/*
 * 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) 2018 by Blender Foundation.
 * All rights reserved.
 */

/** \file
 * \ingroup bke
 */

#include "BKE_subdiv_eval.h"

#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"

#include "BLI_bitmap.h"
#include "BLI_math_vector.h"
#include "BLI_utildefines.h"

#include "BKE_customdata.h"
#include "BKE_subdiv.h"

#include "MEM_guardedalloc.h"

#include "opensubdiv_evaluator_capi.h"
#include "opensubdiv_topology_refiner_capi.h"

bool BKE_subdiv_eval_begin(Subdiv *subdiv)
{
  BKE_subdiv_stats_reset(&subdiv->stats, SUBDIV_STATS_EVALUATOR_CREATE);
  if (subdiv->topology_refiner == NULL) {
    /* Happens on input mesh with just loose geometry,
     * or when OpenSubdiv is disabled */
    return false;
  }
  if (subdiv->evaluator == NULL) {
    BKE_subdiv_stats_begin(&subdiv->stats, SUBDIV_STATS_EVALUATOR_CREATE);
    subdiv->evaluator = openSubdiv_createEvaluatorFromTopologyRefiner(subdiv->topology_refiner);
    BKE_subdiv_stats_end(&subdiv->stats, SUBDIV_STATS_EVALUATOR_CREATE);
    if (subdiv->evaluator == NULL) {
      return false;
    }
  }
  else {
    /* TODO(sergey): Check for topology change. */
  }
  BKE_subdiv_eval_init_displacement(subdiv);
  return true;
}

static void set_coarse_positions(Subdiv *subdiv,
                                 const Mesh *mesh,
                                 const float (*coarse_vertex_cos)[3])
{
  const MVert *mvert = mesh->mvert;
  const MLoop *mloop = mesh->mloop;
  const MPoly *mpoly = mesh->mpoly;
  /* Mark vertices which needs new coordinates. */
  /* TODO(sergey): This is annoying to calculate this on every update,
   * maybe it's better to cache this mapping. Or make it possible to have
   * OpenSubdiv's vertices match mesh ones? */
  BLI_bitmap *vertex_used_map = BLI_BITMAP_NEW(mesh->totvert, "vert used map");
  for (int poly_index = 0; poly_index < mesh->totpoly; poly_index++) {
    const MPoly *poly = &mpoly[poly_index];
    for (int corner = 0; corner < poly->totloop; corner++) {
      const MLoop *loop = &mloop[poly->loopstart + corner];
      BLI_BITMAP_ENABLE(vertex_used_map, loop->v);
    }
  }
  for (int vertex_index = 0, manifold_vertex_index = 0; vertex_index < mesh->totvert;
       vertex_index++) {
    if (!BLI_BITMAP_TEST_BOOL(vertex_used_map, vertex_index)) {
      continue;
    }
    const float *vertex_co;
    if (coarse_vertex_cos != NULL) {
      vertex_co = coarse_vertex_cos[vertex_index];
    }
    else {
      const MVert *vertex = &mvert[vertex_index];
      vertex_co = vertex->co;
    }
    subdiv->evaluator->setCoarsePositions(subdiv->evaluator, vertex_co, manifold_vertex_index, 1);
    manifold_vertex_index++;
  }
  MEM_freeN(vertex_used_map);
}

static void set_face_varying_data_from_uv(Subdiv *subdiv,
                                          const MLoopUV *mloopuv,
                                          const int layer_index)
{
  OpenSubdiv_TopologyRefiner *topology_refiner = subdiv->topology_refiner;
  OpenSubdiv_Evaluator *evaluator = subdiv->evaluator;
  const int num_faces = topology_refiner->getNumFaces(topology_refiner);
  const MLoopUV *mluv = mloopuv;
  /* TODO(sergey): OpenSubdiv's C-API converter can change winding of
   * loops of a face, need to watch for that, to prevent wrong UVs assigned.
   */
  for (int face_index = 0; face_index < num_faces; face_index++) {
    const int num_face_vertices = topology_refiner->getNumFaceVertices(topology_refiner,
                                                                       face_index);
    const int *uv_indices = topology_refiner->getFaceFVarValueIndices(
        topology_refiner, face_index, layer_index);
    for (int vertex_index = 0; vertex_index < num_face_vertices; vertex_index++, mluv++) {
      evaluator->setFaceVaryingData(evaluator, layer_index, mluv->uv, uv_indices[vertex_index], 1);
    }
  }
}

