#! /usr/bin/python
## vim: fileencoding=utf-8

"""Open Debian BTS mboxes with Mutt, à la /usr/bin/bts show --mbox.

A cache of mboxes is kept, and changed mboxes will be merged with existing
files instead of replacing them, so that e.g. read-status is preserved for each
message.
"""

import os
import re
import sys
import urllib
import mailbox
import tempfile
import email.Parser

MBOX_DIR = os.path.expanduser('~/.mail/y.bug-cache')

##

def main():
    if len(sys.argv) != 2:
        print >>sys.stderr, 'Usage: %s <bugnumber>' % (sys.argv[0],)
        sys.exit(1)

    bug = re.sub(r'[^0-9]', '', sys.argv[1])
    if not re.match(r'\d{4,}$', bug):
        print >>sys.stderr, \
            'E: %s does not seem a valid number' % (sys.argv[1],)
        sys.exit(1)

    path = mbox_update(bug)
    invoke_mailer(path)

##

def mbox_update(bug):
    """Return a path with an up-to-date copy of the mbox for bug."""
    path = os.path.join(MBOX_DIR, bug + '.mbox')

    if not os.path.exists(path):
        f = file(path, 'wb')
        try:
            retrieve_mbox(bug, f)
        except:
            os.unlink(path)
            raise
        else:
            f.close()
    else:
        # make a list of Message-Id we have
        fp1 = file(path, 'ab+')
        ids1 = [ x.get('Message-Id') for x in mailbox.UnixMailbox(fp1) ]

        # get remote mbox again
        fp2 = tempfile.TemporaryFile()
        retrieve_mbox(bug, fp2)

        # parse its messages
        fp2.seek(0)
        parser = email.Parser.Parser()
        msgs2 = dict((x['Message-Id'], x)
                    for x in mailbox.UnixMailbox(fp2, parser.parse))

        # now append the new ones
        for msgid in set(msgs2.keys()) - set(ids1):
            fp1.write('\n' + msgs2[msgid].as_string(unixfrom=True))

    return path

def retrieve_mbox(bug, fileobj):
    """Retrieve mbox for bug from bugs.debian.org, writing it to fileobj."""
    for line in urllib.urlopen(
            'http://bugs.debian.org/cgi-bin/bugreport.cgi?mboxstatus=yes;mboxmaint=yes;mbox=yes;bug=%s' % (bug,)):
        fileobj.write(line)

def invoke_mailer(path):
    """Exec mutt, opening path."""
    os.execlp('mutt', 'mutt', '-f', path)

##

if __name__ == '__main__':
    try:
        sys.exit(main())
    except KeyboardInterrupt:
        print >>sys.stderr, '\nCancelled.'
        sys.exit(1)