use std::f64;

use sdl2::pixels::Color;

fn put_pixel(data: &mut [u8], x: usize, y: usize, color: Color) {
    data[y * 3 * 800 + x * 3] = color.r;
    data[y * 3 * 800 + x * 3 + 1] = color.g;
    data[y * 3 * 800 + x * 3 + 2] = color.b;
}

pub fn render(data: &mut [u8], frame_count: u32) {
    let time = frame_count as f64 / 60. * 6.28;
    let ct = f64::cos(time);
    let st = f64::sin(time);
    for x in 0..800 {
        for y in 0..800 {
            let cx: f64 = f64::cos(st * 1.0 + (x as f64 - 400.) / 39.123 * ct) + 1.;
            let cy: f64 = f64::cos(ct * 1.1 + (y as f64 - 400.) / 40.123 * st) + 1.;
            let sx: f64 = f64::sin(ct * 1.2 + (x as f64 - 400.) / 41.123 * ct) + 1.;
            let sy: f64 = f64::sin(st * 1.3 + (y as f64 - 400.) / 42.123 * st) + 1.;
            put_pixel(
                &mut *data,
                x,
                y,
                Color {
                    r: (cx * 128.) as u8,
                    g: (cy * sx * 64.) as u8,
                    b: (sy * 128.) as u8,
                    a: 0,
                },
            );
        }
    }
}