server : (webui) Enable communication with parent html (if webui is in iframe) (#11940)

* Webui: Enable communication with parent html (if webui is in iframe):
- Listens for "setText" command from parent with "text" and "context" fields. "text" is set in inputMsg, "context" is used as hidden context on the following requests to the llama.cpp server
- On pressing na Escape button sends command "escapePressed" to the parent

Example handling from the parent html side:
- Send command "setText" from parent html to webui in iframe:
const iframe = document.getElementById('askAiIframe');
if (iframe) {
	iframe.contentWindow.postMessage({ command: 'setText', text: text, context: context }, '*');
}

- Listen for Escape key from webui on parent html:
// Listen for escape key event in the iframe
window.addEventListener('keydown', (event) => {
	if (event.key === 'Escape') {
		// Process case when Escape is pressed inside webui
	}
});

* Move the extraContext from storage to app.context.

* Fix formatting.

* add Message.extra

* format + build

* MessageExtraContext

* build

* fix display

* rm console.log

---------

Co-authored-by: igardev <ivailo.gardev@akros.ch>
Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

examples/server/webui/src/utils/llama-vscode.ts

@@ -0,0 +1,62 @@
+import { useEffect, useState } from 'react';
+import { MessageExtraContext } from './types';
+
+// Extra context when using llama.cpp WebUI from llama-vscode, inside an iframe
+// Ref: https://github.com/ggml-org/llama.cpp/pull/11940
+
+interface SetTextEvData {
+  text: string;
+  context: string;
+}
+
+/**
+ * To test it:
+ * window.postMessage({ command: 'setText', text: 'Spot the syntax error', context: 'def test()\n  return 123' }, '*');
+ */
+
+export const useVSCodeContext = (
+  inputRef: React.RefObject<HTMLTextAreaElement>,
+  setInputMsg: (text: string) => void
+) => {
+  const [extraContext, setExtraContext] = useState<MessageExtraContext | null>(
+    null
+  );
+
+  // Accept setText message from a parent window and set inputMsg and extraContext
+  useEffect(() => {
+    const handleMessage = (event: MessageEvent) => {
+      if (event.data?.command === 'setText') {
+        const data: SetTextEvData = event.data;
+        setInputMsg(data?.text);
+        if (data?.context && data.context.length > 0) {
+          setExtraContext({
+            type: 'context',
+            content: data.context,
+          });
+        }
+        inputRef.current?.focus();
+      }
+    };
+
+    window.addEventListener('message', handleMessage);
+    return () => window.removeEventListener('message', handleMessage);
+  }, []);
+
+  // Add a keydown listener that sends the "escapePressed" message to the parent window
+  useEffect(() => {
+    const handleKeyDown = (event: KeyboardEvent) => {
+      if (event.key === 'Escape') {
+        window.parent.postMessage({ command: 'escapePressed' }, '*');
+      }
+    };
+
+    window.addEventListener('keydown', handleKeyDown);
+    return () => window.removeEventListener('keydown', handleKeyDown);
+  }, []);
+
+  return {
+    extraContext,
+    // call once the user message is sent, to clear the extra context
+    clearExtraContext: () => setExtraContext(null),
+  };
+};