#ifndef SHADER_H
#define SHADER_H

#include <iostream>
#include <fstream>
#include <stdexcept>
#include <map>
#include <iterator>

#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>

// TODO: do glValidateProgram, like in the OpenGL template
// TODO: add error checking at set_uniforms?

class shader {
    typedef std::map<GLenum, GLuint> ShaderMap;
    
	GLuint program;
	ShaderMap shaders;

public:

	shader(std::string vertex_shader_filename, std::string fragment_shader_filename) :
	program(0), shaders() {
		program = glCreateProgram();
		if(program == 0) {
			throw std::runtime_error("Program couldn't be created");
		}

		{   // vertex shader
            // NOTE: C++03 mandates .c_str(), ugly, nothing to do about it...
			std::ifstream vertex_shader(vertex_shader_filename.c_str());
			if(!vertex_shader)
				throw std::runtime_error(vertex_shader_filename + " couldn't be opened");
			read_shader(vertex_shader, GL_VERTEX_SHADER);
		}
		{   // fragment shader
			std::ifstream fragment_shader(fragment_shader_filename.c_str());
			if(!fragment_shader)
				throw std::runtime_error(fragment_shader_filename + " couldn't be opened");
			read_shader(fragment_shader, GL_FRAGMENT_SHADER);
		}

		link_program();
	}

	~shader(){
		begin();
		for(ShaderMap::const_iterator i = shaders.begin(); i != shaders.end(); ++i){
            ShaderMap::value_type const & it = *i;
			GLuint shader = it.second;
			glDetachShader(program, shader);
			glDeleteShader(shader);
		}

		glDeleteProgram(program);

		end();
	}

	void begin() {
		glUseProgram(program);
	}

	void end() {
		glUseProgram(0);
	}

	void set_uniform(char const* name, float x) const {
		glUniform1f(glGetUniformLocation(program, name), x);
	}

	void set_uniform(char const* name, float x, float y) const {
		glUniform2f(glGetUniformLocation(program, name), x, y);
	}

	void set_uniform(char const* name, float x, float y, float z) const {
		glUniform3f(glGetUniformLocation(program, name), x, y, z);
	}

	void set_uniform(char const* name, float x, float y, float z, float w) const {
		glUniform4f(glGetUniformLocation(program, name), x, y, z, w);
	}

	void set_uniform(char const* name, int x) const {
		glUniform1i(glGetUniformLocation(program, name), x);
	}

	void set_uniform(char const* name, int x, int y) const {
		glUniform2i(glGetUniformLocation(program, name), x, y);
	}

	void set_uniform(char const* name, int x, int y, int z) const {
		glUniform3i(glGetUniformLocation(program, name), x, y, z);
	}

	void set_uniform(char const* name, int x, int y, int z, int w) const {
		glUniform4i(glGetUniformLocation(program, name), x, y, z, w);
	}

    // TODO: add support for other matrices (not only 4x4), in ES2 only square matrices
	void set_matrix(char const* name, bool trans, const GLfloat* value) const {
		glUniformMatrix4fv(glGetUniformLocation(program, name), 1, trans, value);
	}
    
    // TODO: add support for other vectors (not only length 4)
	void set_uniform(char const* name, const GLfloat* value, GLsizei count = 1) const {
		glUniform4fv(glGetUniformLocation(program, name), count, value);
	}

    // TODO: add support for other vectors (not only length 4)
	void set_uniform(char const* name, const GLint* value, GLsizei count = 1) const {
		glUniform4iv(glGetUniformLocation(program, name), count, value);
	}

	void set_texture(const char* name, GLenum target, GLuint tex, int textureLocation) const {
		glActiveTexture(GL_TEXTURE0 + textureLocation);
		glBindTexture(target, tex);
		set_uniform(name, textureLocation);
	}

private:

    // FIXME: this also compiles, bad name
	void read_shader(std::istream& file, GLenum type) {
		// get the c-string, the shortest way (not fastest)
		std::string buffer((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
		const char* sptr = buffer.c_str();
		int ssize = buffer.size();

		// create and compile shader
		GLuint shader = glCreateShader(type);
		glShaderSource(shader, 1, &sptr, &ssize);
		glCompileShader(shader);

#if defined(DEBUG)
		// check compile status
		GLint status = GL_FALSE;
		glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
		if(status == GL_FALSE || shader == 0) {
			GLsizei infoLength = 0;
			glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLength);
			char* infoBuffer = new GLchar[infoLength];
			glGetShaderInfoLog(shader, infoLength, &infoLength, infoBuffer);
			std::cerr << "source:\n" << buffer << std::endl;
			std::cerr << "shader reports:\n" << infoBuffer << std::endl;
			delete [] infoBuffer;
			throw std::runtime_error("Shader failed to compile");
		}
#endif

		// put it in tha map
		shaders[type] = shader;
	}

	void link_program() {
		// attach all shaders
		for(ShaderMap::const_iterator i = shaders.begin(); i != shaders.end(); ++i){
            ShaderMap::value_type const & it = *i;
			GLuint shader = it.second;
			glAttachShader(program, shader);
		}

		// link
		glLinkProgram(program);

#if defined(DEBUG)
		// check link status
		GLint status;
		glGetProgramiv(program, GL_LINK_STATUS, &status);
		if(status == GL_FALSE) {
            GLsizei infoLength = 0;
            glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLength);
			char* infoBuffer = new GLchar[infoLength];
            glGetProgramInfoLog(program, infoLength, &infoLength, infoBuffer);
            std::cerr << "linker reports:\n" << infoBuffer << std::endl;
            delete [] infoBuffer;
			throw std::runtime_error("Shader failed to link");
		}
#endif
	}

};

#endif // SHADER_H