Add receive support for pin/unpin message

ts/messageModifiers/helpers/findMessageModifierTarget.preload.ts

@@ -0,0 +1,45 @@
+// Copyright 2025 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { AciString } from '../../types/ServiceId.std.js';
+import { getAuthorId } from '../../messages/sources.preload.js';
+import type { ConversationModel } from '../../models/conversations.preload.js';
+import { strictAssert } from '../../util/assert.std.js';
+import type { MessageModel } from '../../models/messages.preload.js';
+
+export type MessageModifierTarget = Readonly<{
+  targetMessage: MessageModel;
+  targetConversation: ConversationModel;
+}>;
+
+export async function findMessageModifierTarget(
+  targetSentTimestamp: number,
+  targetAuthorAci: AciString
+): Promise<MessageModifierTarget | null> {
+  const authorConversation = window.ConversationController.lookupOrCreate({
+    serviceId: targetAuthorAci,
+    reason: 'findTargetMessageBySentAtAndAuthorAci',
+  });
+
+  if (authorConversation == null) {
+    return null;
+  }
+
+  const targetMessage = await window.MessageCache.findBySentAt(
+    targetSentTimestamp,
+    message => {
+      return getAuthorId(message.attributes) === authorConversation.id;
+    }
+  );
+
+  if (targetMessage == null) {
+    return null;
+  }
+
+  const targetConversation = window.ConversationController.get(
+    targetMessage.get('conversationId')
+  );
+  strictAssert(targetConversation, 'Missing conversation for target message');
+
+  return { targetMessage, targetConversation };
+}