first-commit

web_src/js/features/eventsource.sharedworker.ts

@@ -0,0 +1,147 @@
+class Source {
+  url: string;
+  eventSource: EventSource;
+  listening: Record<string, boolean>;
+  clients: Array<MessagePort>;
+
+  constructor(url: string) {
+    this.url = url;
+    this.eventSource = new EventSource(url);
+    this.listening = {};
+    this.clients = [];
+    this.listen('open');
+    this.listen('close');
+    this.listen('logout');
+    this.listen('notification-count');
+    this.listen('stopwatches');
+    this.listen('error');
+  }
+
+  register(port: MessagePort) {
+    if (this.clients.includes(port)) return;
+
+    this.clients.push(port);
+
+    port.postMessage({
+      type: 'status',
+      message: `registered to ${this.url}`,
+    });
+  }
+
+  deregister(port: MessagePort) {
+    const portIdx = this.clients.indexOf(port);
+    if (portIdx < 0) {
+      return this.clients.length;
+    }
+    this.clients.splice(portIdx, 1);
+    return this.clients.length;
+  }
+
+  close() {
+    if (!this.eventSource) return;
+
+    this.eventSource.close();
+    this.eventSource = null;
+  }
+
+  listen(eventType: string) {
+    if (this.listening[eventType]) return;
+    this.listening[eventType] = true;
+    this.eventSource.addEventListener(eventType, (event) => {
+      this.notifyClients({
+        type: eventType,
+        data: event.data,
+      });
+    });
+  }
+
+  notifyClients(event: {type: string, data: any}) {
+    for (const client of this.clients) {
+      client.postMessage(event);
+    }
+  }
+
+  status(port: MessagePort) {
+    port.postMessage({
+      type: 'status',
+      message: `url: ${this.url} readyState: ${this.eventSource.readyState}`,
+    });
+  }
+}
+
+const sourcesByUrl: Map<string, Source | null> = new Map();
+const sourcesByPort: Map<MessagePort, Source | null> = new Map();
+
+// @ts-expect-error: typescript bug?
+self.addEventListener('connect', (e: MessageEvent) => {
+  for (const port of e.ports) {
+    port.addEventListener('message', (event) => {
+      if (!self.EventSource) {
+        // some browsers (like PaleMoon, Firefox<53) don't support EventSource in SharedWorkerGlobalScope.
+        // this event handler needs EventSource when doing "new Source(url)", so just post a message back to the caller,
+        // in case the caller would like to use a fallback method to do its work.
+        port.postMessage({type: 'no-event-source'});
+        return;
+      }
+      if (event.data.type === 'start') {
+        const url = event.data.url;
+        if (sourcesByUrl.get(url)) {
+          // we have a Source registered to this url
+          const source = sourcesByUrl.get(url);
+          source.register(port);
+          sourcesByPort.set(port, source);
+          return;
+        }
+        let source = sourcesByPort.get(port);
+        if (source) {
+          if (source.eventSource && source.url === url) return;
+
+          // How this has happened I don't understand...
+          // deregister from that source
+          const count = source.deregister(port);
+          // Clean-up
+          if (count === 0) {
+            source.close();
+            sourcesByUrl.set(source.url, null);
+          }
+        }
+        // Create a new Source
+        source = new Source(url);
+        source.register(port);
+        sourcesByUrl.set(url, source);
+        sourcesByPort.set(port, source);
+      } else if (event.data.type === 'listen') {
+        const source = sourcesByPort.get(port);
+        source.listen(event.data.eventType);
+      } else if (event.data.type === 'close') {
+        const source = sourcesByPort.get(port);
+
+        if (!source) return;
+
+        const count = source.deregister(port);
+        if (count === 0) {
+          source.close();
+          sourcesByUrl.set(source.url, null);
+          sourcesByPort.set(port, null);
+        }
+      } else if (event.data.type === 'status') {
+        const source = sourcesByPort.get(port);
+        if (!source) {
+          port.postMessage({
+            type: 'status',
+            message: 'not connected',
+          });
+          return;
+        }
+        source.status(port);
+      } else {
+        // just send it back
+        port.postMessage({
+          type: 'error',
+          message: `received but don't know how to handle: ${event.data}`,
+        });
+      }
+    });
+    port.start();
+  }
+});