/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2014 Intel Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see
 * <http://www.gnu.org/licenses/>.
 *
 *
 */

#include <config.h>

#include "cogl-types.h"
#include "cogl-context-private.h"
#include "cogl-framebuffer-private.h"
#include "cogl-framebuffer-deprecated.h"

typedef struct _CoglFramebufferStackEntry
{
  CoglFramebuffer *draw_buffer;
  CoglFramebuffer *read_buffer;
} CoglFramebufferStackEntry;


static CoglFramebufferStackEntry *
create_stack_entry (CoglFramebuffer *draw_buffer,
                    CoglFramebuffer *read_buffer)
{
  CoglFramebufferStackEntry *entry = g_slice_new (CoglFramebufferStackEntry);

  entry->draw_buffer = draw_buffer;
  entry->read_buffer = read_buffer;

  return entry;
}

GSList *
_cogl_create_framebuffer_stack (void)
{
  CoglFramebufferStackEntry *entry;
  GSList *stack = NULL;

  entry = create_stack_entry (NULL, NULL);

  return g_slist_prepend (stack, entry);
}

void
_cogl_free_framebuffer_stack (GSList *stack)
{
  GSList *l;

  for (l = stack; l != NULL; l = l->next)
    {
      CoglFramebufferStackEntry *entry = l->data;

      if (entry->draw_buffer)
        cogl_object_unref (entry->draw_buffer);

      if (entry->read_buffer)
        cogl_object_unref (entry->draw_buffer);

      g_slice_free (CoglFramebufferStackEntry, entry);
    }
  g_slist_free (stack);
}

static void
notify_buffers_changed (CoglFramebuffer *old_draw_buffer,
                        CoglFramebuffer *new_draw_buffer,
                        CoglFramebuffer *old_read_buffer,
                        CoglFramebuffer *new_read_buffer)
{
  /* XXX: To support the deprecated cogl_set_draw_buffer API we keep
   * track of the last onscreen framebuffer that was set so that it
   * can be restored if the COGL_WINDOW_BUFFER enum is used. A
   * reference isn't taken to the framebuffer because otherwise we
   * would have a circular reference between the context and the
   * framebuffer. Instead the pointer is set to NULL in
   * _cogl_onscreen_free as a kind of a cheap weak reference */
  if (new_draw_buffer &&
      new_draw_buffer->type == COGL_FRAMEBUFFER_TYPE_ONSCREEN)
    new_draw_buffer->context->window_buffer = new_draw_buffer;
}

/* Set the current framebuffer without checking if it's already the
 * current framebuffer. This is used by cogl_pop_framebuffer while
 * the top of the stack is currently not up to date. */
static void
_cogl_set_framebuffers_real (CoglFramebuffer *draw_buffer,
                             CoglFramebuffer *read_buffer)
{
  CoglFramebufferStackEntry *entry;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  _COGL_RETURN_IF_FAIL (ctx != NULL);
  _COGL_RETURN_IF_FAIL (draw_buffer && read_buffer ?
                    draw_buffer->context == read_buffer->context : TRUE);

  entry = ctx->framebuffer_stack->data;

  notify_buffers_changed (entry->draw_buffer,
                          draw_buffer,
                          entry->read_buffer,
                          read_buffer);

  if (draw_buffer)
    cogl_object_ref (draw_buffer);
  if (entry->draw_buffer)
    cogl_object_unref (entry->draw_buffer);

  if (read_buffer)
    cogl_object_ref (read_buffer);
  if (entry->read_buffer)
    cogl_object_unref (entry->read_buffer);

  entry->draw_buffer = draw_buffer;
  entry->read_buffer = read_buffer;
}

static void
_cogl_set_framebuffers (CoglFramebuffer *draw_buffer,
                        CoglFramebuffer *read_buffer)
{
  CoglFramebuffer *current_draw_buffer;
  CoglFramebuffer *current_read_buffer;

  _COGL_RETURN_IF_FAIL (cogl_is_framebuffer (draw_buffer));
  _COGL_RETURN_IF_FAIL (cogl_is_framebuffer (read_buffer));

  current_draw_buffer = cogl_get_draw_framebuffer ();
  current_read_buffer = _cogl_get_read_framebuffer ();

  if (current_draw_buffer != draw_buffer ||
      current_read_buffer != read_buffer)
    _cogl_set_framebuffers_real (draw_buffer, read_buffer);
}

void
cogl_set_framebuffer (CoglFramebuffer *framebuffer)
{
  _cogl_set_framebuffers (framebuffer, framebuffer);
}

