material-motion/src/operators/inverted.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 {
  isBoolean,
} from '../typeGuards';

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

export interface MotionInvertible<T> {
  inverted<U extends T & number>(): ObservableWithMotionOperators<U>;
}

export function withInverted<T, S extends Constructor<MotionNextOperable<T>>>(superclass: S): S & Constructor<MotionInvertible<T>> {
  return class extends superclass implements MotionInvertible<T> {
    /**
     * Emits the complementary percentage of a number between 0 and 1
     * (inclusive).
     *
     * For instance, if it receives `.33`, it will emit `.67`.
     */
    inverted<U extends T & number>(): ObservableWithMotionOperators<U> {
      return (this as any as MotionNextOperable<U>)._nextOperator({
        operation: ({ emit }) => ({ upstream }) => {
          emit((1 - (upstream as number)) as U);
        }
      });
    }
  };
}