// Copyright 2008 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

// Fast image conversion using OpenGL shaders.

#include "VideoBackends/OGL/TextureConverter.h"

#include <string>

#include "Common/CommonTypes.h"
#include "Common/FileUtil.h"
#include "Common/Logging/Log.h"
#include "Common/MsgHandler.h"
#include "Common/StringUtil.h"

#include "Core/HW/Memmap.h"

#include "VideoBackends/OGL/FramebufferManager.h"
#include "VideoBackends/OGL/ProgramShaderCache.h"
#include "VideoBackends/OGL/Render.h"
#include "VideoBackends/OGL/SamplerCache.h"
#include "VideoBackends/OGL/TextureCache.h"

#include "VideoCommon/ImageWrite.h"
#include "VideoCommon/TextureConversionShader.h"
#include "VideoCommon/VideoCommon.h"
#include "VideoCommon/VideoConfig.h"

namespace OGL
{
namespace TextureConverter
{
using OGL::TextureCache;

static GLuint s_texConvFrameBuffer[2] = {0, 0};
static GLuint s_srcTexture = 0;  // for decoding from RAM
static GLuint s_dstTexture = 0;  // for encoding to RAM

const int renderBufferWidth = EFB_WIDTH * 4;
const int renderBufferHeight = 1024;

static SHADER s_rgbToYuyvProgram;
static int s_rgbToYuyvUniform_loc;

static SHADER s_yuyvToRgbProgram;

struct EncodingProgram
{
  SHADER program;
  GLint copy_position_uniform;
};
static std::map<EFBCopyFormat, EncodingProgram> s_encoding_programs;

static GLuint s_PBO = 0;  // for readback with different strides

static void CreatePrograms()
{
  /* TODO: Accuracy Improvements
   *
   * This shader doesn't really match what the GameCube does internally in the
   * copy pipeline.
   *  1. It uses OpenGL's built in filtering when yscaling, someone could work
   *     out how the copypipeline does it's filtering and implement it correctly
   *     in this shader.
   *  2. Deflickering isn't implemented, a futher filtering over 3 lines.
   *     Isn't really needed on non-interlaced monitors (and would lower quality;
   *     But hey, accuracy!)
   *  3. Flipper's YUYV conversion implements a 3 pixel horizontal blur on the
   *     UV channels, centering the U channel on the Left pixel and the V channel
   *     on the Right pixel.
   *     The current implementation Centers both UV channels at the same place
   *     inbetween the two Pixels, and only blurs over these two pixels.
   */
  // Output is BGRA because that is slightly faster than RGBA.
  const char* VProgramRgbToYuyv =
      "out vec2 uv0;\n"
      "uniform vec4 copy_position;\n"  // left, top, right, bottom
      "SAMPLER_BINDING(9) uniform sampler2DArray samp9;\n"
      "void main()\n"
      "{\n"
      "	vec2 rawpos = vec2(gl_VertexID&1, gl_VertexID&2);\n"
      "	gl_Position = vec4(rawpos*2.0-1.0, 0.0, 1.0);\n"
      "	uv0 = mix(copy_position.xy, copy_position.zw, rawpos) / vec2(textureSize(samp9, 0).xy);\n"
      "}\n";
  const char* FProgramRgbToYuyv =
      "SAMPLER_BINDING(9) uniform sampler2DArray samp9;\n"
      "in vec2 uv0;\n"
      "out vec4 ocol0;\n"
      "void main()\n"
      "{\n"
      "	vec3 c0 = texture(samp9, vec3(uv0 - dFdx(uv0) * 0.25, 0.0)).rgb;\n"
      "	vec3 c1 = texture(samp9, vec3(uv0 + dFdx(uv0) * 0.25, 0.0)).rgb;\n"
      "	vec3 c01 = (c0 + c1) * 0.5;\n"
      "	vec3 y_const = vec3(0.257,0.504,0.098);\n"
      "	vec3 u_const = vec3(-0.148,-0.291,0.439);\n"
      "	vec3 v_const = vec3(0.439,-0.368,-0.071);\n"
      "	vec4 const3 = vec4(0.0625,0.5,0.0625,0.5);\n"
      "	ocol0 = vec4(dot(c1,y_const),dot(c01,u_const),dot(c0,y_const),dot(c01, v_const)) + "
      "const3;\n"
      "}\n";
  ProgramShaderCache::CompileShader(s_rgbToYuyvProgram, VProgramRgbToYuyv, FProgramRgbToYuyv);
  s_rgbToYuyvUniform_loc = glGetUniformLocation(s_rgbToYuyvProgram.glprogid, "copy_position");

