text: /** @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.
   */
  "use strict";
  const symbol_observable_1 = require("symbol-observable");
  const wrapWithObserver_1 = require("./wrapWithObserver");
  /**
   * Observable is a standard interface that's useful for modeling multiple,
   * asynchronous events.
   *
   * IndefiniteObservable is a minimalist implementation of a subset of the TC39
   * Observable proposal.  It is indefinite because it will never call `complete`
   * or `error` on the provided observer.
   */
  class IndefiniteObservable {
      /**
       * The provided function should receive an observer and connect that
       * observer's `next` method to an event source (for instance,
       * `element.addEventListener('click', observer.next)`).
       *
       * It must return a function that will disconnect the observer from the event
       * source.
       */
      constructor(connect) {
          this._connect = connect;
      }
      /**
       * `subscribe` uses the function supplied to the constructor to connect an
       * observer to an event source.  Each observer is connected independently:
       * each call to `subscribe` calls `connect` with the new observer.
       *
       * To disconnect the observer from the event source, call `unsubscribe` on the
       * returned subscription.
       *
       * Note: `subscribe` accepts either a function or an object with a
       * next method.
       */
      subscribe(observerOrNext) {
          // For simplicity's sake, `subscribe` accepts `next` either as either an
          // anonymous function or wrapped in an object (the observer).  Since
          // `connect` always expects to receive an observer, wrap any loose
          // functions in an object.
          const observer = wrapWithObserver_1.default(observerOrNext);
          let disconnect = this._connect(observer);
          return {
              unsubscribe() {
                  if (disconnect) {
                      disconnect();
                      disconnect = undefined;
                  }
              }
          };
      }
      /**
       * Tells other libraries that know about observables that we are one.
       *
       * https://github.com/tc39/proposal-observable#observable
       */
      [symbol_observable_1.default]() {
          return this;
      }
  }
  Object.defineProperty(exports, "__esModule", { value: true });
  exports.default = IndefiniteObservable;
  //# sourceMappingURL=IndefiniteObservable.js.map