import machine

# -------------------------
# Global variables
# -------------------------
debounce_time_ms = 50 #ms
debouncing = False
debounce_timer = machine.Timer()

red_led_state = 0

# -------------------------
# Timer callback
# -------------------------
def end_debounce(timer):
    global debouncing
    debouncing = False
    # NOTE: no print here (still IRQ context)

# -------------------------
# GPIO interrupt handler
# -------------------------
def gpio_handler(pin):
    global debouncing, red_led_state

    if debouncing:
        return

    debouncing = True

    # Minimal work inside IRQ
    debounce_timer.init(
        period = debounce_time_ms,
        mode = machine.Timer.ONE_SHOT,
        callback = end_debounce
    )

    # Set a flag ONLY (safe)
    red_led_state ^= 1 # toggle the value
    led_red.value(red_led_state)
    #print("Button pressed!")  # OK for demos, but mention risk

# -------------------------
# GPIO setup
# -------------------------
button = machine.Pin(5, machine.Pin.IN, machine.Pin.PULL_DOWN)
button.irq(trigger = machine.Pin.IRQ_RISING, handler = gpio_handler)
led_red = machine.Pin(2, machine.Pin.OUT)
led_red.value(red_led_state)

print("Waiting for GPIO 5 interrupts with debounce...")

# -------------------------
# Main loop
# -------------------------
while True:
    pass