  /* TODO: Accuracy Improvements
   *
   * The YVYU to RGB conversion here matches the RGB to YUYV done above, but
   * if a game modifies or adds images to the XFB then it should be using the
   * same algorithm as the flipper, and could result in slight color inaccuracies
   * when run back through this shader.
   */
  const char* VProgramYuyvToRgb = "void main()\n"
                                  "{\n"
                                  "	vec2 rawpos = vec2(gl_VertexID&1, gl_VertexID&2);\n"
                                  "	gl_Position = vec4(rawpos*2.0-1.0, 0.0, 1.0);\n"
                                  "}\n";
  const char* FProgramYuyvToRgb = "SAMPLER_BINDING(9) uniform sampler2D samp9;\n"
                                  "in vec2 uv0;\n"
                                  "out vec4 ocol0;\n"
                                  "void main()\n"
                                  "{\n"
                                  "	ivec2 uv = ivec2(gl_FragCoord.xy);\n"
                                  // We switch top/bottom here. TODO: move this to screen blit.
                                  "	ivec2 ts = textureSize(samp9, 0);\n"
                                  "	vec4 c0 = texelFetch(samp9, ivec2(uv.x>>1, ts.y-uv.y-1), 0);\n"
                                  "	float y = mix(c0.r, c0.b, (uv.x & 1) == 1);\n"
                                  "	float yComp = 1.164 * (y - 0.0625);\n"
                                  "	float uComp = c0.g - 0.5;\n"
                                  "	float vComp = c0.a - 0.5;\n"
                                  "	ocol0 = vec4(yComp + (1.596 * vComp),\n"
                                  "		yComp - (0.813 * vComp) - (0.391 * uComp),\n"
                                  "		yComp + (2.018 * uComp),\n"
                                  "		1.0);\n"
                                  "}\n";
  ProgramShaderCache::CompileShader(s_yuyvToRgbProgram, VProgramYuyvToRgb, FProgramYuyvToRgb);
}

static EncodingProgram& GetOrCreateEncodingShader(const EFBCopyFormat& format)
{
  auto iter = s_encoding_programs.find(format);
  if (iter != s_encoding_programs.end())
    return iter->second;

  const char* shader = TextureConversionShader::GenerateEncodingShader(format, APIType::OpenGL);

#if defined(_DEBUG) || defined(DEBUGFAST)
  if (g_ActiveConfig.iLog & CONF_SAVESHADERS && shader)
  {
    static int counter = 0;
    std::string filename =
        StringFromFormat("%senc_%04i.txt", File::GetUserPath(D_DUMP_IDX).c_str(), counter++);

    SaveData(filename, shader);
  }
#endif

  const char* VProgram = "void main()\n"
                         "{\n"
                         "	vec2 rawpos = vec2(gl_VertexID&1, gl_VertexID&2);\n"
                         "	gl_Position = vec4(rawpos*2.0-1.0, 0.0, 1.0);\n"
                         "}\n";

  EncodingProgram program;
  if (!ProgramShaderCache::CompileShader(program.program, VProgram, shader))
    PanicAlert("Failed to compile texture encoding shader.");

  program.copy_position_uniform = glGetUniformLocation(program.program.glprogid, "position");
  return s_encoding_programs.emplace(format, program).first->second;
}

void Init()
{
  glGenFramebuffers(2, s_texConvFrameBuffer);

  glActiveTexture(GL_TEXTURE9);
  glGenTextures(1, &s_srcTexture);
  glBindTexture(GL_TEXTURE_2D, s_srcTexture);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);

  glGenTextures(1, &s_dstTexture);
  glBindTexture(GL_TEXTURE_2D, s_dstTexture);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, renderBufferWidth, renderBufferHeight, 0, GL_RGBA,
               GL_UNSIGNED_BYTE, nullptr);

  FramebufferManager::SetFramebuffer(s_texConvFrameBuffer[0]);
  glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, s_dstTexture, 0);
  FramebufferManager::SetFramebuffer(0);

  glGenBuffers(1, &s_PBO);

  CreatePrograms();
}

void Shutdown()
{
  glDeleteTextures(1, &s_srcTexture);
  glDeleteTextures(1, &s_dstTexture);
  glDeleteBuffers(1, &s_PBO);
  glDeleteFramebuffers(2, s_texConvFrameBuffer);

  s_rgbToYuyvProgram.Destroy();
  s_yuyvToRgbProgram.Destroy();

  for (auto& program : s_encoding_programs)
    program.second.program.Destroy();
  s_encoding_programs.clear();

  s_srcTexture = 0;
  s_dstTexture = 0;
  s_PBO = 0;
  s_texConvFrameBuffer[0] = 0;
  s_texConvFrameBuffer[1] = 0;
}

// dst_line_size, writeStride in bytes

static void EncodeToRamUsingShader(GLuint srcTexture, u8* destAddr, u32 dst_line_size,
                                   u32 dstHeight, u32 writeStride, bool linearFilter)
{
  // switch to texture converter frame buffer
  // attach render buffer as color destination
  FramebufferManager::SetFramebuffer(s_texConvFrameBuffer[0]);

  OpenGL_BindAttributelessVAO();

  // set source texture
  glActiveTexture(GL_TEXTURE9);
  glBindTexture(GL_TEXTURE_2D_ARRAY, srcTexture);

