from machine import Pin
import utime

# initialize pins 
push_button = Pin(21, Pin.IN, Pin.PULL_DOWN)
red = Pin(2, Pin.OUT)
yellow = Pin(1, Pin.OUT)
green = Pin(0, Pin.OUT)

# initial values 
red.value(0)
yellow.value(0)
green.value(0)

lastInterruptTime = 0

# debounce function so the interrupt handler is activated once per button push
# note: not necessary if 'bounce' setting on push button is not checked 
def debounce():
    # print("CHECK BOUNCE")
    global lastInterruptTime
    currentTime = utime.ticks_ms() # get current time in ms 
    if currentTime - lastInterruptTime < 400: # find difference in time between current and last interrupt time, check if less than 400ms 
        return False
    lastInterruptTime = currentTime
    return True # ready to be used again! 

def push_button_interrupt_handler(pin): 
    if debounce(): # check that debounce returns true so the logic is ready to be run
        print("Interrupt detected..." + str(pin))
        if ((green.value() == 0 and yellow.value() == 0 and red.value() == 0) or (green.value() == 0 and red.value() == 1)): # conditions for green to be toggled on 
            print("GREEN LIGHT")
            green.toggle()
            if (red.value() == 1): 
                red.toggle()
        elif (green.value() == 1 and yellow.value() == 0): # conditions for yellow to be toggled on and green to be toggled off
            print("YELLOW LIGHT")
            green.toggle()
            yellow.toggle()
        elif (yellow.value() == 1 and red.value() == 0): # conditions for red to be toggled on and yellow to be toggled off
            print("RED LIGHT")
            yellow.toggle()
            red.toggle()
        utime.sleep_ms(200)

# calls button interrupt handler on rising edge of button signal
push_button.irq(trigger = Pin.IRQ_RISING, handler = push_button_interrupt_handler)