//
//  shader.h
//  J
//
//  Created by Joshua Moerman on 7/01/11.
//  Copyright 2011 Vadovas. All rights reserved.
//

/*
 This is a very basic shader class. The compilation and linking is done in the constructor, and deletion is don in the destructor. As a result, you can't copy a shader, use smart pointers instead. Because OpenGL ES2 uses attribute-indices at link-time, you have to specify your attributes in the constructor (this is a bit cumbersome).
 
 There are a lot of uniform setters, for both values and array's, they are called set_uniform() for all types. For matrices a additional parameter (trans) can be given, but in ES2 this value has to be false. It's still a parameter to avoid ambiguity, because the overload works with c-style arrays (vector4 is not distinguishable from matrix2x2). A fix would be to introduce types like vector4 and matrix2x2 and such, but Astrant already has those, so I refrain to do that.
 
 Using the setters should only be done between the begin() and end() functions.
 */

#ifndef SHADER_H
#define SHADER_H

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

#include "basic.h"
#include "array.h"

// TODO: add error checking at set_uniforms?
// TODO: use an uniform map? (benchmark first!)
// TODO: allow arrays in uniforms (now all counts are 1). To make this possible, first make vector and matrix structs. (But Astrant already has those)
// TODO: matrix attributes are not handled well (they take up 4 indices in the attributes instead of one)
// TODO: make the attribute-list nicer (it is really cumbersome now, with the vector)
// NOTE: there is only 1 set_uniform for std::array...

namespace J {

class shader {
    // NOTE: it could be hardcoded to use vertex_shader and fragment_shader, for ShaderMap. There is no geometry_shader in ES2.
    typedef std::map<GLenum, GLuint> ShaderMap;             // shader_type -> shader_name
    typedef std::map<std::string, GLuint> AttributeMap;     // attribute_name -> attribute_index
    
	GLuint program;
	ShaderMap shaders;
    AttributeMap attributes;

public:

    // ***********
    // constructor
	shader(const std::string& vertex_shader_filename, const std::string& fragment_shader_filename, const std::vector<std::string>& attributes_to_use = std::vector<std::string>()) :
	program(0), shaders(), attributes() {
		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");
			compile_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");
			compile_shader(fragment_shader, GL_FRAGMENT_SHADER);
		}
        for (unsigned int i = 0; i < attributes_to_use.size(); ++i) {
            glBindAttribLocation(program, i, attributes_to_use[i].c_str());
            attributes[attributes_to_use[i]] = i;
        }

		link_program();
        check_error();
	}

	~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);
            // NOTE: If a shader object to be deleted is attached to a program object, it will be flagged for deletion, but it will not be deleted until it is no longer attached to any program object. Also deleting a shader with name '0' is safe.
		}
        
		end();
		glDeleteProgram(program);
	}

    // *****
    // usage
	void begin() {
		glUseProgram(program);
	}

	void end() {
		glUseProgram(0);
	}
    
    // *****************
    // attribute setters
	// NOTE: the normalized parameter is for integer types, if true they will be mapped to [0, 1], if false it stays in [0, 256] or so.
    void set_attribute(const std::string& name, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const GLvoid* ptr) const {
		auto it = attributes.find(name);
		if(it == attributes.end()) throw std::runtime_error(name + " attribute could not be found");
		glEnableVertexAttribArray(it->second);
        glVertexAttribPointer(it->second, size, type, normalized, stride, ptr);
    }

    // ***************
    // uniform setters
    
    // float vectors (multiple values)
	void set_uniform(char const* name, float x) const {
		glUniform1f(get_uniform_location(name), x);
	}

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

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

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

    // integer vectors (multiple values)
	void set_uniform(char const* name, int x) const {
		glUniform1i(get_uniform_location(name), x);
	}

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

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

	void set_uniform(char const* name, int x, int y, int z, int w) const {
		glUniform4i(get_uniform_location(name), x, y, z, w);
	}
    
    // Float vectors (array)
	void set_uniform(char const* name, const GLfloat (&value)[4]) const {
		glUniform4fv(get_uniform_location(name), 1, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[3]) const {
		glUniform3fv(get_uniform_location(name), 1, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[2]) const {
		glUniform2fv(get_uniform_location(name), 1, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[1]) const {
		glUniform1fv(get_uniform_location(name), 1, value);
	}
    
