--- /dev/null
+import { WebSocketSubject, WebSocketSubjectConfig } from './WebSocketSubject';
+
+/**
+ * Wrapper around the w3c-compatible WebSocket object provided by the browser.
+ *
+ * <span class="informal">{@link Subject} that communicates with a server via WebSocket</span>
+ *
+ * `webSocket` is a factory function that produces a `WebSocketSubject`,
+ * which can be used to make WebSocket connection with an arbitrary endpoint.
+ * `webSocket` accepts as an argument either a string with url of WebSocket endpoint, or an
+ * {@link WebSocketSubjectConfig} object for providing additional configuration, as
+ * well as Observers for tracking lifecycle of WebSocket connection.
+ *
+ * When `WebSocketSubject` is subscribed, it attempts to make a socket connection,
+ * unless there is one made already. This means that many subscribers will always listen
+ * on the same socket, thus saving resources. If however, two instances are made of `WebSocketSubject`,
+ * even if these two were provided with the same url, they will attempt to make separate
+ * connections. When consumer of a `WebSocketSubject` unsubscribes, socket connection is closed,
+ * only if there are no more subscribers still listening. If after some time a consumer starts
+ * subscribing again, connection is reestablished.
+ *
+ * Once connection is made, whenever a new message comes from the server, `WebSocketSubject` will emit that
+ * message as a value in the stream. By default, a message from the socket is parsed via `JSON.parse`. If you
+ * want to customize how deserialization is handled (if at all), you can provide custom `resultSelector`
+ * function in {@link WebSocketSubject}. When connection closes, stream will complete, provided it happened without
+ * any errors. If at any point (starting, maintaining or closing a connection) there is an error,
+ * stream will also error with whatever WebSocket API has thrown.
+ *
+ * By virtue of being a {@link Subject}, `WebSocketSubject` allows for receiving and sending messages from the server. In order
+ * to communicate with a connected endpoint, use `next`, `error` and `complete` methods. `next` sends a value to the server, so bear in mind
+ * that this value will not be serialized beforehand. Because of This, `JSON.stringify` will have to be called on a value by hand,
+ * before calling `next` with a result. Note also that if at the moment of nexting value
+ * there is no socket connection (for example no one is subscribing), those values will be buffered, and sent when connection
+ * is finally established. `complete` method closes socket connection. `error` does the same,
+ * as well as notifying the server that something went wrong via status code and string with details of what happened.
+ * Since status code is required in WebSocket API, `WebSocketSubject` does not allow, like regular `Subject`,
+ * arbitrary values being passed to the `error` method. It needs to be called with an object that has `code`
+ * property with status code number and optional `reason` property with string describing details
+ * of an error.
+ *
+ * Calling `next` does not affect subscribers of `WebSocketSubject` - they have no
+ * information that something was sent to the server (unless of course the server
+ * responds somehow to a message). On the other hand, since calling `complete` triggers
+ * an attempt to close socket connection. If that connection is closed without any errors, stream will
+ * complete, thus notifying all subscribers. And since calling `error` closes
+ * socket connection as well, just with a different status code for the server, if closing itself proceeds
+ * without errors, subscribed Observable will not error, as one might expect, but complete as usual. In both cases
+ * (calling `complete` or `error`), if process of closing socket connection results in some errors, *then* stream
+ * will error.
+ *
+ * **Multiplexing**
+ *
+ * `WebSocketSubject` has an additional operator, not found in other Subjects. It is called `multiplex` and it is
+ * used to simulate opening several socket connections, while in reality maintaining only one.
+ * For example, an application has both chat panel and real-time notifications about sport news. Since these are two distinct functions,
+ * it would make sense to have two separate connections for each. Perhaps there could even be two separate services with WebSocket
+ * endpoints, running on separate machines with only GUI combining them together. Having a socket connection
+ * for each functionality could become too resource expensive. It is a common pattern to have single
+ * WebSocket endpoint that acts as a gateway for the other services (in this case chat and sport news services).
+ * Even though there is a single connection in a client app, having the ability to manipulate streams as if it
+ * were two separate sockets is desirable. This eliminates manually registering and unregistering in a gateway for
+ * given service and filter out messages of interest. This is exactly what `multiplex` method is for.
+ *
+ * Method accepts three parameters. First two are functions returning subscription and unsubscription messages
+ * respectively. These are messages that will be sent to the server, whenever consumer of resulting Observable
+ * subscribes and unsubscribes. Server can use them to verify that some kind of messages should start or stop
+ * being forwarded to the client. In case of the above example application, after getting subscription message with proper identifier,
+ * gateway server can decide that it should connect to real sport news service and start forwarding messages from it.
