#! /usr/bin/python3

import os
import requests
import time
import calendar
import logging
import subprocess
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_ts = 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, allow_redirects=False)

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

def check_shutdown():
    if subprocess.call(['dsa-is-shutdown-scheduled']) == 0:
        logging.info("considering myself unhealthy, shutdown scheduled")
        return False
    return True

def check_uptodate():
    global latest_ts
    for host in HOSTS:
        try:
            lm = last_modified(retrieve_from_host(host, URL))
            logging.debug("lm for host %s: %s", host, lm)
            if lm > latest_ts:
                latest_ts = lm
        except requests.exceptions.ProxyError:
            pass
    local_lm = last_modified(retrieve_from_host('localhost', URL))
    logging.debug("lm for localhost: %s", local_lm)
    if local_lm < latest_ts:
        logging.info("considering myself unhealthy my ts=%s latest_ts=%s", local_lm, latest_ts)
        return False
    return True

while True:
    start = time.time()
    if check_shutdown() and check_uptodate():
        logging.info("considering myself healthy")
        open(HEALTH_FILE, 'w').write("OK")
    else:
        try:
            os.remove(HEALTH_FILE)
        except OSError:
            pass
    sleep_time = start + INTERVAL - time.time()
    logging.debug("sleeping for %d seconds", sleep_time)
    time.sleep(sleep_time)