# Copyright (C) 2011-2012  Patrick Totzke <patricktotzke@gmail.com>
# This file is released under the GNU GPL, version 3 or a later revision.
# For further details see the COPYING file
from __future__ import absolute_import

import email
import email.charset as charset
import functools
from datetime import datetime

from notmuch import NullPointerError

from . import utils
from .utils import extract_body
from .utils import decode_header
from .attachment import Attachment
from .. import helper
from ..settings.const import settings

charset.add_charset('utf-8', charset.QP, charset.QP, 'utf-8')

MISSING_HTML_MSG = ("This message contains a text/html part that was not "
                    "rendered due to a missing mailcap entry. "
                    "Please refer to item 5 in our FAQ: "
                    "http://alot.rtfd.io/en/latest/faq.html")


@functools.total_ordering
class Message(object):

    """
    a persistent notmuch message object.
    It it uses a :class:`~alot.db.DBManager` for cached manipulation
    and lazy lookups.
    """
    def __init__(self, dbman, msg, thread=None):
        """
        :param dbman: db manager that is used for further lookups
        :type dbman: alot.db.DBManager
        :param msg: the wrapped message
        :type msg: notmuch.database.Message
        :param thread: this messages thread (will be looked up later if `None`)
        :type thread: :class:`~alot.db.Thread` or `None`
        """
        self._dbman = dbman
        self._id = msg.get_message_id()
        self._thread_id = msg.get_thread_id()
        self._thread = thread
        try:
            self._datetime = datetime.fromtimestamp(msg.get_date())
        except ValueError:
            self._datetime = None
        self._filename = msg.get_filename()
        self._email = None  # will be read upon first use
        self._attachments = None  # will be read upon first use
        self._tags = set(msg.get_tags())

        try:
            sender = decode_header(msg.get_header('From'))
            if not sender:
                sender = decode_header(msg.get_header('Sender'))
        except NullPointerError:
            sender = None
        if sender:
            self._from = sender
        elif 'draft' in self._tags:
            acc = settings.get_accounts()[0]
            self._from = '"{}" <{}>'.format(acc.realname, str(acc.address))
        else:
            self._from = '"Unknown" <>'

    def __str__(self):
        """prettyprint the message"""
        aname, aaddress = self.get_author()
        if not aname:
            aname = aaddress
        return "%s (%s)" % (aname, self.get_datestring())

    def __hash__(self):
        """needed for sets of Messages"""
        return hash(self._id)

    def __eq__(self, other):
        if isinstance(other, type(self)):
            return self._id == other.get_message_id()
        return NotImplemented

    def __ne__(self, other):
        if isinstance(other, type(self)):
            return self._id != other.get_message_id()
        return NotImplemented

    def __lt__(self, other):
        if isinstance(other, type(self)):
            return self._id < other.get_message_id()
        return NotImplemented

    def get_email(self):
        """returns :class:`email.Message` for this message"""
        path = self.get_filename()
        warning = "Subject: Caution!\n"\
                  "Message file is no longer accessible:\n%s" % path
        if not self._email:
            try:
                with open(path, 'rb') as f:
                    self._email = utils.message_from_bytes(f.read())
            except IOError:
                self._email = email.message_from_string(warning)
        return self._email

    def get_date(self):
        """returns Date header value as :class:`~datetime.datetime`"""
        return self._datetime

    def get_filename(self):
        """returns absolute path of message files location"""
        return self._filename

    def get_message_id(self):
        """returns messages id (str)"""
        return self._id

    def get_thread_id(self):
        """returns id (str) of the thread this message belongs to"""
        return self._thread_id

    def get_message_parts(self):
        """yield all body parts of this message"""
        for msg in self.get_email().walk():
            if not msg.is_multipart():
                yield msg

    def get_tags(self):
        """returns tags attached to this message as list of strings"""
        return sorted(self._tags)

    def get_thread(self):
        """returns the :class:`~alot.db.Thread` this msg belongs to"""
        if not self._thread:
            self._thread = self._dbman.get_thread(self._thread_id)
        return self._thread

    def has_replies(self):
        """returns true if this message has at least one reply"""
        return len(self.get_replies()) > 0

    def get_replies(self):
        """returns replies to this message as list of :class:`Message`"""
        t = self.get_thread()
        return t.get_replies_to(self)

    def get_datestring(self):
        """
        returns reformated datestring for this message.

