/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Contributor(s): Joseph Eagar.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/bmesh/operators/bmo_beautify.c
 *  \ingroup bmesh
 *
 * Beautify the mesh by rotating edges between triangles
 * to more attractive positions until no more rotations can be made.
 *
 * In principle this is very simple however there is the possibility of
 * going into an eternal loop where edges keep rotating.
 * To avoid this - each edge stores a hash of it previous
 * states so as not to rotate back.
 *
 * TODO
 * - Take face normals into account.
 */

#include "BLI_math.h"
#include "BLI_heap.h"

#include "MEM_guardedalloc.h"

#include "bmesh.h"
#include "intern/bmesh_operators_private.h"

// #define DEBUG_TIME

#ifdef DEBUG_TIME
#  include "PIL_time.h"
#endif

enum {
	VERT_RESTRICT_TAG = (1 << 0),
};

/* -------------------------------------------------------------------- */
/* GHash for edge rotation */

typedef struct EdRotState {
	int v1, v2; /*	edge vert, small -> large */
	int f1, f2; /*	face vert, small -> large */
} EdRotState;

static unsigned int erot_ghashutil_hash(const void *ptr)
{
	const EdRotState *e_state = (const EdRotState *)ptr;
	unsigned int
	hash  = BLI_ghashutil_inthash(SET_INT_IN_POINTER(e_state->v1));
	hash ^= BLI_ghashutil_inthash(SET_INT_IN_POINTER(e_state->v2));
	hash ^= BLI_ghashutil_inthash(SET_INT_IN_POINTER(e_state->f1));
	hash ^= BLI_ghashutil_inthash(SET_INT_IN_POINTER(e_state->f2));
	return hash;
}
static int erot_ghashutil_cmp(const void *a, const void *b)
{
	const EdRotState *e_state_a = (const EdRotState *)a;
	const EdRotState *e_state_b = (const EdRotState *)b;
	if      (e_state_a->v1 < e_state_b->v1) return -1;
	else if (e_state_a->v1 > e_state_b->v1) return  1;
	else if (e_state_a->v2 < e_state_b->v2) return -1;
	else if (e_state_a->v2 > e_state_b->v2) return  1;
	else if (e_state_a->f1 < e_state_b->f1) return -1;
	else if (e_state_a->f1 > e_state_b->f1) return  1;
	else if (e_state_a->f2 < e_state_b->f2) return -1;
	else if (e_state_a->f2 > e_state_b->f2) return  1;
	else                                    return  0;
}

static GHash *erot_ghash_new(void)
{
	return BLI_ghash_new(erot_ghashutil_hash, erot_ghashutil_cmp, __func__);
}

/* ensure v0 is smaller */
#define EDGE_ORD(v0, v1) \
	if (v0 > v1) {       \
		v0 ^= v1;        \
		v1 ^= v0;        \
		v0 ^= v1;        \
	} (void)0

static void erot_state_ex(const BMEdge *e, int v_index[2], int f_index[2])
{
	BLI_assert(BM_edge_is_manifold((BMEdge *)e));
	BLI_assert(BM_vert_in_edge(e, e->l->prev->v)              == false);
	BLI_assert(BM_vert_in_edge(e, e->l->radial_next->prev->v) == false);

	/* verts of the edge */
	v_index[0] = BM_elem_index_get(e->v1);
	v_index[1] = BM_elem_index_get(e->v2);
	EDGE_ORD(v_index[0], v_index[1]);

	/* verts of each of the 2 faces attached to this edge
	 * (that are not apart of this edge) */
	f_index[0] = BM_elem_index_get(e->l->prev->v);
	f_index[1] = BM_elem_index_get(e->l->radial_next->prev->v);
	EDGE_ORD(f_index[0], f_index[1]);
}

static void erot_state_current(const BMEdge *e, EdRotState *e_state)
{
	erot_state_ex(e, &e_state->v1, &e_state->f1);
}

static void erot_state_alternate(const BMEdge *e, EdRotState *e_state)
{
	erot_state_ex(e, &e_state->f1, &e_state->v1);
}

/* -------------------------------------------------------------------- */
/* Calculate the improvement of rotating the edge */

