/*
OpenGL IS A very strict language for talking to the GPU: A state machine, A GPU command API, A way to feed data + programs to the GPU

OpenGL expects: 
1.You describe data -> “Here are vertices”
2.You describe how to process it -> “Here is how to transform them”
3.GPU does the rest -> “Here is how to color pixels”
Nothing happens unless everything is provided.

OpenGL = Set state -> Issue command

*/

// the art of adapt

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>

/*
1. Describe data        -> vertices (VBO)
2. Describe processing  -> shaders
3. GPU does the rest    -> rasterization + fragment coloring
*/

int main(void)
{
    GLFWwindow* window;

    /* Initialize the library */
    if (!glfwInit())
        return -1;

    /* Create a windowed mode window and its OpenGL context */
    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }

    /* Make the window's context current */
    glfwMakeContextCurrent(window);


    // -------------------- STEP 1: DESCRIBE DATA --------------------
    float vertices[] = {
        -0.5f, -0.5f, 0.0f,  // left
         0.5f, -0.5f, 0.0f,  // right
         0.0f,  0.5f, 0.0f   // top
    };

    

    unsigned int VBO = 0;
    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    {
        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT);

        /* Swap front and back buffers */
        glfwSwapBuffers(window);

        /* Poll for and process events */
        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}