pass client token through API via caller ID

packages/backend/src/misc/attach-caller-id.ts

@@ -0,0 +1,42 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import type { MiAccessToken } from '@/models/AccessToken.js';
+
+const callerIdSymbol = Symbol('callerId');
+
+/**
+ * Client metadata associated with an object (typically an instance of MiUser).
+ */
+export interface CallerId {
+	/**
+	 * Client's access token, or null if no token was used.
+	 */
+	accessToken?: MiAccessToken | null;
+}
+
+interface ObjectWithCallerId {
+	[callerIdSymbol]?: CallerId;
+}
+
+/**
+ * Attaches client metadata to an object.
+ * Calling this repeatedly will overwrite the previous value.
+ * Pass undefined to erase the attached data.
+ * @param target Object to attach to (typically an instance of MiUser).
+ * @param callerId Data to attach.
+ */
+export function attachCallerId(target: object, callerId: CallerId | undefined): void {
+	(target as ObjectWithCallerId)[callerIdSymbol] = callerId;
+}
+
+/**
+ * Fetches client metadata from an object.
+ * Returns undefined if no metadata is attached.
+ * @param target Object to fetch from.
+ */
+export function getCallerId(target: object): CallerId | undefined {
+	return (target as ObjectWithCallerId)[callerIdSymbol];
+}