/*
 * 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) 2016 by Mike Erwin.
 * All rights reserved.
 */

/** \file
 * \ingroup gpu
 *
 * GPU vertex buffer
 */

#include "MEM_guardedalloc.h"

#include "GPU_vertex_buffer.h"

#include "gpu_context_private.h"
#include "gpu_vertex_format_private.h"

#include <stdlib.h>
#include <string.h>

#define KEEP_SINGLE_COPY 1

static uint vbo_memory_usage;

static GLenum convert_usage_type_to_gl(GPUUsageType type)
{
  static const GLenum table[] = {
      [GPU_USAGE_STREAM] = GL_STREAM_DRAW,
      [GPU_USAGE_STATIC] = GL_STATIC_DRAW,
      [GPU_USAGE_DYNAMIC] = GL_DYNAMIC_DRAW,
  };
  return table[type];
}

GPUVertBuf *GPU_vertbuf_create(GPUUsageType usage)
{
  GPUVertBuf *verts = MEM_mallocN(sizeof(GPUVertBuf), "GPUVertBuf");
  GPU_vertbuf_init(verts, usage);
  return verts;
}

GPUVertBuf *GPU_vertbuf_create_with_format_ex(const GPUVertFormat *format, GPUUsageType usage)
{
  GPUVertBuf *verts = GPU_vertbuf_create(usage);
  GPU_vertformat_copy(&verts->format, format);
  if (!format->packed) {
    VertexFormat_pack(&verts->format);
  }
  return verts;

  /* this function might seem redundant, but there is potential for memory savings here... */
  /* TODO: implement those memory savings */
}

void GPU_vertbuf_init(GPUVertBuf *verts, GPUUsageType usage)
{
  memset(verts, 0, sizeof(GPUVertBuf));
  verts->usage = usage;
  verts->dirty = true;
}

void GPU_vertbuf_init_with_format_ex(GPUVertBuf *verts,
                                     const GPUVertFormat *format,
                                     GPUUsageType usage)
{
  GPU_vertbuf_init(verts, usage);
  GPU_vertformat_copy(&verts->format, format);
  if (!format->packed) {
    VertexFormat_pack(&verts->format);
  }
}

/** Same as discard but does not free. */
void GPU_vertbuf_clear(GPUVertBuf *verts)
{
  if (verts->vbo_id) {
    GPU_buf_free(verts->vbo_id);
    verts->vbo_id = 0;
#if VRAM_USAGE
    vbo_memory_usage -= GPU_vertbuf_size_get(verts);
#endif
  }
  if (verts->data) {
    MEM_SAFE_FREE(verts->data);
  }
}

void GPU_vertbuf_discard(GPUVertBuf *verts)
{
  GPU_vertbuf_clear(verts);
  MEM_freeN(verts);
}

uint GPU_vertbuf_size_get(const GPUVertBuf *verts)
{
  return vertex_buffer_size(&verts->format, verts->vertex_len);
}

/* create a new allocation, discarding any existing data */
void GPU_vertbuf_data_alloc(GPUVertBuf *verts, uint v_len)
{
  GPUVertFormat *format = &verts->format;
  if (!format->packed) {
    VertexFormat_pack(format);
  }
#if TRUST_NO_ONE
  /* catch any unnecessary use */
  assert(verts->vertex_alloc != v_len || verts->data == NULL);
#endif
  /* discard previous data if any */
  if (verts->data) {
    MEM_freeN(verts->data);
  }
#if VRAM_USAGE
  uint new_size = vertex_buffer_size(&verts->format, v_len);
  vbo_memory_usage += new_size - GPU_vertbuf_size_get(verts);
#endif
  verts->dirty = true;
  verts->vertex_len = verts->vertex_alloc = v_len;
  verts->data = MEM_mallocN(sizeof(GLubyte) * GPU_vertbuf_size_get(verts), "GPUVertBuf data");
}

/* resize buffer keeping existing data */
void GPU_vertbuf_data_resize(GPUVertBuf *verts, uint v_len)
{
#if TRUST_NO_ONE
  assert(verts->data != NULL);
  assert(verts->vertex_alloc != v_len);
#endif

#if VRAM_USAGE
  uint new_size = vertex_buffer_size(&verts->format, v_len);
  vbo_memory_usage += new_size - GPU_vertbuf_size_get(verts);
#endif
  verts->dirty = true;
  verts->vertex_len = verts->vertex_alloc = v_len;
  verts->data = MEM_reallocN(verts->data, sizeof(GLubyte) * GPU_vertbuf_size_get(verts));
}

