1 files changed, 341 insertions, 0 deletions

diff --git a/language-web/src/main/js/xtext/XtextWebSocketClient.ts b/language-web/src/main/js/xtext/XtextWebSocketClient.ts
new file mode 100644
index 00000000..488e4b3b
--- /dev/null
+++ b/language-web/src/main/js/xtext/XtextWebSocketClient.ts
@@ -0,0 +1,341 @@
+import { nanoid } from 'nanoid';
+
+import { getLogger } from '../utils/logger';
+import { PendingTask } from '../utils/PendingTask';
+import { Timer } from '../utils/Timer';
+import {
+  isErrorResponse,
+  isOkResponse,
+  isPushMessage,
+  IXtextWebRequest,
+} from './xtextMessages';
+import { isPongResult } from './xtextServiceResults';
+
+const XTEXT_SUBPROTOCOL_V1 = 'tools.refinery.language.web.xtext.v1';
+
+const WEBSOCKET_CLOSE_OK = 1000;
+
+const RECONNECT_DELAY_MS = [200, 1000, 5000, 30_000];
+
+const MAX_RECONNECT_DELAY_MS = RECONNECT_DELAY_MS[RECONNECT_DELAY_MS.length - 1];
+
+const BACKGROUND_IDLE_TIMEOUT_MS = 5 * 60 * 1000;
+
+const PING_TIMEOUT_MS = 10 * 1000;
+
+const REQUEST_TIMEOUT_MS = 1000;
+
+const log = getLogger('xtext.XtextWebSocketClient');
+
+export type ReconnectHandler = () => void;
+
+export type PushHandler = (
+  resourceId: string,
+  stateId: string,
+  service: string,
+  data: unknown,
+) => void;
+
+enum State {
+  Initial,
+  Opening,
+  TabVisible,
+  TabHiddenIdle,
+  TabHiddenWaiting,
+  Error,
+  TimedOut,
+}
+
+export class XtextWebSocketClient {
+  private nextMessageId = 0;
+
+  private connection!: WebSocket;
+
+  private readonly pendingRequests = new Map<string, PendingTask<unknown>>();
+
+  private readonly onReconnect: ReconnectHandler;
+
+  private readonly onPush: PushHandler;
+
+  private state = State.Initial;
+
+  private reconnectTryCount = 0;
+
+  private readonly idleTimer = new Timer(() => {
+    this.handleIdleTimeout();
+  }, BACKGROUND_IDLE_TIMEOUT_MS);
+
+  private readonly pingTimer = new Timer(() => {
+    this.sendPing();
+  }, PING_TIMEOUT_MS);
+
+  private readonly reconnectTimer = new Timer(() => {
+    this.handleReconnect();
+  });
+
+  constructor(onReconnect: ReconnectHandler, onPush: PushHandler) {
+    this.onReconnect = onReconnect;
+    this.onPush = onPush;
+    document.addEventListener('visibilitychange', () => {
+      this.handleVisibilityChange();
+    });
+    this.reconnect();
+  }
+
+  private get isLogicallyClosed(): boolean {
+    return this.state === State.Error || this.state === State.TimedOut;
+  }
+
+  get isOpen(): boolean {
+    return this.state === State.TabVisible
+      || this.state === State.TabHiddenIdle
+      || this.state === State.TabHiddenWaiting;
+  }
+
+  private reconnect() {
+    if (this.isOpen || this.state === State.Opening) {
+      log.error('Trying to reconnect from', this.state);
+      return;
+    }
+    this.state = State.Opening;
+    const webSocketServer = window.origin.replace(/^http/, 'ws');
+    const webSocketUrl = `${webSocketServer}/xtext-service`;
+    this.connection = new WebSocket(webSocketUrl, XTEXT_SUBPROTOCOL_V1);
+    this.connection.addEventListener('open', () => {
+      if (this.connection.protocol !== XTEXT_SUBPROTOCOL_V1) {
+        log.error('Unknown subprotocol', this.connection.protocol, 'selected by server');
+        this.forceReconnectOnError();
+      }
+      if (document.visibilityState === 'hidden') {
+        this.handleTabHidden();
+      } else {
+        this.handleTabVisibleConnected();
+      }
+      log.info('Connected to websocket');
+      this.nextMessageId = 0;
