#[macro_use]
extern crate glium;

fn main() {
    use glium::DisplayBuild;
    use glium::Surface;

    let display = glium::glutin::WindowBuilder::new()
        .with_dimensions(1024, 768)
        .with_title(format!("Hello world"))
        .build_glium()
        .unwrap();

    // let display = glium::glutin::WindowBuilder::new().build_glium().unwrap();

    #[derive(Copy, Clone)]
    struct Vertex {
        position: [f32; 2],
    }

    implement_vertex!(Vertex, position);

    let vertex1 = Vertex { position: [-0.5, -0.5] };
    let vertex2 = Vertex { position: [ 0.0,  0.5] };
    let vertex3 = Vertex { position: [ 0.5, -0.25] };
    let shape = vec![vertex1, vertex2, vertex3];

    let vertex_buffer = glium::VertexBuffer::new(&display, &shape).unwrap();
    let indices = glium::index::NoIndices(glium::index::PrimitiveType::TrianglesList);

    let vertex_shader_src = r#"
        #version 140
        in vec2 position;
        uniform float t;
        void main() {
            vec2 p = position;
            p.x += t;
            gl_Position = vec4(p, 0.0, 1.0);
        }
    "#;

    let fragment_shader_src = r#"
        #version 140
        out vec4 color;
        void main() {
            color = vec4(0.7, 0.3, 0.2, 1.0);
        }
    "#;

    let program = glium::Program::from_source(&display, vertex_shader_src, fragment_shader_src, None).unwrap();

    let mut t: f32 = -0.5;
    loop {
        t += 0.002;
        if t > 0.5 {
            t = -0.5;
        }

        let mut target = display.draw();
        target.clear_color(0.3, 0.3, 0.2, 1.0);
        target.draw(&vertex_buffer, &indices, &program, &uniform! { t: t },
                    &Default::default()).unwrap();
        target.finish().unwrap();

        for ev in display.poll_events() {
            match ev {
                glium::glutin::Event::Closed => return,
                _ => ()
            }
        }
    }

}