bool BKE_subdiv_eval_begin_from_mesh(Subdiv *subdiv,
                                     const Mesh *mesh,
                                     const float (*coarse_vertex_cos)[3])
{
  if (!BKE_subdiv_eval_begin(subdiv)) {
    return false;
  }
  return BKE_subdiv_eval_refine_from_mesh(subdiv, mesh, coarse_vertex_cos);
}

bool BKE_subdiv_eval_refine_from_mesh(Subdiv *subdiv,
                                      const Mesh *mesh,
                                      const float (*coarse_vertex_cos)[3])
{
  if (subdiv->evaluator == NULL) {
    /* NOTE: This situation is supposed to be handled by begin(). */
    BLI_assert(!"Is not supposed to happen");
    return false;
  }
  /* Set coordinates of base mesh vertices. */
  set_coarse_positions(subdiv, mesh, coarse_vertex_cos);
  /* Set face-varyign data to UV maps. */
  const int num_uv_layers = CustomData_number_of_layers(&mesh->ldata, CD_MLOOPUV);
  for (int layer_index = 0; layer_index < num_uv_layers; layer_index++) {
    const MLoopUV *mloopuv = CustomData_get_layer_n(&mesh->ldata, CD_MLOOPUV, layer_index);
    set_face_varying_data_from_uv(subdiv, mloopuv, layer_index);
  }
  /* Update evaluator to the new coarse geometry. */
  BKE_subdiv_stats_begin(&subdiv->stats, SUBDIV_STATS_EVALUATOR_REFINE);
  subdiv->evaluator->refine(subdiv->evaluator);
  BKE_subdiv_stats_end(&subdiv->stats, SUBDIV_STATS_EVALUATOR_REFINE);
  return true;
}

void BKE_subdiv_eval_init_displacement(Subdiv *subdiv)
{
  if (subdiv->displacement_evaluator == NULL) {
    return;
  }
  if (subdiv->displacement_evaluator->initialize == NULL) {
    return;
  }
  subdiv->displacement_evaluator->initialize(subdiv->displacement_evaluator);
}

/* ========================== Single point queries ========================== */

void BKE_subdiv_eval_limit_point(
    Subdiv *subdiv, const int ptex_face_index, const float u, const float v, float r_P[3])
{
  BKE_subdiv_eval_limit_point_and_derivatives(subdiv, ptex_face_index, u, v, r_P, NULL, NULL);
}

void BKE_subdiv_eval_limit_point_and_derivatives(Subdiv *subdiv,
                                                 const int ptex_face_index,
                                                 const float u,
                                                 const float v,
                                                 float r_P[3],
                                                 float r_dPdu[3],
                                                 float r_dPdv[3])
{
  subdiv->evaluator->evaluateLimit(subdiv->evaluator, ptex_face_index, u, v, r_P, r_dPdu, r_dPdv);

  /* NOTE: In a very rare occasions derivatives are evaluated to zeros or are exactly equal.
   * This happens, for example, in single vertex on Suzannne's nose (where two quads have 2 common
   * edges).
   *
   * This makes tangent space displacement (such as multires) impossible to be used in those
   * vertices, so those needs to be addressed in one way or another.
   *
   * Simplest thing to do: step inside of the face a little bit, where there is known patch at
   * which there must be proper derivatives. This might break continuity of normals, but is better
   * that giving totally unusable derivatives. */

