feat: Implement the Solid WebSocket protocol.

.eslintrc.js

@@ -38,6 +38,7 @@ module.exports = {
     'class-methods-use-this': 'off', // conflicts with functions from interfaces that sometimes don't require `this`
     'comma-dangle': ['error', 'always-multiline'],
     'dot-location': ['error', 'property'],
+    'lines-around-comment': 'off', // conflicts with padded-blocks
     'lines-between-class-members': ['error', 'always', { exceptAfterSingleLine: true }],
     'max-len': ['error', { code: 120, ignoreUrls: true }],
     'new-cap': 'off', // used for RDF constants

src/ldp/UnsecureWebSocketsProtocol.ts

@@ -0,0 +1,145 @@
+import { EventEmitter } from 'events';
+import type WebSocket from 'ws';
+import { getLoggerFor } from '../logging/LogUtil';
+import type { HttpRequest } from '../server/HttpRequest';
+import { WebSocketHandler } from '../server/WebSocketHandler';
+import type { ResourceIdentifier } from './representation/ResourceIdentifier';
+
+const VERSION = 'solid/0.1.0-alpha';
+
+/**
+ * Implementation of Solid WebSockets API Spec solid/0.1.0-alpha
+ * at https://github.com/solid/solid-spec/blob/master/api-websockets.md
+ */
+class WebSocketListener extends EventEmitter {
+  private host = '';
+  private protocol = '';
+  private readonly socket: WebSocket;
+  private readonly subscribedPaths = new Set<string>();
+  private readonly logger = getLoggerFor(this);
+
+  public constructor(socket: WebSocket) {
+    super();
+    this.socket = socket;
+    socket.addListener('error', (): void => this.stop());
+    socket.addListener('close', (): void => this.stop());
+    socket.addListener('message', (message: string): void => this.onMessage(message));
+  }
+
+  public start(upgradeRequest: HttpRequest): void {
+    // Greet the client
+    this.sendMessage('protocol', VERSION);
+    this.sendMessage('warning', 'Unstandardized protocol version, proceed with care');
+
+    // Verify the WebSocket protocol version
+    const protocolHeader = upgradeRequest.headers['sec-websocket-protocol'];
+    if (!protocolHeader) {
+      this.sendMessage('warning', `Missing Sec-WebSocket-Protocol header, expected value '${VERSION}'`);
+    } else {
+      const supportedProtocols = protocolHeader.split(/\s*,\s*/u);
+      if (!supportedProtocols.includes(VERSION)) {
+        this.sendMessage('error', `Client does not support protocol ${VERSION}`);
+        this.stop();
+      }
+    }
+
+    // Store the HTTP host and protocol
+    this.host = upgradeRequest.headers.host ?? '';
+    this.protocol = (upgradeRequest.socket as any).secure ? 'https:' : 'http:';
+  }
+
+  private stop(): void {
+    try {
+      this.socket.close();
+    } catch {
+      // Ignore
+    }
+    this.subscribedPaths.clear();
+    this.socket.removeAllListeners();
+    this.emit('closed');
+  }
+
+  public onResourceChanged({ path }: ResourceIdentifier): void {
+    if (this.subscribedPaths.has(path)) {
+      this.sendMessage('pub', path);
+    }
+  }
+
+  private onMessage(message: string): void {
+    // Parse the message
+    const match = /^(\w+)\s+(.+)$/u.exec(message);
+    if (!match) {
+      this.sendMessage('warning', `Unrecognized message format: ${message}`);
+      return;
+    }
+
+    // Process the message
+    const [ , type, value ] = match;
+    switch (type) {
+      case 'sub':
+        this.subscribe(value);
+        break;
+      default:
+        this.sendMessage('warning', `Unrecognized message type: ${type}`);
+    }
+  }
+
+  private subscribe(path: string): void {
+    try {
+      // Resolve and verify the URL
+      const resolved = new URL(path, `${this.protocol}${this.host}`);
+      if (resolved.host !== this.host) {
+        throw new Error(`Mismatched host: ${resolved.host} instead of ${this.host}`);
+      }
+      if (resolved.protocol !== this.protocol) {
+        throw new Error(`Mismatched protocol: ${resolved.protocol} instead of ${this.protocol}`);
+      }
+      // Subscribe to the URL
+      const url = resolved.toString();
+      this.subscribedPaths.add(url);
+      this.sendMessage('ack', url);
+      this.logger.debug(`WebSocket subscribed to changes on ${url}`);
+    } catch (error: unknown) {
+      // Report errors to the socket
+      const errorText: string = (error as any).message;
+      this.sendMessage('error', errorText);
+      this.logger.warn(`WebSocket could not subscribe to ${path}: ${errorText}`);
+    }
+  }
+
+  private sendMessage(type: string, value: string): void {
+    this.socket.send(`${type} ${value}`);
+  }
+}
+
+/**
+ * Provides live update functionality following
+ * the Solid WebSockets API Spec solid/0.1.0-alpha
+ */
+export class UnsecureWebSocketsProtocol extends WebSocketHandler {
+  private readonly logger = getLoggerFor(this);
+  private readonly listeners = new Set<WebSocketListener>();
+
+  public constructor(source: EventEmitter) {
+    super();
+    source.on('changed', (changed: ResourceIdentifier): void => this.onResourceChanged(changed));
+  }
+
+  public async handle(input: { webSocket: WebSocket; upgradeRequest: HttpRequest }): Promise<void> {
+    const listener = new WebSocketListener(input.webSocket);
+    this.listeners.add(listener);
+    this.logger.info(`New WebSocket added, ${this.listeners.size} in total`);
+
+    listener.on('closed', (): void => {
+      this.listeners.delete(listener);
+      this.logger.info(`WebSocket closed, ${this.listeners.size} remaining`);
+    });
+    listener.start(input.upgradeRequest);
+  }
+
+  private onResourceChanged(changed: ResourceIdentifier): void {
+    for (const listener of this.listeners) {
+      listener.onResourceChanged(changed);
+    }
+  }
+}

