/*
 * 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) 2020 Blender Foundation.
 * All rights reserved.
 */

/** \file
 * \ingroup gpu
 *
 * GPU Framebuffer
 * - this is a wrapper for an OpenGL framebuffer object (FBO). in practice
 *   multiple FBO's may be created.
 * - actual FBO creation & config is deferred until GPU_framebuffer_bind or
 *   GPU_framebuffer_check_valid to allow creation & config while another
 *   opengl context is bound (since FBOs are not shared between ogl contexts).
 */

#pragma once

#include "BLI_math_vector.h"
#include "BLI_span.hh"

#include "MEM_guardedalloc.h"

#include "GPU_framebuffer.h"

struct GPUTexture;

typedef enum GPUAttachmentType : int {
  GPU_FB_DEPTH_ATTACHMENT = 0,
  GPU_FB_DEPTH_STENCIL_ATTACHMENT,
  GPU_FB_COLOR_ATTACHMENT0,
  GPU_FB_COLOR_ATTACHMENT1,
  GPU_FB_COLOR_ATTACHMENT2,
  GPU_FB_COLOR_ATTACHMENT3,
  GPU_FB_COLOR_ATTACHMENT4,
  GPU_FB_COLOR_ATTACHMENT5,
  /* Number of maximum output slots.
   * We support 6 outputs for now (usually we wouldn't need more to preserve fill rate). */
  /* Keep in mind that GL max is GL_MAX_DRAW_BUFFERS and is at least 8, corresponding to
   * the maximum number of COLOR attachments specified by glDrawBuffers. */
  GPU_FB_MAX_ATTACHMENT,

} GPUAttachmentType;

#define GPU_FB_MAX_COLOR_ATTACHMENT (GPU_FB_MAX_ATTACHMENT - GPU_FB_COLOR_ATTACHMENT0)

inline constexpr GPUAttachmentType operator-(GPUAttachmentType a, int b)
{
  return static_cast<GPUAttachmentType>(static_cast<int>(a) - b);
}

inline constexpr GPUAttachmentType operator+(GPUAttachmentType a, int b)
{
  return static_cast<GPUAttachmentType>(static_cast<int>(a) + b);
}

inline GPUAttachmentType &operator++(GPUAttachmentType &a)
{
  a = a + 1;
  return a;
}

inline GPUAttachmentType &operator--(GPUAttachmentType &a)
{
  a = a - 1;
  return a;
}

namespace blender {
namespace gpu {

#ifdef DEBUG
#  define DEBUG_NAME_LEN 64
#else
#  define DEBUG_NAME_LEN 16
#endif

class FrameBuffer {
 protected:
  /** Set of texture attachments to render to. DEPTH and DEPTH_STENCIL are mutually exclusive. */
  GPUAttachment attachments_[GPU_FB_MAX_ATTACHMENT];
  /** Is true if internal representation need to be updated. */
  bool dirty_attachments_;
  /** Size of attachment textures. */
  int width_, height_;
  /** Debug name. */
  char name_[DEBUG_NAME_LEN];
  /** Frame-buffer state. */
  int viewport_[4] = {0};
  int scissor_[4] = {0};
  bool scissor_test_ = false;
  bool dirty_state_ = true;

 public:
  FrameBuffer(const char *name);
  virtual ~FrameBuffer();

  virtual void bind(bool enabled_srgb) = 0;
  virtual bool check(char err_out[256]) = 0;
  virtual void clear(eGPUFrameBufferBits buffers,
                     const float clear_col[4],
                     float clear_depth,
                     uint clear_stencil) = 0;
  virtual void clear_multi(const float (*clear_col)[4]) = 0;
  virtual void clear_attachment(GPUAttachmentType type,
                                eGPUDataFormat data_format,
                                const void *clear_value) = 0;

  virtual void read(eGPUFrameBufferBits planes,
                    eGPUDataFormat format,
                    const int area[4],
                    int channel_len,
                    int slot,
                    void *r_data) = 0;

  virtual void blit_to(eGPUFrameBufferBits planes,
                       int src_slot,
                       FrameBuffer *dst,
                       int dst_slot,
                       int dst_offset_x,
                       int dst_offset_y) = 0;

  void attachment_set(GPUAttachmentType type, const GPUAttachment &new_attachment);
  void attachment_remove(GPUAttachmentType type);

  void recursive_downsample(int max_lvl,
                            void (*callback)(void *userData, int level),
                            void *userData);

  inline void size_set(int width, int height)
  {
    width_ = width;
    height_ = height;
    dirty_state_ = true;
  }

  inline void viewport_set(const int viewport[4])
  {
    if (!equals_v4v4_int(viewport_, viewport)) {
      copy_v4_v4_int(viewport_, viewport);
      dirty_state_ = true;
    }
  }

  inline void scissor_set(const int scissor[4])
  {
    if (!equals_v4v4_int(scissor_, scissor)) {
      copy_v4_v4_int(scissor_, scissor);
      dirty_state_ = true;
    }
  }

  inline void scissor_test_set(bool test)
  {
    scissor_test_ = test;
  }

  inline void viewport_get(int r_viewport[4]) const
  {
    copy_v4_v4_int(r_viewport, viewport_);
  }

  inline void scissor_get(int r_scissor[4]) const
  {
    copy_v4_v4_int(r_scissor, scissor_);
  }

  inline bool scissor_test_get(void) const
  {
    return scissor_test_;
  }

  inline void viewport_reset(void)
  {
    int viewport_rect[4] = {0, 0, width_, height_};
    viewport_set(viewport_rect);
  }

  inline void scissor_reset(void)
  {
    int scissor_rect[4] = {0, 0, width_, height_};
    scissor_set(scissor_rect);
  }

  inline GPUTexture *depth_tex(void) const
  {
    if (attachments_[GPU_FB_DEPTH_ATTACHMENT].tex) {
      return attachments_[GPU_FB_DEPTH_ATTACHMENT].tex;
    }
    return attachments_[GPU_FB_DEPTH_STENCIL_ATTACHMENT].tex;
  };

  inline GPUTexture *color_tex(int slot) const
  {
    return attachments_[GPU_FB_COLOR_ATTACHMENT0 + slot].tex;
  };
};

/* Syntacting suggar. */
static inline GPUFrameBuffer *wrap(FrameBuffer *vert)
{
  return reinterpret_cast<GPUFrameBuffer *>(vert);
}
static inline FrameBuffer *unwrap(GPUFrameBuffer *vert)
{
  return reinterpret_cast<FrameBuffer *>(vert);
}
static inline const FrameBuffer *unwrap(const GPUFrameBuffer *vert)
{
  return reinterpret_cast<const FrameBuffer *>(vert);
}

#undef DEBUG_NAME_LEN

}  // namespace gpu
}  // namespace blender