#! /usr/bin/python3

import os
import requests
import time
import calendar
import logging
from email.utils import parsedate
logging.basicConfig(level=logging.INFO)

HOSTS = os.environ['MIRROR_CHECK_HOSTS'].split()
OUTPUT_DIR = "/run/dsa-mirror-health-{}".format(os.environ['MIRROR_CHECK_SERVICE'])
HEALTH_FILE = os.path.join(OUTPUT_DIR, "health")
URL = os.environ['MIRROR_CHECK_URL']
INTERVAL = int(os.environ.get('MIRROR_CHECK_INTERVAL', '60'))

latest_tz = 0

def retrieve_from_host(host, url):
    proxies = {
        'http': 'http://{}:80'.format(host),
        'https': 'http://{}:443'.format(host),
    }
    return requests.get(url, timeout=5, proxies=proxies)

def last_modified(response):
    lm = 0
    if response.status_code == '200' and response.headers.get('last-modified'):
        lm = calendar.timegm(parsedate(response.headers['last-modified']))
    return lm

while True:
    start = time.time()
    for host in HOSTS:
        lm = last_modified(retrieve_from_host(host, URL))
        logging.debug("lm for host %s: %s", host, lm)
        if lm > latest_tz:
            latest_tz = lm
    local_lm = last_modified(retrieve_from_host('localhost', URL))
    logging.debug("lm for localhost: %s", lm)
    if latest_tz <= local_lm:
        try:
            logging.debug("considering myself unhealthy")
            os.remove(HEALTH_FILE)
        except OSError:
            pass
    else:
        logging.debug("considering myself healthy")
        open(HEALTH_FILE, 'w').write("OK")
    sleep_time = start + INTERVAL - time.time()
    logging.debug("sleeping for %d seconds", sleep_time)
    time.sleep(sleep_time)