list(frame.f_locals.items())
                        vars.sort()
                        for k, v in vars:
                            try:
                                v = repr(v)[:80]
                            except Exception:
                                v = "<Unable to convert to string>"
                            self.write(self.stderr, "%10s = %s\n" % (k, v))
                    self.write(self.stderr, "\n%s: %s\n" % (eclass, repr(eval)))

                self.write(self.stderr, self.colour.error_)

            eval._handle_exception_saw_this = True
            if self.bail:
                raise

        def _query_details(self, sql, bindings):
            "Internal routine to iterate over statements"
            # The return from this would be way better as a dataclass
            # but Py 3.6 doesn't have them
            cur = self.db.cursor()
            saved = sql
            explain = None

            def et(cursor, statement, bindings):
                nonlocal saved, explain
                saved = statement
                explain = cursor.is_explain
                return False

            cur.exectrace = et

            try:
                cur.execute(sql, bindings)
            except apsw.ExecTraceAbort:
                pass
            except apsw.Error as e:
                return (sql[:len(saved)], sql[len(saved):], str(e), e.error_offset, e, explain)
            except KeyError as e:
                var = e.args[0]
                return (None, None, f"No binding present for '{ var }' - use .parameter set { var } VALUE to provide one",
                        -1, e, explain)
            return (sql[:len(saved)], sql[len(saved):], None, None, explain)

        def process_sql(self, sql, bindings=None, internal=False, summary=None):
            """Processes SQL text consisting of one or more statements

            :param sql: SQL to execute

            :param bindings: bindings for the *sql*

            :param internal: If True then this is an internal execution
              (eg the .tables or .database command).  When executing
              internal sql timings are not shown nor is the SQL echoed.

            :param summary: If not None then should be a tuple of two
              items.  If the ``sql`` returns any data then the first item
              is printed before the first row, and the second item is
              printed after the last row.  An example usage is the .find
              command which shows table names.
            """

            changes_start = self.db.totalchanges()

            def fixws(s: str):
                return re.sub(r"\s", " ", s, flags=re.UNICODE)

            def fmt_sql(s):
                s = s.strip()
                if len(s) > 4096:
                    s = s[:4096] + "..."
                return s

            if not internal and bindings is None:
                bindings = self.bindings

            while sql.strip():
                qd = self._query_details(sql, bindings)
                sql = qd[1]
                if not internal:
                    if self.echo:
                        self.write_error(fmt_sql(qd[0]) + "\n")
                if qd[2]:
                    self.write_error(f"{ qd[2] }\n")
                    if qd[3] >= 0:
                        offset = qd[3]
                        query = qd[0].encode("utf8")
                        before, after = fixws(query[:offset][-35:].decode("utf8")), \
                            fixws(query[offset:][:35].decode("utf8"))
                        print("  ", before + after, file=self.stderr)
                        print("   " + (" " * len(before)) + "^--- error here", file=self.stderr)
                    qd[4]._handle_exception_saw_this = True
                    raise qd[4]

                if qd[4] == 1:  # explain
                    self.push_output()
                    self.header = True
                    self.widths = [-4, 13, 4, 4, 4, 13, 2, 13]
                    self.truncate = False
                    self.output = self.output_column
                elif qd[4] == 2:  # explain query plan
                    self.push_output()
                    self.header = True
                    self.widths = [-4, -6, 22]
                    self.truncate = False
                    self.output = self.output_column

                timing_start = self.get_resource_usage()

                column_names = None
                rows = [] if getattr(self.output, "all_at_once", False) else None

                cur = self.db.cursor()
                if self.db.exectrace:
                    cur.exectrace = lambda *args: True
                if self.db.rowtrace:
                    cur.rowtrace = lambda x, y: y

                for row in cur.execute(qd[0], bindings):
                    if column_names is None:
                        column_names = [h for h, d in cur.getdescription()]
                        if qd[4] == 2:
                            del column_names[2]
                        if summary:
                            self._output_summary(summary[0])
                        if rows is None:
                            self.output(True, column_names)
                    if qd[4] == 2:
                        row = list(row)
                        del row[2]
                        row = tuple(row)
                    if rows is None:
                        self.output(False, row)
                    else:
                        rows.append(list(row))

                if column_names and rows:
                    self.output(column_names, rows)

                if column_names and summary:
                    self._output_summary(summary[1])

                if self.timer:
                    self.display_timing(timing_start, self.get_resource_usage())

                if qd[4]:
                    self.pop_output()

            changes = self.db.totalchanges() - changes_start
            if not internal and changes and self.changes:
                text = ("changes: " + self.colour.colour_value(changes, str(changes)) + "\t" + "total changes: " +
                        self.colour.colour_value(self.db.totalchanges(), str(self.db.totalchanges())) + "\n")
                self.write(self.stdout, text)

        def process_command(self, command):
            """Processes a dot command.

            It is split into parts using :func:`shlex.split`
            which is roughly the same method used by Unix/POSIX
            shells.
            """
            if self.echo:
                self.write(self.stderr, command + "\n")
            cmd = shlex.split(command)
            assert cmd[0][0] == "."
            cmd[0] = cmd[0][1:]
            fn = getattr(self, "command_" + cmd[0], None)
            if not fn:
                raise self.Error("Unknown command \"%s\".  Enter \".help\" for help" % (cmd[0], ))
            # special handling for .parameter set because we need the value to preserve quoting
            # '33' and 33 are different
            if len(cmd) > 3 and cmd[0] == "parameter" and cmd[1] == "set":
                pos = command.index(cmd[2], command.index("set") + 4) + len(cmd[2]) + 1
                cmd = cmd[:3] + [command[pos:]]
            # special handling for shell / py because we want to preserve the text exactly
            if cmd[0] in {"shell", "py"}:
                rest = command[command.index(cmd[0]) + len(cmd[0]):].strip()
                if rest:
                    cmd = [cmd[0], rest]
            res = fn(cmd[1:])

        ###
        ### Commands start here
        ###

        def _boolean_command(self, name, cmd):
            "Parse and verify boolean parameter"
            if len(cmd) != 1 or cmd[0].lower() not in ("on", "off"):
                raise self.Error(name + " expected ON or OFF")
            return cmd[0].lower() == "on"

        # Note that doc text is used for generating help output.

        def command_backup(self, cmd):
            """backup ?DB? FILE: Backup DB (default "main") to FILE

            Copies the contents of the current database to FILE
            overwriting whatever was in FILE.  If you have attached databases
            then you can specify their name instead of the default of "main".

            The backup is done at the page level - SQLite copies the pages
            as is.  There is no round trip through SQL code.
            """
            dbname = "main"
            if len(cmd) == 1:
                fname = cmd[0]
            elif len(cmd) == 2:
                dbname = cmd[0]
                fname = cmd[1]
            else:
                raise self.Error("Backup takes one or two parameters")
            out = apsw.Connection(fname)
            b = out.backup("main", self.db, dbname)
            try:
                while not b.done:
                    b.step()
            finally:
                b.finish()
                out.close()

        def command_bail(self, cmd):
            """bail ON|OFF: Stop after hitting an error (default OFF)

            If an error is encountered while processing commands or SQL
            then exit.  (Note this is different than SQLite shell which
            only exits for errors in SQL.)
            """
            self.bail = self._boolean_command("bail", cmd)

        def command_cd(self, cmd):
            """cd ?DIR?: Changes current directory

            If no directory supplied then change to home directory"""
            if len(cmd) > 1:
                raise self.Error("Too many directories")
            d = cmd and cmd[0] or os.path.expanduser("~")
            if not os.path.isdir(d):
                raise self.Error(f"'{ d }' is not a directory")
            os.chdir(d)

        def command_changes(self, cmd):
            """changes ON|OFF: Show changes from last SQL and total changes (default OFF)

            After executing SQL that makes changes, the number of affected
            rows is displayed as well as a running count of all changes.
            """
            self.changes = self._boolean_command("changes", cmd)

        def command_close(self, cmd):
            """close: Closes the current database

            Use .open to open a database, or .connection to switch to another
            connection
            """
            if len(cmd):
                raise self.Error("Unexpected arguments")
            self.db.close()

        def command_connection(self, cmd):
            """connection ?NUMBER?: List connections, or switch active connection

            This covers all connections, not just those started in this
            shell.  Closed connections are not shown.
            """
            self.db_references.add(self.db)
            dbs = []
            for c in apsw.connections():
                try:
                    c.filename
                except apsw.ConnectionClosedError:
                    continue
                dbs.append(c)

            if len(cmd) == 0:
                co = self.colour
                if self.db not in dbs:
                    self.write(self.stdout, co.bold + "(Current connection is closed)" + co.bold_ + "\n")
                for i, c in enumerate(dbs):
                    sel = "*" if self.db is c else " "
                    self.write(
                        self.stdout,
                        f"{ co.bold}{ sel }{ co.bold_} { co.vnumber }{ i: 2}{ co.vnumber_ } - ({ c.open_vfs }) \"{ co.vstring }{ c.filename }{ co.vstring_ }\"\n"
                    )
            elif len(cmd) == 1:
                c = dbs[int(cmd[0])]
                if self.db is not c:
                    self._db = c
                    self.dbfilename = c.filename
            else:
                raise self.Error("Too many arguments")

        def command_colour(self, cmd=[]):
            """colour SCHEME: Selects a colour scheme

            If using a colour terminal in interactive mode then output is
            automatically coloured to make it more readable.  Use 'off' to
            turn off colour, and no name or 'default' for the default colour
            scheme.
            """
            if len(cmd) > 1:
                raise self.Error("Too many colour schemes")
            c = cmd and cmd[0] or "default"
            if c not in self._colours:
                raise self.Error("No such colour scheme: " + c)
            self.colour_scheme = c
            self._out_colour()

        command_color = command_colour

        def command_databases(self, cmd):
            """databases: Lists names and files of attached databases

            """
            if len(cmd):
                raise self.Error("databases command doesn't take any parameters")
            self.push_output()
            self.header = True
            self.output = self.output_column
            self.truncate = False
            self.widths = [3, 15, 58]
            try:
                self.process_sql("pragma database_list", internal=True)
            finally:
                self.pop_output()

        _dbconfig_ignore = {
            "SQLITE_DBCONFIG_MAINDBNAME", "SQLITE_DBCONFIG_LOOKASIDE", "SQLITE_DBCONFIG_MAX",
            "SQLITE_DBCONFIG_STMT_SCANSTATUS"
        }

        def command_dbconfig(self, cmd):
            """dbconfig ?NAME VALUE?: Show all dbconfig, or set a specific one

            With no arguments lists all settings.  Supply a name and integer value
            to change.  For example:

                .dbconfig enable_fkey 1
            """
            if len(cmd) == 0:
                outputs = {}
                for k in apsw.mapping_db_config:
                    if type(k) is not str or k in self._dbconfig_ignore:
                        continue
                    pretty = k[len("SQLITE_DBCONFIG_"):].lower()
                    outputs[pretty] = self.db.config(getattr(apsw, k), -1)
                w = max(len(k) for k in outputs.keys())
                for k, v in outputs.items():
                    self.write(self.stdout, " " * (w - len(k)))
                    self.write(self.stdout, k + ":  ")
                    self.write_value(v)
                    self.write(self.stdout, "\n")
                return
            elif len(cmd) != 2:
                raise self.Error("Expected zero or two parameters")
            key = "SQLITE_DBCONFIG_" + cmd[0].upper()
            if key not in apsw.mapping_db_config:
                raise self.Error(f"Unknown config option { key }")
            v = self.db.config(getattr(apsw, key), int(cmd[1]))
            self.write(self.stdout, cmd[0].lower() + ": ")
            self.write_value(v)
            self.write(self.stdout, "\n")

        def command_dbinfo(self, cmd):
            """dbinfo ?NAME?: Shows summary and file information about the database

            This includes the numbers of tables, indices etc, as well as fields from
            the files as returned by :func:`apsw.ext.dbinfo`.

