#!/usr/bin/env python3

from gpiozero import Button, LED
import time

# define both traffic lights in order: red, amber, green
# set main light to green and side light to red
MAIN_LIGHTS = [LED(p, initial_value = i == 2) for i, p in enumerate((0, 5, 6))]
SIDE_LIGHTS = [LED(p, initial_value = i == 0) for i, p in enumerate((13, 19, 26))]
BTN = Button(20)

# constants
GREEN_BLINK_RATE = 0.5
AMBER_STOP_DURATION = 2.5
AMBER_GO_DURATION = 1
SWITCH_SIDE_DELAY = 3
SIDE_GREEN_DURATION = 5

def green_to_red(lights):
    # blink green
    lights[2].blink(GREEN_BLINK_RATE, GREEN_BLINK_RATE, 2, False)
    lights[2].off()
    # show amber
    lights[1].blink(AMBER_STOP_DURATION, 0, 1, False)
    # show red
    lights[0].on()

def red_to_green(lights):
    # show amber and red
    lights[1].blink(AMBER_GO_DURATION, 0, 1, False)
    lights[0].off()
    # show green
    lights[2].on()

ongoing = False
def sequence():
    global ongoing
    if ongoing:
        return # block input if there's an ongoing sequence
    ongoing = True

    green_to_red(MAIN_LIGHTS)
    time.sleep(SWITCH_SIDE_DELAY)
    red_to_green(SIDE_LIGHTS)
    time.sleep(SIDE_GREEN_DURATION)
    green_to_red(SIDE_LIGHTS)
    time.sleep(SWITCH_SIDE_DELAY)
    red_to_green(MAIN_LIGHTS)

    ongoing = False

BTN.when_pressed = sequence

input()