/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2009,2010 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/>.
 *
 *
 *
 * Authors:
 *   Havoc Pennington <hp@pobox.com> for litl
 *   Robert Bragg <robert@linux.intel.com>
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "cogl.h"
#include "cogl-context-private.h"
#include "cogl-internal.h"
#include "cogl-matrix-stack.h"
#include "cogl-framebuffer-private.h"
#include "cogl-object-private.h"

typedef struct {
  CoglMatrix matrix;
  gboolean is_identity;
  /* count of pushes with no changes; when a change is
   * requested, we create a new state and decrement this
   */
  int push_count;
} CoglMatrixState;

/**
 * CoglMatrixStack:
 *
 * Stores a cogl-side matrix stack, which we use as a cache
 * so we can get the matrix efficiently when using indirect
 * rendering.
 */
struct _CoglMatrixStack
{
  CoglObject _parent;

  GArray *stack;

  /* which state does GL have, NULL if unknown */
  CoglMatrixState *flushed_state;
  gboolean flushed_identity;

  unsigned int age;
};

static void _cogl_matrix_stack_free (CoglMatrixStack *stack);

COGL_OBJECT_INTERNAL_DEFINE (MatrixStack, matrix_stack);

/* XXX: this doesn't initialize the matrix! */
static void
_cogl_matrix_state_init (CoglMatrixState *state)
{
  state->push_count = 0;
  state->is_identity = FALSE;
}

static CoglMatrixState *
_cogl_matrix_stack_top (CoglMatrixStack *stack)
{
  return &g_array_index (stack->stack, CoglMatrixState, stack->stack->len - 1);
}

/* XXX:
 * Operations like scale, translate, rotate etc need to have an
 * initialized state->matrix to work with, so they will pass
 * initialize = TRUE.
 *
 * _cogl_matrix_stack_load_identity and _cogl_matrix_stack_set on the
 * other hand don't so they will pass initialize = FALSE
 *
 * NB: Identity matrices are represented by setting
 * state->is_identity=TRUE in which case state->matrix will be
 * uninitialized.
 */
static CoglMatrixState *
_cogl_matrix_stack_top_mutable (CoglMatrixStack *stack,
                                gboolean initialize)
{
  CoglMatrixState *state;
  CoglMatrixState *new_top;

  state = _cogl_matrix_stack_top (stack);

  if (state->push_count == 0)
    {
      if (state->is_identity && initialize)
        cogl_matrix_init_identity (&state->matrix);
      return state;
    }

  state->push_count -= 1;

  g_array_set_size (stack->stack, stack->stack->len + 1);
  new_top = &g_array_index (stack->stack, CoglMatrixState,
                            stack->stack->len - 1);
  _cogl_matrix_state_init (new_top);

  if (initialize)
    {
      if (state->is_identity)
        cogl_matrix_init_identity (&new_top->matrix);
      else
        new_top->matrix = state->matrix;

      if (stack->flushed_state == state)
        stack->flushed_state = new_top;
    }

  return new_top;
}

CoglMatrixStack*
_cogl_matrix_stack_new (void)
{
  CoglMatrixStack *stack;
  CoglMatrixState *state;

  stack = g_slice_new0 (CoglMatrixStack);

  stack->stack = g_array_sized_new (FALSE, FALSE,
                                    sizeof (CoglMatrixState), 10);
  g_array_set_size (stack->stack, 1);
  state = &g_array_index (stack->stack, CoglMatrixState, 0);
  _cogl_matrix_state_init (state);
  state->is_identity = TRUE;

  stack->age = 0;

  return _cogl_matrix_stack_object_new (stack);
}

static void
_cogl_matrix_stack_free (CoglMatrixStack *stack)
{
  g_array_free (stack->stack, TRUE);
  g_slice_free (CoglMatrixStack, stack);
}

void
_cogl_matrix_stack_push (CoglMatrixStack *stack)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top (stack);

