docs(agent): better comments for injected script

agent/main/lib/WebsocketSession.ts

@@ -84,7 +84,7 @@ export class WebsocketSession extends TypedEventEmitter<IWebsocketEvents> {
   injectWebsocketCallbackIntoScript(script: string): string {
     // We could do this as a simple template script but this logic might get
     // complex over time and we want typescript to be able to check proxyScript();
-    const scriptBody = this.proxyScript
+    const scriptBody = injectedScript
       .toString()
       // eslint-disable-next-line no-template-curly-in-string
       .replaceAll('${this.host}', this.host)
@@ -99,56 +99,6 @@ export class WebsocketSession extends TypedEventEmitter<IWebsocketEvents> {
     return wsScript;
   }
 
-  private proxyScript(): void {
-    const clientId = Math.random();
-    const url = `${this.host}:${this.port}?secret=${this.secret}&clientId=${clientId}`;
-    // This will signal to network manager we are trying to make websocket connection
-    // This is needed later to map clientId to frameId
-    // eslint-disable-next-line no-console
-    fetch(`http://${url}`).catch(error => console.log(error));
-    let callback: WebsocketCallback;
-    try {
-      const socket = new WebSocket(`ws://${url}`);
-      let isReady = false;
-      const queuedCallbacks: { name: string; payload: string }[] = [];
-
-      const sendOverSocket = (name: string, payload: string): void => {
-        try {
-          socket.send(JSON.stringify({ name, payload }));
-        } catch (error) {
-          // eslint-disable-next-line no-console
-          console.log(`failed to send over websocket: ${error}`);
-        }
-      };
-
-      // eslint-disable-next-line @typescript-eslint/no-unused-vars
-      callback = (name, payload): void => {
-        if (!isReady) {
-          queuedCallbacks.push({ name, payload });
-          return;
-        }
-        sendOverSocket(name, payload);
-      };
-
-      socket.addEventListener('open', _event => {
-        let queuedCallback = queuedCallbacks.shift();
-        while (queuedCallback) {
-          sendOverSocket(queuedCallback.name, queuedCallback.payload);
-          queuedCallback = queuedCallbacks.shift();
-        }
-        // Only ready when all older messages have been send so we
-        // keep original order of messages.
-        isReady = true;
-      });
-    } catch (error) {
-      // eslint-disable-next-line no-console
-      console.log(`failed to use websocket: ${error}`);
-    }
-
-    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
-    SCRIPT_PLACEHOLDER;
-  }
-
   private handleUpgrade(request: IncomingMessage, socket: Socket, head: Buffer): void {
     const url = new URL(request.url, `ws://${this.host}`);
     // Close and dont send 403 so this acts as an invisible websocket server
@@ -198,3 +148,57 @@ export class WebsocketSession extends TypedEventEmitter<IWebsocketEvents> {
     this.emit('message-received', { id: frameId, name, payload });
   }
 }
+
+/** This function will be stringified and inserted as a wrapper script so all injected
+ * scripts have access to a callback function (over a websocket). This function takes
+ * care of setting up that websocket and all other logic it needs as glue to make it all work.
+ * */
+function injectedScript(): void {
+  const clientId = Math.random();
+  const url = `${this.host}:${this.port}?secret=${this.secret}&clientId=${clientId}`;
+  // This will signal to network manager we are trying to make websocket connection
+  // This is needed later to map clientId to frameId
+  // eslint-disable-next-line no-console
+  fetch(`http://${url}`).catch(error => console.log(error));
+  let callback: WebsocketCallback;
+  try {
+    const socket = new WebSocket(`ws://${url}`);
+    let isReady = false;
+    const queuedCallbacks: { name: string; payload: string }[] = [];
+
+    const sendOverSocket = (name: string, payload: string): void => {
+      try {
+        socket.send(JSON.stringify({ name, payload }));
+      } catch (error) {
+        // eslint-disable-next-line no-console
+        console.log(`failed to send over websocket: ${error}`);
+      }
+    };
+
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    callback = (name, payload): void => {
+      if (!isReady) {
+        queuedCallbacks.push({ name, payload });
+        return;
+      }
+      sendOverSocket(name, payload);
+    };
+
+    socket.addEventListener('open', _event => {
+      let queuedCallback = queuedCallbacks.shift();
+      while (queuedCallback) {
+        sendOverSocket(queuedCallback.name, queuedCallback.payload);
+        queuedCallback = queuedCallbacks.shift();
+      }
+      // Only ready when all older messages have been send so we
+      // keep original order of messages.
+      isReady = true;
+    });
+  } catch (error) {
+    // eslint-disable-next-line no-console
+    console.log(`failed to use websocket: ${error}`);
+  }
+
+  // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+  SCRIPT_PLACEHOLDER;
+}