/*
 * 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.
 *
 * The Original Code is Copyright (C) 2017 by Blender Foundation.
 * All rights reserved.
 */

/** \file
 * \ingroup draw
 *
 * \brief MetaBall API for render engines
 */

#include "MEM_guardedalloc.h"

#include "BLI_math_base.h"
#include "BLI_utildefines.h"

#include "DNA_meta_types.h"
#include "DNA_object_types.h"

#include "BKE_curve.h"
#include "BKE_mball.h"

#include "GPU_batch.h"

#include "DRW_render.h"
#include "draw_cache_impl.h" /* own include */

static void metaball_batch_cache_clear(MetaBall *mb);

/* ---------------------------------------------------------------------- */
/* MetaBall GPUBatch Cache */

typedef struct MetaBallBatchCache {
  GPUBatch *batch;
  GPUBatch **shaded_triangles;

  int mat_len;

  /* Shared */
  GPUVertBuf *pos_nor_in_order;

  /* Wireframe */
  struct {
    GPUBatch *batch;
  } face_wire;

  /* Edge detection */
  GPUBatch *edge_detection;
  GPUIndexBuf *edges_adj_lines;

  /* settings to determine if cache is invalid */
  bool is_dirty;

  /* Valid only if edge_detection is up to date. */
  bool is_manifold;
} MetaBallBatchCache;

/* GPUBatch cache management. */

static bool metaball_batch_cache_valid(MetaBall *mb)
{
  MetaBallBatchCache *cache = mb->batch_cache;

  if (cache == NULL) {
    return false;
  }

  return cache->is_dirty == false;
}

static void metaball_batch_cache_init(MetaBall *mb)
{
  MetaBallBatchCache *cache = mb->batch_cache;

  if (!cache) {
    cache = mb->batch_cache = MEM_mallocN(sizeof(*cache), __func__);
  }
  cache->batch = NULL;
  cache->mat_len = 0;
  cache->shaded_triangles = NULL;
  cache->is_dirty = false;
  cache->pos_nor_in_order = NULL;
  cache->face_wire.batch = NULL;
  cache->edge_detection = NULL;
  cache->edges_adj_lines = NULL;
  cache->is_manifold = false;
}

void DRW_mball_batch_cache_validate(MetaBall *mb)
{
  if (!metaball_batch_cache_valid(mb)) {
    metaball_batch_cache_clear(mb);
    metaball_batch_cache_init(mb);
  }
}

static MetaBallBatchCache *metaball_batch_cache_get(MetaBall *mb)
{
  return mb->batch_cache;
}

void DRW_mball_batch_cache_dirty_tag(MetaBall *mb, int mode)
{
  MetaBallBatchCache *cache = mb->batch_cache;
  if (cache == NULL) {
    return;
  }
  switch (mode) {
    case BKE_MBALL_BATCH_DIRTY_ALL:
      cache->is_dirty = true;
      break;
    default:
      BLI_assert(0);
  }
}

static void metaball_batch_cache_clear(MetaBall *mb)
{
  MetaBallBatchCache *cache = mb->batch_cache;
  if (!cache) {
    return;
  }

  GPU_BATCH_DISCARD_SAFE(cache->face_wire.batch);
  GPU_BATCH_DISCARD_SAFE(cache->batch);
  GPU_BATCH_DISCARD_SAFE(cache->edge_detection);
  GPU_VERTBUF_DISCARD_SAFE(cache->pos_nor_in_order);
  GPU_INDEXBUF_DISCARD_SAFE(cache->edges_adj_lines);
  /* Note: shaded_triangles[0] is already freed by cache->batch */
  MEM_SAFE_FREE(cache->shaded_triangles);
  cache->mat_len = 0;
  cache->is_manifold = false;
}

void DRW_mball_batch_cache_free(MetaBall *mb)
{
  metaball_batch_cache_clear(mb);
  MEM_SAFE_FREE(mb->batch_cache);
}

static GPUVertBuf *mball_batch_cache_get_pos_and_normals(Object *ob,
                                                         MetaBallBatchCache *cache,
                                                         const struct Scene *scene)
{
  if (cache->pos_nor_in_order == NULL) {
    ListBase *lb = &ob->runtime.curve_cache->disp;
    cache->pos_nor_in_order = GPU_vertbuf_calloc();
    DRW_displist_vertbuf_create_pos_and_nor(lb, cache->pos_nor_in_order, scene);
  }
  return cache->pos_nor_in_order;
}

static GPUIndexBuf *mball_batch_cache_get_edges_adj_lines(Object *ob, MetaBallBatchCache *cache)
{
  if (cache->edges_adj_lines == NULL) {
    ListBase *lb = &ob->runtime.curve_cache->disp;
    cache->edges_adj_lines = GPU_indexbuf_calloc();
    DRW_displist_indexbuf_create_edges_adjacency_lines(
        lb, cache->edges_adj_lines, &cache->is_manifold);
  }
  return cache->edges_adj_lines;
}

