// external libs
#include "glad/glad.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

// project headers
#include "shader.hpp"

// std libs
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>

namespace Ogle
{
	Shader::Shader(const char* vertexPath, const char* fragmentPath)
	{
		// -- read shaders from file --
		std::string vertexCode;
		std::string fragmentCode;
		std::ifstream vShaderFile;
		std::ifstream fShaderFile;
		// ensure ifstream objects can throw exceptions:
		vShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
		fShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
		try 
		{
			// open files
			vShaderFile.open(vertexPath);
			fShaderFile.open(fragmentPath);
			std::stringstream vShaderStream, fShaderStream;
			// read file's buffer contents into streams
			vShaderStream << vShaderFile.rdbuf();
			fShaderStream << fShaderFile.rdbuf();		
			// close file handlers
			vShaderFile.close();
			fShaderFile.close();
			// convert stream into string
			vertexCode   = vShaderStream.str();
			fragmentCode = fShaderStream.str();
		}
		catch(std::ifstream::failure e)
		{
			std::cout << "ERROR::SHADER::FILE_NOT_SUCCESSFULLY_READ" << std::endl;
		}
		const char* vShaderCode = vertexCode.c_str();
		const char* fShaderCode = fragmentCode.c_str();

		// -- compile shaders --
		unsigned int vertex, fragment;
		int success;
		char infoLog[512];

		// vertex Shader
		vertex = glCreateShader(GL_VERTEX_SHADER);
		glShaderSource(vertex, 1, &vShaderCode, NULL);
		glCompileShader(vertex);
		glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
		if(!success)
		{
			glGetShaderInfoLog(vertex, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
		};

		// fragment Shader
		fragment = glCreateShader(GL_FRAGMENT_SHADER);
		glShaderSource(fragment, 1, &fShaderCode, NULL);
		glCompileShader(fragment);
		glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);
		if(!success)
		{
			glGetShaderInfoLog(fragment, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
		};

		// linking shaders
		this->ID = glCreateProgram();
		glAttachShader(ID, vertex);
		glAttachShader(ID, fragment);
		glLinkProgram(ID);
		glGetProgramiv(ID, GL_LINK_STATUS, &success);
		if(!success)
		{
			glGetProgramInfoLog(ID, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
		}

		// cleanup uneeded pre-linked shaders
		glDeleteShader(vertex);
		glDeleteShader(fragment);
	}

	void Shader::use()
	{
		glUseProgram(ID);
	}


	// -- various setters for shader uniforms --

	void Shader::setBool(const std::string &name, bool value) const
	{
		glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value);
	}

	void Shader::setInt(const std::string &name, int value) const
	{
		glUniform1i(glGetUniformLocation(ID, name.c_str()), value);
	}

	void Shader::set1f(const std::string &name, float value) const
	{
		glUniform1f(glGetUniformLocation(ID, name.c_str()), value);
	}

	void Shader::set4f(const std::string &name, float value0, float value1, float value2, float value3) const
	{
		glUniform4f(glGetUniformLocation(ID, name.c_str()), value0, value1, value2, value3);
	}

	void Shader::setMatrix4fv(const std::string &name, glm::mat4 matrix)
	{
		glUniformMatrix4fv(
				glGetUniformLocation(ID, name.c_str()),
				1,
				GL_FALSE,
				glm::value_ptr(matrix)
				);
	}
}