#!/usr/bin/python3
# -*- coding: utf-8 -*-

import RPi.GPIO as GPIO
from datetime import date
from os import path
from os import getenv
import time
import sys

# Configuration
FAN_PIN = getenv('RPI_FAN_PIN', 21)  # BCM pin used to drive transistor's base
WAIT_TIME = getenv('RPI_FAN_WAITTIME', 10)  # [s] Time to wait between each refresh
FAN_MIN = getenv('RPI_FAN_MIN', 80)  # [%] Fan minimum speed.
PWM_FREQ = getenv('RPI_FAN_PWMFREQ', 25000)  # [Hz] Change this value if fan has strange behavior
# Fan speed will change only of the difference of temperature is higher than hysteresis
hyst = getenv('RPI_FAN_HYST', 1)
debug = bool(getenv('RPI_FAN_DEBUG', 'False'))

prom_collect_dir = getenv('RPI_PROM_COLLECTDIR','/tmp/textfile-collector')
prom_collect_file = prom_collect_dir + '/rpi_fan.prom'

# Configurable temperature and fan speed steps
tempSteps = [60, 70, 75, 80]  # [°C]
speedSteps = [0, 80, 90, 100]  # [%]
# tempSteps = [40, 45]
# speedSteps = [0, 100]

# Setup GPIO pin
GPIO.setmode(GPIO.BCM)
GPIO.setup(FAN_PIN, GPIO.OUT, initial=GPIO.LOW)
fan = GPIO.PWM(FAN_PIN, PWM_FREQ)
fan.start(0)

i = 0
cpuTemp = 0
fanSpeed = 0
cpuTempOld = 0
fanSpeedOld = 0

if debug:
    print('%s Temp: %s, Fan: %s' % (date.today(), cpuTemp, fanSpeed))

# We must set a speed value for each temperature step
if len(speedSteps) != len(tempSteps):
    print('Numbers of temp steps and speed steps are different')
    exit(0)

try:
    while 1:
        # Read CPU temperature
        cpuTempFile = open('/sys/class/thermal/thermal_zone0/temp', 'r')
        cpuTemp = float(cpuTempFile.read()) / 1000
        cpuTempFile.close()
        if debug:
            print('%s Temp: %s, Fan: %s' % (date.today(), cpuTemp, fanSpeed))
        # Calculate desired fan speed
        if abs(cpuTemp - cpuTempOld) > hyst:
            # Below first value, fan will run at min speed.
            if cpuTemp < tempSteps[0]:
                fanSpeed = speedSteps[0]
            # Above last value, fan will run at max speed
            elif cpuTemp >= tempSteps[len(tempSteps) - 1]:
                fanSpeed = speedSteps[len(tempSteps) - 1]
            # If temperature is between 2 steps, fan speed is calculated by linear interpolation
            else:
                for i in range(0, len(tempSteps) - 1):
                    if (cpuTemp >= tempSteps[i]) and (cpuTemp < tempSteps[i + 1]):
                        fanSpeed = round((speedSteps[i + 1] - speedSteps[i])
                                         / (tempSteps[i + 1] - tempSteps[i])
                                         * (cpuTemp - tempSteps[i])
                                         +speedSteps[i], 1)

            if fanSpeed != fanSpeedOld:
                if (fanSpeed != fanSpeedOld
                        and (fanSpeed >= FAN_MIN or fanSpeed == 0)):
                    fan.ChangeDutyCycle(fanSpeed)
                    fanSpeedOld = fanSpeed
                    if path.isdir(prom_collect_dir):
                        with open(prom_collect_file, 'w') as f:
                            str = '#HELP rpi_fan fan running at percent duty cycle\n'
                            str += '#TYPE rpi_fan gauge\n'
                            str += 'rpi_fan{component="sys"} %s\n' % fanSpeed
                            f.write(str)
                    if debug:
                        print('%s Temp: %s, Fan: %s' % (date.today(), cpuTemp, fanSpeed))
            cpuTempOld = cpuTemp

        # Wait until next refresh
        time.sleep(WAIT_TIME)

except Exception as exception:
    print('Exception: {}'.format(type(exception).__name__))
    print('Exception message: {}'.format(exception))
    GPIO.cleanup()
    sys.exit()