/* -------------------------------------------------------------------- */
/** \name Public Object/MetaBall API
 * \{ */

GPUBatch *DRW_metaball_batch_cache_get_triangles_with_normals(Object *ob)
{
  if (!BKE_mball_is_basis(ob)) {
    return NULL;
  }

  MetaBall *mb = ob->data;
  MetaBallBatchCache *cache = metaball_batch_cache_get(mb);
  const DRWContextState *draw_ctx = DRW_context_state_get();
  const struct Scene *scene = draw_ctx->scene;

  if (cache->batch == NULL) {
    ListBase *lb = &ob->runtime.curve_cache->disp;
    GPUIndexBuf *ibo = GPU_indexbuf_calloc();
    DRW_displist_indexbuf_create_triangles_in_order(lb, ibo);
    cache->batch = GPU_batch_create_ex(GPU_PRIM_TRIS,
                                       mball_batch_cache_get_pos_and_normals(ob, cache, scene),
                                       ibo,
                                       GPU_BATCH_OWNS_INDEX);
  }

  return cache->batch;
}

GPUBatch **DRW_metaball_batch_cache_get_surface_shaded(Object *ob,
                                                       MetaBall *mb,
                                                       struct GPUMaterial **UNUSED(gpumat_array),
                                                       uint gpumat_array_len)
{
  if (!BKE_mball_is_basis(ob)) {
    return NULL;
  }

  BLI_assert(gpumat_array_len == DRW_metaball_material_count_get(mb));

  MetaBallBatchCache *cache = metaball_batch_cache_get(mb);
  if (cache->shaded_triangles == NULL) {
    cache->mat_len = gpumat_array_len;
    cache->shaded_triangles = MEM_callocN(sizeof(*cache->shaded_triangles) * cache->mat_len,
                                          __func__);
    cache->shaded_triangles[0] = DRW_metaball_batch_cache_get_triangles_with_normals(ob);
    for (int i = 1; i < cache->mat_len; i++) {
      cache->shaded_triangles[i] = NULL;
    }
  }
  return cache->shaded_triangles;
}

GPUBatch *DRW_metaball_batch_cache_get_wireframes_face(Object *ob)
{
  if (!BKE_mball_is_basis(ob)) {
    return NULL;
  }

  MetaBall *mb = ob->data;
  MetaBallBatchCache *cache = metaball_batch_cache_get(mb);
  const DRWContextState *draw_ctx = DRW_context_state_get();
  const struct Scene *scene = draw_ctx->scene;

  if (cache->face_wire.batch == NULL) {
    ListBase *lb = &ob->runtime.curve_cache->disp;

    GPUVertBuf *vbo_wiredata = GPU_vertbuf_calloc();
    DRW_displist_vertbuf_create_wiredata(lb, vbo_wiredata);

    GPUIndexBuf *ibo = GPU_indexbuf_calloc();
    DRW_displist_indexbuf_create_lines_in_order(lb, ibo);

    cache->face_wire.batch = GPU_batch_create_ex(
        GPU_PRIM_LINES,
        mball_batch_cache_get_pos_and_normals(ob, cache, scene),
        ibo,
        GPU_BATCH_OWNS_INDEX);

    GPU_batch_vertbuf_add_ex(cache->face_wire.batch, vbo_wiredata, true);
  }

  return cache->face_wire.batch;
}

struct GPUBatch *DRW_metaball_batch_cache_get_edge_detection(struct Object *ob,
                                                             bool *r_is_manifold)
{
  if (!BKE_mball_is_basis(ob)) {
    return NULL;
  }

  MetaBall *mb = ob->data;
  MetaBallBatchCache *cache = metaball_batch_cache_get(mb);
  const DRWContextState *draw_ctx = DRW_context_state_get();
  const struct Scene *scene = draw_ctx->scene;

  if (cache->edge_detection == NULL) {
    cache->edge_detection = GPU_batch_create(
        GPU_PRIM_LINES_ADJ,
        mball_batch_cache_get_pos_and_normals(ob, cache, scene),
        mball_batch_cache_get_edges_adj_lines(ob, cache));
  }

  if (r_is_manifold) {
    *r_is_manifold = cache->is_manifold;
  }

  return cache->edge_detection;
}

struct GPUVertBuf *DRW_mball_batch_cache_pos_vertbuf_get(Object *ob)
{
  if (!BKE_mball_is_basis(ob)) {
    return NULL;
  }

  MetaBall *mb = ob->data;
  MetaBallBatchCache *cache = metaball_batch_cache_get(mb);
  const DRWContextState *draw_ctx = DRW_context_state_get();
  const struct Scene *scene = draw_ctx->scene;

  return mball_batch_cache_get_pos_and_normals(ob, cache, scene);
}

int DRW_metaball_material_count_get(MetaBall *mb)
{
  return max_ii(1, mb->totcol);
}