/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2003-2007 University of Maryland
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.ba.jsr305;

import java.util.HashSet;
import java.util.Iterator;

import javax.annotation.meta.When;

import org.apache.bcel.Constants;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.FieldInstruction;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.RETURN;
import org.apache.bcel.generic.ReturnInstruction;

import edu.umd.cs.findbugs.ba.BasicBlock;
import edu.umd.cs.findbugs.ba.BlockOrder;
import edu.umd.cs.findbugs.ba.CFG;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.DepthFirstSearch;
import edu.umd.cs.findbugs.ba.Edge;
import edu.umd.cs.findbugs.ba.Location;
import edu.umd.cs.findbugs.ba.ReverseDFSOrder;
import edu.umd.cs.findbugs.ba.ReverseDepthFirstSearch;
import edu.umd.cs.findbugs.ba.SignatureParser;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XField;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.ba.vna.ValueNumber;
import edu.umd.cs.findbugs.ba.vna.ValueNumberDataflow;
import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;
import edu.umd.cs.findbugs.classfile.Global;

/**
 * Backwards type qualifier dataflow analysis.
 *
 * @author David Hovemeyer
 */
public class BackwardTypeQualifierDataflowAnalysis extends TypeQualifierDataflowAnalysis {
    private static final boolean PRUNE_CONFLICTING_VALUES = true; // SystemProperties.getBoolean("ctq.pruneconflicting");

    private final DepthFirstSearch dfs;

    private final ReverseDepthFirstSearch rdfs;

    private ForwardTypeQualifierDataflow forwardTypeQualifierDataflow;

    /**
     * Constructor.
     *
     * @param dfs
     *            DepthFirstSearch on the analyzed method
     * @param rdfs
     *            ReverseDepthFirstSearch on the analyzed method
     * @param xmethod
     *            XMethod for the analyzed method
     * @param cfg
     *            CFG of the analyzed method
     * @param vnaDataflow
     *            ValueNumberDataflow on the analyzed method
     * @param cpg
     *            ConstantPoolGen of the analyzed method
     * @param typeQualifierValue
     *            TypeQualifierValue representing type qualifier the analysis
     *            should check
     */
    public BackwardTypeQualifierDataflowAnalysis(DepthFirstSearch dfs, ReverseDepthFirstSearch rdfs, XMethod xmethod, CFG cfg,
            ValueNumberDataflow vnaDataflow, ConstantPoolGen cpg, TypeQualifierValue typeQualifierValue) {
        super(xmethod, cfg, vnaDataflow, cpg, typeQualifierValue);
        this.dfs = dfs;
        this.rdfs = rdfs;
    }

    /**
     * @param forwardTypeQualifierDataflow
     *            The forwardTypeQualifierDataflow to set.
     */
    public void setForwardTypeQualifierDataflow(ForwardTypeQualifierDataflow forwardTypeQualifierDataflow) {
        this.forwardTypeQualifierDataflow = forwardTypeQualifierDataflow;
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * edu.umd.cs.findbugs.ba.jsr305.TypeQualifierDataflowAnalysis#edgeTransfer
     * (edu.umd.cs.findbugs.ba.Edge,
     * edu.umd.cs.findbugs.ba.jsr305.TypeQualifierValueSet)
     */
    @Override
    public void edgeTransfer(Edge edge, TypeQualifierValueSet fact) throws DataflowAnalysisException {
        if (PRUNE_CONFLICTING_VALUES && forwardTypeQualifierDataflow != null) {
            pruneConflictingValues(fact, forwardTypeQualifierDataflow.getFactOnEdge(edge));
        }

        super.edgeTransfer(edge, fact);
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis#transferInstruction(org
     * .apache.bcel.generic.InstructionHandle,
     * edu.umd.cs.findbugs.ba.BasicBlock, java.lang.Object)
     */
    @Override
    public void transferInstruction(InstructionHandle handle, BasicBlock basicBlock, TypeQualifierValueSet fact)
            throws DataflowAnalysisException {

        if (!fact.isValid()) {
            return;
        }

        if (PRUNE_CONFLICTING_VALUES && forwardTypeQualifierDataflow != null) {
            Location location = new Location(handle, basicBlock);
            pruneConflictingValues(fact, forwardTypeQualifierDataflow.getFactAfterLocation(location));
        }

        super.transferInstruction(handle, basicBlock, fact);
    }

    private void pruneConflictingValues(TypeQualifierValueSet fact, TypeQualifierValueSet forwardFact) {
        if (forwardFact.isValid()) {
            HashSet<ValueNumber> valueNumbers = new HashSet<ValueNumber>();
            valueNumbers.addAll(fact.getValueNumbers());
            valueNumbers.retainAll(forwardFact.getValueNumbers());

            for (ValueNumber vn : valueNumbers) {
                if (FlowValue.valuesConflict(typeQualifierValue.isStrictQualifier() && !xmethod.isIdentity(), 
                        forwardFact.getValue(vn), fact.getValue(vn))) {
                    fact.pruneValue(vn);
                }
            }
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * edu.umd.cs.findbugs.ba.DataflowAnalysis#getBlockOrder(edu.umd.cs.findbugs
     * .ba.CFG)
     */
    public BlockOrder getBlockOrder(CFG cfg) {
        return new ReverseDFSOrder(cfg, rdfs, dfs);
    }

    /*
     * (non-Javadoc)
     *
     * @see edu.umd.cs.findbugs.ba.DataflowAnalysis#isForwards()
     */
    public boolean isForwards() {
        return false;
    }