  if (r_dPdu != NULL && r_dPdv != NULL) {
    if ((is_zero_v3(r_dPdu) || is_zero_v3(r_dPdv)) || equals_v3v3(r_dPdu, r_dPdv)) {
      subdiv->evaluator->evaluateLimit(subdiv->evaluator,
                                       ptex_face_index,
                                       u * 0.999f + 0.0005f,
                                       v * 0.999f + 0.0005f,
                                       r_P,
                                       r_dPdu,
                                       r_dPdv);
    }
  }
}

void BKE_subdiv_eval_limit_point_and_normal(Subdiv *subdiv,
                                            const int ptex_face_index,
                                            const float u,
                                            const float v,
                                            float r_P[3],
                                            float r_N[3])
{
  float dPdu[3], dPdv[3];
  BKE_subdiv_eval_limit_point_and_derivatives(subdiv, ptex_face_index, u, v, r_P, dPdu, dPdv);
  cross_v3_v3v3(r_N, dPdu, dPdv);
  normalize_v3(r_N);
}

void BKE_subdiv_eval_limit_point_and_short_normal(Subdiv *subdiv,
                                                  const int ptex_face_index,
                                                  const float u,
                                                  const float v,
                                                  float r_P[3],
                                                  short r_N[3])
{
  float N_float[3];
  BKE_subdiv_eval_limit_point_and_normal(subdiv, ptex_face_index, u, v, r_P, N_float);
  normal_float_to_short_v3(r_N, N_float);
}

void BKE_subdiv_eval_face_varying(Subdiv *subdiv,
                                  const int face_varying_channel,
                                  const int ptex_face_index,
                                  const float u,
                                  const float v,
                                  float r_face_varying[2])
{
  subdiv->evaluator->evaluateFaceVarying(
      subdiv->evaluator, face_varying_channel, ptex_face_index, u, v, r_face_varying);
}

void BKE_subdiv_eval_displacement(Subdiv *subdiv,
                                  const int ptex_face_index,
                                  const float u,
                                  const float v,
                                  const float dPdu[3],
                                  const float dPdv[3],
                                  float r_D[3])
{
  if (subdiv->displacement_evaluator == NULL) {
    zero_v3(r_D);
    return;
  }
  subdiv->displacement_evaluator->eval_displacement(
      subdiv->displacement_evaluator, ptex_face_index, u, v, dPdu, dPdv, r_D);
}

void BKE_subdiv_eval_final_point(
    Subdiv *subdiv, const int ptex_face_index, const float u, const float v, float r_P[3])
{
  if (subdiv->displacement_evaluator) {
    float dPdu[3], dPdv[3], D[3];
    BKE_subdiv_eval_limit_point_and_derivatives(subdiv, ptex_face_index, u, v, r_P, dPdu, dPdv);
    BKE_subdiv_eval_displacement(subdiv, ptex_face_index, u, v, dPdu, dPdv, D);
    add_v3_v3(r_P, D);
  }
  else {
    BKE_subdiv_eval_limit_point(subdiv, ptex_face_index, u, v, r_P);
  }
}

/* ===================  Patch queries at given resolution =================== */

/* Move buffer forward by a given number of bytes. */
static void buffer_apply_offset(void **buffer, const int offset)
{
  *buffer = ((unsigned char *)*buffer) + offset;
}

/* Write given number of floats to the beginning of given buffer.  */
static void buffer_write_float_value(void **buffer, const float *values_buffer, int num_values)
{
  memcpy(*buffer, values_buffer, sizeof(float) * num_values);
}