    // Integer vectors (array)
	void set_uniform(char const* name, const GLint (&value)[4]) const {
		glUniform4iv(get_uniform_location(name), 1, value);
	}
    
    void set_uniform(char const* name, const GLint (&value)[3]) const {
		glUniform3iv(get_uniform_location(name), 1, value);
	}
    
    void set_uniform(char const* name, const GLint (&value)[2]) const {
		glUniform2iv(get_uniform_location(name), 1, value);
	}
    
    void set_uniform(char const* name, const GLint (&value)[1]) const {
		glUniform1iv(get_uniform_location(name), 1, value);
	}

    // matrices
	// NOTE: in ES2 there are only square matrices
	void set_uniform(char const* name, const GLfloat (&value)[16], GLboolean trans) const {
		glUniformMatrix4fv(get_uniform_location(name), 1, trans, value);
	}
	
	void set_uniform(char const* name, const std::array<GLfloat, 16> & value, GLboolean trans) const {
		glUniformMatrix4fv(get_uniform_location(name), 1, trans, &value[0]);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[9], GLboolean trans) const {
		glUniformMatrix3fv(get_uniform_location(name), 1, trans, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[4], GLboolean trans) const {
		glUniformMatrix2fv(get_uniform_location(name), 1, trans, value);
	}

    // textures
	// NOTE: with a texture class this can be made prettier (also se the TODO in fbo.h)
	void set_texture(const char* name, GLenum target, GLuint tex, int textureLocation, GLenum filter = GL_LINEAR) const {
		glActiveTexture(GL_TEXTURE0 + textureLocation);
		glBindTexture(target, tex);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, filter);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);
		set_uniform(name, textureLocation);
	}
    
    // *********
    // validator
    void validate() {
        #if defined(DEBUG)
        GLint status;
        glValidateProgram(program);
        glGetProgramiv(program, GL_VALIDATE_STATUS, &status);
        if(status == GL_FALSE){
            std::cerr << "validator reports:" << std::endl;
            show_program_log();
			throw std::runtime_error("Program not valid");
        }
        #endif
    }

private:
	mutable std::map<std::string, GLint> uniforms;
	GLint get_uniform_location(char const * name) const {
		auto it = uniforms.find(name);
		if(it != uniforms.end())
			return it->second;
		
		return uniforms[name] = glGetUniformLocation(program, name);
	}

    // *******************
    // compiling / linking
	void compile_shader(std::istream& file, GLenum type) {
		// get the c-string, the shortest way (not fastest), from http://tinodidriksen.com/
		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);

		check_compile_status(shader, buffer);

		// 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);

		check_link_status();
	}
    
    // ***************
    // status checking
    void check_compile_status(GLuint shader, std::string source = "") {
        #if defined(DEBUG)
		GLint status = GL_FALSE;
		glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
		if(status == GL_FALSE || shader == 0) {
			std::cerr << "source:\n" << source << std::endl;
			std::cerr << "shader reports:" << std::endl;
            show_shader_log(shader);
			throw std::runtime_error("Shader failed to compile");
		}
        #endif
    }

    void check_link_status() {
        #if defined(DEBUG)
		GLint status;
		glGetProgramiv(program, GL_LINK_STATUS, &status);
		if(status == GL_FALSE) {
            std::cerr << "linker reports:" << std::endl;
            show_program_log();
			throw std::runtime_error("Shader failed to link");
		}
        #endif
    }
    
    void show_program_log(std::ostream& out = std::cerr) {
        GLint infoLength = 0;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLength);
        char* infoBuffer = new GLchar[infoLength+10];
        glGetProgramInfoLog(program, infoLength+10, &infoLength, infoBuffer);
        out << infoBuffer << std::endl;
        delete [] infoBuffer;
    }
    
    void show_shader_log(GLuint shader, std::ostream& out = std::cerr) {
        GLint infoLength = 0;
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLength);
        char* infoBuffer = new GLchar[infoLength+10];
        glGetShaderInfoLog(shader, infoLength+10, &infoLength, infoBuffer);
        out << infoBuffer << std::endl;
        delete [] infoBuffer;
    }
};
    
} // namespace J

#endif // SHADER_H