module main;

import std.stdio;
import derelict.opengl3.gl;
import derelict.glfw3.glfw3;

extern (C) void onError(int error, const (char)* desc) nothrow
{
    scope(failure) assert(0);
    writeln("Houston, we've had a problem: [", error, "] ", desc);
}

extern (C) void onKey(GLFWwindow* window, int key, int scancode, int action, int mods) nothrow
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);
}

extern (C) void onResize(GLFWwindow* window, int width, int height) nothrow
{
    glViewport(0, 0, width, height);
}

void main(string[] args)
{
    // start
    writeln("Starting...");
    DerelictGLFW3.load();
    DerelictGL.load();
    glfwSetErrorCallback(&onError);
    if (!glfwInit())
        return;

    // init
    GLFWwindow* window = glfwCreateWindow(640, 480, "Snake 4D", null, null);
    if (window == null)
        return;
    glfwSetKeyCallback(window, &onKey);
    glfwSetFramebufferSizeCallback(window, &onResize);
    glfwMakeContextCurrent(window);

    // run
    while (!glfwWindowShouldClose(window))
    {
        float ratio;
        int width, height;
        glfwGetFramebufferSize(window, &width, &height);
        ratio = width / cast(float) height;
        glViewport(0, 0, width, height);
        glClear(GL_COLOR_BUFFER_BIT);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-ratio, ratio, -1.0f, 1.0f, 1.0f, -1.0f);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glRotatef(cast(float) glfwGetTime() * 50.0f, 0.0f, 0.0f, 1.0f);
        glBegin(GL_TRIANGLES);
        glColor3f(1.0f, 0.0f, 0.0f);
        glVertex3f(-0.6f, -0.4f, 0.0f);
        glColor3f(0.0f, 1.0f, 0.0f);
        glVertex3f(0.6f, -0.4f, 0.0f);
        glColor3f(0.0f, 0.0f, 1.0f);
        glVertex3f(0.0f, 0.6f, 0.0f);
        glEnd();
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // finish
    if (window != null)
        glfwDestroyWindow(window);
    glfwTerminate();
}