/**
 * \return a negative value means the edge can be rotated.
 */
static float bm_edge_calc_rotate_beauty(const BMEdge *e, const int flag)
{
	/* not a loop (only to be able to break out) */
	do {
		float v1_xy[2], v2_xy[2], v3_xy[2], v4_xy[2];

		/* first get the 2d values */
		{
			const float *v1, *v2, *v3, *v4;
			bool is_zero_a, is_zero_b;
			float no[3];
			float axis_mat[3][3];

			v1 = e->l->prev->v->co;               /* first face co */
			v2 = e->l->v->co;                     /* e->v1 or e->v2*/
			v3 = e->l->radial_next->prev->v->co;  /* second face co */
			v4 = e->l->next->v->co;               /* e->v1 or e->v2*/

			if (flag & VERT_RESTRICT_TAG) {
				BMVert *v_a = e->l->prev->v, *v_b = e->l->radial_next->prev->v;
				if (BM_elem_flag_test(v_a, BM_ELEM_TAG) ==  BM_elem_flag_test(v_b, BM_ELEM_TAG)) {
					break;
				}
			}

			if (UNLIKELY(v1 == v3)) {
				// printf("This should never happen, but does sometimes!\n");
				break;
			}

			// printf("%p %p %p %p - %p %p\n", v1, v2, v3, v4, e->l->f, e->l->radial_next->f);
			BLI_assert((ELEM3(v1, v2, v3, v4) == false) &&
			           (ELEM3(v2, v1, v3, v4) == false) &&
			           (ELEM3(v3, v1, v2, v4) == false) &&
			           (ELEM3(v4, v1, v2, v3) == false));

			is_zero_a = area_tri_v3(v2, v3, v4) <= FLT_EPSILON;
			is_zero_b = area_tri_v3(v2, v4, v1) <= FLT_EPSILON;

			if (LIKELY(is_zero_a == false && is_zero_b == false)) {
				float no_a[3], no_b[3];
				normal_tri_v3(no_a, v2, v3, v4);  /* a */
				normal_tri_v3(no_b, v2, v4, v1);  /* b */
				add_v3_v3v3(no, no_a, no_b);
				if (UNLIKELY(normalize_v3(no) <= FLT_EPSILON)) {
					break;
				}
			}
			else if (is_zero_a == false) {
				normal_tri_v3(no, v2, v3, v4);  /* a */
			}
			else if (is_zero_b == false) {
				normal_tri_v3(no, v2, v4, v1);  /* b */
			}
			else {
				/* both zero area, no useful normal can be calculated */
				break;
			}

			// { float a = angle_normalized_v3v3(no_a, no_b); printf("~ %.7f\n", a); fflush(stdout);}

			axis_dominant_v3_to_m3(axis_mat, no);
			mul_v2_m3v3(v1_xy, axis_mat, v1);
			mul_v2_m3v3(v2_xy, axis_mat, v2);
			mul_v2_m3v3(v3_xy, axis_mat, v3);
			mul_v2_m3v3(v4_xy, axis_mat, v4);
		}

		// printf("%p %p %p %p - %p %p\n", v1, v2, v3, v4, e->l->f, e->l->radial_next->f);

		if (is_quad_convex_v2(v1_xy, v2_xy, v3_xy, v4_xy)) {
			float len1, len2, len3, len4, len5, len6, opp1, opp2, fac1, fac2;
			/* testing rule:
			 * the area divided by the total edge lengths
			 */
			len1 = len_v2v2(v1_xy, v2_xy);
			len2 = len_v2v2(v2_xy, v3_xy);
			len3 = len_v2v2(v3_xy, v4_xy);
			len4 = len_v2v2(v4_xy, v1_xy);
			len5 = len_v2v2(v1_xy, v3_xy);
			len6 = len_v2v2(v2_xy, v4_xy);

			opp1 = area_tri_v2(v1_xy, v2_xy, v3_xy);
			opp2 = area_tri_v2(v1_xy, v3_xy, v4_xy);

			fac1 = opp1 / (len1 + len2 + len5) + opp2 / (len3 + len4 + len5);

			opp1 = area_tri_v2(v2_xy, v3_xy, v4_xy);
			opp2 = area_tri_v2(v2_xy, v4_xy, v1_xy);

			fac2 = opp1 / (len2 + len3 + len6) + opp2 / (len4 + len1 + len6);
			/* negative number if we're OK */
			return fac2 - fac1;
		}
	} while (false);

	return FLT_MAX;
}

/* -------------------------------------------------------------------- */
/* Update the edge cost of rotation in the heap */