+      this.reconnectTryCount = 0;
+      this.pingTimer.schedule();
+      this.onReconnect();
+    });
+    this.connection.addEventListener('error', (event) => {
+      log.error('Unexpected websocket error', event);
+      this.forceReconnectOnError();
+    });
+    this.connection.addEventListener('message', (event) => {
+      this.handleMessage(event.data);
+    });
+    this.connection.addEventListener('close', (event) => {
+      if (this.isLogicallyClosed && event.code === WEBSOCKET_CLOSE_OK
+        && this.pendingRequests.size === 0) {
+        log.info('Websocket closed');
+        return;
+      }
+      log.error('Websocket closed unexpectedly', event.code, event.reason);
+      this.forceReconnectOnError();
+    });
+  }
+
+  private handleVisibilityChange() {
+    if (document.visibilityState === 'hidden') {
+      if (this.state === State.TabVisible) {
+        this.handleTabHidden();
+      }
+      return;
+    }
+    this.idleTimer.cancel();
+    if (this.state === State.TabHiddenIdle || this.state === State.TabHiddenWaiting) {
+      this.handleTabVisibleConnected();
+      return;
+    }
+    if (this.state === State.TimedOut) {
+      this.reconnect();
+    }
+  }
+
+  private handleTabHidden() {
+    log.debug('Tab hidden while websocket is connected');
+    this.state = State.TabHiddenIdle;
+    this.idleTimer.schedule();
+  }
+
+  private handleTabVisibleConnected() {
+    log.debug('Tab visible while websocket is connected');
+    this.state = State.TabVisible;
+  }
+
+  private handleIdleTimeout() {
+    log.trace('Waiting for pending tasks before disconnect');
+    if (this.state === State.TabHiddenIdle) {
+      this.state = State.TabHiddenWaiting;
+      this.handleWaitingForDisconnect();
+    }
+  }
+
+  private handleWaitingForDisconnect() {
+    if (this.state !== State.TabHiddenWaiting) {
+      return;
+    }
+    const pending = this.pendingRequests.size;
+    if (pending === 0) {
+      log.info('Closing idle websocket');
+      this.state = State.TimedOut;
+      this.closeConnection(1000, 'idle timeout');
+      return;
+    }
+    log.info('Waiting for', pending, 'pending requests before closing websocket');
+  }
+
+  private sendPing() {
+    if (!this.isOpen) {
+      return;
+    }
+    const ping = nanoid();
+    log.trace('Ping', ping);
+    this.send({ ping }).then((result) => {
+      if (isPongResult(result) && result.pong === ping) {
+        log.trace('Pong', ping);
+        this.pingTimer.schedule();
+      } else {
+        log.error('Invalid pong');
+        this.forceReconnectOnError();
+      }
+    }).catch((error) => {
+      log.error('Error while waiting for ping', error);
+      this.forceReconnectOnError();
+    });
+  }
+
+  send(request: unknown): Promise<unknown> {
+    if (!this.isOpen) {
+      throw new Error('Not open');
+    }
+    const messageId = this.nextMessageId.toString(16);
+    if (messageId in this.pendingRequests) {
+      log.error('Message id wraparound still pending', messageId);
+      this.rejectRequest(messageId, new Error('Message id wraparound'));
+    }
+    if (this.nextMessageId >= Number.MAX_SAFE_INTEGER) {
+      this.nextMessageId = 0;
+    } else {
+      this.nextMessageId += 1;
+    }
+    const message = JSON.stringify({
+      id: messageId,
+      request,
+    } as IXtextWebRequest);
+    log.trace('Sending message', message);
+    return new Promise((resolve, reject) => {
+      const task = new PendingTask(resolve, reject, REQUEST_TIMEOUT_MS, () => {