+ * Note that both messages will be sent as returned by the functions, they are by default serialized using JSON.stringify, just
+ * as messages pushed via `next`. Also bear in mind that these messages will be sent on *every* subscription and
+ * unsubscription. This is potentially dangerous, because one consumer of an Observable may unsubscribe and the server
+ * might stop sending messages, since it got unsubscription message. This needs to be handled
+ * on the server or using {@link publish} on a Observable returned from 'multiplex'.
+ *
+ * Last argument to `multiplex` is a `messageFilter` function which should return a boolean. It is used to filter out messages
+ * sent by the server to only those that belong to simulated WebSocket stream. For example, server might mark these
+ * messages with some kind of string identifier on a message object and `messageFilter` would return `true`
+ * if there is such identifier on an object emitted by the socket. Messages which returns `false` in `messageFilter` are simply skipped,
+ * and are not passed down the stream.
+ *
+ * Return value of `multiplex` is an Observable with messages incoming from emulated socket connection. Note that this
+ * is not a `WebSocketSubject`, so calling `next` or `multiplex` again will fail. For pushing values to the
+ * server, use root `WebSocketSubject`.
+ *
+ * ### Examples
+ * #### Listening for messages from the server
+ * ```ts
+ * import { webSocket } from "rxjs/webSocket";
+ * const subject = webSocket("ws://localhost:8081");
+ *
+ * subject.subscribe(
+ * msg => console.log('message received: ' + msg), // Called whenever there is a message from the server.
+ * err => console.log(err), // Called if at any point WebSocket API signals some kind of error.
+ * () => console.log('complete') // Called when connection is closed (for whatever reason).
+ * );
+ * ```
+ *
+ * #### Pushing messages to the server
+ * ```ts
+ * import { webSocket } from "rxjs/webSocket";
+ * const subject = webSocket('ws://localhost:8081');
+ *
+ * subject.subscribe();
+ * // Note that at least one consumer has to subscribe to the created subject - otherwise "nexted" values will be just buffered and not sent,
+ * // since no connection was established!
+ *
+ * subject.next({message: 'some message'});
+ * // This will send a message to the server once a connection is made. Remember value is serialized with JSON.stringify by default!
+ *
+ * subject.complete(); // Closes the connection.
+ *
+ * subject.error({code: 4000, reason: 'I think our app just broke!'});
+ * // Also closes the connection, but let's the server know that this closing is caused by some error.
+ * ```
+ *
+ * #### Multiplexing WebSocket
+ * ```ts
+ * import { webSocket } from "rxjs/webSocket";
+ * const subject = webSocket('ws://localhost:8081');
+ *
+ * const observableA = subject.multiplex(
+ * () => ({subscribe: 'A'}), // When server gets this message, it will start sending messages for 'A'...
+ * () => ({unsubscribe: 'A'}), // ...and when gets this one, it will stop.
+ * message => message.type === 'A' // If the function returns `true` message is passed down the stream. Skipped if the function returns false.
+ * );
+ *
+ * const observableB = subject.multiplex( // And the same goes for 'B'.
+ * () => ({subscribe: 'B'}),
+ * () => ({unsubscribe: 'B'}),
+ * message => message.type === 'B'
+ * );
+ *
+ * const subA = observableA.subscribe(messageForA => console.log(messageForA));
+ * // At this moment WebSocket connection is established. Server gets '{"subscribe": "A"}' message and starts sending messages for 'A',
+ * // which we log here.
+ *
+ * const subB = observableB.subscribe(messageForB => console.log(messageForB));
+ * // Since we already have a connection, we just send '{"subscribe": "B"}' message to the server. It starts sending messages for 'B',
+ * // which we log here.
+ *
+ * subB.unsubscribe();
+ * // Message '{"unsubscribe": "B"}' is sent to the server, which stops sending 'B' messages.
+ *
+ * subA.unsubscribe();
+ * // Message '{"unsubscribe": "A"}' makes the server stop sending messages for 'A'. Since there is no more subscribers to root Subject,
+ * // socket connection closes.
+ * ```
+ *
+ *
+ * @param {string|WebSocketSubjectConfig} urlConfigOrSource The WebSocket endpoint as an url or an object with
+ * configuration and additional Observers.
+ * @return {WebSocketSubject} Subject which allows to both send and receive messages via WebSocket connection.
+ */
+export function webSocket<T>(urlConfigOrSource: string | WebSocketSubjectConfig<T>): WebSocketSubject<T> {
+ return new WebSocketSubject<T>(urlConfigOrSource);
+}
projects / dotfiles / .git / blobdiff