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

#include <memory>

#include "Common/Assert.h"
#include "Common/GL/GLInterfaceBase.h"
#include "Common/GL/GLUtil.h"
#include "Common/Logging/Log.h"

std::unique_ptr<cInterfaceBase> GLInterface;
static GLuint attributelessVAO = 0;
static GLuint attributelessVBO = 0;

void InitInterface()
{
  GLInterface = HostGL_CreateGLInterface();
}

GLuint OpenGL_CompileProgram(const std::string& vertexShader, const std::string& fragmentShader)
{
  // generate objects
  GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
  GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
  GLuint programID = glCreateProgram();

  // compile vertex shader
  const char* shader = vertexShader.c_str();
  glShaderSource(vertexShaderID, 1, &shader, nullptr);
  glCompileShader(vertexShaderID);
#if defined(_DEBUG) || defined(DEBUGFAST) || defined(DEBUG_GLSL)
  GLint Result = GL_FALSE;
  char stringBuffer[1024];
  GLsizei stringBufferUsage = 0;
  glGetShaderiv(vertexShaderID, GL_COMPILE_STATUS, &Result);
  glGetShaderInfoLog(vertexShaderID, 1024, &stringBufferUsage, stringBuffer);

  if (Result && stringBufferUsage)
  {
    ERROR_LOG(VIDEO, "GLSL vertex shader warnings:\n%s%s", stringBuffer, vertexShader.c_str());
  }
  else if (!Result)
  {
    ERROR_LOG(VIDEO, "GLSL vertex shader error:\n%s%s", stringBuffer, vertexShader.c_str());
  }
  else
  {
    DEBUG_LOG(VIDEO, "GLSL vertex shader compiled:\n%s", vertexShader.c_str());
  }

  bool shader_errors = !Result;
#endif

  // compile fragment shader
  shader = fragmentShader.c_str();
  glShaderSource(fragmentShaderID, 1, &shader, nullptr);
  glCompileShader(fragmentShaderID);
#if defined(_DEBUG) || defined(DEBUGFAST) || defined(DEBUG_GLSL)
  glGetShaderiv(fragmentShaderID, GL_COMPILE_STATUS, &Result);
  glGetShaderInfoLog(fragmentShaderID, 1024, &stringBufferUsage, stringBuffer);

  if (Result && stringBufferUsage)
  {
    ERROR_LOG(VIDEO, "GLSL fragment shader warnings:\n%s%s", stringBuffer, fragmentShader.c_str());
  }
  else if (!Result)
  {
    ERROR_LOG(VIDEO, "GLSL fragment shader error:\n%s%s", stringBuffer, fragmentShader.c_str());
  }
  else
  {
    DEBUG_LOG(VIDEO, "GLSL fragment shader compiled:\n%s", fragmentShader.c_str());
  }

  shader_errors |= !Result;
#endif

  // link them
  glAttachShader(programID, vertexShaderID);
  glAttachShader(programID, fragmentShaderID);
  glLinkProgram(programID);
#if defined(_DEBUG) || defined(DEBUGFAST) || defined(DEBUG_GLSL)
  glGetProgramiv(programID, GL_LINK_STATUS, &Result);
  glGetProgramInfoLog(programID, 1024, &stringBufferUsage, stringBuffer);

  if (Result && stringBufferUsage)
  {
    ERROR_LOG(VIDEO, "GLSL linker warnings:\n%s%s%s", stringBuffer, vertexShader.c_str(),
              fragmentShader.c_str());
  }
  else if (!Result && !shader_errors)
  {
    ERROR_LOG(VIDEO, "GLSL linker error:\n%s%s%s", stringBuffer, vertexShader.c_str(),
              fragmentShader.c_str());
  }
#endif

  // cleanup
  glDeleteShader(vertexShaderID);
  glDeleteShader(fragmentShaderID);

  return programID;
}

void OpenGL_CreateAttributelessVAO()
{
  glGenVertexArrays(1, &attributelessVAO);
  _dbg_assert_msg_(VIDEO, attributelessVAO != 0,
                   "Attributeless VAO should have been created successfully.")

      // In a compatibility context, we require a valid, bound array buffer.
      glGenBuffers(1, &attributelessVBO);
  _dbg_assert_msg_(VIDEO, attributelessVBO != 0,
                   "Attributeless VBO should have been created successfully.")

      // Initialize the buffer with nothing.  16 floats is an arbitrary size that may work around
      // driver issues.
      glBindBuffer(GL_ARRAY_BUFFER, attributelessVBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 16, nullptr, GL_STATIC_DRAW);

  // We must also define vertex attribute 0.
  glBindVertexArray(attributelessVAO);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, nullptr);
  glEnableVertexAttribArray(0);
}

void OpenGL_BindAttributelessVAO()
{
  _dbg_assert_msg_(VIDEO, attributelessVAO != 0,
                   "Attributeless VAO should have already been created.")
      glBindVertexArray(attributelessVAO);
}

void OpenGL_DeleteAttributelessVAO()
{
  _dbg_assert_msg_(VIDEO, attributelessVAO != 0,
                   "Attributeless VAO should have already been created.") if (attributelessVAO != 0)
  {
    glDeleteVertexArrays(1, &attributelessVAO);
    glDeleteBuffers(1, &attributelessVBO);

    attributelessVAO = 0;
    attributelessVBO = 0;
  }
}