# Copyright 2014  Lars Wirzenius
#
# 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.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# =*= License: GPL-3+ =*=


import contextlib
import mailbox
import os

import distixlib


class TicketDirectoryExistsError(distixlib.StructuredError):

    msg = "Can't save to directory {dirname}: it already exists"


class TicketDirectoryDoesNotExistError(distixlib.StructuredError):

    msg = (
        "Can't save ticket changes to directory {dirname}: "
        "it does not exist")


class TicketSaver(object):

    _tag_name = '.this-dir-not-empty'

    def create_ticket_on_disk(self, ticket, dirname):
        '''Create new ticket on disk.

        Return list of pathnames to regular files that got created.

        '''

        if os.path.exists(dirname):
            raise distixlib.TicketDirectoryExistsError(dirname=dirname)

        self._create_ticket_directory(dirname)
        filenames = [self._save_ticket_metadata(ticket, dirname)]
        return filenames

    def _create_ticket_directory(self, dirname):
        os.mkdir(dirname)

    def _save_ticket_metadata(self, ticket, dirname):
        filename = os.path.join(dirname, 'ticket.yaml')
        saver = distixlib.MetadataSaver()
        saver.save_to_file(filename, ticket.get_ticket_metadata())
        return filename

    def _save_messages(self, messages, dirname):  # pragma: no cover
        maildir_pathname = self._get_maildir_pathname(dirname)
        maildir = self._open_maildir(maildir_pathname)
        filenames = self._tag_empty_maildir_subdirs(maildir_pathname)
        with contextlib.closing(maildir):
            return (
                filenames +
                self._save_messages_to_maildir(messages, maildir))

    def _get_maildir_pathname(self, dirname):  # pragma: no cover
        return os.path.join(dirname, distixlib.maildir_name)

    def _tag_empty_maildir_subdirs(self, maildir_pathname):  # pragma: no cover
        subdirs = ('tmp', 'new', 'cur')
        filenames = [
            os.path.join(maildir_pathname, subdir, self._tag_name)
            for subdir in subdirs]
        for filename in filenames:
            self._tag_directory(filename)
        return filenames

    def _tag_directory(self, dirname):  # pragma: no cover
        # Python's mailbox.Maildir does NOT ignore files with a
        # leading dot, despite the spec
        # (http://cr.yp.to/proto/maildir.html) clearly saying it should.
        # We work around this by creating a dot-something subdirectory
        # putting an empty file there.

        subdir = os.path.join(dirname, '.empty')
        if not os.path.exists(subdir):
            os.makedirs(subdir)

        filename = os.path.join(subdir, 'empty-file')
        with open(filename, 'wb'):
            pass

    def _save_messages_to_maildir(self, messages, maildir):  # pragma: no cover
        filenames = []
        for message in messages:
            filenames.extend(self._save_message_to_maildir(message, maildir))
        return filenames

    def _save_message_to_maildir(self, message, maildir):  # pragma: no cover
        key = maildir.add(message)
        with contextlib.closing(maildir.get_file(key)) as f:
            # The following is really ugly. It uses a private
            # attribute of the file-like object that the Maildir
            # object returns. The file-like object is, in Python 2.7,
            # an instance of mailbox._ProxyFile, and for Maildir
            # objects it wraps around a real file object. Real file
            # objects store the name of the file they access in the
            # name attribute.
            #
            # I could not find any other name to get the name of the
            # file of the message we have just added to the Maildir.
            return [f._file.name]

    def _open_maildir(self, maildir_path):  # pragma: no cover
        return mailbox.Maildir(maildir_path, factory=None, create=True)

    def save_changes_to_ticket(self, ticket, dirname):  # pragma: no cover
        if not os.path.exists(dirname):
            raise distixlib.TicketDirectoryDoesNotExistError(
                dirname=dirname)
        filenames = [self._save_ticket_metadata(ticket, dirname)]
        filenames.extend(
            self._save_messages(ticket.get_dirty_messages(), dirname))
        return filenames