/* SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup modifiers
 */

#include <errno.h>
#include <stdio.h>
#include <string.h>

#include "BLI_utildefines.h"

#include "BLI_fileops.h"
#include "BLI_math.h"
#ifdef __LITTLE_ENDIAN__
#  include "BLI_endian_switch.h"
#endif
#ifdef WIN32
#  include "BLI_winstuff.h"
#endif

#include "DNA_modifier_types.h"

#include "MOD_meshcache_util.h" /* own include */

typedef struct MDDHead {
  int frame_tot;
  int verts_tot;
} MDDHead; /* frames, verts */

static bool meshcache_read_mdd_head(FILE *fp,
                                    const int verts_tot,
                                    MDDHead *mdd_head,
                                    const char **err_str)
{
  if (!fread(mdd_head, sizeof(*mdd_head), 1, fp)) {
    *err_str = "Missing header";
    return false;
  }

#ifdef __LITTLE_ENDIAN__
  BLI_endian_switch_int32_array((int *)mdd_head, 2);
#endif

  if (mdd_head->verts_tot != verts_tot) {
    *err_str = "Vertex count mismatch";
    return false;
  }

  if (mdd_head->frame_tot <= 0) {
    *err_str = "Invalid frame total";
    return false;
  }
  /* Intentionally don't seek back. */

  return true;
}

/**
 * Gets the index range and factor.
 */
static bool meshcache_read_mdd_range(FILE *fp,
                                     const int verts_tot,
                                     const float frame,
                                     const char interp,
                                     int r_index_range[2],
                                     float *r_factor,
                                     const char **err_str)
{
  MDDHead mdd_head;

  /* first check interpolation and get the vert locations */

  if (meshcache_read_mdd_head(fp, verts_tot, &mdd_head, err_str) == false) {
    return false;
  }

  MOD_meshcache_calc_range(frame, interp, mdd_head.frame_tot, r_index_range, r_factor);

  return true;
}

static bool meshcache_read_mdd_range_from_time(FILE *fp,
                                               const int verts_tot,
                                               const float time,
                                               const float UNUSED(fps),
                                               float *r_frame,
                                               const char **err_str)
{
  MDDHead mdd_head;
  int i;
  float f_time, f_time_prev = FLT_MAX;
  float frame;

  if (meshcache_read_mdd_head(fp, verts_tot, &mdd_head, err_str) == false) {
    return false;
  }

  size_t frames_num_read = 0;
  size_t frames_num_expect = mdd_head.frame_tot;
  errno = 0;
  for (i = 0; i < mdd_head.frame_tot; i++) {
    frames_num_read += fread(&f_time, sizeof(float), 1, fp);
#ifdef __LITTLE_ENDIAN__
    BLI_endian_switch_float(&f_time);
#endif
    if (f_time >= time) {
      frames_num_expect = i + 1;
      break;
    }
    f_time_prev = f_time;
  }

  if (frames_num_read != frames_num_expect) {
    *err_str = errno ? strerror(errno) : "Timestamp read failed";
    return false;
  }

  if (i == mdd_head.frame_tot) {
    frame = (float)(mdd_head.frame_tot - 1);
  }
  if (UNLIKELY(f_time_prev == FLT_MAX)) {
    frame = 0.0f;
  }
  else {
    const float range = f_time - f_time_prev;

    if (range <= FRAME_SNAP_EPS) {
      frame = (float)i;
    }
    else {
      frame = (float)(i - 1) + ((time - f_time_prev) / range);
    }
  }

  *r_frame = frame;
  return true;
}

bool MOD_meshcache_read_mdd_index(FILE *fp,
                                  float (*vertexCos)[3],
                                  const int verts_tot,
                                  const int index,
                                  const float factor,
                                  const char **err_str)
{
  MDDHead mdd_head;

  if (meshcache_read_mdd_head(fp, verts_tot, &mdd_head, err_str) == false) {
    return false;
  }

  if (BLI_fseek(fp, mdd_head.frame_tot * sizeof(int), SEEK_CUR) != 0) {
    *err_str = "Header seek failed";
    return false;
  }

  if (BLI_fseek(fp, sizeof(float[3]) * index * mdd_head.verts_tot, SEEK_CUR) != 0) {
    *err_str = "Failed to seek frame";
    return false;
  }

  size_t verts_read_num = 0;
  errno = 0;
  if (factor >= 1.0f) {
#if 1
    float *vco = *vertexCos;
    uint i;
    for (i = mdd_head.verts_tot; i != 0; i--, vco += 3) {
      verts_read_num += fread(vco, sizeof(float[3]), 1, fp);