/* recalc an edge in the heap (surrounding geometry has changed) */
static void bm_edge_update_beauty_cost_single(BMEdge *e, Heap *eheap, HeapNode **eheap_table, GHash **edge_state_arr,
                                              const int flag)
{
	if (BM_elem_flag_test(e, BM_ELEM_TAG)) {
		const int i = BM_elem_index_get(e);
		GHash *e_state_hash = edge_state_arr[i];

		if (eheap_table[i]) {
			BLI_heap_remove(eheap, eheap_table[i]);
			eheap_table[i] = NULL;
		}

		/* check if we can add it back */
		BLI_assert(BM_edge_is_manifold(e) == true);
		//BLI_assert(BMO_elem_flag_test(bm, e->l->f, FACE_MARK) &&
		//           BMO_elem_flag_test(bm, e->l->radial_next->f, FACE_MARK));

		/* check we're not moving back into a state we have been in before */
		if (e_state_hash != NULL) {
			EdRotState e_state_alt;
			erot_state_alternate(e, &e_state_alt);
			if (BLI_ghash_haskey(e_state_hash, (void *)&e_state_alt)) {
				// printf("  skipping, we already have this state\n");
				return;
			}
		}

		{
			/* recalculate edge */
			const float cost = bm_edge_calc_rotate_beauty(e, flag);
			if (cost < 0.0f) {
				eheap_table[i] = BLI_heap_insert(eheap, cost, e);
			}
			else {
				eheap_table[i] = NULL;
			}
		}
	}
}

/* we have rotated an edge, tag other egdes and clear this one */
static void bm_edge_update_beauty_cost(BMEdge *e, Heap *eheap, HeapNode **eheap_table, GHash **edge_state_arr,
                                       const int flag)
{
	BMLoop *l;
	BLI_assert(e->l->f->len == 3 &&
	           e->l->radial_next->f->len == 3);

	l = e->l;
	bm_edge_update_beauty_cost_single(l->next->e, eheap, eheap_table, edge_state_arr, flag);
	bm_edge_update_beauty_cost_single(l->prev->e, eheap, eheap_table, edge_state_arr, flag);
	l = l->radial_next;
	bm_edge_update_beauty_cost_single(l->next->e, eheap, eheap_table, edge_state_arr, flag);
	bm_edge_update_beauty_cost_single(l->prev->e, eheap, eheap_table, edge_state_arr, flag);
}

/* -------------------------------------------------------------------- */
/* Beautify Fill */

#define ELE_NEW		1
#define FACE_MARK	2

/**
 * \note All edges in \a edge_array must be tagged and
 * have their index values set according to their position in the array.
 */
static void bm_mesh_beautify_fill(BMesh *bm, BMEdge **edge_array, const int edge_array_len,
                                  const int flag)
{
	Heap *eheap;             /* edge heap */
	HeapNode **eheap_table;  /* edge index aligned table pointing to the eheap */

	GHash      **edge_state_arr  = MEM_callocN(edge_array_len * sizeof(GHash *), __func__);
	BLI_mempool *edge_state_pool = BLI_mempool_create(sizeof(EdRotState), 512, 512, BLI_MEMPOOL_SYSMALLOC);
	int i;

#ifdef DEBUG_TIME
	TIMEIT_START(beautify_fill);
#endif

	eheap = BLI_heap_new_ex(edge_array_len);
	eheap_table = MEM_mallocN(sizeof(HeapNode *) * edge_array_len, __func__);