  /* we lazily create a new stack top if someone changes the matrix
   * while push_count > 0
   */
  state->push_count += 1;
}

void
_cogl_matrix_stack_pop (CoglMatrixStack *stack)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top (stack);

  if (state->push_count > 0)
    {
      state->push_count -= 1;
    }
  else
    {
      if (stack->stack->len == 1)
        {
          g_warning ("Too many matrix pops");
          return;
        }

      if (stack->flushed_state == state)
        {
          stack->flushed_state = NULL;
        }

      stack->age++;
      g_array_set_size (stack->stack, stack->stack->len - 1);
    }
}

void
_cogl_matrix_stack_load_identity (CoglMatrixStack *stack)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, FALSE);

  /* NB: Identity matrices are represented by setting
   * state->is_identity = TRUE and leaving state->matrix
   * uninitialized.
   *
   * This is done to optimize the heavy usage of
   * _cogl_matrix_stack_load_identity by the Cogl Journal.
   */
  if (!state->is_identity)
    {
      state->is_identity = TRUE;

      /* mark dirty */
      stack->flushed_state = NULL;
      stack->age++;
    }
}

void
_cogl_matrix_stack_scale (CoglMatrixStack *stack,
                          float            x,
                          float            y,
                          float            z)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_scale (&state->matrix, x, y, z);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

void
_cogl_matrix_stack_translate (CoglMatrixStack *stack,
                              float            x,
                              float            y,
                              float            z)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_translate (&state->matrix, x, y, z);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

void
_cogl_matrix_stack_rotate (CoglMatrixStack *stack,
                           float            angle,
                           float            x,
                           float            y,
                           float            z)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_rotate (&state->matrix, angle, x, y, z);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

void
_cogl_matrix_stack_multiply (CoglMatrixStack  *stack,
                             const CoglMatrix *matrix)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_multiply (&state->matrix, &state->matrix, matrix);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

void
_cogl_matrix_stack_frustum (CoglMatrixStack *stack,
                            float            left,
                            float            right,
                            float            bottom,
                            float            top,
                            float            z_near,
                            float            z_far)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_frustum (&state->matrix,
                       left, right, bottom, top,
                       z_near, z_far);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

void
_cogl_matrix_stack_perspective (CoglMatrixStack *stack,
                                float            fov_y,
                                float            aspect,
                                float            z_near,
                                float            z_far)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_perspective (&state->matrix,
                           fov_y, aspect, z_near, z_far);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

void
_cogl_matrix_stack_ortho (CoglMatrixStack *stack,
                          float            left,
                          float            right,
                          float            bottom,
                          float            top,
                          float            z_near,
                          float            z_far)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);
  cogl_matrix_ortho (&state->matrix,
                     left, right, bottom, top, z_near, z_far);
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

gboolean
_cogl_matrix_stack_get_inverse (CoglMatrixStack *stack,
                                CoglMatrix      *inverse)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, TRUE);

  return cogl_matrix_get_inverse (&state->matrix, inverse);
}

void
_cogl_matrix_stack_get (CoglMatrixStack *stack,
                        CoglMatrix      *matrix)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top (stack);

  /* NB: identity matrices are lazily initialized because we can often avoid
   * initializing them at all if nothing is pushed on top of them since we
   * load them using glLoadIdentity()
   *
   * The Cogl journal typically loads an identiy matrix because it performs
   * software transformations, which is why we have optimized this case.
   */
  if (state->is_identity)
    cogl_matrix_init_identity (matrix);
  else
    *matrix = state->matrix;
}

void
_cogl_matrix_stack_set (CoglMatrixStack  *stack,
                        const CoglMatrix *matrix)
{
  CoglMatrixState *state;

  state = _cogl_matrix_stack_top_mutable (stack, FALSE);
  state->matrix = *matrix;
  /* mark dirty */
  stack->flushed_state = NULL;
  state->is_identity = FALSE;
  stack->age++;
}

#ifndef HAVE_COGL_GLES2

static void
flush_to_fixed_api_gl (gboolean is_identity,
                       const CoglMatrix *matrix,
                       void *user_data)
{
  CoglMatrixStack *stack = user_data;

  if (is_identity)
    {
      if (!stack->flushed_identity)
        GE (glLoadIdentity ());
      stack->flushed_identity = TRUE;
    }
  else
    {
      GE (glLoadMatrixf (cogl_matrix_get_array (matrix)) );
      stack->flushed_identity = FALSE;
    }
}

