#!/usr/bin/env python3
import os
import glob
import datetime
import time
import RPi.GPIO as GPIO

control_pin = 6 # broadcom pin 4

def F_to_C(t):
    return (t-32)/1.8

min_temperature = F_to_C(67.0)
max_temperature = F_to_C(68.0)
heater_on = False
heater_change_ts = 0
heater_hysteresis = 5 * 60  # five minutes

os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

base_dir = '/sys/bus/w1/devices/'
device_folder = glob.glob(base_dir + '28*')[0]
device_file = device_folder + '/w1_slave'

def update_setting(t):
    global heater_on, heater_change_ts, heater_hysteresis
    global min_temperature, max_temperature

    want_on = True if t <= min_temperature else heater_on
    if t >= max_temperature: want_on = False

    if want_on != heater_on:
        now = unix_ts()
        date_time = ymdhms(now)
        if now - heater_change_ts < heater_hysteresis:
            print(date_time, 'Heater changed too recently...not changing')
        else:
            heater_on = want_on
            heater_change_ts = now
            set_heater_on(heater_on)
            print(date_time, 'Heater on' if heater_on else 'Heater off')

def read_temperature_raw():
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines

def read_temperature():
    lines = read_temperature_raw()
    while lines[0].strip()[-3:] != 'YES':
        time.sleep(0.2)
        lines = read_temperature_raw()
    equals_pos = lines[1].find('t=')
    if equals_pos != -1:
        temp_string = lines[1][equals_pos+2:]
        temp_c = float(temp_string) / 1000.0
        return temp_c, time.time()
    else:
        return 0, 0

def unix_ts():
    return int(datetime.datetime.now(tz=datetime.timezone.utc).timestamp())

def ymdhms(ts):
    return datetime.datetime.utcfromtimestamp(ts).strftime('%Y-%m-%d %H:%M:%S')

def init_control():
    global control_pin
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)
    GPIO.setup(control_pin, GPIO.OUT)
    GPIO.output(control_pin, GPIO.LOW)

def set_heater_on(want_on):
    GPIO.output(control_pin, GPIO.HIGH if want_on else GPIO.LOW)

def read_range():
    with open("range.txt") as f:
        low = (float(f.readline()) - 32)/1.8;
        high = (float(f.readline()) - 32)/1.8;
    return low, high

def mainloop():
    global min_temperature, max_temperature, heater_on
    error_count = 0
    while True:
        temperature, temperature_ts = read_temperature()
        if temperature_ts == 0:
            error_count += 1
            if error_count > 20:
                set_heater_on(False)
                return
            time.sleep(60)
        else:
            error_count = 0
            print(temperature, temperature_ts, min_temperature, max_temperature, heater_on)
            update_setting(temperature)
            time.sleep(60)
            min_temperature, max_temperature = read_range()

init_control()
try:
    mainloop()
except Exception as e:
    print('Exception', e)
    set_heater_on(False)
    GPIO.cleanup()