	/* build heap */
	for (i = 0; i < edge_array_len; i++) {
		BMEdge *e = edge_array[i];
		const float cost = bm_edge_calc_rotate_beauty(e, flag);
		if (cost < 0.0f) {
			eheap_table[i] = BLI_heap_insert(eheap, cost, e);
		}
		else {
			eheap_table[i] = NULL;
		}
	}

	while (BLI_heap_is_empty(eheap) == false) {
		BMEdge *e = BLI_heap_popmin(eheap);
		i = BM_elem_index_get(e);
		eheap_table[i] = NULL;

		e = BM_edge_rotate(bm, e, false, BM_EDGEROT_CHECK_EXISTS);
		if (LIKELY(e)) {
			GHash *e_state_hash = edge_state_arr[i];

			/* add the new state into the hash so we don't move into this state again
			 * note: we could add the previous state too but this isn't essential)
			 *       for avoiding eternal loops */
			EdRotState *e_state = BLI_mempool_alloc(edge_state_pool);
			erot_state_current(e, e_state);
			if (UNLIKELY(e_state_hash == NULL)) {
				edge_state_arr[i] = e_state_hash = erot_ghash_new();  /* store previous state */
			}
			BLI_assert(BLI_ghash_haskey(e_state_hash, (void *)e_state) == false);
			BLI_ghash_insert(e_state_hash, e_state, NULL);


			// printf("  %d -> %d, %d\n", i, BM_elem_index_get(e->v1), BM_elem_index_get(e->v2));

			/* maintain the index array */
			edge_array[i] = e;
			BM_elem_index_set(e, i);

			/* recalculate faces connected on the heap */
			bm_edge_update_beauty_cost(e, eheap, eheap_table, edge_state_arr, flag);

			/* update flags */
			BMO_elem_flag_enable(bm, e, ELE_NEW);
			BMO_elem_flag_enable(bm, e->l->f, FACE_MARK | ELE_NEW);
			BMO_elem_flag_enable(bm, e->l->radial_next->f, FACE_MARK | ELE_NEW);
		}
	}

	BLI_heap_free(eheap, NULL);
	MEM_freeN(eheap_table);

	for (i = 0; i < edge_array_len; i++) {
		if (edge_state_arr[i]) {
			BLI_ghash_free(edge_state_arr[i], NULL, NULL);
		}
	}

	MEM_freeN(edge_state_arr);
	BLI_mempool_destroy(edge_state_pool);

#ifdef DEBUG_TIME
	TIMEIT_END(beautify_fill);
#endif
}


void bmo_beautify_fill_exec(BMesh *bm, BMOperator *op)
{
	BMIter iter;
	BMOIter siter;
	BMFace *f;
	BMEdge *e;
	const bool use_restrict_tag = BMO_slot_bool_get(op->slots_in,  "use_restrict_tag");
	const int flag = (use_restrict_tag ? VERT_RESTRICT_TAG : 0);

	BMEdge **edge_array;
	int edge_array_len = 0;

	BMO_ITER (f, &siter, op->slots_in, "faces", BM_FACE) {
		if (f->len == 3) {
			BMO_elem_flag_enable(bm, f, FACE_MARK);
		}
	}

	BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
		BM_elem_flag_disable(e, BM_ELEM_TAG);
	}

	/* will over alloc if some edges can't be rotated */
	edge_array = MEM_mallocN(sizeof(*edge_array) *  BMO_slot_buffer_count(op->slots_in, "edges"), __func__);

	BMO_ITER (e, &siter, op->slots_in, "edges", BM_EDGE) {

		/* edge is manifold and can be rotated */
		if (BM_edge_rotate_check(e) &&
			/* faces are tagged */
			BMO_elem_flag_test(bm, e->l->f, FACE_MARK) &&
			BMO_elem_flag_test(bm, e->l->radial_next->f, FACE_MARK))
		{
			BM_elem_index_set(e, edge_array_len);  /* set_dirty */
			BM_elem_flag_enable(e, BM_ELEM_TAG);
			edge_array[edge_array_len] = e;
			edge_array_len++;
		}
	}
	bm->elem_index_dirty |= BM_EDGE;

	bm_mesh_beautify_fill(bm, edge_array, edge_array_len, flag);

	MEM_freeN(edge_array);

	BMO_slot_buffer_from_enabled_flag(bm, op, op->slots_out, "geom.out", BM_EDGE | BM_FACE, ELE_NEW);
}