            NAME defaults to 'main', and can be the attached name of a database.
            """
            if len(cmd) > 1:
                raise self.Error("too many parameters")
            schema = cmd[0] if cmd else "main"

            def total(t):
                return self.db.execute(f"select count(*) from [{ schema }].sqlite_schema where type='{ t }'").get

            outputs = [
                ("number of tables", total("table")),
                ("number of indexes", total("index")),
                ("number of triggers", total("trigger")),
                ("number of views", total("view")),
                ("schema size", int(self.db.execute(f"select total(length(sql)) from [{ schema }].sqlite_schema").get)),
            ]
            for i, info in enumerate(apsw.ext.dbinfo(self.db, schema)):
                if i == 1:
                    outputs.append(("journal mode", self.db.pragma("journal_mode")))
                if info:
                    outputs.extend(v for v in dataclasses.asdict(info).items())
                else:
                    if i == 0:
                        outputs.append(("filename", self.db.filename))
                    else:
                        outputs.append(
                            ("filename",
                             self.db.filename_wal if self.db.pragma("journal_mode") == "wal" else self.db.filename_journal))

            w = max(len(k) for k, v in outputs)
            for k, v in outputs:
                self.write(self.stdout, " " * (w - len(k)))
                self.write(self.stdout, k + ":  ")
                self.write_value(v)
                self.write(self.stdout, "\n")

        def command_dump(self, cmd):
            """dump ?TABLE? [TABLE...]: Dumps all or specified tables in SQL text format

            The table name is treated as like pattern so you can use % as
            a wildcard.  You can use dump to make a text based backup of
            the database.  It is also useful for comparing differences or
            making the data available to other databases.  Indices and
            triggers for the table(s) are also dumped.  Finally views
            matching the table pattern name are dumped (it isn't possible
            to work out which views access which table and views can
            access multiple tables anyway).

            Note that if you are dumping virtual tables such as used by
            the FTS5 module then they may use other tables to store
            information.  For example if you create a FTS5 table named
            *recipes* then it also creates *recipes_content*,
            *recipes_segdir* etc.  Consequently to dump this example
            correctly use:

               .dump recipes recipes_%

            If the database is empty or no tables/views match then there
            is no output.
            """
            # Simple tables are easy to dump.  More complicated is dealing
            # with virtual tables, foreign keys etc.

            # Lock the database while doing the dump so nothing changes
            # under our feet
            self.process_sql("BEGIN IMMEDIATE", internal=True)

            # Used in comment() - see issue 142
            outputstrtype = str

            # Python 2.3 can end up with nonsense like "en_us" so we fall
            # back to ascii in that case
            outputstrencoding = getattr(self.stdout, "encoding", "ascii")
            try:
                codecs.lookup(outputstrencoding)
            except Exception:
                outputstrencoding = "ascii"

            def unicodify(s):
                if not isinstance(s, outputstrtype):
                    # See issue 142 - it may not be in an expected encoding
                    return s.decode(outputstrencoding, "replace")
                return s

            try:
                # first pass -see if virtual tables or foreign keys are in
                # use.  If they are we emit pragmas to deal with them, but
                # prefer not to emit them
                v = {"virtuals": False, "foreigns": False}

                def check(name, sql):
                    if name.lower().startswith("sqlite_"):
                        return False
                    sql = sql.lower()
                    if re.match(r"^\s*create\s+virtual\s+.*", sql):
                        v["virtuals"] = True
                    # pragma table_info doesn't tell us if foreign keys
                    # are involved so we guess if any the various strings are
                    # in the sql somewhere
                    if re.match(r".*\b(foreign\s*key|references)\b.*", sql):
                        v["foreigns"] = True
                    return True

                if len(cmd) == 0:
                    cmd = ["%"]

                tables = []
                for pattern in cmd:
                    for name, sql in self.db.execute(
                            "SELECT name,sql FROM sqlite_schema "
                            "WHERE sql NOT NULL AND type IN ('table','view') "
                            "AND tbl_name LIKE ?1", (pattern, )):
                        if check(name, sql) and name not in tables:
                            tables.append(name)

                if not tables:
                    return

                # will we need to analyze anything later?
                analyze_needed = []
                for stat in self.db.execute(
                        "select name from sqlite_schema where sql not null and type='table' and tbl_name like 'sqlite_stat%'"
                ):
                    for name in tables:
                        if len(
                                self.db.execute("select * from " + self._fmt_sql_identifier(stat[0]) + " WHERE tbl=?",
                                                (name, )).fetchall()):
                            if name not in analyze_needed:
                                analyze_needed.append(name)
                analyze_needed.sort()

                def blank():
                    self.write(self.stdout, "\n")

                def comment(s):
                    s = unicodify(s)
                    self.write(self.stdout, textwrap.fill(s, 78, initial_indent="-- ", subsequent_indent="-- ") + "\n")

                pats = ", ".join([(x, "(All)")[x == "%"] for x in cmd])
                comment("SQLite dump (by APSW %s)" % (apsw.apswversion(), ))
                comment("SQLite version " + apsw.sqlitelibversion())
                comment("Date: " + unicodify(time.strftime("%c")))
                comment("Tables like: " + pats)
                comment("Database: " + self.db.filename)
                try:
                    import getpass
                    import socket
                    comment("User: %s @ %s" % (unicodify(getpass.getuser()), unicodify(socket.gethostname())))
                except ImportError:
                    pass
                blank()

                comment("The values of various per-database settings")
                self.write(self.stdout, "PRAGMA page_size=" + str(self.db.pragma("page_size")) + ";\n")
                comment("PRAGMA encoding='" + self.db.pragma("encoding") + "';\n")
                vac = {0: "NONE", 1: "FULL", 2: "INCREMENTAL"}
                vacvalue = self.db.pragma("auto_vacuum")
                comment("PRAGMA auto_vacuum=" + vac.get(vacvalue, str(vacvalue)) + ";\n")
                comment("PRAGMA max_page_count=" + str(self.db.pragma("max_page_count")) + ";\n")
                blank()

                # different python versions have different requirements
                # about specifying cmp to sort routine so we use this
                # portable workaround with a decorated list instead
                dectables = [(x.lower(), x) for x in tables]
                dectables.sort()
                tables = [y for x, y in dectables]

                virtuals = v["virtuals"]
                foreigns = v["foreigns"]

                if virtuals:
                    comment("This pragma is needed to restore virtual tables")
                    self.write(self.stdout, "PRAGMA writable_schema=ON;\n")
                if foreigns:
                    comment("This pragma turns off checking of foreign keys "
                            "as tables would be inconsistent while restoring.  It was introduced "
                            "in SQLite 3.6.19.")
                    self.write(self.stdout, "PRAGMA foreign_keys=OFF;\n")

                if virtuals or foreigns:
                    blank()

                self.write(self.stdout, "BEGIN TRANSACTION;\n")
                blank()

                def sqldef(s):
                    # return formatted sql watching out for embedded
                    # comments at the end forcing trailing ; onto next
                    # line https://sqlite.org/src/info/c04a8b8a4f
                    if "--" in s.split("\n")[-1]:
                        nl = "\n"
                    else:
                        nl = ""
                    return s + nl + ";\n"

                # do the table dumping loops
                oldtable = self._output_table
                try:
                    self.push_output()
                    self.output = self.output_insert
                    # Dump the table
                    for table in tables:
                        for sql in self.db.execute("SELECT sql FROM sqlite_schema WHERE name=?1 AND type='table'",
                                                   (table, )):
                            comment("Table  " + table)
                            # Special treatment for virtual tables - they
                            # get called back on drops and creates and
                            # could thwart us so we have to manipulate
                            # sqlite_schema directly
                            if sql[0].lower().split()[:3] == ["create", "virtual", "table"]:
                                self.write(
                                    self.stdout, "DELETE FROM sqlite_schema WHERE name=" + apsw.format_sql_value(table) +
                                    " AND type='table';\n")
                                self.write(
                                    self.stdout,
                                    "INSERT INTO sqlite_schema(type,name,tbl_name,rootpage,sql) VALUES('table',%s,%s,0,%s);\n"
                                    % (apsw.format_sql_value(table), apsw.format_sql_value(table),
                                       apsw.format_sql_value(sql[0])))
                            else:
                                self.write(self.stdout, "DROP TABLE IF EXISTS " + self._fmt_sql_identifier(table) + ";\n")
                                self.write(self.stdout, sqldef(sql[0]))
                                self._output_table = self._fmt_sql_identifier(table)
                                self.process_sql("select * from " + self._fmt_sql_identifier(table), internal=True)
                            # Now any indices or triggers
                            first = True
                            for name, sql in self.db.execute(
                                    "SELECT name,sql FROM sqlite_schema "
                                    "WHERE sql NOT NULL AND type IN ('index', 'trigger') "
                                    "AND tbl_name=?1 AND name NOT LIKE 'sqlite_%' "
                                    "ORDER BY lower(name)", (table, )):
                                if first:
                                    comment("Triggers and indices on  " + table)
                                    first = False
                                self.write(self.stdout, sqldef(sql))
                            blank()
                    # Views done last.  They have to be done in the same order as they are in sqlite_schema
                    # as they could refer to each other
                    first = True
                    for name, sql in self.db.execute("SELECT name,sql FROM sqlite_schema "
                                                     "WHERE sql NOT NULL AND type='view' "
                                                     "AND name IN ( " + ",".join([apsw.format_sql_value(i)
                                                                                  for i in tables]) + ") ORDER BY _ROWID_"):
                        if first:
                            comment("Views")
                            first = False
                        self.write(self.stdout, "DROP VIEW IF EXISTS %s;\n" % (self._fmt_sql_identifier(name), ))
                        self.write(self.stdout, sqldef(sql))
                    if not first:
                        blank()

                    # sqlite sequence
                    # does it exist
                    if len(self.db.execute("select * from sqlite_schema where name='sqlite_sequence'").fetchall()):
                        first = True
                        for t in tables:
                            v = self.db.execute("select seq from main.sqlite_sequence where name=?1", (t, )).fetchall()
                            if len(v):
                                assert len(v) == 1
                                if first:
                                    comment("For primary key autoincrements the next id "
                                            "to use is stored in sqlite_sequence")
                                    first = False
                                self.write(
                                    self.stdout,
                                    'DELETE FROM main.sqlite_sequence WHERE name=%s;\n' % (apsw.format_sql_value(t), ))
                                self.write(
                                    self.stdout, 'INSERT INTO main.sqlite_sequence VALUES (%s, %s);\n' %
                                    (apsw.format_sql_value(t), v[0][0]))
                        if not first:
                            blank()
                finally:
                    self.pop_output()
                    self._output_table = oldtable

