--- /dev/null
+import { Observable } from '../Observable';
+import { isArray } from '../util/isArray';
+import { isFunction } from '../util/isFunction';
+import { NodeEventHandler } from './fromEvent';
+import { map } from '../operators/map';
+
+/* tslint:disable:max-line-length */
+export function fromEventPattern<T>(addHandler: (handler: NodeEventHandler) => any, removeHandler?: (handler: NodeEventHandler, signal?: any) => void): Observable<T>;
+/** @deprecated resultSelector no longer supported, pipe to map instead */
+export function fromEventPattern<T>(addHandler: (handler: NodeEventHandler) => any, removeHandler?: (handler: NodeEventHandler, signal?: any) => void, resultSelector?: (...args: any[]) => T): Observable<T>;
+/* tslint:enable:max-line-length */
+
+/**
+ * Creates an Observable from an arbitrary API for registering event handlers.
+ *
+ * <span class="informal">When that method for adding event handler was something {@link fromEvent}
+ * was not prepared for.</span>
+ *
+ * 
+ *
+ * `fromEventPattern` allows you to convert into an Observable any API that supports registering handler functions
+ * for events. It is similar to {@link fromEvent}, but far
+ * more flexible. In fact, all use cases of {@link fromEvent} could be easily handled by
+ * `fromEventPattern` (although in slightly more verbose way).
+ *
+ * This operator accepts as a first argument an `addHandler` function, which will be injected with
+ * handler parameter. That handler is actually an event handler function that you now can pass
+ * to API expecting it. `addHandler` will be called whenever Observable
+ * returned by the operator is subscribed, so registering handler in API will not
+ * necessarily happen when `fromEventPattern` is called.
+ *
+ * After registration, every time an event that we listen to happens,
+ * Observable returned by `fromEventPattern` will emit value that event handler
+ * function was called with. Note that if event handler was called with more
+ * then one argument, second and following arguments will not appear in the Observable.
+ *
+ * If API you are using allows to unregister event handlers as well, you can pass to `fromEventPattern`
+ * another function - `removeHandler` - as a second parameter. It will be injected
+ * with the same handler function as before, which now you can use to unregister
+ * it from the API. `removeHandler` will be called when consumer of resulting Observable
+ * unsubscribes from it.
+ *
+ * In some APIs unregistering is actually handled differently. Method registering an event handler
+ * returns some kind of token, which is later used to identify which function should
+ * be unregistered or it itself has method that unregisters event handler.
+ * If that is the case with your API, make sure token returned
+ * by registering method is returned by `addHandler`. Then it will be passed
+ * as a second argument to `removeHandler`, where you will be able to use it.
+ *
+ * If you need access to all event handler parameters (not only the first one),
+ * or you need to transform them in any way, you can call `fromEventPattern` with optional
+ * third parameter - project function which will accept all arguments passed to
+ * event handler when it is called. Whatever is returned from project function will appear on
+ * resulting stream instead of usual event handlers first argument. This means
+ * that default project can be thought of as function that takes its first parameter
+ * and ignores the rest.
+ *
+ * ## Example
+ * ### Emits clicks happening on the DOM document
+ *
+ * ```ts
+ * import { fromEventPattern } from 'rxjs';
+ *
+ * function addClickHandler(handler) {
+ * document.addEventListener('click', handler);
+ * }
+ *
+ * function removeClickHandler(handler) {
+ * document.removeEventListener('click', handler);
+ * }
+ *
+ * const clicks = fromEventPattern(
+ * addClickHandler,
+ * removeClickHandler
+ * );
+ * clicks.subscribe(x => console.log(x));
+ *
+ * // Whenever you click anywhere in the browser, DOM MouseEvent
+ * // object will be logged.
+ * ```
+ *
+ * ## Example
+ * ### Use with API that returns cancellation token
+ *
+ * ```ts
+ * import { fromEventPattern } from 'rxjs';
+ *
+ * const token = someAPI.registerEventHandler(function() {});
+ * someAPI.unregisterEventHandler(token); // this APIs cancellation method accepts
+ * // not handler itself, but special token.
+ *
+ * const someAPIObservable = fromEventPattern(
+ * function(handler) { return someAPI.registerEventHandler(handler); }, // Note that we return the token here...
+ * function(handler, token) { someAPI.unregisterEventHandler(token); } // ...to then use it here.
+ * );
+ * ```
+ *
+ * ## Example
+ * ### Use with project function
+ *
+ * ```ts
+ * import { fromEventPattern } from 'rxjs';
+ *
+ * someAPI.registerEventHandler((eventType, eventMessage) => {
+ * console.log(eventType, eventMessage); // Logs "EVENT_TYPE" "EVENT_MESSAGE" to console.
+ * });
+ *
+ * const someAPIObservable = fromEventPattern(
+ * handler => someAPI.registerEventHandler(handler),
+ * handler => someAPI.unregisterEventHandler(handler)
+ * (eventType, eventMessage) => eventType + " --- " + eventMessage // without that function only "EVENT_TYPE"
+ * ); // would be emitted by the Observable
+ *
+ * someAPIObservable.subscribe(value => console.log(value));
+ *
+ * // Logs:
+ * // "EVENT_TYPE --- EVENT_MESSAGE"
+ * ```
+ *
+ * @see {@link fromEvent}
+ * @see {@link bindCallback}
+ * @see {@link bindNodeCallback}
+ *
+ * @param {function(handler: Function): any} addHandler A function that takes
+ * a `handler` function as argument and attaches it somehow to the actual
+ * source of events.
+ * @param {function(handler: Function, token?: any): void} [removeHandler] A function that
+ * takes a `handler` function as an argument and removes it from the event source. If `addHandler`
+ * returns some kind of token, `removeHandler` function will have it as a second parameter.
+ * @param {function(...args: any): T} [project] A function to
+ * transform results. It takes the arguments from the event handler and
+ * should return a single value.
+ * @return {Observable<T>} Observable which, when an event happens, emits first parameter
+ * passed to registered event handler. Alternatively it emits whatever project function returns
+ * at that moment.
+ * @static true
+ * @name fromEventPattern
+ * @owner Observable
+ */
+
+export function fromEventPattern<T>(addHandler: (handler: NodeEventHandler) => any,
+ removeHandler?: (handler: NodeEventHandler, signal?: any) => void,
+ resultSelector?: (...args: any[]) => T): Observable<T | T[]> {
+
+ if (resultSelector) {
+ // DEPRECATED PATH
+ return fromEventPattern<T>(addHandler, removeHandler).pipe(
+ map(args => isArray(args) ? resultSelector(...args) : resultSelector(args))
+ );
+ }
+
+ return new Observable<T | T[]>(subscriber => {
+ const handler = (...e: T[]) => subscriber.next(e.length === 1 ? e[0] : e);
+
+ let retValue: any;
+ try {
+ retValue = addHandler(handler);
+ } catch (err) {
+ subscriber.error(err);
+ return undefined;
+ }
+
+ if (!isFunction(removeHandler)) {
+ return undefined;
+ }
+
+ return () => removeHandler(handler, retValue) ;
+ });
+}
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