#
# This source file is part of the EdgeDB open source project.
#
# Copyright 2011-present MagicStack Inc. and the EdgeDB authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#


from __future__ import annotations


def distance(s: str, t: str) -> int:
    """Calculates Levenshtein distance between s and t."""

    m, n = len(s), len(t)

    if m > n:
        s, t = t, s
        m, n = n, m

    ri = list(range(m + 1))

    for i in range(1, n + 1):
        ri_1, ri = ri, [i] + [0] * m

        for j in range(1, m + 1):
            ri[j] = min(ri_1[j] + 1,
                        ri[j - 1] + 1,
                        ri_1[j - 1] + int(s[j - 1] != t[i - 1]))

    return ri[m]
