import os
import time
import RPi.GPIO as GPIO

'''
Pinout:
* P26 ----> r_ch1
* P20 ----> r_ch2
* P21 ----> r_ch3
'''
# Channels
r_ch1 = 26
r_ch2 = 20
r_ch3 = 21

# time constants in seconds
t_large_beer = 6
t_small_beer = 2

# double tap
t_left_tap = 6
t_right_tap = 6
t_flush = 20

# Syntax suger because of negative logic
S_ON = GPIO.LOW
S_OFF = GPIO.HIGH

def __setup_GPIO(channel=r_ch1):
    """
        Setup all GPIOs, set output mode, and set gpio mode to bcm
    """
    GPIO.setwarnings(False)
    GPIO.setmode(GPIO.BCM)

    print("setting up gpio_{}".format(channel))
    GPIO.setup(channel, GPIO.OUT)
    __set_gpio(channel, S_OFF)

def __set_gpio(channel=r_ch1, value=S_OFF):
    """
        Try to safely change the value of a gpio, catch exception if it fails
        TODO: Exception Handling
    """
    try:
        GPIO.output(channel, value)
    except:
        print("GPIO Error")
        GPIO.cleanup()

def gpio_test():
    """
        Test all channels
    """
    for i, gpio in enumerate([r_ch1, r_ch2, r_ch3], start=1):
        # Setup gpio pin
        __setup_GPIO(gpio)

        __set_gpio(gpio, S_ON)
        print("Channel_{}: gpio_{} on".format(i, gpio))
        time.sleep(0.1)
        __set_gpio(gpio, S_OFF)
        print("Channel_{}: gpio_{} off".format(i, gpio))
        time.sleep(0.1)

def draw_beer(channel=r_ch1, wait=t_large_beer):
    """
        Draw a delicious beer, keep the tap on for n_wait seconds
    """
    # Setup gpio pin
    __setup_GPIO(channel)

    __set_gpio(channel, S_ON)
    time.sleep(wait)
    __set_gpio(channel, S_OFF)