#define SDL_MAIN_HANDLED
#include <SDL2/SDL.h>
#include <GL/glew.h>
#include <GL/glu.h>
#include <GL/gl.h>
#include <string>

SDL_Window* window;

void createWindow() {
    auto pos = SDL_WINDOWPOS_UNDEFINED;
    auto flag = SDL_WINDOW_OPENGL;
    window = SDL_CreateWindow("OpenGL",pos,pos,800,600,flag);
    SDL_GL_CreateContext(window);
    glewInit();
}

int main(int argc, char* argv[]) {
    createWindow();

    float positions[6] = {
        -1.0f,-1.0f,
        0.0f,1.0f,
        1.0f,-1.0f
    };

    GLuint vbo;
    glGenBuffers(1,&vbo);
    glBindBuffer(GL_ARRAY_BUFFER,vbo);
    glBufferData(GL_ARRAY_BUFFER,sizeof(positions), positions, GL_STATIC_DRAW);

    const char* vertexShaderSource {
        "#version 150 core;"
        "in vec2 position;"
        "void main() {"
        "gl_Position = vec4(position,0.,1.);"
        "}"
    };

    const char* fragmentShaderSource {
        "#version 150 core;"
        "out vec4 outColor;"
        "void main() {"
        "outColor = vec4(1.);"
        "}"
    };

    //Create the vertex shader program
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader,1,&vertexShaderSource,0);
    glCompileShader(vertexShader);

    //Create the fragment shader program
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader,1,&fragmentShaderSource,0);
    glCompileShader(fragmentShader);

    //Create the main program
    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram,vertexShader);
    glAttachShader(shaderProgram,fragmentShader);
    glBindFragDataLocation(shaderProgram, 0, "outColor");

    //Link, and then tell OpenGL to use it
    glLinkProgram(shaderProgram);
    glUseProgram(shaderProgram);
    glCompileShader(shaderProgram);



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


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

    bool running = true;
    while(running) {
        SDL_Event event;
        while(SDL_PollEvent(&event)) {
            if(event.type == SDL_QUIT)
                running = false;
        }

        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        SDL_GL_SwapWindow(window);
    }

}