                # analyze
                if analyze_needed:
                    comment("You had used the analyze command on these tables before.  Rerun for this new data.")
                    for n in analyze_needed:
                        self.write(self.stdout, "ANALYZE " + self._fmt_sql_identifier(n) + ";\n")
                    blank()

                # user version pragma
                uv = self.db.pragma("user_version")
                if uv:
                    comment(
                        "Your database may need this.  It is sometimes used to keep track of the schema version (eg Firefox does this)."
                    )
                    self.write(self.stdout, "pragma user_version=%d;" % (uv, ))
                    blank()

                # Save it all
                self.write(self.stdout, "COMMIT TRANSACTION;\n")

                # cleanup pragmas
                if foreigns:
                    blank()
                    comment("Restoring foreign key checking back on.  Note that SQLite 3.6.19 is off by default")
                    self.write(self.stdout, "PRAGMA foreign_keys=ON;\n")
                if virtuals:
                    blank()
                    comment("Restoring writable schema back to default")
                    self.write(self.stdout, "PRAGMA writable_schema=OFF;\n")
                    # schema reread
                    blank()
                    comment("We need to force SQLite to reread the schema because otherwise it doesn't know that "
                            "the virtual tables we inserted directly into sqlite_schema exist.  See "
                            "last comments of https://sqlite.org/cvstrac/tktview?tn=3425")
                    self.write(self.stdout, "BEGIN;\nCREATE TABLE no_such_table(x,y,z);\nROLLBACK;\n")

            finally:
                self.process_sql("END", internal=True)

        def command_echo(self, cmd):
            """echo ON|OFF: If ON then each SQL statement or command is printed before execution (default OFF)

            The SQL statement or command is sent to error output so that
            it is not intermingled with regular output.
            """
            self.echo = self._boolean_command("echo", cmd)

        def set_encoding(self, enc):
            """Saves *enc* as the default encoding, after verifying that
            it is valid.  You can also include :error to specify error
            handling - eg 'cp437:replace'

            Raises an exception on invalid encoding or error
            """
            enc = enc.split(":", 1)
            if len(enc) > 1:
                enc, errors = enc
            else:
                enc = enc[0]
                errors = None
            try:
                codecs.lookup(enc)
            except LookupError:
                raise self.Error("No known encoding '%s'" % (enc, ))
            try:
                if errors is not None:
                    codecs.lookup_error(errors)
            except LookupError:
                raise self.Error("No known codec error handler '%s'" % (errors, ))
            self.encoding = enc, errors

        def command_encoding(self, cmd):
            """encoding ENCODING: Set the encoding used for new files opened via .output and imports

            SQLite and APSW work internally using Unicode and characters.
            Files however are a sequence of bytes.  An encoding describes
            how to convert between bytes and characters.  The default
            encoding is utf8 and that is generally the best value to use
            when other programs give you a choice.

            You can also specify an error handler.  For example
            `cp437:replace` will use code page 437 and any Unicode
            codepoints not present in cp437 will be replaced (typically
            with something like a question mark).  Other error handlers
            include `ignore`, `strict` (default) and `xmlcharrefreplace`.

            For the default input/output/error streams on startup the
            shell defers to Python's detection of encoding.  For example
            on Windows it asks what code page is in use and on Unix it
            looks at the LC_CTYPE environment variable.  You can set the
            PYTHONIOENCODING environment variable to override this
            detection.

            This command affects files opened after setting the encoding
            as well as imports.
            """
            if len(cmd) != 1:
                raise self.Error("Encoding takes one argument")
            self.set_encoding(cmd[0])

        def command_exceptions(self, cmd):
            """exceptions ON|OFF: If ON then detailed tracebacks are shown on exceptions (default OFF)

            Normally when an exception occurs the error string only is
            displayed.  However it is sometimes useful to get a full
            traceback.  An example would be when you are developing
            virtual tables and using the shell to exercise them.  In
            addition to displaying each stack frame, the local variables
            within each frame are also displayed.
            """
            self.exceptions = self._boolean_command("exceptions", cmd)

        def command_exit(self, cmd):
            """exit ?CODE?: Exit this program with optional exit code"""
            if len(cmd) > 1:
                raise self.Error("Too many parameters for exit")
            try:
                c = 0 if not cmd else int(cmd[0])
            except ValueError:
                raise self.Error(f"{ cmd[0] } isn't an exit code")
            sys.exit(c)

        def command_find(self, cmd):
            """find value ?TABLE?: Searches all columns of all tables for a value

            The find command helps you locate data across your database
            for example to find a string or any references to an id.

            You can specify a like pattern to limit the search to a subset
            of tables (eg specifying CUSTOMER% for all tables beginning
            with CUSTOMER).

            The value will be treated as a string and/or integer if
            possible.  If value contains '%' or '_' then it is also treated as
            a like pattern.

            This command can take a long time to execute needing to scan
            all of the relevant tables.
            """
            if len(cmd) < 1 or len(cmd) > 2:
                raise self.Error("At least one argument required and at most two accepted")
            tablefilter = "%"
            if len(cmd) == 2:
                tablefilter = cmd[1]
            querytemplate = []
            queryparams = []

            def qp():  # binding for current queryparams
                return "?" + str(len(queryparams))

            s = cmd[0]
            if '%' in s or '_' in s:
                queryparams.append(s)
                querytemplate.append("%s LIKE " + qp())
            queryparams.append(s)
            querytemplate.append("%s = " + qp())
            try:
                i = int(s)
                queryparams.append(i)
                querytemplate.append("%s = " + qp())
            except ValueError:
                pass
            querytemplate = " OR ".join(querytemplate)
            for (table, ) in self.db.execute("SELECT name FROM sqlite_schema WHERE type='table' AND name LIKE ?1",
                                             (tablefilter, )):
                t = self._fmt_sql_identifier(table)
                query = "SELECT * from %s WHERE " % (t, )
                colq = []
                for _, column, _, _, _, _ in self.db.execute("pragma table_info(%s)" % (t, )):
                    colq.append(querytemplate % ((self._fmt_sql_identifier(column), ) * len(queryparams)))
                query = query + " OR ".join(colq)
                self.process_sql(query, queryparams, internal=True, summary=("Table " + table + "\n", "\n"))

        def command_header(self, cmd):
            """header(s) ON|OFF: Display the column names in output (default OFF)

            """
            self.header = self._boolean_command("header", cmd)

        command_headers = command_header

        _help_info = None

        def command_help(self, cmd):
            """help ?COMMAND?: Shows list of commands and their usage

            If COMMAND is specified then shows detail about that COMMAND.
            ``.help all`` will show detailed help about all commands.
            """
            if not self._help_info:
                # buildup help database
                self._help_info = {}
                for c in dir(self):
                    if not c.startswith("command_"):
                        continue
                    # help is 3 parts
                    # - the syntax string (eg backup ?dbname? filename)
                    # - the one liner description (eg saves database to filename)
                    # - the multi-liner detailed description
                    # We grab this from the doc string for the function in the form
                    #   syntax: one liner\nmulti\nliner
                    d = getattr(self, c).__doc__
                    assert d, c + " command must have documentation"
                    c = c[len("command_"):]
                    if c in ("headers", "color"): continue
                    while d[0] == "\n":
                        d = d[1:]
                    parts = d.split("\n", 1)
                    firstline = parts[0].strip().split(":", 1)
                    assert len(firstline) == 2, c + " command must have usage: description doc"
                    if len(parts) == 1 or len(parts[1].strip()) == 0:  # work around textwrap bug
                        multi = ""
                    else:
                        multi = textwrap.dedent(parts[1])
                    if c == "mode":
                        firstline[1] = firstline[1] + " " + " ".join(self._output_modes)
                        multi = multi + "\n\n" + "\n\n".join(self._output_modes_detail)
                    if c == "colour":
                        colours = list(self._colours.keys())
                        colours.sort()
                        firstline[1] = firstline[1] + " from " + ", ".join(colours)
                    if len(multi.strip()) == 0:  # All whitespace
                        multi = None
                    else:
                        # break into paragraphs
                        lines = multi.strip("\n").split("\n")
                        # make whitespace only lines be empty
                        for i in range(len(lines)):
                            if not lines[i].strip():
                                lines[i] = ""
                        multi = [lines[0]]
                        for l in lines[1:]:
                            if multi[-1] and l and l.lstrip() == l:
                                multi[-1] += " " + l
                            else:
                                multi.append(l)

                    self._help_info[c] = ('.' + firstline[0].strip(), firstline[1].strip(), multi)

            self.write(self.stderr, "\n")

            tw = self._terminal_width(32)
            if len(cmd) == 0:
                commands = list(self._help_info.keys())
                commands.sort()
                w = 0
                for command in commands:
                    if len(self._help_info[command][0]) > w:
                        w = len(self._help_info[command][0])
                out = []
                for command in commands:
                    hi = self._help_info[command]
                    # usage string
                    out.append(hi[0])
                    # space padding (including 2 for between columns)
                    out.append(" " * (2 + w - len(hi[0])))
                    # usage message wrapped if need be
                    out.append(("\n" + " " * (2 + w)).join(textwrap.wrap(hi[1], tw - w - 2)))
                    # newline
                    out.append("\n")
                self.write(self.stderr, "".join(out))
            else:
                if cmd[0] == "all":
                    cmd = list(self._help_info.keys())
                    cmd.sort()
                w = 0
                for command in self._help_info:
                    if len(self._help_info[command][0]) > w:
                        w = len(self._help_info[command][0])

                for command in cmd:
                    if command == "headers": command = "header"
                    if command not in self._help_info:
                        raise self.Error("No such command \"%s\"" % (command, ))
                    out = []
                    hi = self._help_info[command]
                    # usage string
                    out.append(hi[0])
                    # space padding (2)
                    out.append(" " * (2 + w - len(hi[0])))
                    # usage message wrapped if need be
                    out.append(("\n" + " " * (2 + w)).join(textwrap.wrap(hi[1], tw - w - 2)) + "\n")
                    if hi[2]:
                        # newlines
                        out.append("\n")
                        # detailed message
                        for i, para in enumerate(hi[2]):
                            out.append(textwrap.fill(para, tw) + "\n")
                    # if not first one then print separator header
                    if command != cmd[0]:
                        self.write(self.stderr, "\n" + "=" * tw + "\n")
                    self.write(self.stderr, "".join(out))
            self.write(self.stderr, "\n")

        def command_import(self, cmd):
            """import FILE TABLE: Imports separated data from FILE into TABLE

            Reads data from the file into the named table using the
            current separator and encoding.  For example if the separator
            is currently a comma then the file should be CSV (comma
            separated values).

            All values read in are supplied to SQLite as strings.  If you
            want SQLite to treat them as other types then declare your
            columns appropriately.  For example declaring a column 'REAL'
            will result in the values being stored as floating point if
            they can be safely converted.

