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

/** \file
 * \ingroup gpu
 */

#include "MEM_guardedalloc.h"

#include "BLI_math.h"
#include "BLI_polyfill_2d.h"
#include "BLI_sort_utils.h"
#include "BLI_utildefines.h"

#include "GPU_batch.h"
#include "GPU_batch_utils.h" /* own include */

/* -------------------------------------------------------------------- */
/** \name Polygon Creation (2D)
 * \{ */

GPUBatch *GPU_batch_tris_from_poly_2d_encoded(const uchar *polys_flat,
                                              uint polys_flat_len,
                                              const rctf *rect)
{
  const uchar(*polys)[2] = (const void *)polys_flat;
  const uint polys_len = polys_flat_len / 2;
  BLI_assert(polys_flat_len == polys_len * 2);

  /* Over alloc in both cases */
  float(*verts)[2] = MEM_mallocN(sizeof(*verts) * polys_len, __func__);
  float(*verts_step)[2] = verts;
  uint(*tris)[3] = MEM_mallocN(sizeof(*tris) * polys_len, __func__);
  uint(*tris_step)[3] = tris;

  const float range_uchar[2] = {
      (rect ? (rect->xmax - rect->xmin) : 2.0f) / 255.0f,
      (rect ? (rect->ymax - rect->ymin) : 2.0f) / 255.0f,
  };
  const float min_uchar[2] = {
      (rect ? rect->xmin : -1.0f),
      (rect ? rect->ymin : -1.0f),
  };

  uint i_poly = 0;
  uint i_vert = 0;
  while (i_poly != polys_len) {
    for (uint j = 0; j < 2; j++) {
      verts[i_vert][j] = min_uchar[j] + ((float)polys[i_poly][j] * range_uchar[j]);
    }
    i_vert++;
    i_poly++;
    if (polys[i_poly - 1][0] == polys[i_poly][0] && polys[i_poly - 1][1] == polys[i_poly][1]) {
      const uint verts_step_len = (&verts[i_vert]) - verts_step;
      BLI_assert(verts_step_len >= 3);
      const uint tris_len = (verts_step_len - 2);
      BLI_polyfill_calc(verts_step, verts_step_len, -1, tris_step);
      /* offset indices */
      if (verts_step != verts) {
        uint *t = tris_step[0];
        const uint offset = (verts_step - verts);
        uint tot = tris_len * 3;
        while (tot--) {
          *t += offset;
          t++;
        }
        BLI_assert(t == tris_step[tris_len]);
      }
      verts_step += verts_step_len;
      tris_step += tris_len;
      i_poly++;
      /* ignore the duplicate point */
    }
  }

  /* We have vertices and tris, make a batch from this. */
  static GPUVertFormat format = {0};
  static struct {
    uint pos;
  } attr_id;
  if (format.attr_len == 0) {
    attr_id.pos = GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
  }

  const uint verts_len = (verts_step - verts);
  const uint tris_len = (tris_step - tris);
  GPUVertBuf *vbo = GPU_vertbuf_create_with_format(&format);
  GPU_vertbuf_data_alloc(vbo, verts_len);

  GPUVertBufRaw pos_step;
  GPU_vertbuf_attr_get_raw_data(vbo, attr_id.pos, &pos_step);

  for (uint i = 0; i < verts_len; i++) {
    copy_v2_v2(GPU_vertbuf_raw_step(&pos_step), verts[i]);
  }

  GPUIndexBufBuilder elb;
  GPU_indexbuf_init(&elb, GPU_PRIM_TRIS, tris_len, verts_len);
  for (uint i = 0; i < tris_len; i++) {
    GPU_indexbuf_add_tri_verts(&elb, UNPACK3(tris[i]));
  }
  GPUIndexBuf *indexbuf = GPU_indexbuf_build(&elb);

  MEM_freeN(tris);
  MEM_freeN(verts);

  return GPU_batch_create_ex(
      GPU_PRIM_TRIS, vbo, indexbuf, GPU_BATCH_OWNS_VBO | GPU_BATCH_OWNS_INDEX);
}

