from machine import Pin, PWM, time_pulse_us
from time import sleep, sleep_us

trig = Pin(22, Pin.OUT)
echo = Pin(21, Pin.IN)

red = Pin(17, Pin.OUT)
yellow = Pin(18, Pin.OUT)
green = Pin(19, Pin.OUT)

servo = PWM(Pin(23), freq=50)

LIMIT = 150

free_spaces  = 15

def get_distance():
    trig.value(0)
    sleep_us(2)

    trig.value(1)
    sleep_us(10)
    trig.value(0)

    duration = time_pulse_us(echo, 1, 30000)


    distance = (duration * 0.0343) / 2

    return distance


def open_gate():
    servo.duty(120)


def close_gate():
    servo.duty(25)


flag = 1

while True:
    distance = get_distance()
    if free_spaces > 0:
        green.on()
    print("Distance:", distance, "cm")

    if distance < LIMIT:
        if flag and free_spaces > 0:
            open_gate()
            print("Gate Open")
            free_spaces = free_spaces -1
            if free_spaces == 0:
                green.off()
                red.on()
            yellow.on()
            sleep(0.25)
            yellow.off()
            flag =0

    else:
        close_gate()
        print("Gate Closed")
        flag = 1

    sleep(0.3)