/* XXX: deprecated API */
void
cogl_set_draw_buffer (CoglBufferTarget target, CoglHandle handle)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  if (target == COGL_WINDOW_BUFFER)
    handle = ctx->window_buffer;

  /* This is deprecated public API. The public API doesn't currently
     really expose the concept of separate draw and read buffers so
     for the time being this actually just sets both buffers */
  cogl_set_framebuffer (handle);
}

CoglFramebuffer *
cogl_get_draw_framebuffer (void)
{
  CoglFramebufferStackEntry *entry;

  _COGL_GET_CONTEXT (ctx, NULL);

  g_assert (ctx->framebuffer_stack);

  entry = ctx->framebuffer_stack->data;

  return entry->draw_buffer;
}

CoglFramebuffer *
_cogl_get_read_framebuffer (void)
{
  CoglFramebufferStackEntry *entry;

  _COGL_GET_CONTEXT (ctx, NULL);

  g_assert (ctx->framebuffer_stack);

  entry = ctx->framebuffer_stack->data;

  return entry->read_buffer;
}

void
_cogl_push_framebuffers (CoglFramebuffer *draw_buffer,
                         CoglFramebuffer *read_buffer)
{
  CoglContext *ctx;
  CoglFramebuffer *old_draw_buffer, *old_read_buffer;

  _COGL_RETURN_IF_FAIL (cogl_is_framebuffer (draw_buffer));
  _COGL_RETURN_IF_FAIL (cogl_is_framebuffer (read_buffer));

  ctx = draw_buffer->context;
  _COGL_RETURN_IF_FAIL (ctx != NULL);
  _COGL_RETURN_IF_FAIL (draw_buffer->context == read_buffer->context);

  _COGL_RETURN_IF_FAIL (ctx->framebuffer_stack != NULL);

  /* Copy the top of the stack so that when we call cogl_set_framebuffer
     it will still know what the old framebuffer was */
  old_draw_buffer = cogl_get_draw_framebuffer ();
  if (old_draw_buffer)
    cogl_object_ref (old_draw_buffer);
  old_read_buffer = _cogl_get_read_framebuffer ();
  if (old_read_buffer)
    cogl_object_ref (old_read_buffer);
  ctx->framebuffer_stack =
    g_slist_prepend (ctx->framebuffer_stack,
                     create_stack_entry (old_draw_buffer,
                                         old_read_buffer));

  _cogl_set_framebuffers (draw_buffer, read_buffer);
}

void
cogl_push_framebuffer (CoglFramebuffer *buffer)
{
  _cogl_push_framebuffers (buffer, buffer);
}

/* XXX: deprecated API */
void
cogl_push_draw_buffer (void)
{
  cogl_push_framebuffer (cogl_get_draw_framebuffer ());
}

void
cogl_pop_framebuffer (void)
{
  CoglFramebufferStackEntry *to_pop;
  CoglFramebufferStackEntry *to_restore;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  g_assert (ctx->framebuffer_stack != NULL);
  g_assert (ctx->framebuffer_stack->next != NULL);

  to_pop = ctx->framebuffer_stack->data;
  to_restore = ctx->framebuffer_stack->next->data;

  if (to_pop->draw_buffer != to_restore->draw_buffer ||
      to_pop->read_buffer != to_restore->read_buffer)
    notify_buffers_changed (to_pop->draw_buffer,
                            to_restore->draw_buffer,
                            to_pop->read_buffer,
                            to_restore->read_buffer);

  cogl_object_unref (to_pop->draw_buffer);
  cogl_object_unref (to_pop->read_buffer);
  g_slice_free (CoglFramebufferStackEntry, to_pop);

  ctx->framebuffer_stack =
    g_slist_delete_link (ctx->framebuffer_stack,
                         ctx->framebuffer_stack);
}

/* XXX: deprecated API */
void
cogl_pop_draw_buffer (void)
{
  cogl_pop_framebuffer ();
}

CoglPixelFormat
cogl_framebuffer_get_color_format (CoglFramebuffer *framebuffer)
{
  return framebuffer->internal_format;
}