# -*- coding: utf-8 -*-
#
# Copyright © 2012 - 2017 Michal Čihař <michal@cihar.com>
#
# This file is part of Weblate <https://weblate.org/>
#
# 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 <https://www.gnu.org/licenses/>.
#
from __future__ import unicode_literals

from difflib import SequenceMatcher


def html_diff(old, new):
    """Generate HTML formatted diff of two strings."""
    diff = SequenceMatcher(None, old, new)
    result = []
    for tag, oldpos1, oldpos2, newpos1, newpos2 in diff.get_opcodes():
        if tag == 'replace':
            result.append(
                '<del>{0}</del><ins>{1}</ins>'.format(
                    old[oldpos1:oldpos2], new[newpos1:newpos2]
                )
            )
        elif tag == 'delete':
            result.append(
                '<del>{0}</del>'.format(
                    old[oldpos1:oldpos2]
                )
            )
        elif tag == 'insert':
            result.append(
                '<ins>{0}</ins>'.format(
                    new[newpos1:newpos2]
                )
            )
        elif tag == 'equal':
            result.append(new[newpos1:newpos2])
    return ''.join(result)
