#!/usr/bin/python3
# -*- coding: utf-8 -*-
# Copyright © 2008 Canonical Ltd.
# Author: Scott James Remnant <scott at ubuntu.com>.
# Hacked up by: Bryce Harrington <bryce at ubuntu.com>
# Change merge_changelog to merge-changelog: Ryan Kavanagh
#                                            <ryanakca@kubuntu.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of version 3 of the GNU General Public License as
# published by the Free Software Foundation.
#
# 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/>.

import sys

from debian.changelog import Changelog


def usage(exit_code=1):
    print('''Usage: merge-changelog <left changelog> <right changelog>

merge-changelog takes two changelogs that once shared a common source,
merges them back together, and prints the merged result to stdout.  This
is useful if you need to manually merge a ubuntu package with a new
Debian release of the package.
''')
    sys.exit(exit_code)

########################################################################
# Changelog Management
########################################################################


def merge_changelog(left_changelog, right_changelog):
    """Merge a changelog file."""

    with open(left_changelog) as f:
        left_cl = Changelog(f)
    with open(right_changelog) as f:
        right_cl = Changelog(f)

    left_versions = set(left_cl.versions)
    right_versions = set(right_cl.versions)
    left_blocks = iter(left_cl)
    right_blocks = iter(right_cl)

    for version in sorted(left_versions | right_versions, reverse=True):
        if version in left_versions:
            block = next(left_blocks)
            if version in right_versions:
                next(right_blocks)
        else:
            block = next(right_blocks)

        assert block.version == version

        print(str(block).strip(), end='\n\n')


def main():
    if len(sys.argv) > 1 and sys.argv[1] in ('-h', '--help'):
        usage(0)
    if len(sys.argv) != 3:
        usage(1)

    left_changelog = sys.argv[1]
    right_changelog = sys.argv[2]

    merge_changelog(left_changelog, right_changelog)
    sys.exit(0)


if __name__ == '__main__':
    main()