from machine import Pin
import time

CAPACITY = 15          # maximum number of cars the garage can hold

# ----- INPUT: push buttons (internal pull-up, so a press reads 0) -----
btn_in  = Pin(14, Pin.IN, Pin.PULL_UP)   # increment: a car enters
btn_out = Pin(27, Pin.IN, Pin.PULL_UP)   # decrement: a car exits

# ----- OUTPUT: the four LEDs -----
led_green  = Pin(2,  Pin.OUT)   # space still available
led_red    = Pin(4,  Pin.OUT)   # garage full
led_yellow = Pin(5,  Pin.OUT)   # a car entered (event pulse)
led_blue   = Pin(18, Pin.OUT)   # a car exited  (event pulse)

count = 0               # number of cars currently inside the garage


def update_status_leds():
    # GREEN and RED are STATE LEDs: exactly one of them is on at any moment.
    if count >= CAPACITY:
        led_green.value(0)      # no free space
        led_red.value(1)        # garage is full
    else:
        led_green.value(1)      # at least one free space
        led_red.value(0)


def blink(led):
    # YELLOW and BLUE are EVENT LEDs: a short pulse to mark an action.
    led.value(1)
    time.sleep_ms(300)
    led.value(0)


# Start-up state: the garage is empty, so GREEN is on.
update_status_leds()

prev_in  = 1            # remember the previous reading to detect a new press
prev_out = 1

while True:
    cur_in  = btn_in.value()
    cur_out = btn_out.value()

    # ---- a car ENTERS: falling edge (1 -> 0) on the increment button ----
    if prev_in == 1 and cur_in == 0:
        if count < CAPACITY:
            count += 1
            print("Car entered.  Count =", count)
            blink(led_yellow)          # yellow pulse for one entry
            update_status_leds()       # refresh green / red
        else:
            print("Garage FULL. Entry ignored. Count =", count)
        time.sleep_ms(50)              # simple debounce

    # ---- a car EXITS: falling edge (1 -> 0) on the decrement button ----
    if prev_out == 1 and cur_out == 0:
        if count > 0:
            count -= 1
            print("Car exited.   Count =", count)
            blink(led_blue)            # blue pulse for one exit
            update_status_leds()       # refresh green / red
        else:
            print("Garage EMPTY. Exit ignored. Count =", count)
        time.sleep_ms(50)              # simple debounce

    prev_in  = cur_in
    prev_out = cur_out
    time.sleep_ms(10)