            Another alternative is to create a temporary table, insert the
            values into that and then use casting.:

              CREATE TEMPORARY TABLE import(a,b,c);
              .import filename import
              CREATE TABLE final AS SELECT cast(a as BLOB), cast(b as INTEGER),
                   cast(c as CHAR) from import;
              DROP TABLE import;

            You can also get more sophisticated using the SQL CASE
            operator.  For example this will turn zero length strings into
            null:

              SELECT CASE col WHEN '' THEN null ELSE col END FROM ...
            """
            if len(cmd) != 2:
                raise self.Error("import takes two parameters")

            try:
                final = None
                # start transaction so database can't be changed
                # underneath us
                self.db.execute("BEGIN IMMEDIATE")
                final = "ROLLBACK"

                # how many columns?
                ncols = len(self.db.execute("pragma table_info(" + self._fmt_sql_identifier(cmd[1]) + ")").fetchall())
                if ncols < 1:
                    raise self.Error("No such table '%s'" % (cmd[1], ))

                cur = self.db.cursor()
                sql = "insert into %s values(%s)" % (self._fmt_sql_identifier(cmd[1]), ",".join("?" * ncols))

                kwargs = {}
                if self.separator == ",":
                    kwargs["dialect"] = "excel"
                elif self.separator == "\t":
                    kwargs["dialect"] = "excel-tab"
                else:
                    kwargs["quoting"] = csv.QUOTE_NONE
                    kwargs["delimiter"] = self.separator
                    kwargs["doublequote"] = False
                    kwargs["quotechar"] = "\x00"
                row = 1
                for line in self._csvin_wrapper(cmd[0], kwargs):
                    if len(line) != ncols:
                        raise self.Error("row %d has %d columns but should have %d" % (row, len(line), ncols))
                    try:
                        cur.execute(sql, line)
                    except Exception:
                        self.write_error(f"Error inserting row { row }")
                        raise
                    row += 1
                self.db.execute("COMMIT")

            except Exception:
                if final:
                    self.db.execute(final)
                raise

        def _csvin_wrapper(self, filename, dialect):
            # Returns a csv reader that works around python bugs and uses
            # dialect dict to configure reader
            thefile = codecs.open(filename, "r", self.encoding[0])
            for line in csv.reader(thefile, **dialect.copy()):
                yield line
            thefile.close()
            return

        def command_autoimport(self, cmd):
            """autoimport FILENAME ?TABLE?: Imports filename creating a table and automatically working out separators and data types (alternative to .import command)

            The import command requires that you precisely pre-setup the
            table and schema, and set the data separators (eg commas or
            tabs).  This command figures out the separator and csv dialect
            automatically.  There must be at least two columns and two rows.

            If the table is not specified then the basename of the file
            will be used.

            Additionally the type of the contents of each column is also
            deduced - for example if it is a number or date.  Empty values
            are turned into nulls.  Dates are normalized into YYYY-MM-DD
            format and DateTime are normalized into ISO8601 format to
            allow easy sorting and searching.  4 digit years must be used
            to detect dates.  US (swapped day and month) versus rest of
            the world is also detected providing there is at least one
            value that resolves the ambiguity.

            Care is taken to ensure that columns looking like numbers are
            only treated as numbers if they do not have unnecessary
            leading zeroes or plus signs.  This is to avoid treating phone
            numbers and similar number like strings as integers.

            This command can take quite some time on large files as they
            are effectively imported twice.  The first time is to
            determine the format and the types for each column while the
            second pass actually imports the data.
            """
            if len(cmd) < 1 or len(cmd) > 2:
                raise self.Error("Expected one or two parameters")
            if not os.path.exists(cmd[0]):
                raise self.Error("File \"%s\" does not exist" % (cmd[0], ))
            if len(cmd) == 2:
                tablename = cmd[1]
            else:
                tablename = None
            try:
                final = None
                c = self.db.cursor()
                c.execute("BEGIN IMMEDIATE")
                final = "ROLLBACK"

                if not tablename:
                    tablename = os.path.splitext(os.path.basename(cmd[0]))[0]

                if c.execute("pragma table_info(%s)" % (self._fmt_sql_identifier(tablename), )).fetchall():
                    raise self.Error("Table \"%s\" already exists" % (tablename, ))

                # The types we support deducing
                def DateUS(v):  # US formatted date with wrong ordering of day and month
                    return DateWorld(v, switchdm=True)

                def DateWorld(v, switchdm=False):  # Sensibly formatted date as used anywhere else in the world
                    y, m, d = self._getdate(v)
                    if switchdm: m, d = d, m
                    if m < 1 or m > 12 or d < 1 or d > 31:
                        raise ValueError
                    return "%d-%02d-%02d" % (y, m, d)

                def DateTimeUS(v):  # US date and time
                    return DateTimeWorld(v, switchdm=True)

                def DateTimeWorld(v, switchdm=False):  # Sensible date and time
                    y, m, d, h, M, s = self._getdatetime(v)
                    if switchdm: m, d = d, m
                    if m < 1 or m > 12 or d < 1 or d > 31 or h < 0 or h > 23 or M < 0 or M > 59 or s < 0 or s > 65:
                        raise ValueError
                    return "%d-%02d-%02dT%02d:%02d:%02d" % (y, m, d, h, M, s)

                def Number(v):  # we really don't want phone numbers etc to match
                    # Python's float & int constructors allow whitespace which we don't
                    if re.search(r"\s", v):
                        raise ValueError
                    if v == "0": return 0
                    if v[0] == "+":  # idd prefix
                        raise ValueError
                    if re.match("^[0-9]+$", v):
                        if v[0] == "0": raise ValueError  # also a phone number
                        return int(v)
                    if v[0] == "0" and not v.startswith("0."):  # deceptive not a number
                        raise ValueError
                    return float(v)

                # Work out the file format
                formats = [{"dialect": "excel"}, {"dialect": "excel-tab"}]
                seps = ["|", ";", ":"]
                if self.separator not in seps:
                    seps.append(self.separator)
                for sep in seps:
                    formats.append({"quoting": csv.QUOTE_NONE, "delimiter": sep, "doublequote": False, "quotechar": "\x00"})
                possibles = []
                errors = []
                encodingissue = False
                # format is copy() on every use.  This appears bizarre and
                # unnecessary.  However Python 2.3 and 2.4 somehow manage
                # to empty it if not copied.
                for format in formats:
                    ncols = -1
                    lines = 0
                    try:
                        for line in self._csvin_wrapper(cmd[0], format.copy()):
                            if lines == 0:
                                lines = 1
                                ncols = len(line)
                                # data type guess setup
                                datas = []
                                for i in range(ncols):
                                    datas.append([DateUS, DateWorld, DateTimeUS, DateTimeWorld, Number])
                                allblanks = [True] * ncols
                                continue
                            if len(line) != ncols:
                                raise ValueError("Expected %d columns - got %d" % (ncols, len(line)))
                            lines += 1
                            for i in range(ncols):
                                if not line[i]:
                                    continue
                                allblanks[i] = False
                                if not datas[i]:
                                    continue
                                # remove datas that give ValueError
                                d = []
                                for dd in datas[i]:
                                    try:
                                        dd(line[i])
                                        d.append(dd)
                                    except ValueError:
                                        pass
                                datas[i] = d
                        if ncols > 1 and lines > 1:
                            # if a particular column was allblank then clear datas for it
                            for i in range(ncols):
                                if allblanks[i]:
                                    datas[i] = []
                            possibles.append((format.copy(), ncols, lines, datas))
                    except UnicodeDecodeError:
                        encodingissue = True
                    except Exception:
                        s = str(sys.exc_info()[1])
                        if s not in errors:
                            errors.append(s)

                if len(possibles) == 0:
                    if encodingissue:
                        raise self.Error(
                            "The file is probably not in the current encoding \"%s\" and didn't match a known file format" %
                            (self.encoding[0], ))
                    v = "File doesn't appear to match a known type."
                    if len(errors):
                        v += "  Errors reported:\n" + "\n".join(["  " + e for e in errors])
                    raise self.Error(v)
                if len(possibles) > 1:
                    raise self.Error("File matches more than one type!")
                format, ncols, lines, datas = possibles[0]
                fmt = format.get("dialect", None)
                if fmt is None:
                    fmt = "(delimited by \"%s\")" % (format["delimiter"], )
                self.write(self.stdout, "Detected Format %s  Columns %d  Rows %d\n" % (fmt, ncols, lines))
                # Header row
                reader = self._csvin_wrapper(cmd[0], format)
                for header in reader:
                    break
                # Check schema
                identity = lambda x: x
                for i in range(ncols):
                    if len(datas[i]) > 1:
                        raise self.Error("Column #%d \"%s\" has ambiguous data format - %s" %
                                         (i + 1, header[i], ", ".join([d.__name__ for d in datas[i]])))
                    if datas[i]:
                        datas[i] = datas[i][0]
                    else:
                        datas[i] = identity
                # Make the table
                sql = "CREATE TABLE %s(%s)" % (self._fmt_sql_identifier(tablename), ", ".join(
                    [self._fmt_sql_identifier(h) for h in header]))
                c.execute(sql)
                # prep work for each row
                sql = "INSERT INTO %s VALUES(%s)" % (self._fmt_sql_identifier(tablename), ",".join(["?"] * ncols))
                for line in reader:
                    vals = []
                    for i in range(ncols):
                        l = line[i]
                        if not l:
                            vals.append(None)
                        else:
                            vals.append(datas[i](l))
                    c.execute(sql, vals)

                c.execute("COMMIT")
                self.write(self.stdout, "Auto-import into table \"%s\" complete\n" % (tablename, ))
            except Exception:
                if final:
                    self.db.execute(final)
                raise

        def _getdate(self, v):
            # Returns a tuple of 3 items y,m,d from string v
            m = re.match(r"^([0-9]+)[^0-9]([0-9]+)[^0-9]([0-9]+)$", v)
            if not m:
                raise ValueError
            y, m, d = int(m.group(1)), int(m.group(2)), int(m.group(3))
            if d > 1000:  # swap order
                y, m, d = d, m, y
            if y < 1000 or y > 9999:
                raise ValueError
            return y, m, d

        def _getdatetime(self, v):
            # must be at least HH:MM
            m = re.match(r"^([0-9]+)[^0-9]([0-9]+)[^0-9]([0-9]+)[^0-9]+([0-9]+)[^0-9]([0-9]+)([^0-9]([0-9]+))?$", v)
            if not m:
                raise ValueError
            items = list(m.group(1, 2, 3, 4, 5, 7))
            for i in range(len(items)):
                if items[i] is None:
                    items[i] = 0
            items = [int(i) for i in items]
            if items[2] > 1000:
                items = [items[2], items[1], items[0]] + items[3:]
            if items[0] < 1000 or items[0] > 9999:
                raise ValueError
            return items

        def command_indices(self, cmd):
            """indices TABLE: Lists all indices on table TABLE

            """
            if len(cmd) != 1:
                raise self.Error("indices takes one table name")
            self.push_output()
            self.header = False
            self.output = self.output_list
            try:
                self.process_sql(
                    "SELECT name FROM sqlite_schema WHERE type='index' AND tbl_name LIKE ?1 "
                    "UNION ALL SELECT name FROM sqlite_temp_schema WHERE type='index' AND tbl_name LIKE "
                    "?1 ORDER by name",
                    cmd,
                    internal=True)
            finally:
                self.pop_output()

        def command_load(self, cmd):
            """load FILE ?ENTRY?: Loads a SQLite extension library

            Note: Extension loading may not be enabled in the SQLite
            library version you are using.

