/**
 * @file shader.hpp
 *
 * Copyright (C) 2019  Belle-Isle, Andrew <drumsetmonkey@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef SYSTEM_SHADER_HPP_
#define SYSTEM_SHADER_HPP_

#include <string>
#include <unordered_map>

#include <GL/glew.h>
#include <SDL2/SDL_opengl.h>

class Shader
{
private:
    /**
     * Reads the contents of a shader file and returns a c++ string
     * object representing the contents
     * @param The file path
     * @return The shader contents
     */
    std::string readShader(std::string); 

    /**
     * Creates a shader from a filename and a shader type
     * @param The file path containing the shader data
     * @param What type of shader to create
     * @return Memory address of shader location
     */
    GLuint createShader(std::string, GLenum);

    GLuint program; /**< GPU Memory address of shader program */

    /**
     * Name of shader attributes and their corresponding memory
     * locations in which the data exists
     */
    std::unordered_map<std::string, GLuint> attributes;
    
    /**
     * Name of shader uniforms in and their corresponding memory
     * locations in which the data exists
     */
    std::unordered_map<std::string, GLuint> uniforms;

public:
    Shader(void) :
        program(-1) {}

    /**
     * Given the file paths of two shaders, create a shader program.
     * @param v The file path of the vertex shader file.
     * @param f The file path of the fragment shader file.
     * @return The GPU Memory location of the shader program
     */
    GLuint createProgram(std::string v, std::string f); 

    /**
     * Finds and binds an attribute to the current shader if possible
     * @param The attribute to bind in the shader
     * @return The memory address of the new attribute, or -1 if the
     * attribute doesn't exist in the shader
     */
    GLint addAttribute(std::string);

    /**
     * Finds and binds a uniform to the current shader if possible
     * @param The uniform to bind in the shader
     * @return The memory address of the new uniform, or -1 if the
     * uniform doesn't exist in the shader
     */
    GLint addUniform(std::string);

    /**
     * Finds the GPU memory address of the given attribute in the shader
     * program
     * @param The attribute to find
     * @return The attribute memory location, or -1 if it doesn't exist
     */
    GLint getAttribute(std::string);

    /**
     * Finds the GPU memory address of the given uniform in the shader
     * program
     * @param The uniform to find
     * @return The uniform memory location, or -1 if it doesn't exist
     */
    GLint getUniform(std::string);

    /**
     * Gets the memory address of the program stored in this object
     * @return The GPU memory address of the shader program stored
     */
    GLuint getProgram();
};

#endif // SYSTEM_SHADER_HPP_