/* Set vertex count but does not change allocation.
 * Only this many verts will be uploaded to the GPU and rendered.
 * This is useful for streaming data. */
void GPU_vertbuf_data_len_set(GPUVertBuf *verts, uint v_len)
{
#if TRUST_NO_ONE
  assert(verts->data != NULL); /* only for dynamic data */
  assert(v_len <= verts->vertex_alloc);
#endif

#if VRAM_USAGE
  uint new_size = vertex_buffer_size(&verts->format, v_len);
  vbo_memory_usage += new_size - GPU_vertbuf_size_get(verts);
#endif
  verts->vertex_len = v_len;
}

void GPU_vertbuf_attr_set(GPUVertBuf *verts, uint a_idx, uint v_idx, const void *data)
{
  const GPUVertFormat *format = &verts->format;
  const GPUVertAttr *a = &format->attrs[a_idx];

#if TRUST_NO_ONE
  assert(a_idx < format->attr_len);
  assert(v_idx < verts->vertex_alloc);
  assert(verts->data != NULL);
#endif
  verts->dirty = true;
  memcpy((GLubyte *)verts->data + a->offset + v_idx * format->stride, data, a->sz);
}

void GPU_vertbuf_attr_fill(GPUVertBuf *verts, uint a_idx, const void *data)
{
  const GPUVertFormat *format = &verts->format;
  const GPUVertAttr *a = &format->attrs[a_idx];

#if TRUST_NO_ONE
  assert(a_idx < format->attr_len);
#endif
  const uint stride = a->sz; /* tightly packed input data */

  GPU_vertbuf_attr_fill_stride(verts, a_idx, stride, data);
}

/** Fills a whole vertex (all attributes). Data must match packed layout.  */
void GPU_vertbuf_vert_set(GPUVertBuf *verts, uint v_idx, const void *data)
{
  const GPUVertFormat *format = &verts->format;

#if TRUST_NO_ONE
  assert(v_idx < verts->vertex_alloc);
  assert(verts->data != NULL);
#endif
  verts->dirty = true;
  memcpy((GLubyte *)verts->data + v_idx * format->stride, data, format->stride);
}

void GPU_vertbuf_attr_fill_stride(GPUVertBuf *verts, uint a_idx, uint stride, const void *data)
{
  const GPUVertFormat *format = &verts->format;
  const GPUVertAttr *a = &format->attrs[a_idx];

#if TRUST_NO_ONE
  assert(a_idx < format->attr_len);
  assert(verts->data != NULL);
#endif
  verts->dirty = true;
  const uint vertex_len = verts->vertex_len;

  if (format->attr_len == 1 && stride == format->stride) {
    /* we can copy it all at once */
    memcpy(verts->data, data, vertex_len * a->sz);
  }
  else {
    /* we must copy it per vertex */
    for (uint v = 0; v < vertex_len; v++) {
      memcpy((GLubyte *)verts->data + a->offset + v * format->stride,
             (const GLubyte *)data + v * stride,
             a->sz);
    }
  }
}

void GPU_vertbuf_attr_get_raw_data(GPUVertBuf *verts, uint a_idx, GPUVertBufRaw *access)
{
  const GPUVertFormat *format = &verts->format;
  const GPUVertAttr *a = &format->attrs[a_idx];

#if TRUST_NO_ONE
  assert(a_idx < format->attr_len);
  assert(verts->data != NULL);
#endif

  verts->dirty = true;

  access->size = a->sz;
  access->stride = format->stride;
  access->data = (GLubyte *)verts->data + a->offset;
  access->data_init = access->data;
#if TRUST_NO_ONE
  access->_data_end = access->data_init + (size_t)(verts->vertex_alloc * format->stride);
#endif
}

static void VertBuffer_upload_data(GPUVertBuf *verts)
{
  uint buffer_sz = GPU_vertbuf_size_get(verts);

  /* orphan the vbo to avoid sync */
  glBufferData(GL_ARRAY_BUFFER, buffer_sz, NULL, convert_usage_type_to_gl(verts->usage));
  /* upload data */
  glBufferSubData(GL_ARRAY_BUFFER, 0, buffer_sz, verts->data);

  if (verts->usage == GPU_USAGE_STATIC) {
    MEM_freeN(verts->data);
    verts->data = NULL;
  }
  verts->dirty = false;
}

void GPU_vertbuf_use(GPUVertBuf *verts)
{
  /* only create the buffer the 1st time */
  if (verts->vbo_id == 0) {
    verts->vbo_id = GPU_buf_alloc();
  }
  glBindBuffer(GL_ARRAY_BUFFER, verts->vbo_id);
  if (verts->dirty) {
    VertBuffer_upload_data(verts);
  }
}

uint GPU_vertbuf_get_memory_usage(void)
{
  return vbo_memory_usage;
}