fix: preserve paired input evidence context (#204)

src/message-runtime-task-context.ts

@@ -0,0 +1,35 @@
+import { getMessagesSince, getRecentChatMessages } from './db.js';
+import type { NewMessage, PairedTask } from './types.js';
+
+export const TASK_USER_CONTEXT_START_SKEW_MS = 5_000;
+const TASK_CONTEXT_MESSAGE_LIMIT = 200;
+const NO_BOT_PREFIX_FILTER = '';
+
+function taskContextStartTimestamp(task: PairedTask): string | null {
+  const taskCreatedMs = Date.parse(task.created_at);
+  if (!Number.isFinite(taskCreatedMs)) {
+    return null;
+  }
+  return new Date(
+    taskCreatedMs - TASK_USER_CONTEXT_START_SKEW_MS,
+  ).toISOString();
+}
+
+export function getTaskContextMessages(
+  chatJid: string,
+  task: PairedTask,
+): NewMessage[] {
+  const sinceTimestamp = taskContextStartTimestamp(task);
+  if (!sinceTimestamp) {
+    return getRecentChatMessages(chatJid, 20);
+  }
+  const taskMessages = getMessagesSince(
+    chatJid,
+    sinceTimestamp,
+    NO_BOT_PREFIX_FILTER,
+    TASK_CONTEXT_MESSAGE_LIMIT,
+  );
+  return taskMessages.length > 0
+    ? taskMessages
+    : getRecentChatMessages(chatJid, 20);
+}