            By default sqlite3_extension_init is called in the library but
            you can specify an alternate entry point.

            If you get an error about the extension not being found you
            may need to explicitly specify the directory.  For example if
            it is in the current directory then use:

              .load ./extension.so
            """
            if len(cmd) < 1 or len(cmd) > 2:
                raise self.Error("load takes one or two parameters")
            try:
                self.db.enableloadextension(True)
            except Exception:
                raise self.Error("Extension loading is not supported")

            self.db.loadextension(*cmd)

        def log_handler(self, code, message):
            code = f"( { code } - { apsw.mapping_result_codes.get(code, 'unknown') } ) "
            self.write_error(code + message + "\n")

        def command_log(self, cmd):
            "log ON|OFF: Shows SQLite log messages (default off)"
            setting = self._boolean_command("log", cmd)
            apsw.config(apsw.SQLITE_CONFIG_LOG, self.log_handler if setting else None)

        _output_modes = None

        def command_mode(self, cmd):
            """mode MODE ?OPTIONS?: Sets output mode to one of"""
            if not cmd:
                raise self.Error("Specify an output mode")
            w = cmd[0]
            if w == "tabs":
                w = "list"
            if not hasattr(self, "output_" + w):
                raise self.Error("Expected a valid output mode: " + ", ".join(self._output_modes))

            m = getattr(self, "output_" + w)

            # argument parsing
            if w == "insert":
                if len(cmd) not in (1, 2):
                    raise self.Error("Output mode %s doesn't take parameters" % (cmd[0]))
                table_name = cmd[1] if len(cmd) == 2 else "table"
                self._output_table = self._fmt_sql_identifier(table_name)
                self.output = m
                return

            if w not in {"box", "qbox", "table"}:
                if len(cmd) != 1:
                    raise self.Error("Output mode %s doesn't take parameters" % (cmd[0]))
                if cmd[0] == "csv":
                    self.separator = ","
                elif cmd[0] == "tabs":
                    self.separator = "\t"
                self.truncate = True
                self.output = m
                return

            defaults = {
                "quote": w in {"qbox"},
                "string_sanitize": {
                    "box": 0,
                    "table": 2,
                    "qbox": 1
                }[w],
                "null": "NULL",
                "truncate": {
                    "box": 1024,
                    "table": 2048,
                    "qbox": 4096
                }[w],
                "text_width": 0 if self.interactive else 80,
                "use_unicode": {
                    "box": True,
                    "table": False,
                    "qbox": True
                }[w],
                "word_wrap": True,
            }

            # argparse unfortunately tries to do too much and really is about program arguments,
            # but it isn't worthwhile re-implementing this
            p = argparse.ArgumentParser(allow_abbrev=False, usage=f".mode { w }", prog="")
            if hasattr(p, "exit_on_error"):
                p.exit_on_error = False
            p.set_defaults(**defaults)
            p.add_argument("--quote", dest="quote", action="store_true", help="Show values in SQL syntax [%(default)s]")
            p.add_argument("--no-quote", dest="quote", action="store_false", help="Show values as strings")
            p.add_argument(
                "--string-sanitize",
                type=int,
                choices=(0, 1, 2),
                help="How much to clean up string characters (0 - none, 1 - medium, 2 - everything) [%(default)s]")
            p.add_argument("--null", help="How to show NULL [%(default)s]")
            p.add_argument("--truncate", type=int, help="How many characters to truncate long output at [%(default)s]")
            p.add_argument("--width",
                           type=int,
                           dest="text_width",
                           help="Maximum width of the table [Screen width if terminal, else 80 chars]")
            p.add_argument("--unicode",
                           action="store_true",
                           dest="use_unicode",
                           help="Use unicode line drawing [%(default)s]")
            p.add_argument("--no-unicode",
                           action="store_true",
                           dest="use_unicode",
                           help="Use ascii line drawing like +=-+ ")
            p.add_argument("--word-wrap",
                           action="store_true",
                           dest="word_wrap",
                           help="Wrap text at word boundaries [%(default)s]")
            p.add_argument("--no-word-wrap",
                           action="store_false",
                           dest="word_wrap",
                           help="Wrap at column width ignoring words")
            text = io.StringIO()
            try:
                with contextlib.redirect_stderr(text):
                    with contextlib.redirect_stdout(text):
                        self.box_options = vars(p.parse_args(cmd[1:]))
            except:
                # bare except because SystemExit can be raised
                raise Shell.Error(text.getvalue())
            self.output = self.output_box

        # needed so command completion and help can use it
        def _calculate_output_modes(self):
            modes = [m[len("output_"):] for m in dir(self) if m.startswith("output_")]
            modes.append("tabs")
            modes.sort()
            self._output_modes = modes

            detail = []

            for m in modes:
                if m in {'tabs', "column", "line"}:
                    continue
                d = getattr(self, "output_" + m).__doc__
                assert d, "output mode " + m + " needs doc"
                d = d.replace("\n", " ").strip()
                while "  " in d:
                    d = d.replace("  ", " ")
                detail.append(m + ": " + d)
            self._output_modes_detail = detail

        def command_nullvalue(self, cmd):
            """nullvalue STRING: Print STRING in place of null values

            This affects textual output modes like column and list and
            sets how SQL null values are shown.  The default is a zero
            length string.  Insert mode and dumps are not affected by this
            setting.  You can use double quotes to supply a zero length
            string.  For example:

              .nullvalue ""         # the default
              .nullvalue <NULL>     # rather obvious
              .nullvalue " \\t "     # A tab surrounded by spaces
            """
            if len(cmd) != 1:
                raise self.Error("nullvalue takes exactly one parameter")
            self.nullvalue = self.fixup_backslashes(cmd[0])

        def command_open(self, cmd):
            """open ?OPTIONS? ?FILE?: Opens a database connection

            Options are:

            --wipe     Closes any existing connections in this process referring to
                       the same file  and deletes the database file, journals etc
                       before opening

            --vfs VFS  Which vfs to use when opening

            If FILE is omitted then a memory database is opened
            """
            wipe = False
            vfs = None
            dbname = None
            c = cmd
            while c:
                p = c.pop(0)
                if p.startswith("--"):
                    if p == "--wipe":
                        wipe = True
                        continue
                    if p == "--vfs":
                        vfs = c.pop(0)
                        continue
                    raise self.Error("Unknown open param: " + p)
                if dbname is not None:
                    raise self.Error("Too many arguments: " + p)
                dbname = p

            if wipe:
                if not dbname:
                    raise self.Error("You must specify a filename with --wipe")
                for c in apsw.connections():
                    try:
                        if c.filename and os.path.samefile(c.filename, dbname):
                            c.close()
                    except (apsw.ConnectionClosedError, FileNotFoundError):
                        pass
                for suffix in "", "-journal", "-wal", "-shm":
                    try:
                        os.remove(dbname + suffix)
                    except OSError:
                        pass
            self.db_references.add(self.db)
            self.dbfilename = dbname if dbname is not None else ""
            self._db = apsw.Connection(self.dbfilename,
                                       vfs=vfs,
                                       flags=apsw.SQLITE_OPEN_URI | apsw.SQLITE_OPEN_READWRITE
                                       | apsw.SQLITE_OPEN_CREATE)

        def command_output(self, cmd):
            """output FILENAME: Send output to FILENAME (or stdout)

            If the FILENAME is 'stdout' then output is sent to standard
            output from when the shell was started.  The file is opened
            using the current encoding (change with 'encoding' command).
            """
            # Flush everything
            self.stdout.flush()
            self.stderr.flush()
            if hasattr(self.stdin, "flush"):
                try:
                    self.stdin.flush()
                except IOError:  # see issue 117
                    pass

            # we will also close stdout but only do so once we have a
            # replacement so that stdout is always valid

            if len(cmd) != 1:
                raise self.Error("You must specify a filename")

            try:
                fname = cmd[0]
                if fname == "stdout":
                    old = None
                    if self.stdout != self._original_stdout:
                        old = self.stdout
                    self.stdout = self._original_stdout
                    if old is not None:  # done here in case close raises exception
                        old.close()
                    return

                newf = codecs.open(fname, "w", self.encoding[0], self.encoding[1])
                old = None
                if self.stdout != self._original_stdout:
                    old = self.stdout
                self.stdout = newf
                if old is not None:
                    old.close()
            finally:
                self._out_colour()

        def command_parameter(self, cmd):
            """parameter CMD ...:  Maintain named bindings you can use in your queries.

            Specify a subcommand:

               list            -- shows current bindings
               clear           -- deletes all bindings
               unset NAME      -- deletes named binding
               set NAME VALUE  -- sets binding to VALUE

            The value must be a valid SQL literal or expression.  For example
            `3` will be an integer 3 while '3' will be a string.

            Example::

              .parameter set floor 10.99
              .parameter set text 'Acme''s Glove'
              SELECT * FROM sales WHERE price > $floor AND description != $text;
            """
            if cmd:
                if len(cmd) == 1 and cmd[0] in {"clear", "init"}:
                    self.bindings = {}
                    return
                if len(cmd) == 1 and cmd[0] == "list":
                    if not self.bindings:
                        self.write(self.stdout, "No parameters set\n")
                        return
                    w = max(10, max(len(k) for k in self.bindings) + 1)
                    for k, v in sorted(self.bindings.items()):
                        self.write(self.stdout, k + " " * (w - len(k)))
                        self.write_value(v)
                        self.write(self.stdout, "\n")
                    return
                if len(cmd) == 2 and cmd[0] == "unset":
                    try:
                        del self.bindings[cmd[1]]
                        return
                    except KeyError:
                        raise self.Error(f"'{ cmd[1] }' is not in parameters")
                if len(cmd) == 3 and cmd[0] == "set":
                    try:
                        v = self.db.execute(f"select ({ cmd[2] })").get
                    except Exception:
                        raise self.Error(f"Does not appear to be a valid SQLite value: { cmd[2] }")
                    self.bindings[cmd[1]] = v
                    return
            raise self.Error(".parameter command not understood.  Use .help parameter to get usage")

        def command_print(self, cmd):
            """print STRING: print the literal STRING

            If more than one argument is supplied then they are printed
            space separated.  You can use backslash escapes such as \\n
            and \\t.
            """
            self.write(self.stdout, " ".join([self.fixup_backslashes(i) for i in cmd]) + "\n")

        def command_prompt(self, cmd):
            """prompt MAIN ?CONTINUE?: Changes the prompts for first line and continuation lines

            The default is to print 'sqlite> ' for the main prompt where
            you can enter a dot command or a SQL statement.  If the SQL
            statement is not complete (eg not ; terminated) then you are
            prompted for more using the continuation prompt which defaults
            to ' ..> '.  Example:

              .prompt "command> " "more command> "

            You can use backslash escapes such as \\n and \\t.
            """
            if len(cmd) < 1 or len(cmd) > 2:
                raise self.Error("prompt takes one or two arguments")
            self.prompt = self.fixup_backslashes(cmd[0])
            if len(cmd) == 2:
                self.moreprompt = self.fixup_backslashes(cmd[1])

        def command_py(self, cmd):
            """py ?PYTHON?: Starts a python REPL or runs the Python statement provided

            The namespace provided includes ``apsw`` for the module, ``shell`` for this
            shell and ``db`` for the current database.