GPUBatch *GPU_batch_wire_from_poly_2d_encoded(const uchar *polys_flat,
                                              uint polys_flat_len,
                                              const rctf *rect)
{
  const uchar(*polys)[2] = (const void *)polys_flat;
  const uint polys_len = polys_flat_len / 2;
  BLI_assert(polys_flat_len == polys_len * 2);

  /* Over alloc */
  /* Lines are pairs of (x, y) byte locations packed into an int32_t. */
  int32_t *lines = MEM_mallocN(sizeof(*lines) * polys_len, __func__);
  int32_t *lines_step = lines;

  const float range_uchar[2] = {
      (rect ? (rect->xmax - rect->xmin) : 2.0f) / 255.0f,
      (rect ? (rect->ymax - rect->ymin) : 2.0f) / 255.0f,
  };
  const float min_uchar[2] = {
      (rect ? rect->xmin : -1.0f),
      (rect ? rect->ymin : -1.0f),
  };

  uint i_poly_prev = 0;
  uint i_poly = 0;
  while (i_poly != polys_len) {
    i_poly++;
    if (polys[i_poly - 1][0] == polys[i_poly][0] && polys[i_poly - 1][1] == polys[i_poly][1]) {
      const uchar(*polys_step)[2] = polys + i_poly_prev;
      const uint polys_step_len = i_poly - i_poly_prev;
      BLI_assert(polys_step_len >= 2);
      for (uint i_prev = polys_step_len - 1, i = 0; i < polys_step_len; i_prev = i++) {
        union {
          uint16_t as_u16[2];
          uint32_t as_u32;
        } data;
        data.as_u16[0] = *((const uint16_t *)polys_step[i_prev]);
        data.as_u16[1] = *((const uint16_t *)polys_step[i]);
        if (data.as_u16[0] > data.as_u16[1]) {
          SWAP(uint16_t, data.as_u16[0], data.as_u16[1]);
        }
        *lines_step = data.as_u32;
        lines_step++;
      }
      i_poly++;
      i_poly_prev = i_poly;
      /* ignore the duplicate point */
    }
  }

  uint lines_len = lines_step - lines;

  /* Hide Lines (we could make optional) */
  {
    qsort(lines, lines_len, sizeof(int32_t), BLI_sortutil_cmp_int);
    lines_step = lines;
    for (uint i_prev = 0, i = 1; i < lines_len; i_prev = i++) {
      if (lines[i] != lines[i_prev]) {
        *lines_step++ = lines[i_prev];
      }
      else {
        i++;
      }
    }
    *lines_step++ = lines[lines_len - 1];
    lines_len = lines_step - lines;
  }

  /* We have vertices and tris, make a batch from this. */
  static GPUVertFormat format = {0};
  static struct {
    uint pos;
  } attr_id;
  if (format.attr_len == 0) {
    attr_id.pos = GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
  }

  GPUVertBuf *vbo = GPU_vertbuf_create_with_format(&format);
  const uint vbo_len_capacity = lines_len * 2;
  GPU_vertbuf_data_alloc(vbo, vbo_len_capacity);

  GPUVertBufRaw pos_step;
  GPU_vertbuf_attr_get_raw_data(vbo, attr_id.pos, &pos_step);

  for (uint i = 0; i < lines_len; i++) {
    union {
      uint8_t as_u8_pair[2][2];
      uint32_t as_u32;
    } data;
    data.as_u32 = lines[i];
    for (uint k = 0; k < 2; k++) {
      float *pos_v2 = GPU_vertbuf_raw_step(&pos_step);
      for (uint j = 0; j < 2; j++) {
        pos_v2[j] = min_uchar[j] + ((float)data.as_u8_pair[k][j] * range_uchar[j]);
      }
    }
  }
  BLI_assert(vbo_len_capacity == GPU_vertbuf_raw_used(&pos_step));
  MEM_freeN(lines);
  return GPU_batch_create_ex(GPU_PRIM_LINES, vbo, NULL, GPU_BATCH_OWNS_VBO);
}

/** \} */