'''
mail_iterator.py - The module contains the MailIterator class.

Copyright (c) 2012 Intra2net AG
Author: Plamen Dimitrov

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
'''

import imaplib
import re
import time
import logging

MAILBOX_RESP = re.compile(r'\((?P<flags>.*?)\) "(?P<delimiter>.*)" (?P<name>.*)')
UIDVAL_RESP = re.compile(r'(?P<name>.*) \(UIDVALIDITY (?P<uidval>.*)\)')

class MailIterator:
    """This class communicates with the e-mail server."""

    # class attributes
    # IMAP4_SSL for connection with an IMAP server
    mail_con = None
    # list of tuples (uidvalidity, mailboxname) for the retrieved mailboxes
    mailboxes = None

    def __init__(self, server, username, password):
        """Creates a connection and a user session."""
        self.mail_con = imaplib.IMAP4_SSL(server)
        result, data = self.mail_con.login(username, password)
        if(result!="OK"):
            raise UserWarning("Could not log in as user " + username + ". " + data)
        result, self.mailboxes = self.mail_con.list()
        if(result!="OK"):
            raise UserWarning("Could not retrieve mailboxes for user " + username + ".")

    def __del__(self):
        """Closes the connection and the user session."""
        self.mail_con.close()
        self.mail_con.logout()

    def __iter__(self):
        """Iterates through all mailboxes, returns (uidval,name)."""
        for mailbox in self.mailboxes:
            logging.debug("Checking mailbox %s.", mailbox)
            mailbox = MAILBOX_RESP.match(mailbox.decode('iso-8859-1')).groups()
            result, data = self.mail_con.status(mailbox[2], '(UIDVALIDITY)')
            if(result!="OK"):
                raise UserWarning("Could not retrieve mailbox uidvalidity.")
            uidval = UIDVAL_RESP.match(data[0].decode('iso-8859-1')).groups()
            logging.debug("Extracted mailbox info is %s %s.", data[0], uidval)
            self.mail_con.select(mailbox[2])
            yield (mailbox[2], uidval[1])

    def fetch_messages(self):
        """Fetches the messages from the current mailbox, return list of uids."""
        result, data = self.mail_con.uid('search', None, "ALL")
        if(result!="OK"):
            raise UserWarning("Could not fetch messages.")
        mailid_list = data[0].split()
        return mailid_list

    def fetch_internal_date(self, mid):
        """Fetches the internal date of a message, returns a time tuple."""
        result, data = self.mail_con.uid('fetch', mid, '(INTERNALDATE)')
        if(result!="OK"):
            raise UserWarning("Could not fetch the internal date of message" + mid + ".")
        internal_date = imaplib.Internaldate2tuple(data[0])
        return internal_date

    def fetch_received_date(self, mid):
        """Fetches the received date of a message, returns bytes reponse."""
        result, data = self.mail_con.uid('fetch', mid, '(BODY.PEEK[HEADER.FIELDS (RECEIVED)])')
        if(result!="OK"):
            raise UserWarning("Could not fetch the received header of message" + mid + ".")
        return data[0][1].decode('iso-8859-1')

    def update_message(self, mid, mailbox, internal_date):
        """Replaces a message with one with correct internal date."""
        internal_date_seconds = time.mktime(internal_date.timetuple())
        internal_date_str = imaplib.Time2Internaldate(internal_date_seconds)
        result, data = self.mail_con.uid('fetch', mid, '(RFC822)')
        if(result!="OK"):
            raise UserWarning("Could not retrieve the entire e-mail" + mid + ".")
        #logging.debug("Entire e-mail is: %s", data[0][1])

        fetched_flags = self.mail_con.uid('fetch', mid, '(FLAGS)')[1][0]
        parsed_flags = imaplib.ParseFlags(fetched_flags)
        flags_str = " ".join(flag.decode('iso-8859-1') for flag in parsed_flags)
        result, data = self.mail_con.append(mailbox, flags_str,
                                            internal_date_str, data[0][1])
        logging.debug("Adding corrected copy of the message reponse: %s %s", result, data)
        if(result!="OK"):
            raise UserWarning("Could not replace the e-mail" + mid + ".")
        else:
            result, data = self.mail_con.uid('STORE', mid, '+FLAGS', r'(\Deleted)')
            logging.debug("Removing old copy of the message reponse: %s %s", result, data)
            if(result!="OK"):
                raise UserWarning("Could not delete the e-mail" + mid + ".")
            else: self.mail_con.expunge()
        return