import RPi.GPIO as GPIO    # import GPIO library
import subprocess          # needed for subprocess call
from time import sleep     # this lets us have a time delay

GPIO.setmode(GPIO.BCM)     # set up BCM GPIO numbering
GPIO.setup(26, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) # set up pin 26 for input detection of 3.3V

init = 1  # set inital state for boot message

try:
    while True:            # this will carry on until you hit CTRL+C
        if GPIO.input(26): # if port 26 == 1 (there is power)
            if init == 1:  # we must have cold booted on purpose or from a failure on UPS dead battery extended outage
                email = 'echo "REBOOT from extended power failure or device reset. Power is ON." | mail email1@email.com, email2@email.com'
                subprocess.call(email, shell=True) # send email command
            else:
                email = 'echo "Power restored at site. Commercial power is ON." | mail email1@email.com, email2@email.com'
                subprocess.call(email, shell=True) # send email command
            while GPIO.input(26): # do nothing if the power state stays on
                sleep(0.1)
        else: # there is no power detected at pin 26
            init = 0 # why bother checking every time it happens only once
            email = 'echo "Power failure at site. Commercial power is OFF." | mail email1@email.com, email2@email.com'
            subprocess.call(email, shell=True) # send email command
            while GPIO.input(26) == 0: # do nothing if the power state stays off
                sleep(0.1)

finally:                   # this block will run no matter how the try block exits
    GPIO.cleanup()         # clean up on exit