#include <stdio.h>
#include <glew.h>
#include <GLFW/glfw3.h>
#include <string>
#include <stdlib.h>
#include <fstream>

std::string LoadFileToString( const char* filepath ) {
    std::string fileData = "";
    std::ifstream stream( filepath, std::ios::in );

    if ( stream.is_open() ) {
        std::string line = "";

        while ( getline( stream, line ) ) {
            fileData += "\n" + line;
        }

        stream.close();

    }

    return fileData;
}

GLuint LoadShaders ( const char* vertShaderPath, const char* fragShaderPath ) {
    GLuint vertShader = glCreateShader( GL_VERTEX_SHADER );
    GLuint fragShader = glCreateShader( GL_FRAGMENT_SHADER );

    std::string vertShaderSource = LoadFileToString( vertShaderPath );
    std::string fragShaderSource = LoadFileToString( fragShaderPath );
    const char* rawVertShaderSource = vertShaderSource.c_str();
    const char* rawFragShaderSource = fragShaderSource.c_str();

    glShaderSource( vertShader, 1, &rawVertShaderSource, NULL );
    glShaderSource( fragShader, 1, &rawFragShaderSource, NULL) ;
    glCompileShader( vertShader );
    glCompileShader( fragShader );

    GLuint program = glCreateProgram();

    glAttachShader( program, vertShader );
    glAttachShader( program, fragShader );
    glLinkProgram(program);

    return program;
}

int main(void){

    if( !glfwInit() )
    {
        fprintf( stderr, "Failed to initialize GLFW\n" );
        return -1;
    }

    GLFWwindow* window;

    window = glfwCreateWindow( glfwGetVideoMode(glfwGetPrimaryMonitor()) -> width, glfwGetVideoMode(glfwGetPrimaryMonitor()) -> height, "Test", NULL, NULL);

    if( !window ){
        fprintf( stderr, "Failed to open window.\n" );
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    if (glewInit()) {
        fprintf( stderr, "Failed to initialize GLEW\n" );
        glfwTerminate();
        return -1;
    }

    GLuint vaoID;
    glGenVertexArrays( 1, &vaoID );
    glBindVertexArray( vaoID );

    static const GLfloat verts[] = {

        -1.0f, -1.0f, 0.0f,
         1.0f, -1.0f, 0.0f,
         0.0f,  1.0f, 0.0f

    };

    GLuint program = LoadShaders("shader.vertshader", "shader.fragshader");

    GLuint vboID;
    glGenBuffers( 1, &vboID );
    glBindBuffer( GL_ARRAY_BUFFER, vboID );
    glBufferData( GL_ARRAY_BUFFER, sizeof( verts ), verts, GL_STATIC_DRAW );


    while (!glfwWindowShouldClose(window)) {
        glEnableVertexAttribArray( 0 );
        glBindBuffer( GL_ARRAY_BUFFER, vboID );
        glVertexAttribPointer( 0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0 );
        glUseProgram(program);
        glDrawArrays( GL_TRIANGLES, 0, 3 );
        glDisableVertexAttribArray( 0 );

        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glfwTerminate();
    return 0;
}