# Copyright 2016  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 email


class MessageRenderer(object):

    def summary(self, msg):
        sender = self._get_header(msg, 'From')
        date = self._get_header(msg, 'Date')
        body = self._plain_text_body(msg)
        indented_body = self._indent(body.strip())
        return u'From: {}\nDate: {}\n\n{}'.format(
            sender, date, indented_body)

    def _indent(self, text):
        fmt = u'   {}\n'
        return u''.join(fmt.format(line) for line in text.splitlines())

    def _get_header(self, msg, name):
        decoded = email.header.decode_header(msg[name])
        combined = u' '.join(
            self._decode_safely(value, encoding)
            for value, encoding in decoded)
        return combined

    def _decode_safely(self, s, encoding):
        try:
            return s.decode(encoding or 'us-ascii')
        except LookupError:
            return repr(s)
        except UnicodeDecodeError:
            return repr(s)

    def _plain_text_body(self, msg):
        body = self._find_first_plain_text_part(msg)
        if body is None:
            return u''
        text = self._get_payload_as_unicode(body)
        return self._strip_signature(text)

    def _find_first_plain_text_part(self, msg):
        for part in msg.walk():
            if part.get_content_type() == 'text/plain':
                return part
        return None

    def _get_payload_as_unicode(self, body):
        charset = body.get_param('charset', 'us-ascii')
        text = body.get_payload(decode=True)
        return self._decode_safely(text, charset)

    def _strip_signature(self, text):
        sigsep = u'\n-- \n'
        parts = text.split(sigsep)
        return parts[0]