        It uses :meth:`SettingsManager.represent_datetime` to represent
        this messages `Date` header

        :rtype: str
        """
        if self._datetime is None:
            res = None
        else:
            res = settings.represent_datetime(self._datetime)
        return res

    def get_author(self):
        """
        returns realname and address of this messages author

        :rtype: (str,str)
        """
        return email.utils.parseaddr(self._from)

    def add_tags(self, tags, afterwards=None, remove_rest=False):
        """
        adds tags to message

        .. note::

            This only adds the requested operation to this objects
            :class:`DBManager's <alot.db.DBManager>` write queue.
            You need to call :meth:`~alot.db.DBManager.flush` to write out.

        :param tags: a list of tags to be added
        :type tags: list of str
        :param afterwards: callback that gets called after successful
                           application of this tagging operation
        :type afterwards: callable
        :param remove_rest: remove all other tags
        :type remove_rest: bool
        """
        def myafterwards():
            if remove_rest:
                self._tags = set(tags)
            else:
                self._tags = self._tags.union(tags)
            if callable(afterwards):
                afterwards()

        self._dbman.tag('id:' + self._id, tags, afterwards=myafterwards,
                        remove_rest=remove_rest)
        self._tags = self._tags.union(tags)

    def remove_tags(self, tags, afterwards=None):
        """remove tags from message

        .. note::

            This only adds the requested operation to this objects
            :class:`DBManager's <alot.db.DBManager>` write queue.
            You need to call :meth:`~alot.db.DBManager.flush` to actually out.

        :param tags: a list of tags to be added
        :type tags: list of str
        :param afterwards: callback that gets called after successful
                           application of this tagging operation
        :type afterwards: callable
        """
        def myafterwards():
            self._tags = self._tags.difference(tags)
            if callable(afterwards):
                afterwards()

        self._dbman.untag('id:' + self._id, tags, myafterwards)

    def get_attachments(self):
        """
        returns messages attachments

        Derived from the leaves of the email mime tree
        that and are not part of :rfc:`2015` syntax for encrypted/signed mails
        and either have :mailheader:`Content-Disposition` `attachment`
        or have :mailheader:`Content-Disposition` `inline` but specify
        a filename (as parameter to `Content-Disposition`).

        :rtype: list of :class:`Attachment`
        """
        if not self._attachments:
            self._attachments = []
            for part in self.get_message_parts():
                cd = part.get('Content-Disposition', '')
                filename = part.get_filename()
                ct = part.get_content_type()
                # replace underspecified mime description by a better guess
                if ct in ['octet/stream', 'application/octet-stream']:
                    content = part.get_payload(decode=True)
                    ct = helper.guess_mimetype(content)

                if cd.lower().startswith('attachment'):
                    if ct.lower() not in ['application/pgp-encrypted',
                                          'application/pgp-signature']:
                        self._attachments.append(Attachment(part))
                elif cd.lower().startswith('inline'):
                    if (filename is not None and
                            ct.lower() != 'application/pgp'):
                        self._attachments.append(Attachment(part))
        return self._attachments

    def accumulate_body(self):
        """
        returns bodystring extracted from this mail
        """
        # TODO: allow toggle commands to decide which part is considered body
        eml = self.get_email()
        bodytext = extract_body(eml)

        # check if extracted body is empty but msg contains html parts
        if (not bodytext and
           'text/html' in (part.get_content_type() for part in eml.walk())):
            return MISSING_HTML_MSG
        return bodytext

    def get_text_content(self):
        return extract_body(self.get_email(), types=['text/plain'])

    def matches(self, querystring):
        """tests if this messages is in the resultset for `querystring`"""
        searchfor = '( {} ) AND id:{}'.format(querystring, self._id)
        return self._dbman.count_messages(searchfor) > 0