#include "shader.h"
#include <fstream>
#include <iostream>

Shader::Shader(const std::string & fileName)
{
	m_program = glCreateProgram();
	m_shaders[0] = CreateShader(LoadShader(fileName + ".vs"), GL_VERTEX_SHADER);
	m_shaders[1] = CreateShader(LoadShader(fileName + ".fs"), GL_FRAGMENT_SHADER);

	for (unsigned int i = 0; i < NUM_SHADERS; i++)
		glAttachShader(m_program, m_shaders[i]);

	glBindAttribLocation(m_program, 0, "position");
	glBindAttribLocation(m_program, 1, "texCoord");
	glBindAttribLocation(m_program, 2, "normal");

	glLinkProgram(m_program);
	CheckShaderError(m_program, GL_LINK_STATUS, true, "Error linking shader program");

	glValidateProgram(m_program);
	CheckShaderError(m_program, GL_LINK_STATUS, true, "Invalid shader program");

	m_uniforms[0] = glGetUniformLocation(m_program, "MVP");
	m_uniforms[1] = glGetUniformLocation(m_program, "Normal");
	m_uniforms[2] = glGetUniformLocation(m_program, "lightDirection");
}

Shader::~Shader()
{
	for (unsigned int i = 0; i < NUM_SHADERS; i++) {
		glDetachShader(m_program, m_shaders[i]);
		glDeleteShader(m_shaders[i]);
	}

	glDeleteProgram(m_program);
}

void
Shader::Bind()
{
	glUseProgram(m_program);
}

void
Shader::Update(const Transform & transform, const Camera & camera)
{
	glm::mat4 MVP = transform.GetMVP(camera);
	glm::mat4 Normal = transform.GetModel();

	glUniformMatrix4fv(m_uniforms[0], 1, GL_FALSE, &MVP[0][0]);
	glUniformMatrix4fv(m_uniforms[1], 1, GL_FALSE, &Normal[0][0]);
	glUniform3f(m_uniforms[2], 0.0f, 0.0f, 1.0f);
}

std::string
Shader::LoadShader(const std::string & fileName)
{
	std::ifstream file;
	file.open((fileName).c_str());

	std::string output;
	std::string line;

	if (file.is_open()) {
		while (file.good()) {
			getline(file, line);
			output.append(line + "\n");
		}
	}
	else {
		std::cerr << "Unable to load shader: " << fileName << std::endl;
	}

	return output;
}

void
Shader::CheckShaderError(GLuint shader, GLuint flag, bool isProgram, const std::string & errorMessage)
{
	GLint success = 0;
	GLchar error[1024] = {0};

	if (isProgram)
		glGetProgramiv(shader, flag, &success);
	else
		glGetShaderiv(shader, flag, &success);

	if (success == GL_FALSE) {
		if (isProgram)
			glGetProgramInfoLog(shader, sizeof(error), NULL, error);
		else
			glGetShaderInfoLog(shader, sizeof(error), NULL, error);

		std::cerr << errorMessage << ": '" << error << "'" << std::endl;
	}
}

GLuint
Shader::CreateShader(const std::string & text, unsigned int type)
{
	GLuint shader = glCreateShader(type);

	if (shader == 0)
		std::cerr << "Error compiling shader type " << type << std::endl;

	const GLchar * p[1];
	p[0] = text.c_str();
	GLint lengths[1];
	lengths[0] = text.length();

	glShaderSource(shader, 1, p, lengths);
	glCompileShader(shader);

	CheckShaderError(shader, GL_COMPILE_STATUS, false, "Error compiling shader!");

	return shader;
}