use arduino_hal::{clock::Clock, pac::TC0, DefaultClock};

// Sets up timer to rise two interrupts:
// 1. TIMER0_COMPA - every segment_rate_us μs
// 2. TIMER0_COMPB - segment_on_us μs after TIMER0_COMPA
pub fn segment_timer_init(tc0: TC0, segment_rate_us: u32, segment_on_us: u32) {
    // 16_000_000 / 64 * 1000 / 1_000_000 => 250
    let ocra = DefaultClock::FREQ / 64 * segment_rate_us / 1_000_000;
    let ocrb = DefaultClock::FREQ / 64 * segment_on_us / 1_000_000;
    assert!(ocra > ocrb);

    // Use CTC mode: reset counter when matches compare value
    tc0.tccr0a.write(|w| w.wgm0().ctc());
    // Set the compare value for TOP (reset)
    tc0.ocr0a
        .write(|w| w.bits(ocra.try_into().expect("timer init seg_freq out of rage")));
    // Set the compare value for B match
    tc0.ocr0b
        .write(|w| w.bits(ocrb.try_into().expect("timer init on_div out of rage")));
    // Slow down the timer (CLK / prescale)
    tc0.tccr0b.write(|w| w.cs0().prescale_64());
    // Raise interrupt on TOP (reset)
    // Raise interrupt on B match
    tc0.timsk0
        .write(|w| w.ocie0a().set_bit().ocie0b().set_bit());
}