shader.h

// tells compiler to only include this file once
#pragma once

#include <string>
#include <fstream>
#include <sstream>
#include <iostream>

#include <GL/glew.h>

class Shader {

public:
    GLuint program;

    Shader() {
    }

    Shader(const GLchar* vertexPath, const GLchar* fragmentPath) {
        build(vertexPath, fragmentPath);
    }

    bool build(const GLchar* vertexPath, const GLchar* fragmentPath) {
        // 1. Retrieve the vertex/fragment source code from filePath
        std::string vertexCode;
        std::string fragmentCode;
        std::ifstream vShaderFile;
        std::ifstream fShaderFile;
        // ensures ifstream objects can throw exceptions:
        vShaderFile.exceptions(std::ifstream::badbit);
        fShaderFile.exceptions(std::ifstream::badbit);
        try {
            // Open files
            vShaderFile.open(vertexPath);
            fShaderFile.open(fragmentPath);
            std::stringstream vShaderStream, fShaderStream;
            // Read file's buffer contents into streams
            vShaderStream << vShaderFile.rdbuf();
            fShaderStream << fShaderFile.rdbuf();
            // close file handlers
            vShaderFile.close();
            fShaderFile.close();
            // Convert stream into string
            vertexCode = vShaderStream.str();
            fragmentCode = fShaderStream.str();
        } catch (std::ifstream::failure e) {
            std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
        }
        const GLchar* vShaderCode = vertexCode.c_str();
        const GLchar * fShaderCode = fragmentCode.c_str();
        // 2. Compile shaders
        GLuint vertex, fragment;
        GLint success;
        GLchar infoLog[512];
        // Vertex Shader
        vertex = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertex, 1, &vShaderCode, NULL);
        glCompileShader(vertex);
        // Print compile errors if any
        glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
        if (!success) {
            glGetShaderInfoLog(vertex, 512, NULL, infoLog);
            std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED: \"" << vertexPath << "\"" << std::endl;
            std::cout << infoLog << std::endl;
        }
        // Fragment Shader
        fragment = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragment, 1, &fShaderCode, NULL);
        glCompileShader(fragment);
        // Print compile errors if any
        glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);
        if (!success) {
            glGetShaderInfoLog(fragment, 512, NULL, infoLog);
            std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED: \"" << fragmentPath << "\"" << std::endl;
            std::cout << infoLog << std::endl;
        }
        // Shader Program
        program = glCreateProgram();
        glAttachShader(program, vertex);
        glAttachShader(program, fragment);
        glLinkProgram(program);
        // Print linking errors if any
        glGetProgramiv(program, GL_LINK_STATUS, &success);
        if (!success) {
            glGetProgramInfoLog(program, 512, NULL, infoLog);
            std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED: \"" << vertexPath << "\",\"" << fragmentPath << "\"" << std::endl;
            std::cout << infoLog << std::endl;
        }

        // Delete the shaders as they're linked into our program now and no longer necessery
        glDeleteShader(vertex);
        glDeleteShader(fragment);

        return (success == 1);
    }

    // Uses the current shader
    void use() {
        glUseProgram(program);
    }
};