#  ifdef __LITTLE_ENDIAN__
      BLI_endian_switch_float(vco + 0);
      BLI_endian_switch_float(vco + 1);
      BLI_endian_switch_float(vco + 2);
#  endif /* __LITTLE_ENDIAN__ */
    }
#else
    /* no blending */
    if (!fread(vertexCos, sizeof(float[3]), mdd_head.verts_tot, f)) {
      *err_str = errno ? strerror(errno) : "Failed to read frame";
      return false;
    }
#  ifdef __LITTLE_ENDIAN__
    BLI_endian_switch_float_array(vertexCos[0], mdd_head.verts_tot * 3);
#  endif
#endif
  }
  else {
    const float ifactor = 1.0f - factor;
    float *vco = *vertexCos;
    uint i;
    for (i = mdd_head.verts_tot; i != 0; i--, vco += 3) {
      float tvec[3];
      verts_read_num += fread(tvec, sizeof(float[3]), 1, fp);

#ifdef __LITTLE_ENDIAN__
      BLI_endian_switch_float(tvec + 0);
      BLI_endian_switch_float(tvec + 1);
      BLI_endian_switch_float(tvec + 2);
#endif

      vco[0] = (vco[0] * ifactor) + (tvec[0] * factor);
      vco[1] = (vco[1] * ifactor) + (tvec[1] * factor);
      vco[2] = (vco[2] * ifactor) + (tvec[2] * factor);
    }
  }

  if (verts_read_num != mdd_head.verts_tot) {
    *err_str = errno ? strerror(errno) : "Vertex coordinate read failed";
    return false;
  }

  return true;
}

bool MOD_meshcache_read_mdd_frame(FILE *fp,
                                  float (*vertexCos)[3],
                                  const int verts_tot,
                                  const char interp,
                                  const float frame,
                                  const char **err_str)
{
  int index_range[2];
  float factor;

  if (meshcache_read_mdd_range(fp,
                               verts_tot,
                               frame,
                               interp,
                               index_range,
                               &factor, /* read into these values */
                               err_str) == false) {
    return false;
  }

  if (index_range[0] == index_range[1]) {
    /* read single */
    if ((BLI_fseek(fp, 0, SEEK_SET) == 0) &&
        MOD_meshcache_read_mdd_index(fp, vertexCos, verts_tot, index_range[0], 1.0f, err_str)) {
      return true;
    }

    return false;
  }

  /* read both and interpolate */
  if ((BLI_fseek(fp, 0, SEEK_SET) == 0) &&
      MOD_meshcache_read_mdd_index(fp, vertexCos, verts_tot, index_range[0], 1.0f, err_str) &&
      (BLI_fseek(fp, 0, SEEK_SET) == 0) &&
      MOD_meshcache_read_mdd_index(fp, vertexCos, verts_tot, index_range[1], factor, err_str)) {
    return true;
  }

  return false;
}

bool MOD_meshcache_read_mdd_times(const char *filepath,
                                  float (*vertexCos)[3],
                                  const int verts_tot,
                                  const char interp,
                                  const float time,
                                  const float fps,
                                  const char time_mode,
                                  const char **err_str)
{
  float frame;

  FILE *fp = BLI_fopen(filepath, "rb");
  bool ok;

  if (fp == NULL) {
    *err_str = errno ? strerror(errno) : "Unknown error opening file";
    return false;
  }

  switch (time_mode) {
    case MOD_MESHCACHE_TIME_FRAME: {
      frame = time;
      break;
    }
    case MOD_MESHCACHE_TIME_SECONDS: {
      /* we need to find the closest time */
      if (meshcache_read_mdd_range_from_time(fp, verts_tot, time, fps, &frame, err_str) == false) {
        fclose(fp);
        return false;
      }
      rewind(fp);
      break;
    }
    case MOD_MESHCACHE_TIME_FACTOR:
    default: {
      MDDHead mdd_head;
      if (meshcache_read_mdd_head(fp, verts_tot, &mdd_head, err_str) == false) {
        fclose(fp);
        return false;
      }

      frame = CLAMPIS(time, 0.0f, 1.0f) * (float)mdd_head.frame_tot;
      rewind(fp);
      break;
    }
  }

  ok = MOD_meshcache_read_mdd_frame(fp, vertexCos, verts_tot, interp, frame, err_str);

  fclose(fp);
  return ok;
}