Fix messaging typo

ext/src/cast/pageMessaging.ts

@@ -0,0 +1,140 @@
+import type { TypedMessagePort } from "../lib/TypedMessagePort";
+import type { Message } from "../messaging";
+
+const INIT_MESSAGE = "__pageMessenger_init__";
+
+/** Strip anything non-serializable for message channel. */
+function simplify(input: any) {
+    return JSON.parse(JSON.stringify(input));
+}
+
+type MessengerListener = (message: Message) => void;
+
+/**
+ * Abstract messenger class for cross-context messages via
+ * MessageChannel.
+ *
+ * Facilitates a message channel between page scripts running in the
+ * page script context and the extension scripts running in the
+ * sandboxed content script context.
+ */
+abstract class Messenger {
+    private listeners = new Set<MessengerListener>();
+
+    protected onMessage = (ev: MessageEvent<Message>) => {
+        for (const listener of this.listeners) {
+            listener(simplify(ev.data));
+        }
+    };
+
+    addListener(listener: MessengerListener) {
+        this.listeners.add(listener);
+    }
+    removeListener(listener: MessengerListener) {
+        this.listeners.delete(listener);
+    }
+
+    /** Sends a message across the  */
+    abstract sendMessage(message: Message): void;
+
+    close() {
+        this.listeners.clear();
+    }
+}
+
+/**
+ * Page-side of page script messaging.
+ *
+ * Creates a message channel, then sends an INIT_MESSAGE window message
+ * with a port that is handled by an ExtensionScriptMessenger in the
+ * content script.
+ */
+export class PageScriptMessenger extends Messenger {
+    private port: TypedMessagePort<Message>;
+
+    constructor() {
+        super();
+
+        // Create message channel and send port2 to
+        const { port1, port2 } = new MessageChannel();
+        window.postMessage(INIT_MESSAGE, window.location.href, [port2]);
+
+        this.port = port1;
+        this.port.addEventListener("message", this.onMessage);
+        this.port.start();
+    }
+
+    sendMessage(message: Message) {
+        this.port.postMessage(simplify(message));
+    }
+    get messagePort() {
+        return this.port;
+    }
+
+    close() {
+        super.close();
+        this.port.removeEventListener("message", this.onMessage);
+        this.port.close();
+    }
+}
+
+/**
+ * Extension-side of page script messaging.
+ *
+ * Listens for a INIT_MESSAGE window message from a PageScriptMessenger
+ * running in a page script and establishes a message channel connection
+ * once received.
+ */
+export class ExtensionScriptMessenger extends Messenger {
+    private port?: TypedMessagePort<Message>;
+
+    constructor() {
+        super();
+        window.addEventListener("message", this.onWindowMessage);
+    }
+
+    /** Handles init message from window and stores transferred port. */
+    private onWindowMessage = (ev: MessageEvent<any>) => {
+        if (ev.source !== window || ev.data !== INIT_MESSAGE) return;
+
+        window.removeEventListener("message", this.onWindowMessage);
+
+        this.port = ev.ports[0];
+        this.port.addEventListener("message", ev => this.onMessage(ev));
+        this.port.start();
+    };
+
+    sendMessage(message: Message) {
+        this.port?.postMessage(simplify(message));
+    }
+
+    close() {
+        super.close();
+
+        window.removeEventListener("message", this.onWindowMessage);
+        this.port?.removeEventListener("message", this.onMessage);
+        this.port?.close();
+    }
+}
+
+let pageMessenger: Nullable<PageScriptMessenger> = null;
+let extensionMessenger: Nullable<ExtensionScriptMessenger> = null;
+
+export default {
+    /** Messenger for page scripts. */
+    get page() {
+        if (!pageMessenger) {
+            pageMessenger = new PageScriptMessenger();
+        }
+
+        return pageMessenger;
+    },
+
+    /** Messenger for extension scripts. */
+    get extension() {
+        if (!extensionMessenger) {
+            extensionMessenger = new ExtensionScriptMessenger();
+        }
+        return extensionMessenger;
+    }
+};