/**
 * @license
 * Copyright (C) 2021 The Android Open Source Project
 *
 * 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.
 */
import {Observable} from 'rxjs';
import {distinctUntilChanged, map, shareReplay} from 'rxjs/operators';
import {deepEqual} from './deep-util';

export function select<A, B>(obs$: Observable<A>, mapper: (_: A) => B) {
  return obs$.pipe(
    map(mapper),
    distinctUntilChanged(deepEqual),
    shareReplay(1)
  );
}