            Using the .output command does not affect output from this command.  You
            can write to `shell.stdout` and `shell.stderr`.
            """
            self.stdout.flush()
            self.stderr.flush()
            vars = {"shell": self, "apsw": apsw, "db": self.db}
            if cmd:
                assert len(cmd) == 1
                interp = code.InteractiveInterpreter(locals=vars)
                try:
                    # we have to make sys.excepthook and sys.__excepthook__ be
                    # the same otherwise the traceback includes methods in the
                    # code module.  Ubuntu's apport messes with excepthook
                    hook = sys.excepthook
                    sys.excepthook = sys.__excepthook__
                    res = interp.runsource(cmd[0])
                finally:
                    sys.excepthook = hook
                if res:
                    self.write_error("Incomplete Python statement\n")
            else:
                # this should be locals (plural) but the method is written
                # in singular and works due to being passed as a positional
                # argument
                code.interact(local=vars, exitmsg=self.colour.intro + "Returning to APSW shell" + self.colour.intro_)

        def command_read(self, cmd):
            """read FILENAME: Processes SQL and commands in FILENAME (or Python if FILENAME ends with .py)

            Treats the specified file as input (a mixture or SQL and/or
            dot commands).  If the filename ends in .py then it is treated
            as Python code instead.

            For Python code the symbol 'db' refers to the current database,
            'shell' refers to the instance of the shell and 'apsw' is the
            apsw module.
            """
            if len(cmd) != 1:
                raise self.Error("read takes a single filename")
            if cmd[0].lower().endswith(".py"):
                g = {}
                g.update({'apsw': apsw, 'shell': self, 'db': self.db})
                # compile step is needed to associate name with code
                f = open(cmd[0], "rb")
                try:
                    exec(compile(f.read(), cmd[0], 'exec'), g, g)
                finally:
                    f.close()
            else:
                f = codecs.open(cmd[0], "r", self.encoding[0])
                try:
                    try:
                        self.push_input()
                        self.stdin = f
                        self.interactive = False
                        self.input_line_number = 0
                        while True:
                            line = self.getcompleteline()
                            if line is None:
                                break
                            self.process_complete_line(line)
                    except Exception:
                        self._append_input_description()
                        raise

                finally:
                    self.pop_input()
                    f.close()

        def command_restore(self, cmd):
            """restore ?DB? FILE: Restore database from FILE into DB (default "main")

            Copies the contents of FILE to the current database (default "main").
            The backup is done at the page level - SQLite copies the pages as
            is.  There is no round trip through SQL code.
            """
            dbname = "main"
            if len(cmd) == 1:
                fname = cmd[0]
            elif len(cmd) == 2:
                dbname = cmd[0]
                fname = cmd[1]
            else:
                raise self.Error("Restore takes one or two parameters")
            input = apsw.Connection(fname)
            b = self.db.backup(dbname, input, "main")
            try:
                while not b.done:
                    b.step()
            finally:
                b.finish()
                input.close()

        def command_schema(self, cmd):
            """schema ?TABLE? [TABLE...]: Shows SQL for table

            If you give one or more tables then their schema is listed
            (including indices).  If you don't specify any then all
            schemas are listed. TABLE is a like pattern so you can % for
            wildcards.
            """
            self.push_output()
            self.output = self.output_list
            self.header = False
            try:
                if len(cmd) == 0:
                    cmd = ['%']
                for n in cmd:
                    self.process_sql(
                        "SELECT sql||';' FROM "
                        "(SELECT sql sql, type type, tbl_name tbl_name, name name "
                        "FROM sqlite_schema UNION ALL "
                        "SELECT sql, type, tbl_name, name FROM sqlite_temp_schema) "
                        "WHERE tbl_name LIKE ?1 AND type!='meta' AND sql NOTNULL AND name NOT LIKE 'sqlite_%' "
                        "ORDER BY substr(type,2,1), name", (n, ),
                        internal=True)
            finally:
                self.pop_output()

        def command_separator(self, cmd):
            """separator STRING: Change separator for output mode and .import

            You can use quotes and backslashes.  For example to set the
            separator to space tab space you can use:

              .separator " \\t "

            The setting is automatically changed when you switch to csv or
            tabs output mode.  You should also set it before doing an
            import (ie , for CSV and \\t for TSV).
            """
            if len(cmd) != 1:
                raise self.Error("separator takes exactly one parameter")
            self.separator = self.fixup_backslashes(cmd[0])

        _shows = ("echo", "headers", "mode", "changes", "nullvalue", "output", "separator", "width", "exceptions",
                  "encoding")

        def command_shell(self, cmd):
            """shell CMD ARGS...: Run CMD ARGS in a system shell

            Note that output goes to the process standard output, not
            whatever the shell .output command has configured.
            """
            if len(cmd) == 0:
                raise self.Error("Specify command and arguments to run")
            assert len(cmd) == 1
            res = os.system(cmd[0])
            if res != 0:
                self.write_error(f"Exit code { res }\n")

        def command_show(self, cmd):
            """show: Show the current values for various settings."""
            if len(cmd) > 1:
                raise self.Error("show takes at most one parameter")
            if len(cmd):
                what = cmd[0]
                if what not in self._shows:
                    raise self.Error("Unknown show: '%s'" % (what, ))
            else:
                what = None

            outs = []
            for i in self._shows:
                k = i
                if what and i != what:
                    continue
                # boolean settings
                if i in ("echo", "headers", "exceptions", "changes"):
                    if i == "headers": i = "header"
                    v = "off"
                    if getattr(self, i):
                        v = "on"
                elif i in ("nullvalue", "separator"):
                    v = self._fmt_c_string(getattr(self, i))
                elif i == "mode":
                    for v in self._output_modes:
                        if self.output == getattr(self, "output_" + v):
                            break
                    else:
                        assert False, "Bug: didn't find output mode"
                elif i == "output":
                    if self.stdout is self._original_stdout:
                        v = "stdout"
                    else:
                        v = getattr(self.stdout, "name", "<unknown stdout>")
                elif i == "width":
                    v = " ".join(["%d" % (i, ) for i in self.widths])
                elif i == "encoding":
                    v = self.encoding[0]
                    if self.encoding[1]:
                        v += " (Errors " + self.encoding[1] + ")"
                else:
                    assert False, "Bug: unknown show handling"
                outs.append((k, v))

            # find width of k column
            l = 0
            for k, v in outs:
                if len(k) > l:
                    l = len(k)

            for k, v in outs:
                self.write(self.stderr, "%*.*s: %s\n" % (l, l, k, v))

        def command_tables(self, cmd):
            """tables ?PATTERN?: Lists names of tables matching LIKE pattern

            This also returns views.
            """
            self.push_output()
            self.output = self.output_list
            self.header = False
            try:
                if len(cmd) == 0:
                    cmd = ['%']

                # The SQLite shell code filters out sqlite_ prefixes if
                # you specified an argument else leaves them in.  It also
                # has a hand coded output mode that does space separation
                # plus wrapping at 80 columns.
                for n in cmd:
                    self.process_sql(
                        "SELECT name FROM sqlite_schema "
                        "WHERE type IN ('table', 'view') AND name NOT LIKE 'sqlite_%' "
                        "AND name like ?1 "
                        "UNION ALL "
                        "SELECT name FROM sqlite_temp_schema "
                        "WHERE type IN ('table', 'view') AND name NOT LIKE 'sqlite_%' "
                        "ORDER BY 1", (n, ),
                        internal=True)
            finally:
                self.pop_output()

        def command_timeout(self, cmd):
            """timeout MS: Try opening locked tables for MS milliseconds

            If a database is locked by another process SQLite will keep
            retrying.  This sets how many thousandths of a second it will
            keep trying for.  If you supply zero or a negative number then
            all busy handlers are disabled.
            """
            if len(cmd) != 1:
                raise self.Error("timeout takes a number")
            try:
                t = int(cmd[0])
            except ValueError:
                raise self.Error("%s is not a number" % (cmd[0], ))
            self.db.setbusytimeout(t)

        def command_timer(self, cmd):
            """timer ON|OFF: Control printing of time and resource usage after each query

            The values displayed are in seconds when shown as floating
            point or an absolute count.  Only items that have changed
            since starting the query are shown.  On non-Windows platforms
            considerably more information can be shown.
            """
            if self._boolean_command("timer", cmd):
                try:
                    self.get_resource_usage()
                except Exception:
                    raise self.Error("Timing not supported by this Python version/platform")
                self.timer = True
            else:
                self.timer = False

        def command_version(self, cmd):
            "version: Displays SQLite, APSW, and Python version information"
            if cmd:
                raise self.Error("No parameters taken")
            versions = {
                "SQLite": f"{ apsw.sqlitelibversion() } { apsw.sqlite3_sourceid() }",
                "Python": f"{ sys.version } - { sys.executable }",
                "APSW": apsw.apswversion(),
                "APSW file": apsw.__file__,
                "Amalgamation": apsw.using_amalgamation,
            }
            maxw = max(len(k) for k in versions)
            for k, v in versions.items():
                self.write(self.stdout, " " * (maxw - len(k)) + f"{ k }  { v}\n")

        def command_vfsname(self, cmd):
            "vfsname: VFS name used to open current database"
            if cmd:
                raise self.Error("No parameters taken")
            self.write(self.stdout, self.db.open_vfs + "\n")

        def _format_vfs(self, vfs):
            w = max(len(k) for k in vfs.keys())
            for k, v in vfs.items():
                self.write(self.stdout, " " * (w - len(k)))
                self.write(self.stdout, k + ":  ")
                vout = "0x%x" % v if k.startswith("x") else str(v)
                self.write_value(v)
                self.write(self.stdout, "\n")

        def command_vfsinfo(self, cmd):
            "vfsinfo: Shows detailed information about the VFS for the database"
            if cmd:
                raise self.Error("No parameters taken")
            for vfs in apsw.vfs_details():
                if vfs["zName"] == self.db.open_vfs:
                    self._format_vfs(vfs)

        def command_vfslist(self, cmd):
            "vfslist: Shows detailed information about all the VFS available"
            if cmd:
                raise self.Error("No parameters taken")
            for i, vfs in enumerate(apsw.vfs_details()):
                if i:
                    self.write(self.stdout, "\n")
                self._format_vfs(vfs)

        def command_width(self, cmd):
            """width NUM NUM ...: Set the column widths for "column" mode

            In "column" output mode, each column is a fixed width with values truncated to
            fit.  Specify new widths using this command.  Use a negative number
            to right justify and zero for default column width.
            """
            if len(cmd) == 0:
                raise self.Error("You need to specify some widths!")
            w = []
            for i in cmd:
                try:
                    w.append(int(i))
                except ValueError:
                    raise self.Error("'%s' is not a valid number" % (i, ))
            self.widths = w

        def _terminal_width(self, minimum):
            """Works out the terminal width which is used for word wrapping
            some output (eg .help)"""

            w = 80
            try:
                # we don't use shutil version because it can't be passed a
                # file descriptor
                if self.stdout.isatty():
                    w = os.get_terminal_size(self.stdout.fileno()).columns
            except Exception:
                pass
            return max(w, minimum)

        def push_output(self):
            """Saves the current output settings onto a stack.  See
            :meth:`pop_output` for more details as to why you would use
            this."""
            o = {}
            for k in "separator", "header", "nullvalue", "output", "widths", "truncate":
                o[k] = getattr(self, k)
            self._output_stack.append(o)

        def pop_output(self):
            """Restores most recently pushed output.  There are many
            output parameters such as nullvalue, mode
            (list/tcl/html/insert etc), column widths, header etc.  If you
            temporarily need to change some settings then
            :meth:`push_output`, change the settings and then pop the old
            ones back.

