#include "say.h"

static void say_pack_pbo_make_current(GLuint pbo) {
  say_context *context = say_context_current();

  if (context->pack_pbo != pbo) {
    glBindBuffer(GL_PIXEL_PACK_BUFFER, pbo);
    context->pack_pbo = pbo;
  }
}

static void say_unpack_pbo_make_current(GLuint pbo) {
  say_context *context = say_context_current();

  if (context->unpack_pbo != pbo) {
    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pbo);
    context->unpack_pbo = pbo;
  }
}

static void say_pbo_will_delete(GLuint pbo) {
  mo_array *contexts = say_context_get_all();
  for (size_t i = 0; i < contexts->size; i++) {
    say_context *context = mo_array_get_as(contexts, i, say_context*);

    if (context->pack_pbo   == pbo) context->pack_pbo   = 0;
    if (context->unpack_pbo == pbo) context->unpack_pbo = 0;
  }
}

bool say_pixel_bus_is_available() {
  say_context_ensure();
  return GLEW_ARB_pixel_buffer_object ||
    GLEW_VERSION_2_1;
}

say_pixel_bus *say_pixel_bus_create(GLenum mode) {
  say_context_ensure();

  say_pixel_bus *bus = malloc(sizeof(say_pixel_bus));

  glGenBuffers(1, &bus->pbo);

  bus->size = 1024;
  bus->mode = mode;

  say_pixel_bus_bind_pack(bus);
  glBufferData(GL_PIXEL_PACK_BUFFER, 1024 * sizeof(say_color), NULL,
               mode);

  return bus;
}

void say_pixel_bus_free(say_pixel_bus *bus) {
  say_context_ensure();
  say_pbo_will_delete(bus->pbo);
  glDeleteBuffers(1, &bus->pbo);
  free(bus);
}

size_t say_pixel_bus_pull_image(say_pixel_bus *bus,
                                say_image *img, size_t offset) {
  say_image_bind(img);
  say_pixel_bus_bind_pack(bus);

  glGetTexImage(GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                (void*)(offset * sizeof(say_color)));
  return offset + say_image_get_width(img) * say_image_get_height(img);
}

size_t say_pixel_bus_pull_target(say_pixel_bus *bus,
                                 say_target *target, size_t offset,
                                 size_t x, size_t y, size_t w, size_t h) {
  if (!say_target_make_current(target))
    return offset + w * h;

  say_pixel_bus_bind_pack(bus);

  glReadPixels(x, target->size.y - y - h, w, h, GL_RGBA,
               GL_UNSIGNED_BYTE, (void*)(offset * sizeof(say_color)));
  return offset + w * h;
}

void say_pixel_bus_push_image(say_pixel_bus *bus,
                                say_image *img, size_t offset,
                                size_t x, size_t y, size_t w, size_t h) {
  say_image_bind(img);
  say_pixel_bus_bind_unpack(bus);

  glTexSubImage2D(GL_TEXTURE_2D, 0,
                  x, y, w, h,
                  GL_RGBA, GL_UNSIGNED_BYTE,
                  (void*)(offset * sizeof(say_color)));
  say_image_mark_out_of_date(img);
}

void say_pixel_bus_bind_pack(say_pixel_bus *bus) {
  say_context_ensure();
  say_pack_pbo_make_current(bus->pbo);
}

void say_pixel_bus_bind_unpack(say_pixel_bus *bus) {
  say_context_ensure();
  say_unpack_pbo_make_current(bus->pbo);
}

void say_pixel_bus_unbind_pack() {
  if (say_pixel_bus_is_available()) say_pack_pbo_make_current(0);
}

void say_pixel_bus_unbind_unpack() {
  if (say_pixel_bus_is_available()) say_unpack_pbo_make_current(0);
}

void say_pixel_bus_bind(say_pixel_bus *bus) {
  say_pixel_bus_bind_pack(bus);
  say_pixel_bus_bind_unpack(bus);
}

void say_pixel_bus_unbind() {
  say_pixel_bus_unbind_pack();
  say_pixel_bus_unbind_unpack();
}

void say_pixel_bus_resize(say_pixel_bus *bus, size_t new_size) {
  /* This is slow, so better not go through this for no reason. */
  if (bus->size == new_size) return;

  say_pixel_bus_bind_pack(bus);

  void *buffer = malloc(sizeof(say_color) * new_size);
  size_t copied_size = new_size > bus->size ? bus->size : new_size;
  glGetBufferSubData(GL_PIXEL_PACK_BUFFER, 0, copied_size * sizeof(say_color),
                     buffer);

  glBufferData(GL_PIXEL_PACK_BUFFER, new_size * sizeof(say_color),
               buffer, bus->mode);

  free(buffer);

  bus->size = new_size;
}

void say_pixel_bus_resize_fast(say_pixel_bus *bus, size_t new_size) {
  if (bus->size == new_size) return;

  say_pixel_bus_bind_pack(bus);
  glBufferData(GL_PIXEL_PACK_BUFFER, new_size * sizeof(say_color), NULL,
               bus->mode);

  bus->size = new_size;
}

size_t say_pixel_bus_get_size(say_pixel_bus *bus) {
  return bus->size;
}

GLuint say_pixel_bus_get_pbo(say_pixel_bus *bus) {
  return bus->pbo;
}