+        this.removePendingRequest(messageId);
+      });
+      this.pendingRequests.set(messageId, task);
+      this.connection.send(message);
+    });
+  }
+
+  private handleMessage(messageStr: unknown) {
+    if (typeof messageStr !== 'string') {
+      log.error('Unexpected binary message', messageStr);
+      this.forceReconnectOnError();
+      return;
+    }
+    log.trace('Incoming websocket message', messageStr);
+    let message: unknown;
+    try {
+      message = JSON.parse(messageStr);
+    } catch (error) {
+      log.error('Json parse error', error);
+      this.forceReconnectOnError();
+      return;
+    }
+    if (isOkResponse(message)) {
+      this.resolveRequest(message.id, message.response);
+    } else if (isErrorResponse(message)) {
+      this.rejectRequest(message.id, new Error(`${message.error} error: ${message.message}`));
+      if (message.error === 'server') {
+        log.error('Reconnecting due to server error: ', message.message);
+        this.forceReconnectOnError();
+      }
+    } else if (isPushMessage(message)) {
+      this.onPush(
+        message.resource,
+        message.stateId,
+        message.service,
+        message.push,
+      );
+    } else {
+      log.error('Unexpected websocket message', message);
+      this.forceReconnectOnError();
+    }
+  }
+
+  private resolveRequest(messageId: string, value: unknown) {
+    const pendingRequest = this.pendingRequests.get(messageId);
+    if (pendingRequest) {
+      pendingRequest.resolve(value);
+      this.removePendingRequest(messageId);
+      return;
+    }
+    log.error('Trying to resolve unknown request', messageId, 'with', value);
+  }
+
+  private rejectRequest(messageId: string, reason?: unknown) {
+    const pendingRequest = this.pendingRequests.get(messageId);
+    if (pendingRequest) {
+      pendingRequest.reject(reason);
+      this.removePendingRequest(messageId);
+      return;
+    }
+    log.error('Trying to reject unknown request', messageId, 'with', reason);
+  }
+
+  private removePendingRequest(messageId: string) {
+    this.pendingRequests.delete(messageId);
+    this.handleWaitingForDisconnect();
+  }
+
+  forceReconnectOnError(): void {
+    if (this.isLogicallyClosed) {
+      return;
+    }
+    this.abortPendingRequests();
+    this.closeConnection(1000, 'reconnecting due to error');
+    log.error('Reconnecting after delay due to error');
+    this.handleErrorState();
+  }
+
+  private abortPendingRequests() {
+    this.pendingRequests.forEach((request) => {
+      request.reject(new Error('Websocket disconnect'));
+    });
+    this.pendingRequests.clear();
+  }
+
+  private closeConnection(code: number, reason: string) {
+    this.pingTimer.cancel();
+    const { readyState } = this.connection;
+    if (readyState !== WebSocket.CLOSING && readyState !== WebSocket.CLOSED) {
+      this.connection.close(code, reason);
+    }
+  }
+
+  private handleErrorState() {
+    this.state = State.Error;
+    this.reconnectTryCount += 1;
+    const delay = RECONNECT_DELAY_MS[this.reconnectTryCount - 1] || MAX_RECONNECT_DELAY_MS;
+    log.info('Reconnecting in', delay, 'ms');
+    this.reconnectTimer.schedule(delay);
+  }
+
+  private handleReconnect() {
+    if (this.state !== State.Error) {
+      log.error('Unexpected reconnect in', this.state);
+      return;
+    }
+    if (document.visibilityState === 'hidden') {
+      this.state = State.TimedOut;
+    } else {
+      this.reconnect();
+    }
+  }
+}