            A simple example is implementing a command like .dump.  Push
            the current output, change the mode to insert so we get SQL
            inserts printed and then pop to go back to what was there
            before.

            """
            # first item should always be present
            assert len(self._output_stack)
            if len(self._output_stack) == 1:
                o = self._output_stack[0]
            else:
                o = self._output_stack.pop()
            for k, v in o.items():
                setattr(self, k, v)

        def _append_input_description(self):
            """When displaying an error in :meth:`handle_exception` we
            want to give context such as when the commands being executed
            came from a .read command (which in turn could execute another
            .read).
            """
            if self.interactive:
                return
            res = []
            res.append("Line %d" % (self.input_line_number, ))
            res.append(": " + getattr(self.stdin, "name", "<stdin>"))
            self._input_descriptions.append(" ".join(res))

        def fixup_backslashes(self, s):
            """Implements the various backlash sequences in s such as
            turning backslash t into a tab.

            This function is needed because shlex does not do it for us.
            """
            if "\\" not in s: return s
            # See the resolve_backslashes function in SQLite shell source
            res = []
            i = 0
            while i < len(s):
                if s[i] != "\\":
                    res.append(s[i])
                    i += 1
                    continue
                i += 1
                if i >= len(s):
                    raise self.Error("Backslash with nothing following")
                c = s[i]
                res.append({"\\": "\\", "r": "\r", "n": "\n", "t": "\t"}.get(c, None))
                i += 1  # advance again
                if res[-1] is None:
                    raise self.Error("Unknown backslash sequence \\" + c)
            return "".join(res)

        def write(self, dest, text):
            "Writes text to dest.  dest will typically be one of self.stdout or self.stderr."
            dest.write(text)

        def write_error(self, text):
            "Writes text to self.stderr colouring it"
            self.write(self.stderr, self.colour.error + text + self.colour.error_)

        def write_value(self, value, fmt=apsw.format_sql_value):
            "Writes colourized value to self.stdout converting to text with fmt"
            self.write(self.stdout, self.colour.colour_value(value, fmt(value)))

        _raw_input = input

        def getline(self, prompt=""):
            """Returns a single line of input (may be incomplete SQL) from self.stdin.

            If EOF is reached then return None.  Do not include trailing
            newline in return.
            """
            self.stdout.flush()
            self.stderr.flush()
            try:
                if self.interactive:
                    if self.stdin is sys.stdin:
                        c = self.colour.prompt, self.colour.prompt_
                        if self._using_readline:
                            # these are needed so that readline knows they are non-printing characters
                            c = "\x01" + c[0] + "\x02", "\x01" + c[1] + "\x02",
                        line = self._raw_input(c[0] + prompt + c[1]) + "\n"  # raw_input excludes newline
                    else:
                        self.write(self.stdout, prompt)
                        line = self.stdin.readline()  # includes newline unless last line of file doesn't have one
                else:
                    line = self.stdin.readline()  # includes newline unless last line of file doesn't have one
                self.input_line_number += 1
            except EOFError:
                return None
            if len(line) == 0:  # always a \n on the end normally so this is EOF
                return None
            if line[-1] == "\n":
                line = line[:-1]
            return line

        def getcompleteline(self):
            """Returns a complete input.

            For dot commands it will be one line.  For SQL statements it
            will be as many as is necessary to have a
            :meth:`~apsw.complete` statement (ie semicolon terminated).
            Returns None on end of file."""
            try:
                self._completion_first = True
                command = self.getline(self.prompt)
                if command is None:
                    return None
                if len(command.strip()) == 0:
                    return ""
                if command[0] == "?": command = ".help " + command[1:]
                # incomplete SQL?
                while command[0] != "." and not apsw.complete(command):
                    self._completion_first = False
                    line = self.getline(self.moreprompt)
                    if line is None:  # unexpected eof
                        raise self.Error("Incomplete SQL (line %d of %s): %s\n" %
                                         (self.input_line_number, getattr(self.stdin, "name", "<stdin>"), command))
                    if line in ("go", "/"):
                        break
                    command = command + "\n" + line
                return command
            except KeyboardInterrupt:
                self.handle_interrupt()
                return ""

        def handle_interrupt(self):
            """Deal with keyboard interrupt (typically Control-C).  It
            will :meth:`~apsw.Connection.interrupt` the database and print"^C" if interactive."""
            self.db.interrupt()
            if not self.bail and self.interactive:
                self.write(self.stderr, "^C\n")
                return
            raise

        def process_complete_line(self, command):
            """Given some text will call the appropriate method to process
            it (eg :meth:`process_sql` or :meth:`process_command`)"""
            try:
                if len(command.strip()) == 0:
                    return
                if command[0] == ".":
                    self.process_command(command)
                else:
                    self.process_sql(command)
            except KeyboardInterrupt:
                self.handle_interrupt()

        def push_input(self):
            """Saves the current input parameters to a stack.  See :meth:`pop_input`."""
            d = {}
            for i in "interactive", "stdin", "input_line_number":
                d[i] = getattr(self, i)
            self._input_stack.append(d)

        def pop_input(self):
            """Restore most recently pushed input parameters (interactive,
            self.stdin, linenumber etc).  Use this if implementing a
            command like read.  Push the current input, read the file and
            then pop the input to go back to before.
            """
            assert (len(self._input_stack)) > 1
            d = self._input_stack.pop()
            for k, v in d.items():
                setattr(self, k, v)

        def complete(self, token, state):
            """Return a possible completion for readline

            This function is called with state starting at zero to get the
            first completion, then one/two/three etc until you return None.  The best
            implementation is to generate the list when state==0, save it,
            and provide members on each increase.

            The default implementation extracts the current full input
            from readline and then calls :meth:`complete_command` or
            :meth:`complete_sql` as appropriate saving the results for
            subsequent calls.
            """
            if state == 0:
                import readline
                # the whole line
                line = readline.get_line_buffer()
                # beginning and end(+1) of the token in line
                beg = readline.get_begidx()
                end = readline.get_endidx()
                # Are we matching a command?
                try:
                    if self._completion_first and line.startswith("."):
                        self.completions = self.complete_command(line, token, beg, end)
                    else:
                        self.completions = self.complete_sql(line, token, beg, end)
                except Exception:
                    # Readline swallows any exceptions we raise.  We
                    # shouldn't be raising any so this is to catch that
                    traceback.print_exc()
                    raise

            if state > len(self.completions):
                return None
            return self.completions[state]

        _sqlite_keywords = apsw.keywords
        # reserved words need to be quoted.  Only a subset of the keywords are reserved
        # but what the heck
        _sqlite_reserved = _sqlite_keywords
        # add a space after each of them except functions which get parentheses
        _sqlite_keywords = [x + (" ", "(")[x in ("VALUES", "CAST")] for x in _sqlite_keywords]

        _sqlite_special_names = """_ROWID_ OID ROWID sqlite_schema
               SQLITE_SEQUENCE""".split()

        _pragmas_bool = ("yes", "true", "on", "no", "false", "off")
        _pragmas = {
            "analysis_limit=": None,
            "application_id": None,
            "auto_vacuum=": ("NONE", "FULL", "INCREMENTAL"),
            "automatic_index=": _pragmas_bool,
            "busy_timeout=": None,
            "cache_size=": None,
            "case_sensitive_like=": _pragmas_bool,
            "cache_spill=": _pragmas_bool,
            "cell_size_check=": _pragmas_bool,
            "checkpoint_fullfsync=": _pragmas_bool,
            "collation_list": None,
            "compile_options": None,
            "data_version": None,
            "database_list": None,
            "defer_foreign_keys=": _pragmas_bool,
            "encoding=": ('UTF-8', 'UTF-16', 'UTF-16le', 'UTF16-16be'),
            "foreign_key_check": None,
            "foreign_key_list(": None,
            "foreign_keys": _pragmas_bool,
            "freelist_count": None,
            "fullfsync=": _pragmas_bool,
            "function_list": None,
            "hard_heap_limit=": None,
            "ignore_check_constraints": _pragmas_bool,
            "incremental_vacuum(": None,
            "index_info(": None,
            "index_list(": None,
            "index_xinfo(": None,
            "integrity_check": None,
            "journal_mode=": ("DELETE", "TRUNCATE", "PERSIST", "MEMORY", "OFF", "WAL"),
            "journal_size_limit=": None,
            "legacy_alter_table=": _pragmas_bool,
            "legacy_file_format=": _pragmas_bool,
            "locking_mode=": ("NORMAL", "EXCLUSIVE"),
            "max_page_count=": None,
            "mmap_size=": None,
            "module_list": None,
            "optimize(": None,
            "page_count;": None,
            "page_size=": None,
            "query_only=": _pragmas_bool,
            "quick_check": None,
            "read_uncommitted=": _pragmas_bool,
            "recursive_triggers=": _pragmas_bool,
            "reverse_unordered_selects=": _pragmas_bool,
            "schema_version": None,
            "secure_delete=": _pragmas_bool,
            "shrink_memory": None,
            "soft_heap_limit=": None,
            "synchronous=": ("OFF", "NORMAL", "FULL"),
            "table_info(": None,
            "table_list": None,
            "table_xinfo(": None,
            "temp_store=": ("DEFAULT", "FILE", "MEMORY"),
            "threads=": None,
            "trusted_schema": _pragmas_bool,
            "user_version=": None,
            "wal_autocheckpoint=": None,
            "wal_checkpoint": None,
            "writable_schema": _pragmas_bool,
        }

        def _get_prev_tokens(self, line, end):
            "Returns the tokens prior to pos end in the line"
            return re.findall(r'"?\w+"?', line[:end])

        def complete_sql(self, line, token, beg, end):
            """Provide some completions for SQL

            :param line: The current complete input line
            :param token: The word readline is looking for matches
            :param beg: Integer offset of token in line
            :param end: Integer end of token in line
            :return: A list of completions, or an empty list if none
            """
            if self._completion_cache is None:
                cur = self.db.cursor()
                collations = [row[1] for row in cur.execute("pragma collation_list")]
                databases = [row[1] for row in cur.execute("pragma database_list")]
                other = [row[0] for row in cur.execute("pragma module_list")]
                for db in databases:
                    if db == "temp":
                        master = "sqlite_temp_schema"
                    else:
                        master = "[%s].sqlite_schema" % (db, )
                    for row in cur.execute("select * from " + master).fetchall():
                        for col in (1, 2):
                            if row[col] not in other and not row[col].startswith("sqlite_"):
                                other.append(row[col])
                        if row[0] == "table":
                            try:
                                for table in cur.execute("pragma [%s].table_info([%s])" % (
                                        db,
                                        row[1],
                                )).fetchall():
                                    if table[1] not in other:
                                        other.append(table[1])
                                    for item in table[2].split():
                                        if item not in other:
                                            other.append(item)
                            except apsw.SQLError:
                                # See https://github.com/rogerbinns/apsw/issues/86
                                pass
                    functions = {}
                    for row in cur.execute("pragma function_list"):
                        name = row[0]
                        narg = row[4]
                        functions[name] = max(narg, functions.get(name, -1))

                    def fmtfunc(name, nargs):
                        if nargs == 0:
                            return name + "()"
                        return name + "("

                    func_list = [fmtfunc(name, narg) for name, narg in functions.items()]

                self._completion_cache = [
                    self._sqlite_keywords, func_list, self._sqlite_special_names, collations, databases, other
                ]
                for i in range(len(self._completion_cache)):
                    self._completion_cache[i].sort()

