material-motion/src/operators/isAnyOf.ts

Makes it easy to add rich, interactive motion to your application.

/** @license
 *  Copyright 2016 - present The Material Motion Authors. All Rights Reserved.
 *
 *  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 {
  combineLatest,
} from '../combineLatest';

import {
  isBoolean,
  isDefined,
} from '../typeGuards';

import {
  Constructor,
  MotionReactiveMappable,
  NextChannel,
  Observable,
  ObservableWithMotionOperators,
} from '../types';

export type IsAnyOfCandidates<T> = Array<T | Observable<T>>;
export type IsAnyOfArgs<T> = {
  // To be consistent with our naming strategy, this should probably be called
  // candidate$s, but it looks weird to combine the two sufficies.
  candidates: IsAnyOfCandidates<T>,
};

export interface MotionIsAnyOfable<T> {
  isAnyOf(kwargs: IsAnyOfArgs<T>): ObservableWithMotionOperators<boolean>;
  isAnyOf(candidates: IsAnyOfCandidates<T>): ObservableWithMotionOperators<boolean>;
}

export function withIsAnyOf<T, S extends Constructor<MotionReactiveMappable<T>>>(superclass: S): S & Constructor<MotionIsAnyOfable<T>> {
  return class extends superclass implements MotionIsAnyOfable<T> {
    /**
     * Emits `true` when it receives a value that matches any of the
     * provided candidates and `false` otherwise.
     */
    isAnyOf(kwargs: IsAnyOfArgs<T>): ObservableWithMotionOperators<boolean>;
    isAnyOf(candidates: IsAnyOfCandidates<T>): ObservableWithMotionOperators<boolean>;
    isAnyOf({ candidates }: IsAnyOfArgs<T> & IsAnyOfCandidates<T>): ObservableWithMotionOperators<boolean> {
      if (!isDefined(candidates)) {
        candidates = arguments[0];
      }

      return combineLatest([ this, ...candidates ])._map({
        transform: ([ upstream, ...currentCandidates ]: Array<T>) => currentCandidates.includes(upstream)
      });
    }
  };
}