#include "OpenGLShaderProgram.h"

namespace sp {

OpenGLShaderProgram::OpenGLShaderProgram()
{
	m_extension = "glsl";
    m_id = glCreateProgram();
}


OpenGLShaderProgram::~OpenGLShaderProgram() 
{
	if (m_id > 0) {
		glDeleteProgram(m_id);
	}
}

bool OpenGLShaderProgram::loadFromMemory(const std::string& source, ShaderType type)
{
	const char *s = source.c_str();

	GLuint shader_id = glCreateShader(type == ShaderType::Vertex
        ? GL_VERTEX_SHADER : GL_FRAGMENT_SHADER);

	glShaderSource(shader_id, 1, &s, NULL);

	if (!compileShader(shader_id)) {
		return false;
	}

	return attachShader(shader_id);
}

bool OpenGLShaderProgram::link()
{
	GLint status;

	glLinkProgram(m_id);

	// Query OpenGL for link status.
	glGetProgramiv(m_id, GL_LINK_STATUS, &status);
	m_linked = status == GL_TRUE;

	if (!m_linked) {
		m_error = fetchErrorLog();
	}
	return m_linked;
}

// Enable this shader
// All shader operations after this call will affect this shader.
void OpenGLShaderProgram::enable() const
{
	glUseProgram(m_id);
}

// Disable this shader
// Operations will no longer affect this shader after this call.
void OpenGLShaderProgram::disable() const
{
	glUseProgram(0);
}

// ---------------------
// Variables.
// ---------------------

bool OpenGLShaderProgram::setMVPMatrix(const Matrix4f& matrix)
{
	return setUniform("u_MVP", matrix);
}

// ---------------------
//  General Variables.
// ---------------------

bool OpenGLShaderProgram::setAttribute(const std::string& name, float value) const
{
	int loc;
	if (getAttribLoc(name, loc)) {
		glVertexAttrib1f(loc, value);
		return true;
	}
	return false;
}

bool OpenGLShaderProgram::setAttribute(const std::string& name, const Matrix4f& matrix) const
{
	int loc;
	if (getAttribLoc(name, loc)) {
		glVertexAttrib4fv(loc, matrix.e);
		return true;
	}
	return false;
}

bool OpenGLShaderProgram::setUniform(const std::string& name, const Matrix4f& matrix) const
{
	int loc;
	if (getUniformLoc(name, loc)) {
		glUniformMatrix4fv(loc, 1, GL_FALSE, matrix.e);
		return true;
	}
	return false;
}

bool OpenGLShaderProgram::setUniform(const std::string& name, const Color& color) const
{
	int loc;
	if (getUniformLoc(name, loc)) {
		Vector4f c = color.toRGBAf();

		glUniform4f(loc, c.x, c.y, c.z, c.w);
		return true;
	}
	return false;
}

bool OpenGLShaderProgram::getAttribLoc(const std::string& name, int& loc) const
{
	loc = glGetAttribLocation(m_id, name.c_str());
	if (loc < 0) {
		m_error = "Attribute variable '" + name + "' was not found in shader.";
		return false;
	}
	return true;
}

bool OpenGLShaderProgram::getUniformLoc(const std::string& name, int& loc) const
{
	loc = glGetUniformLocation(m_id, name.c_str());
	if (loc < 0) {
		m_error = std::string("Uniform variable '" + name + "' was not found in shader.");
		return false;
	}
	return true;
}

std::string OpenGLShaderProgram::fetchErrorLog() const
{
	GLchar buf[4096] = { '\0' };

	glGetProgramInfoLog(m_id, sizeof(buf), NULL, buf);

	return std::string(buf);
}

bool OpenGLShaderProgram::compileShader(GLuint id)
{
	glCompileShader(id);
		GLenum err;

		// Query OpenGL for status.
		GLint status;
		glGetShaderiv(id, GL_COMPILE_STATUS, &status);
		if (status == GL_FALSE) {
			GLchar buf[4096] = { '\0' };
			glGetShaderInfoLog(id, sizeof(buf), NULL, buf);
			m_error = std::string(buf);
			return false;
		}
		return true;
}

bool OpenGLShaderProgram::attachShader(GLuint id)
{
	GLenum err;

	glAttachShader(m_id, id);
	err = glGetError();
	if (err == GL_INVALID_VALUE) {
		m_error = "Invalid Value";
		return false;
	} else if (err == GL_INVALID_OPERATION) {
		m_error = "Invalid operation";
		return false;
	} else if (err != GL_NO_ERROR) {
		m_error = "Unkown Error";
		return false;
	} 
	return true;
}

} // namespace sp