    /*
     * (non-Javadoc)
     *
     * @see edu.umd.cs.findbugs.ba.jsr305.TypeQualifierDataflowAnalysis#
     * registerSourceSinkLocations()
     */
    @Override
    public void registerSourceSinkLocations() throws DataflowAnalysisException {
        registerInstructionSinks();
    }

    private void registerInstructionSinks() throws DataflowAnalysisException {
        TypeQualifierAnnotation returnValueAnnotation = null;
        if (!xmethod.getSignature().endsWith(")V")) {
            returnValueAnnotation = TypeQualifierApplications.getEffectiveTypeQualifierAnnotation(xmethod, typeQualifierValue);
        }

        for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
            Location location = i.next();

            Instruction ins = location.getHandle().getInstruction();

            if (ins instanceof ReturnInstruction && !(ins instanceof RETURN)) {
                // Return instruction which returns a value
                modelReturn(returnValueAnnotation, location);
            } else {
                short opcode = ins.getOpcode();

                if (opcode == Constants.PUTFIELD || opcode == Constants.PUTSTATIC) {
                    modelFieldStore(location);
                } else if (location.getHandle().getInstruction() instanceof InvokeInstruction) {
                    modelArguments(location);
                }
            }
        }
    }

    private void modelReturn(TypeQualifierAnnotation returnValueAnnotation, Location location) throws DataflowAnalysisException {
        When when = (returnValueAnnotation != null) ? returnValueAnnotation.when : When.UNKNOWN;

        // Model return statement
        ValueNumberFrame vnaFrameAtReturn = vnaDataflow.getFactAtLocation(location);
        if (vnaFrameAtReturn.isValid()) {
            ValueNumber topValue = vnaFrameAtReturn.getTopValue();
            SourceSinkInfo sink = new SourceSinkInfo(SourceSinkType.RETURN_VALUE, location, topValue, when);
            registerSourceSink(sink);
        }
    }

    private void modelFieldStore(Location location) throws DataflowAnalysisException {
        // Model field stores
        XField writtenField = XFactory.createXField((FieldInstruction) location.getHandle().getInstruction(), cpg);
        TypeQualifierAnnotation tqa = TypeQualifierApplications.getEffectiveTypeQualifierAnnotation(writtenField,
                typeQualifierValue);
        When when = (tqa != null) ? tqa.when : When.UNKNOWN;

        // The ValueNumberFrame *before* the FieldInstruction should
        // have the ValueNumber of the stored value on the top of the stack.
        ValueNumberFrame vnaFrameAtStore = vnaDataflow.getFactAtLocation(location);
        if (vnaFrameAtStore.isValid()) {
            ValueNumber vn = vnaFrameAtStore.getTopValue();
            SourceSinkInfo sink = new SourceSinkInfo(SourceSinkType.FIELD_STORE, location, vn, when);
            registerSourceSink(sink);
        }
    }

    private void modelArguments(Location location) throws DataflowAnalysisException {
        // Model arguments to called method
        InvokeInstruction inv = (InvokeInstruction) location.getHandle().getInstruction();
        XMethod calledMethod = XFactory.createXMethod(inv, cpg);

        SignatureParser sigParser = new SignatureParser(calledMethod.getSignature());
        if (sigParser.getNumParameters() == 0)
            return;
        ValueNumberFrame vnaFrame = vnaDataflow.getFactAtLocation(location);

        if (!vnaFrame.isValid()) {
            // AnalysisContext.logError("bad vna frame  in " + xmethod +
            // " at location " + location.getHandle().getPosition() +
            // " calling " + calledMethod);
            return;
        }

        if (TypeQualifierDataflowAnalysis.isIdentifyFunctionForTypeQualifiers(calledMethod))
            return;
       
        for (int param = 0; param < calledMethod.getNumParams(); param++) {
            TypeQualifierAnnotation tqa = TypeQualifierApplications.getEffectiveTypeQualifierAnnotation(calledMethod, param,
                    typeQualifierValue);

            boolean interproc = false;
            if (TypeQualifierDatabase.USE_DATABASE && tqa == null) {
                // See if there's an entry for this parameter
                // in the interprocedural type qualifier database.
                TypeQualifierDatabase tqdb = Global.getAnalysisCache().getDatabase(TypeQualifierDatabase.class);
                tqa = tqdb.getParameter(calledMethod.getMethodDescriptor(), param, typeQualifierValue);
                if (tqa != null) {
                    interproc = true;
                }
            }

            When when = (tqa != null) ? tqa.when : When.UNKNOWN;

            ValueNumber vn = vnaFrame.getArgument(inv, cpg, param, sigParser);

            SourceSinkInfo info = new SourceSinkInfo(SourceSinkType.ARGUMENT_TO_CALLED_METHOD, location, vn, when);
            info.setParameter(param);
            info.setInterproc(interproc);

            registerSourceSink(info);

        }
    }

    /*
     * (non-Javadoc)
     *
     * @see edu.umd.cs.findbugs.ba.jsr305.TypeQualifierDataflowAnalysis#
     * propagateAcrossPhiNode
     * (edu.umd.cs.findbugs.ba.jsr305.TypeQualifierValueSet,
     * edu.umd.cs.findbugs.ba.vna.ValueNumber,
     * edu.umd.cs.findbugs.ba.vna.ValueNumber)
     */
    @Override
    protected void propagateAcrossPhiNode(TypeQualifierValueSet fact, ValueNumber sourceVN, ValueNumber targetVN) {
        // Backwards analysis - propagate value from target to source
        fact.propagateAcrossPhiNode(targetVN, sourceVN);
    }
}
