feat: add warning when wrong execution context detected

src/core/extensions/manager.ts

@@ -4,10 +4,15 @@ import logger from '@/utils/logger';
 import { Signal } from '@preact/signals';
 import { Extension, ExtensionConstructor, Interceptor } from './extension';
 
+/**
+ * Global object reference. In some cases, the `unsafeWindow` is not available.
+ */
+const globalObject = unsafeWindow ?? window ?? globalThis;
+
 /**
  * The original XHR method backup.
  */
-const xhrOpen = unsafeWindow.XMLHttpRequest.prototype.open;
+const xhrOpen = globalObject.XMLHttpRequest.prototype.open;
 
 /**
  * The registry for all extensions.
@@ -105,7 +110,19 @@ export class ExtensionManager {
     // eslint-disable-next-line @typescript-eslint/no-this-alias
     const manager = this;
 
-    unsafeWindow.XMLHttpRequest.prototype.open = function (method: string, url: string) {
+    // Check for current running context.
+    // The `window.__SCRIPTS_LOADED__` is injected by the Twitter website.
+    // See: https://violentmonkey.github.io/posts/inject-into-context/
+    if (!('__SCRIPTS_LOADED__' in globalObject)) {
+      logger.error(
+        'Error: Wrong execution context detected.\n  ' +
+          'This script needs to be injected into "page" context rather than "content" context.\n  ' +
+          'The XMLHttpRequest hook will not work properly.\n  ' +
+          'See: https://github.com/prinsss/twitter-web-exporter/issues/19',
+      );
+    }
+
+    globalObject.XMLHttpRequest.prototype.open = function (method: string, url: string) {
       if (manager.debugEnabled) {
         logger.debug(`XHR initialized`, { method, url });
       }