Merge reply-chain documents into AI requests

src/ai/reply-chain-downloads.ts

@@ -0,0 +1,39 @@
+import type {AiDownloadedFile} from "./telegram-attachments.js";
+
+function downloadKey(download: AiDownloadedFile): string {
+    return [
+        download.kind,
+        download.fileId,
+        download.sha256 ?? "",
+        download.fileName,
+    ].join(":");
+}
+
+export function mergeReplyChainDownloads(
+    currentDownloads: readonly AiDownloadedFile[],
+    replyChainDownloads: readonly AiDownloadedFile[],
+): AiDownloadedFile[] {
+    const result: AiDownloadedFile[] = [];
+    const seen = new Set<string>();
+
+    for (const download of [...currentDownloads, ...replyChainDownloads]) {
+        const key = downloadKey(download);
+        if (seen.has(key)) continue;
+        seen.add(key);
+        result.push(download);
+    }
+
+    return result;
+}
+
+export function shouldPreferCurrentDownloads(text: string, currentDownloads: readonly AiDownloadedFile[]): boolean {
+    if (!currentDownloads.length) return false;
+
+    const normalized = text.trim().toLowerCase();
+    if (!normalized) return false;
+
+    return normalized.includes("this file")
+        || normalized.includes("this document")
+        || normalized.includes("этот файл")
+        || normalized.includes("этот документ");
+}