import os
import subprocess
import confparser
import imapclient
import contextlib
import backports.ssl
import socket

def conf_boolean_postprocess(src):
    src = src.lower().strip()
    if src == 'true' or src == 'on' or src == '1':
        return True
    return False

def conf_postprocess(conf):
    d = {
            'imap.tls':                     conf_boolean_postprocess,
            'imap.start_tls':               conf_boolean_postprocess,
            'imap.tls_nocheck_hostname':    conf_boolean_postprocess,
            'imap.tls_nocheck_ca':          conf_boolean_postprocess,
    }
    return {key: d[key](value) if key in d else value
            for key, value in conf.items()}

@contextlib.contextmanager
def connect_to_imap(conf, password):

    cafile = conf.get('imap.tls_ca', None)

    if cafile:
        cafile = os.path.expanduser(cafile)

    ssl_context = imapclient.create_default_context(cafile=cafile)

    if conf.get('imap.tls_nocheck_hostname', False):
        # don't check if certificate hostname doesn't match target hostname
        ssl_context.check_hostname = False

    if conf.get('imap.tls_nocheck_ca', False):
        # don't check if the certificate is trusted by a certificate authority
        ssl_context.verify_mode = backports.ssl.CERT_NONE

    connection = imapclient.IMAPClient(host=conf.get('imap.server'),
            ssl=conf.get('imap.tls', True),
            ssl_context=ssl_context)
    if conf.get('imap.start_tls', False):
        connection.start_tls(ssl_context=ssl_context)
    print('connection succeed')
    connection.login(username=conf.get('imap.username'), password=password)
    print('successfuly logged')

    # TODO: replace shutdown by logouts when it will not timeout through ssl
    try:
        yield connection
        #connection.logout()
    except (connection.AbortError, socket.error, socket.timeout,
            backports.ssl.SSLError, backports.ssl.CertificateError):
        raise
    else:
        pass
        #connection.logout()
    finally:
        connection.shutdown()


def imap_waiter(connection):
    '''
        from dovecot wiki:
        > If IDLE command is started, Dovecot never
        > disconnects. Only if the connection is lost there will be
        > a disconnection. A dead connection is detected by Dovecot
        > periodically sending "I'm still here" notifications to
        > client (imap_idle_notify_interval setting - default every
        > 2 minutes).
        >
        > IMAP clients are supposed to send something before 30
        > minutes are up, but several clients don't do this. Some
        > Outlook versions even stop receiving new mails entirely
        > until manual intervention if IMAP server disconnects the
        > client.

        We are a compliant client. To be compatible with a lot of servers
        (general assumption is a 29minutes timeout), we try to redo idle-mode
        every 24 minutes. Each call to imap_waiter is a single idle iteration.
        Thus this function may return empty list.
    '''
    print('entering idle mode...')
    connection.idle()
    print('waiting for an event')
    try:
        while True:
            events = connection.idle_check(timeout=24*60)
            if len(events) == 1 and \
                    str(bytes(events[0][0]), encoding='ascii') == 'OK':
                # in case of dovecot 'Ok still here' keepalives, timeout did
                # not expired (and never will appart from a disconnection)
                continue
            else:
                break
    except KeyboardInterrupt:
        print('quitting idle mode on interrupt.')
        connection.idle_done()
        raise
    print('quitting idle mode...')
    connection.idle_done()
    return [i for i in events if str(bytes(i[0]), encoding='ascii') != 'OK']


def main(callback=None):
    assert callback
    confpath = os.path.expanduser('~/.config/climl/climl.cfg')
    conf = conf_postprocess(confparser.read_conf(confpath))
    print('Read conf:', conf)
    password_command = conf.get('imap.password_command', None)
    if password_command:
        password = subprocess.check_output(password_command, shell=True)
        password = password.rstrip().decode('utf8')
        print('got pasword:', password)
    while True:
        print('connection...')
        try:
            with connect_to_imap(conf, password) as connection:
                print('selecting folder', conf.get('imap.mailbox'))
                connection.select_folder(conf.get('imap.mailbox'))
                while True:
                    events = imap_waiter(connection)
                    if events:
                        print('events:', events)
                        print('calling callback')
                        callback('mail')
        except (socket.error, socket.timeout):
            pass
        except KeyboardInterrupt:
            break
        print('end of connection')