/* Similar to above, just operates with short values. */
static void buffer_write_short_value(void **buffer, const short *values_buffer, int num_values)
{
  memcpy(*buffer, values_buffer, sizeof(short) * num_values);
}

void BKE_subdiv_eval_limit_patch_resolution_point(Subdiv *subdiv,
                                                  const int ptex_face_index,
                                                  const int resolution,
                                                  void *buffer,
                                                  const int offset,
                                                  const int stride)
{
  buffer_apply_offset(&buffer, offset);
  const float inv_resolution_1 = 1.0f / (float)(resolution - 1);
  for (int y = 0; y < resolution; y++) {
    const float v = y * inv_resolution_1;
    for (int x = 0; x < resolution; x++) {
      const float u = x * inv_resolution_1;
      BKE_subdiv_eval_limit_point(subdiv, ptex_face_index, u, v, buffer);
      buffer_apply_offset(&buffer, stride);
    }
  }
}

void BKE_subdiv_eval_limit_patch_resolution_point_and_derivatives(Subdiv *subdiv,
                                                                  const int ptex_face_index,
                                                                  const int resolution,
                                                                  void *point_buffer,
                                                                  const int point_offset,
                                                                  const int point_stride,
                                                                  void *du_buffer,
                                                                  const int du_offset,
                                                                  const int du_stride,
                                                                  void *dv_buffer,
                                                                  const int dv_offset,
                                                                  const int dv_stride)
{
  buffer_apply_offset(&point_buffer, point_offset);
  buffer_apply_offset(&du_buffer, du_offset);
  buffer_apply_offset(&dv_buffer, dv_offset);
  const float inv_resolution_1 = 1.0f / (float)(resolution - 1);
  for (int y = 0; y < resolution; y++) {
    const float v = y * inv_resolution_1;
    for (int x = 0; x < resolution; x++) {
      const float u = x * inv_resolution_1;
      BKE_subdiv_eval_limit_point_and_derivatives(
          subdiv, ptex_face_index, u, v, point_buffer, du_buffer, dv_buffer);
      buffer_apply_offset(&point_buffer, point_stride);
      buffer_apply_offset(&du_buffer, du_stride);
      buffer_apply_offset(&dv_buffer, dv_stride);
    }
  }
}

void BKE_subdiv_eval_limit_patch_resolution_point_and_normal(Subdiv *subdiv,
                                                             const int ptex_face_index,
                                                             const int resolution,
                                                             void *point_buffer,
                                                             const int point_offset,
                                                             const int point_stride,
                                                             void *normal_buffer,
                                                             const int normal_offset,
                                                             const int normal_stride)
{
  buffer_apply_offset(&point_buffer, point_offset);
  buffer_apply_offset(&normal_buffer, normal_offset);
  const float inv_resolution_1 = 1.0f / (float)(resolution - 1);
  for (int y = 0; y < resolution; y++) {
    const float v = y * inv_resolution_1;
    for (int x = 0; x < resolution; x++) {
      const float u = x * inv_resolution_1;
      float normal[3];
      BKE_subdiv_eval_limit_point_and_normal(subdiv, ptex_face_index, u, v, point_buffer, normal);
      buffer_write_float_value(&normal_buffer, normal, 3);
      buffer_apply_offset(&point_buffer, point_stride);
      buffer_apply_offset(&normal_buffer, normal_stride);
    }
  }
}

void BKE_subdiv_eval_limit_patch_resolution_point_and_short_normal(Subdiv *subdiv,
                                                                   const int ptex_face_index,
                                                                   const int resolution,
                                                                   void *point_buffer,
                                                                   const int point_offset,
                                                                   const int point_stride,
                                                                   void *normal_buffer,
                                                                   const int normal_offset,
                                                                   const int normal_stride)
{
  buffer_apply_offset(&point_buffer, point_offset);
  buffer_apply_offset(&normal_buffer, normal_offset);
  const float inv_resolution_1 = 1.0f / (float)(resolution - 1);
  for (int y = 0; y < resolution; y++) {
    const float v = y * inv_resolution_1;
    for (int x = 0; x < resolution; x++) {
      const float u = x * inv_resolution_1;
      short normal[3];
      BKE_subdiv_eval_limit_point_and_short_normal(
          subdiv, ptex_face_index, u, v, point_buffer, normal);
      buffer_write_short_value(&normal_buffer, normal, 3);
      buffer_apply_offset(&point_buffer, point_stride);
      buffer_apply_offset(&normal_buffer, normal_stride);
    }
  }
}