  // We also linear filtering for both box filtering and downsampling higher resolutions to 1x
  // TODO: This only produces perfect downsampling for 1.5x and 2x IR, other resolution will
  //       need more complex down filtering to average all pixels and produce the correct result.
  // Also, box filtering won't be correct for anything other than 1x IR
  if (linearFilter || g_ActiveConfig.iEFBScale != SCALE_1X)
    g_sampler_cache->BindLinearSampler(9);
  else
    g_sampler_cache->BindNearestSampler(9);

  glViewport(0, 0, (GLsizei)(dst_line_size / 4), (GLsizei)dstHeight);

  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

  int dstSize = dst_line_size * dstHeight;

  // When the dst_line_size and writeStride are the same, we could use glReadPixels directly to RAM.
  // But instead we always copy the data via a PBO, because macOS inexplicably prefers this (most
  // noticeably in the Super Mario Sunshine transition).
  glBindBuffer(GL_PIXEL_PACK_BUFFER, s_PBO);
  glBufferData(GL_PIXEL_PACK_BUFFER, dstSize, nullptr, GL_STREAM_READ);
  glReadPixels(0, 0, (GLsizei)(dst_line_size / 4), (GLsizei)dstHeight, GL_BGRA, GL_UNSIGNED_BYTE,
               nullptr);
  u8* pbo = (u8*)glMapBufferRange(GL_PIXEL_PACK_BUFFER, 0, dstSize, GL_MAP_READ_BIT);

  if (dst_line_size == writeStride)
  {
    memcpy(destAddr, pbo, dst_line_size * dstHeight);
  }
  else
  {
    for (size_t i = 0; i < dstHeight; ++i)
    {
      memcpy(destAddr, pbo, dst_line_size);
      pbo += dst_line_size;
      destAddr += writeStride;
    }
  }

  glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
  glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
}

void EncodeToRamFromTexture(u8* dest_ptr, const EFBCopyFormat& format, u32 native_width,
                            u32 bytes_per_row, u32 num_blocks_y, u32 memory_stride,
                            bool is_depth_copy, const EFBRectangle& src_rect, bool scale_by_half)
{
  g_renderer->ResetAPIState();

  EncodingProgram& texconv_shader = GetOrCreateEncodingShader(format);

  texconv_shader.program.Bind();
  glUniform4i(texconv_shader.copy_position_uniform, src_rect.left, src_rect.top, native_width,
              scale_by_half ? 2 : 1);

  const GLuint read_texture = is_depth_copy ?
                                  FramebufferManager::ResolveAndGetDepthTarget(src_rect) :
                                  FramebufferManager::ResolveAndGetRenderTarget(src_rect);

  EncodeToRamUsingShader(read_texture, dest_ptr, bytes_per_row, num_blocks_y, memory_stride,
                         scale_by_half && !is_depth_copy);

  FramebufferManager::SetFramebuffer(0);
  g_renderer->RestoreAPIState();
}

void EncodeToRamYUYV(GLuint srcTexture, const TargetRectangle& sourceRc, u8* destAddr, u32 dstWidth,
                     u32 dstStride, u32 dstHeight)
{
  g_renderer->ResetAPIState();

  s_rgbToYuyvProgram.Bind();

  glUniform4f(s_rgbToYuyvUniform_loc, static_cast<float>(sourceRc.left),
              static_cast<float>(sourceRc.top), static_cast<float>(sourceRc.right),
              static_cast<float>(sourceRc.bottom));

  // We enable linear filtering, because the GameCube does filtering in the vertical direction when
  // yscale is enabled.
  // Otherwise we get jaggies when a game uses yscaling (most PAL games)
  EncodeToRamUsingShader(srcTexture, destAddr, dstWidth * 2, dstHeight, dstStride, true);
  FramebufferManager::SetFramebuffer(0);
  TextureCache::DisableStage(0);
  g_renderer->RestoreAPIState();
}

// Should be scale free.
void DecodeToTexture(u32 xfbAddr, int srcWidth, int srcHeight, GLuint destTexture)
{
  u8* srcAddr = Memory::GetPointer(xfbAddr);
  if (!srcAddr)
  {
    WARN_LOG(VIDEO, "Tried to decode from invalid memory address");
    return;
  }

  g_renderer->ResetAPIState();  // reset any game specific settings

  OpenGL_BindAttributelessVAO();

  // switch to texture converter frame buffer
  // attach destTexture as color destination
  FramebufferManager::SetFramebuffer(s_texConvFrameBuffer[1]);
  FramebufferManager::FramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D_ARRAY,
                                         destTexture, 0);

  // activate source texture
  // set srcAddr as data for source texture
  glActiveTexture(GL_TEXTURE9);
  glBindTexture(GL_TEXTURE_2D, s_srcTexture);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, srcWidth / 2, srcHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE,
               srcAddr);
  g_sampler_cache->BindNearestSampler(9);

  glViewport(0, 0, srcWidth, srcHeight);
  s_yuyvToRgbProgram.Bind();

  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

  FramebufferManager::SetFramebuffer(0);

  g_renderer->RestoreAPIState();
}

}  // namespace

}  // namespace OGL