#endif /* HAVE_COGL_GLES2 */

void
_cogl_matrix_stack_prepare_for_flush (CoglMatrixStack *stack,
                                      CoglMatrixMode mode,
                                      CoglMatrixStackFlushFunc callback,
                                      void *user_data)
{
  CoglMatrixState *state;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  state = _cogl_matrix_stack_top (stack);

  /* Because Cogl defines texture coordinates to have a top left origin and
   * because offscreen framebuffers may be used for rendering to textures we
   * always render upside down to offscreen buffers.
   */
  if (mode == COGL_MATRIX_PROJECTION &&
      cogl_is_offscreen (cogl_get_draw_framebuffer ()))
    {
      CoglMatrix flipped_projection;
      CoglMatrix *projection =
        state->is_identity ? &ctx->identity_matrix : &state->matrix;

      cogl_matrix_multiply (&flipped_projection,
                            &ctx->y_flip_matrix, projection);
      callback (FALSE, &flipped_projection, user_data);
    }
  else
    callback (state->is_identity,
              state->is_identity ? &ctx->identity_matrix : &state->matrix,
              user_data);
}

void
_cogl_matrix_stack_flush_to_gl (CoglMatrixStack *stack,
                                CoglMatrixMode   mode)
{
  CoglMatrixState *state;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  state = _cogl_matrix_stack_top (stack);

#ifdef HAVE_COGL_GLES2

  /* Under GLES2 we need to flush the matrices differently because
     they are stored in uniforms attached to the program instead of
     the global GL context state. At this point we can't be sure that
     the right program will be generated so instead we'll just store a
     reference to the matrix stack that is intended to be flushed and
     update the uniform once the program is ready. */

  switch (mode)
    {
    case COGL_MATRIX_MODELVIEW:
      cogl_object_ref (stack);
      if (ctx->flushed_modelview_stack)
        cogl_object_unref (ctx->flushed_modelview_stack);
      ctx->flushed_modelview_stack = stack;
      break;

    case COGL_MATRIX_PROJECTION:
      cogl_object_ref (stack);
      if (ctx->flushed_projection_stack)
        cogl_object_unref (ctx->flushed_projection_stack);
      ctx->flushed_projection_stack = stack;
      break;

    case COGL_MATRIX_TEXTURE:
      /* This shouldn't happen because the texture matrices are
         handled by the GLSL pipeline backend */
      g_assert_not_reached ();
      break;
    }

#else /* HAVE_COGL_GLES2 */

  if (stack->flushed_state == state)
    return;

  if (ctx->flushed_matrix_mode != mode)
    {
      GLenum gl_mode = 0;

      switch (mode)
        {
        case COGL_MATRIX_MODELVIEW:
          gl_mode = GL_MODELVIEW;
          break;

        case COGL_MATRIX_PROJECTION:
          gl_mode = GL_PROJECTION;
          break;

        case COGL_MATRIX_TEXTURE:
          gl_mode = GL_TEXTURE;
          break;
        }

      GE (glMatrixMode (gl_mode));
      ctx->flushed_matrix_mode = mode;
    }

  _cogl_matrix_stack_prepare_for_flush (stack,
                                        mode,
                                        flush_to_fixed_api_gl,
                                        stack);

#endif /* HAVE_COGL_GLES2 */

  stack->flushed_state = state;
}

void
_cogl_matrix_stack_dirty (CoglMatrixStack *stack)
{
  stack->flushed_state = NULL;
  stack->flushed_identity = FALSE;
}

unsigned int
_cogl_matrix_stack_get_age (CoglMatrixStack *stack)
{
  return stack->age;
}

gboolean
_cogl_matrix_stack_has_identity_flag (CoglMatrixStack *stack)
{
  return _cogl_matrix_stack_top (stack)->is_identity;
}