            # be somewhat sensible about pragmas
            if "pragma " in line.lower():
                t = self._get_prev_tokens(line.lower(), end)

                # pragma foo = bar
                if len(t) > 2 and t[-3] == "pragma":
                    # t[-2] should be a valid one
                    for p in self._pragmas:
                        if p.replace("=", "") == t[-2]:
                            vals = self._pragmas[p]
                            if not vals:
                                return []
                            return [x + ";" for x in vals if x.startswith(token)]
                # at equals?
                if len(t) > 1 and t[-2] == "pragma" and line[:end].replace(" ", "").endswith("="):
                    for p in self._pragmas:
                        if p.replace("=", "") == t[-1]:
                            vals = self._pragmas[p]
                            if not vals:
                                return []
                            return vals
                # pragma foo
                if len(t) > 1 and t[-2] == "pragma":
                    res = [x for x in self._pragmas.keys() if x.startswith(token)]
                    res.sort()
                    return res

                # pragma
                if len(t) and t[-1] == "pragma":
                    res = list(self._pragmas.keys())
                    res.sort()
                    return res

            # This is currently not context sensitive (eg it doesn't look
            # to see if last token was 'FROM' and hence next should only
            # be table names.  That is a SMOP like pragmas above
            res = []
            ut = token.upper()
            for corpus in self._completion_cache:
                for word in corpus:
                    if word.upper().startswith(ut):
                        # potential match - now match case
                        if word.startswith(token):  # exact
                            if word not in res:
                                res.append(word)
                        elif word.lower().startswith(token):  # lower
                            if word.lower() not in res:
                                res.append(word.lower())
                        elif word.upper().startswith(token):  # upper
                            if word.upper() not in res:
                                res.append(word.upper())
                        else:
                            # match letter by letter otherwise readline mangles what was typed in
                            w = token + word[len(token):]
                            if w not in res:
                                res.append(w)
            return res

        # completion for the dot commands are messy because some take
        # variable numbers of parameters and the meanings of the
        # parameters differ depending on how many there are.  so
        # we make some effort for some of the commands
        _command_params = {
            "bail": bool,
            "changes": bool,
            "echo": bool,
            "exceptions": bool,
            "header": bool,
            "timer": bool,
        }
        _command_params["headers"] = _command_params["header"]

        _builtin_commands = None

        def complete_command(self, line, token, beg, end):
            """Provide some completions for dot commands

            :param line: The current complete input line
            :param token: The word readline is looking for matches
            :param beg: Integer offset of token in line
            :param end: Integer end of token in line
            :return: A list of completions, or an empty list if none
            """
            if not self._builtin_commands:
                self._builtin_commands = [
                    "." + x[len("command_"):] for x in dir(self) if x.startswith("command_") and x != "command_headers"
                ]

            t = self._get_prev_tokens(line, end)
            if len(t) <= 1 and token:
                return [x + " " for x in self._builtin_commands if x.startswith(token)]

            completions = []

            if t[0] in {"colour", "color"}:
                completions = list(self._colours.keys())
            elif t[0] in {"mode"}:
                completions = self._output_modes
            elif t[0] == "help":
                completions = [v[1:] for v in self._builtin_commands] + ["all"]
            elif t[0] == "dbconfig":
                completions = [
                    v[len("SQLITE_DBCONFIG_"):].lower() for v in apsw.mapping_db_config
                    if isinstance(v, str) and v not in self._dbconfig_ignore
                ]
            elif t[0] == "parameter":
                if len(t) == 1 or (len(t) == 2 and token):
                    completions = ["clear", "list", "unset ", "set "]
                elif len(t) >= 2 and t[1] == "unset" and (len(t) == 2 or token):
                    completions = list(self.bindings.keys())
            elif self._command_params.get(t[0], None) is bool:
                completions = ["on", "off", "ON", "OFF"]
            elif t[0] in self._command_params:
                completions = self._command_params[t[0]]

            return [v for v in sorted(completions) if v.startswith(token) and v != token]

        def get_resource_usage(self):
            """Return a dict of various numbers (ints or floats).  The
            .timer command shows the difference between before and after
            results of what this returns by calling :meth:`display_timing`"""
            if sys.platform == "win32":
                import ctypes, time, platform
                ctypes.windll.kernel32.GetProcessTimes.argtypes = [
                    platform.architecture()[0] == '64bit' and ctypes.c_int64 or ctypes.c_int32, ctypes.c_void_p,
                    ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p
                ]

                # All 4 out params have to be present.  FILETIME is really
                # just a 64 bit quantity in 100 nanosecond granularity
                dummy = ctypes.c_ulonglong()
                utime = ctypes.c_ulonglong()
                stime = ctypes.c_ulonglong()
                rc = ctypes.windll.kernel32.GetProcessTimes(
                    ctypes.windll.kernel32.GetCurrentProcess(),
                    ctypes.byref(dummy),  # creation time
                    ctypes.byref(dummy),  # exit time
                    ctypes.byref(stime),
                    ctypes.byref(utime))
                if rc:
                    return {
                        'Wall clock': time.time(),
                        'User time': float(utime.value) / 10000000,
                        'System time': float(stime.value) / 10000000
                    }
                return {}
            else:
                import resource, time
                r = resource.getrusage(resource.RUSAGE_SELF)
                res = {'Wall clock': time.time()}
                for i, desc in (
                    ("utime", "User time"),
                    ("stime", "System time"),
                    ("maxrss", "Max rss"),
                    ("idrss", "Memory"),
                    ("isrss", "Stack"),
                    ("ixrss", "Shared Memory"),
                    ("minflt", "PF (no I/O)"),
                    ("majflt", "PF (I/O)"),
                    ("inblock", "Blocks in"),
                    ("oublock", "Blocks out"),
                    ("nsignals", "Signals"),
                    ("nvcsw", "Voluntary context switches"),
                    ("nivcsw", "Involunary context switches"),
                    ("msgrcv", "Messages received"),
                    ("msgsnd", "Messages sent"),
                    ("nswap", "Swaps"),
                ):
                    f = "ru_" + i
                    if hasattr(r, f):
                        res[desc] = getattr(r, f)
                return res

        def display_timing(self, b4, after):
            """Writes the difference between b4 and after to self.stderr.
            The data is dictionaries returned from
            :meth:`get_resource_usage`."""
            v = list(b4.keys())
            for i in after:
                if i not in v:
                    v.append(i)
            v.sort()
            for k in v:
                if k in b4 and k in after:
                    one = b4[k]
                    two = after[k]
                    val = two - one
                    if val:
                        if type(val) == float:
                            self.write(self.stderr, "+ %s: %.4f\n" % (k, val))
                        else:
                            self.write(self.stderr, "+ %s: %d\n" % (k, val))

        ### Colour support

        def _out_colour(self):
            # Sets up color for output.  Input being interactive doesn't
            # matter.  This method needs to be called on all changes to
            # output.
            if getattr(self.stdout, "isatty", False) and self.stdout.isatty():
                self.colour = self._colours[self.colour_scheme]
            else:
                self.colour = self._colours["off"]

        # This class returns an empty string for all undefined attributes
        # so that it doesn't matter if a colour scheme leaves something
        # out.
        class _colourscheme:

            def __init__(self, **kwargs):
                for k, v in kwargs.items():
                    setattr(self, k, v)

            def __nonzero__(self):
                return True

            def __str__(self):
                return "_colourscheme(" + str(self.__dict__) + ")"

            def __getattr__(self, k):
                return ""

            def colour_value(self, val, formatted):
                c = self.colour
                if val is None:
                    return self.vnull + formatted + self.vnull_
                if isinstance(val, str):
                    return self.vstring + formatted + self.vstring_
                if isinstance(val, bytes):
                    return self.vblob + formatted + self.vblob_
                # must be a number - we don't distinguish between float/int
                return self.vnumber + formatted + self.vnumber_

        # The colour definitions - the convention is the name to turn
        # something on and the name with an underscore suffix to turn it
        # off
        d = _colourscheme(**dict([(v, "\x1b[" + str(n) + "m") for n, v in {
            0: "reset",
            1: "bold",
            4: "underline",
            22: "bold_",
            24: "underline_",
            7: "inverse",
            27: "inverse_",
            30: "fg_black",
            31: "fg_red",
            32: "fg_green",
            33: "fg_yellow",
            34: "fg_blue",
            35: "fg_magenta",
            36: "fg_cyan",
            37: "fg_white",
            39: "fg_",
            40: "bg_black",
            41: "bg_red",
            42: "bg_green",
            43: "bg_yellow",
            44: "bg_blue",
            45: "bg_magenta",
            46: "bg_cyan",
            47: "bg_white",
            49: "bg_"
        }.items()]))

        _colours = {"off": _colourscheme(colour_value=lambda x, y: y)}

        _colours["default"] = _colourscheme(prompt=d.bold,
                                            prompt_=d.bold_,
                                            error=d.fg_red + d.bold,
                                            error_=d.bold_ + d.fg_,
                                            intro=d.fg_blue + d.bold,
                                            intro_=d.bold_ + d.fg_,
                                            transient=d.fg_green,
                                            transient_=d.fg_,
                                            summary=d.fg_blue + d.bold,
                                            summary_=d.bold_ + d.fg_,
                                            header=d.underline,
                                            header_=d.underline_,
                                            vnull=d.fg_red,
                                            vnull_=d.fg_,
                                            vstring=d.fg_yellow,
                                            vstring_=d.fg_,
                                            vblob=d.fg_blue,
                                            vblob_=d.fg_,
                                            vnumber=d.fg_magenta,
                                            vnumber_=d.fg_)
        # unpollute namespace
        del d
        del _colourscheme
        try:
            del n
            del x
            del v
        except Exception:
            pass

    try:
        # uses dataclasses and annotations, only available in Python 3.7+
        import apsw.ext
        import dataclasses
    except (ImportError, SyntaxError):
        for n in "box", "table", "qbox":
            delattr(Shell, f"output_{ n }")
        delattr(Shell, "command_dbinfo")

    def main() -> None:
        # Docstring must start on second line so dedenting works correctly
        """
        Call this to run the :ref:`interactive shell <shell>`.  It
        automatically passes in sys.argv[1:] and exits Python when done.

        """
        try:
            s = Shell()
            _, _, cmds = s.process_args(sys.argv[1:])
            if len(cmds) == 0:
                s.cmdloop()
        except:
            v = sys.exc_info()[1]
            if isinstance(v, SystemExit):
                raise
            if getattr(v, "_handle_exception_saw_this", False):
                pass
            else:
                # Where did this exception come from?
                traceback.print_exc()
            sys.exit(1)

    if __name__ == '__main__':
        main()