#include "SAMDTimerInterrupt.h"
#include "SAMD_ISR_Timer.h"

#define HW_TIMER_INTERVAL_MS 10
SAMDTimer ITimer(TIMER_TC3);
SAMD_ISR_Timer ISR_Timer;

void TimerHandler(void) { ISR_Timer.run(); }

const int COUNTDOWN = 300;
const int PERIOD_MS = 1000;

const uint BUTTON_PIN = 6;
const uint BUTTON_LED_PIN = 5;
const uint BUZZER_PIN = 0;

/* Metronome state is expressed by countdown:
 *  -1 - IDLE
 *   0 - BEATING
 *  >0 - COUNTDOWN
 */
volatile int countdown = -1;

void setup() {
  initButton();

  ITimer.attachInterruptInterval_MS(10, TimerHandler);
  ISR_Timer.setInterval(PERIOD_MS, metronomeBeat);
  ISR_Timer.setInterval(PERIOD_MS, metronomeCountdown);
}

void metronomeCountdown() {
  if (countdown > 0) {
    countdown -= 1;

    digitalWrite(BUTTON_LED_PIN, countdown % 2 ? HIGH : LOW);
  }
}

void metronomeBeat() {
  if (countdown == 0)
    tone(BUZZER_PIN, 1000, 100);
}

void loop() {}