// load the relevant glfw things
use glfw::{Action, Context, Key};

// load the generated OpenGL bindings in a local module
mod gl {
    include!(concat!(env!("OUT_DIR"), "/gl_bindings.rs"));
}

fn main() {
    // set up the GLFW context
    let mut glfw = glfw::init(glfw::FAIL_ON_ERRORS).unwrap();

    // create the GLFW window
    let (mut window, events) = glfw
        .create_window(500, 500, "GL example", glfw::WindowMode::Windowed)
        .expect("Failed to create GLFW window.");

    // let it poll for keyboard events
    window.set_key_polling(true);
    window.make_current();

    // initialize the OpenGL context with the window pointer
    gl::load_with(|s| window.get_proc_address(s) as *const _);

    // continuously poll for events and then redraw the window
    while !window.should_close() {
        glfw.poll_events();
        for (_, event) in glfw::flush_messages(&events) {
            handle_window_event(&mut window, event);
        }
        draw(&mut window);
    }
}

// our immediate mode OpenGL draw function
fn draw(window: &mut glfw::Window) {
    unsafe {
        gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT);
        gl::LoadIdentity();
        gl::Begin(gl::TRIANGLES);
        {
            gl::Color3f(1.0, 0.0, 0.0);
            gl::Vertex2f(0.0, 1.0);

            gl::Color3f(0.0, 1.0, 0.0);
            gl::Vertex2f(0.87, -0.5);

            gl::Color3f(0.0, 0.0, 1.0);
            gl::Vertex2f(-0.87, -0.5);
        }
        gl::End();
    }
    // and swap the buffer to make it visible
    window.swap_buffers();
}

// our "event handler" just listens for the close event
fn handle_window_event(window: &mut glfw::Window, event: glfw::WindowEvent) {
    match event {
        glfw::WindowEvent::Key(Key::Escape, _, Action::Press, _) => window.set_should_close(true),
        _ => {}
    }
}