#!/usr/bin/python

"""
Check that the email-mirror management command is running regularly.

If old messages are in emailgateway@zulip.com's Inbox, the mirror must
not be running or processing messages correctly.
"""

import email
import time

from twisted.internet import protocol, reactor, ssl
from twisted.mail import imap4

GATEWAY_EMAIL = "emailgateway@zulip.com"
# Application-specific password.
PASSWORD = "xxxxxxxxxxxxxxxx"

SERVER = "imap.gmail.com"
PORT = 993

exit_code = 0

def done(_):
    reactor.stop()

def check_for_old_messages(result):
    if not result:
        return 0, "OK: no unprocessed messages."

    message_uids = result.keys()
    if not message_uids:
        return 0, "OK: no unprocessed old messages."
    message_uids.sort()

    oldest_message = email.message_from_string(result[message_uids[0]]["RFC822"])
    last_received_string = oldest_message.get_all("Received")[0].split(";", 1)[-1].strip()
    receipt_time = email.utils.mktime_tz(email.utils.parsedate_tz(last_received_string))
    if time.time() - receipt_time > 60 * 5: # More than 5 minutes old.
        return 2, "CRITICAL: email mirror has unprocessed old messages."
    return 0, "OK: no unprocessed old messages."

def print_nagios_status(result, proto):
    status, message = check_for_old_messages(result)
    print message

    global exit_code
    exit_code = status

    return proto.logout()

def examine_mailbox(result, proto, mailbox):
    # Fetch messages from a particular mailbox.
    return proto.fetchMessage("1:*", uid=True).addCallback(
        print_nagios_status, proto)

def select_mailbox(result, proto):
    # Select which mailbox we care about.
    mbox = filter(lambda x: "INBOX" in x[2], result)[0][2]
    return proto.select(mbox).addCallback(examine_mailbox, proto, result)

def list_mailboxes(res, proto):
    # List all of the mailboxes for this account.
    return proto.list("","*").addCallback(select_mailbox, proto)

def login_failed(failure):
    print "UNKNOWN: login to email gateway failed."
    global exit_code
    exit_code = 3

def connected(proto):
    d = proto.login(GATEWAY_EMAIL, PASSWORD)
    d.addCallback(list_mailboxes, proto)
    d.addErrback(login_failed)
    return d

def main():
    imap_client = protocol.ClientCreator(reactor, imap4.IMAP4Client)
    d = imap_client.connectSSL(SERVER, PORT, ssl.ClientContextFactory())
    d.addCallbacks(connected, login_failed)
    d.addBoth(done)

reactor.callLater(0, main)
reactor.run()
exit(exit_code)