#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <chrono>
#define GLEW_STATIC
#include <GL/glew.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>

int main(int argc, char *argv[])
{
    // init
    SDL_Init(SDL_INIT_VIDEO);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);

    SDL_Window* window = SDL_CreateWindow("OpenGL", 100, 100, 800, 600, SDL_WINDOW_OPENGL);

    SDL_GLContext context = SDL_GL_CreateContext(window);

    glewExperimental = GL_TRUE;
    glewInit();
    
    // shader laden

    std::ifstream frag ("shaders/fragment/simple.glsl");
    std::string fragcodes;

    if(frag.is_open()){
        std::ostringstream ss;
        ss << frag.rdbuf();
        fragcodes = ss.str();
    }else{
        std::cout << "hää? frag shader existiert nicht!";
    }

    std::ifstream vert ("shaders/vertex/simple.glsl");
    std::string vertcodes;

    if(vert.is_open()){
        std::ostringstream ss;
        ss << vert.rdbuf();
        vertcodes = ss.str();
    }else{
        std::cout << "hää? frag shader existiert nicht!";
    }

    char* vertcode = new char[vertcodes.length() + 1];
    strcpy(vertcode, vertcodes.c_str());
    char* fragcode = new char[fragcodes.length() + 1];
    strcpy(fragcode, fragcodes.c_str());

    

    // dreieck

    GLfloat vertices[] = {
        -0.5f,  0.5f, 1.0f, 0.0f, 0.0f, // Top-left
        0.5f,  0.5f, 0.0f, 1.0f, 0.0f, // Top-right
        0.5f, -0.5f, 0.0f, 0.0f, 1.0f, // Bottom-right
        -0.5f, -0.5f, 1.0f, 1.0f, 1.0f  // Bottom-left
    };

    GLuint elements[] = {
        0, 2, 3,
        1, 2, 3
    };


    //shaders

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertcode, NULL);
    glCompileShader(vertexShader);

    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragcode, NULL);
    glCompileShader(fragmentShader);


    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);  
    glLinkProgram(shaderProgram);

    GLuint vao;
    glGenVertexArrays(1, &vao);

    //vbo
    GLuint vbo;
    glGenBuffers(1, &vbo); // Generate 1 buffer

    glBindBuffer(GL_ARRAY_BUFFER, vbo);

    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);


    //ebo
    GLuint ebo;
    glGenBuffers(1, &ebo); // Generate 1 buffer

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);

    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);


    //-----vao-----
    
    glBindVertexArray(vao);
    //-----vao-----
    
    glUseProgram(shaderProgram);

    GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
    glEnableVertexAttribArray(posAttrib);
    glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), 0);

    GLint colAttrib = glGetAttribLocation(shaderProgram, "color");
    glEnableVertexAttribArray(colAttrib);
    glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), (void*)(2*sizeof(GLfloat)));

    //glBindFragDataLocation(shaderProgram, 0, "outColor");

    //GLint uniColor = glGetUniformLocation(shaderProgram, "triangleColor");
    //glUniform3f(uniColor, 1.0f, 0.0f, 0.0f);



    // loopdeloop

    auto t_start = std::chrono::high_resolution_clock::now();
    SDL_Event windowEvent;
    while (true)
    {
        //auto t_now = std::chrono::high_resolution_clock::now();
        //float time = std::chrono::duration_cast<std::chrono::duration<float>>(t_now - t_start).count();
        //glUniform3f(uniColor, (sin(time * 4.0f) + 1.0f) / 2.0f, 0.0f, 0.0f);
        if (SDL_PollEvent(&windowEvent))
        {
            if (windowEvent.type == SDL_QUIT) break;
            if (windowEvent.type == SDL_KEYUP &&
                windowEvent.key.keysym.sym == SDLK_ESCAPE) break;
        }
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, elements);

        SDL_GL_SwapWindow(window);
    }


    // bier bier

    glDeleteProgram(shaderProgram);
    glDeleteShader(fragmentShader);
    glDeleteShader(vertexShader);

    glDeleteBuffers(1, &vbo);

    //glDeleteVertexArrays(1, &vao);

    SDL_GL_DeleteContext(context);

    SDL_Quit();
    return 0;
}