test/unit/ldp/UnsecureWebSocketsProtocol.test.ts

@@ -0,0 +1,171 @@
+import { EventEmitter } from 'events';
+import { UnsecureWebSocketsProtocol } from '../../../src/ldp/UnsecureWebSocketsProtocol';
+import type { HttpRequest } from '../../../src/server/HttpRequest';
+
+class DummySocket extends EventEmitter {
+  public readonly messages = new Array<string>();
+  public readonly close = jest.fn();
+
+  public send(message: string): void {
+    this.messages.push(message);
+  }
+}
+
+describe('An UnsecureWebSocketsProtocol', (): void => {
+  const source = new EventEmitter();
+  const protocol = new UnsecureWebSocketsProtocol(source);
+
+  describe('after registering a socket', (): void => {
+    const webSocket = new DummySocket();
+
+    beforeAll(async(): Promise<void> => {
+      const upgradeRequest = {
+        headers: {
+          host: 'mypod.example',
+          'sec-websocket-protocol': 'solid/0.1.0-alpha, other/1.0.0',
+        },
+        socket: {
+          secure: true,
+        },
+      } as any as HttpRequest;
+      await protocol.handle({ webSocket, upgradeRequest } as any);
+    });
+
+    afterEach((): void => {
+      webSocket.messages.length = 0;
+    });
+
+    it('sends a protocol message.', (): void => {
+      expect(webSocket.messages).toHaveLength(2);
+      expect(webSocket.messages.shift()).toBe('protocol solid/0.1.0-alpha');
+      expect(webSocket.messages.shift()).toBe('warning Unstandardized protocol version, proceed with care');
+    });
+
+    it('warns when receiving an unexpected message.', (): void => {
+      webSocket.emit('message', 'unexpected');
+      expect(webSocket.messages).toHaveLength(1);
+      expect(webSocket.messages.shift()).toBe('warning Unrecognized message format: unexpected');
+    });
+
+    it('warns when receiving an unexpected message type.', (): void => {
+      webSocket.emit('message', 'unknown 1 2 3');
+      expect(webSocket.messages).toHaveLength(1);
+      expect(webSocket.messages.shift()).toBe('warning Unrecognized message type: unknown');
+    });
+
+    describe('before subscribing to resources', (): void => {
+      it('does not emit pub messages.', (): void => {
+        source.emit('changed', { path: 'https://mypod.example/foo/bar' });
+        expect(webSocket.messages).toHaveLength(0);
+      });
+    });
+
+    describe('after subscribing to a resource', (): void => {
+      beforeAll((): void => {
+        webSocket.emit('message', 'sub https://mypod.example/foo/bar');
+      });
+
+      it('sends an ack message.', (): void => {
+        expect(webSocket.messages).toHaveLength(1);
+        expect(webSocket.messages.shift()).toBe('ack https://mypod.example/foo/bar');
+      });
+
+      it('emits pub messages for that resource.', (): void => {
+        source.emit('changed', { path: 'https://mypod.example/foo/bar' });
+        expect(webSocket.messages).toHaveLength(1);
+        expect(webSocket.messages.shift()).toBe('pub https://mypod.example/foo/bar');
+      });
+    });
+
+    describe('after subscribing to a resource via a relative URL', (): void => {
+      beforeAll((): void => {
+        webSocket.emit('message', 'sub /relative/foo');
+      });
+
+      it('sends an ack message.', (): void => {
+        expect(webSocket.messages).toHaveLength(1);
+        expect(webSocket.messages.shift()).toBe('ack https://mypod.example/relative/foo');
+      });
+
+      it('emits pub messages for that resource.', (): void => {
