#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you 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 enum import Enum
from typing import Set

from airflow.compat.functools import cache


class WeightRule(str, Enum):
    """Weight rules."""

    DOWNSTREAM = 'downstream'
    UPSTREAM = 'upstream'
    ABSOLUTE = 'absolute'

    @classmethod
    def is_valid(cls, weight_rule: str) -> bool:
        """Check if weight rule is valid."""
        return weight_rule in cls.all_weight_rules()

    @classmethod
    @cache
    def all_weight_rules(cls) -> Set[str]:
        """Returns all weight rules"""
        return set(cls.__members__.values())

    def __str__(self) -> str:
        return self.value
