#include <scwx/qt/util/shader_program.hpp>

#include <QFile>
#include <QOpenGLFunctions_3_3_Core>

#include <boost/log/trivial.hpp>

namespace scwx
{
namespace qt
{

static const std::string logPrefix_ = "[scwx::qt::util::shader_program] ";

class ShaderProgramImpl
{
public:
   explicit ShaderProgramImpl() : gl_(), id_ {GL_INVALID_INDEX}
   {
      gl_.initializeOpenGLFunctions();

      // Create shader program
      id_ = gl_.glCreateProgram();
   }

   ~ShaderProgramImpl()
   {
      // Delete shader program
      gl_.glDeleteProgram(id_);
   }

   QOpenGLFunctions_3_3_Core gl_;

   GLuint id_;
};

ShaderProgram::ShaderProgram() : p(std::make_unique<ShaderProgramImpl>()) {}
ShaderProgram::~ShaderProgram() = default;

ShaderProgram::ShaderProgram(ShaderProgram&&) noexcept = default;
ShaderProgram& ShaderProgram::operator=(ShaderProgram&&) noexcept = default;

GLuint ShaderProgram::id() const
{
   return p->id_;
}

bool ShaderProgram::Load(const std::string& vertexPath,
                         const std::string& fragmentPath)
{
   BOOST_LOG_TRIVIAL(debug) << logPrefix_ << "Load()";

   QOpenGLFunctions_3_3_Core& gl = p->gl_;

   GLint glSuccess;
   bool  success = true;

   QFile vertexFile(vertexPath.c_str());
   QFile fragmentFile(fragmentPath.c_str());

   vertexFile.open(QIODevice::ReadOnly | QIODevice::Text);
   fragmentFile.open(QIODevice::ReadOnly | QIODevice::Text);

   if (!vertexFile.isOpen())
   {
      BOOST_LOG_TRIVIAL(error)
         << logPrefix_ << "Could not load vertex shader: " << vertexPath;
      return false;
   }

   if (!fragmentFile.isOpen())
   {
      BOOST_LOG_TRIVIAL(error)
         << logPrefix_ << "Could not load fragment shader: " << fragmentPath;
      return false;
   }

   QTextStream vertexShaderStream(&vertexFile);
   QTextStream fragmentShaderStream(&fragmentFile);

   vertexShaderStream.setEncoding(QStringConverter::Utf8);
   fragmentShaderStream.setEncoding(QStringConverter::Utf8);

   std::string vertexShaderSource = vertexShaderStream.readAll().toStdString();
   std::string fragmentShaderSource =
      fragmentShaderStream.readAll().toStdString();

   const char* vertexShaderSourceC   = vertexShaderSource.c_str();
   const char* fragmentShaderSourceC = fragmentShaderSource.c_str();

   // Create a vertex shader
   GLuint vertexShader = gl.glCreateShader(GL_VERTEX_SHADER);

   // Attach the shader source code and compile the shader
   gl.glShaderSource(vertexShader, 1, &vertexShaderSourceC, NULL);
   gl.glCompileShader(vertexShader);

   // Check for errors
   gl.glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &glSuccess);
   if (!glSuccess)
   {
      char infoLog[512];
      gl.glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
      BOOST_LOG_TRIVIAL(error)
         << logPrefix_ << "Vertex shader compilation failed";
      success = false;
   }

   // Create a fragment shader
   GLuint fragmentShader = gl.glCreateShader(GL_FRAGMENT_SHADER);

   // Attach the shader source and compile the shader
   gl.glShaderSource(fragmentShader, 1, &fragmentShaderSourceC, NULL);
   gl.glCompileShader(fragmentShader);

   // Check for errors
   gl.glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &glSuccess);
   if (!glSuccess)
   {
      char infoLog[512];
      gl.glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
      BOOST_LOG_TRIVIAL(error)
         << logPrefix_ << "Fragment shader compilation failed: " << infoLog;
      success = false;
   }

   if (success)
   {
      gl.glAttachShader(p->id_, vertexShader);
      gl.glAttachShader(p->id_, fragmentShader);
      gl.glLinkProgram(p->id_);

      // Check for errors
      gl.glGetProgramiv(p->id_, GL_LINK_STATUS, &glSuccess);
      if (!glSuccess)
      {
         char infoLog[512];
         gl.glGetProgramInfoLog(p->id_, 512, NULL, infoLog);
         BOOST_LOG_TRIVIAL(error)
            << logPrefix_ << "Shader program link failed: " << infoLog;
         success = false;
      }
   }

   // Delete shaders
   gl.glDeleteShader(vertexShader);
   gl.glDeleteShader(fragmentShader);

   return false;
}

void ShaderProgram::Use() const
{
   p->gl_.glUseProgram(p->id_);
}

} // namespace qt
} // namespace scwx