// Copyright 2024 Google LLC
//
// 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.

use std::collections::hash_map::Entry;

pub trait FallibleEntryExt<'a, K, V> {
    fn or_insert_with_result<F, E>(self, default: F) -> Result<&'a mut V, E>
    where
        F: FnOnce() -> Result<V, E>;
}

impl<'a, K, V> FallibleEntryExt<'a, K, V> for Entry<'a, K, V> {
    fn or_insert_with_result<F, E>(self, default: F) -> Result<&'a mut V, E>
    where
        F: FnOnce() -> Result<V, E>,
    {
        Ok(match self {
            Entry::Occupied(entry) => entry.into_mut(),
            Entry::Vacant(entry) => entry.insert(default()?),
        })
    }
}