+        source.emit('changed', { path: 'https://mypod.example/relative/foo' });
+        expect(webSocket.messages).toHaveLength(1);
+        expect(webSocket.messages.shift()).toBe('pub https://mypod.example/relative/foo');
+      });
+    });
+
+    describe('after subscribing to a resource with the wrong host name', (): void => {
+      beforeAll((): void => {
+        webSocket.emit('message', 'sub https://wrong.example/host/foo');
+      });
+
+      it('send an error message.', (): void => {
+        expect(webSocket.messages).toHaveLength(1);
+        expect(webSocket.messages.shift())
+          .toBe('error Mismatched host: wrong.example instead of mypod.example');
+      });
+    });
+
+    describe('after subscribing to a resource with the wrong protocol', (): void => {
+      beforeAll((): void => {
+        webSocket.emit('message', 'sub http://mypod.example/protocol/foo');
+      });
+
+      it('send an error message.', (): void => {
+        expect(webSocket.messages).toHaveLength(1);
+        expect(webSocket.messages.shift())
+          .toBe('error Mismatched protocol: http: instead of https:');
+      });
+    });
+  });
+
+  it('unsubscribes when a socket closes.', async(): Promise<void> => {
+    const newSocket = new DummySocket();
+    await protocol.handle({ webSocket: newSocket, upgradeRequest: { headers: {}, socket: {}}} as any);
+    expect(newSocket.listenerCount('message')).toBe(1);
+    newSocket.emit('close');
+    expect(newSocket.listenerCount('message')).toBe(0);
+    expect(newSocket.listenerCount('close')).toBe(0);
+    expect(newSocket.listenerCount('error')).toBe(0);
+  });
+
+  it('unsubscribes when a socket errors.', async(): Promise<void> => {
+    const newSocket = new DummySocket();
+    await protocol.handle({ webSocket: newSocket, upgradeRequest: { headers: {}, socket: {}}} as any);
+    expect(newSocket.listenerCount('message')).toBe(1);
+    newSocket.emit('error');
+    expect(newSocket.listenerCount('message')).toBe(0);
+    expect(newSocket.listenerCount('close')).toBe(0);
+    expect(newSocket.listenerCount('error')).toBe(0);
+  });
+
+  it('emits a warning when no Sec-WebSocket-Protocol is supplied.', async(): Promise<void> => {
+    const newSocket = new DummySocket();
+    const upgradeRequest = {
+      headers: {},
+      socket: {},
+    } as any as HttpRequest;
+    await protocol.handle({ webSocket: newSocket, upgradeRequest } as any);
+    expect(newSocket.messages).toHaveLength(3);
+    expect(newSocket.messages.pop())
+      .toBe('warning Missing Sec-WebSocket-Protocol header, expected value \'solid/0.1.0-alpha\'');
+    expect(newSocket.close).toHaveBeenCalledTimes(0);
+  });
+
+  it('emits an error and closes the connection with the wrong Sec-WebSocket-Protocol.', async(): Promise<void> => {
+    const newSocket = new DummySocket();
+    const upgradeRequest = {
+      headers: {
+        'sec-websocket-protocol': 'solid/1.0.0, other',
+      },
+      socket: {},
+    } as any as HttpRequest;
+    await protocol.handle({ webSocket: newSocket, upgradeRequest } as any);
+    expect(newSocket.messages).toHaveLength(3);
+    expect(newSocket.messages.pop()).toBe('error Client does not support protocol solid/0.1.0-alpha');
+    expect(newSocket.close).toHaveBeenCalledTimes(1);
+    expect(newSocket.listenerCount('message')).toBe(0);
+    expect(newSocket.listenerCount('close')).toBe(0);
+    expect(newSocket.listenerCount('error')).toBe(0);
+  });
+});