fix: use native fetch for Telegram attachment upload (#898)

* fix: use native fetch for Telegram attachment upload

telegraf's sendMediaGroup uses Node.js streams (multipart-stream) for
file uploads, which is incompatible with CF Workers runtime, causing
"SyntaxError: Unexpected end of JSON input".

Replace with native fetch + FormData + attach:// protocol which works
correctly in CF Workers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: wrap sendTelegramAttachments in top-level try-catch

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

worker/src/telegram_api/telegram.ts

@@ -2,18 +2,17 @@
 import { Context } from "hono";
 import { Telegraf, Context as TgContext, Markup } from "telegraf";
 import { callbackQuery } from "telegraf/filters";
-import { InputMediaDocument } from "telegraf/types";
 
 import { CONSTANTS } from "../constants";
 import { getBooleanValue, getDomains, getJsonObjectValue, getStringValue } from '../utils';
 import { TelegramSettings } from "./settings";
+import { sendTelegramAttachments } from "./tg_file_upload";
 import { bindTelegramAddress, deleteTelegramAddress, jwtListToAddressData, tgUserNewAddress, unbindTelegramAddress, unbindTelegramByAddress } from "./common";
 import { commonParseMail } from "../common";
 import { UserFromGetMe } from "telegraf/types";
 import i18n from "../i18n";
 import { LocaleMessages } from "../i18n/type";
 
-const TG_MAX_FILE_SIZE = 50 * 1024 * 1024; // 50MB Telegram Bot API limit
 
 // Helper to get messages by userId
 const getTgMessages = async (
@@ -438,32 +437,10 @@ export async function sendMailToTelegram(
         await bot.telegram.sendMessage(targetUserId, mail, {
             ...Markup.inlineKeyboard([...buttons])
         });
-        // send attachments
-        if (getBooleanValue(c.env.ENABLE_TG_PUSH_ATTACHMENT)) {
-            const validAttachments = attachments.filter(att => {
-                if (att.content.byteLength > TG_MAX_FILE_SIZE) {
-                    console.log(`Skipping attachment ${att.filename}: ${(att.content.byteLength / 1024 / 1024).toFixed(1)}MB exceeds 50MB limit`);
-                    return false;
-                }
-                return true;
-            });
-            if (validAttachments.length > 0) {
+        // send attachments via native fetch (telegraf multipart upload is incompatible with CF Workers)
+        if (getBooleanValue(c.env.ENABLE_TG_PUSH_ATTACHMENT) && attachments.length > 0) {
             const caption = `From: ${parsedEmailContext.parsedEmail?.sender || ""}\nSubject: ${parsedEmailContext.parsedEmail?.subject || ""}`;
-                const batchSize = 6;
-                for (let i = 0; i < validAttachments.length; i += batchSize) {
-                    const batch = validAttachments.slice(i, i + batchSize);
-                    try {
-                        const mediaGroup: InputMediaDocument[] = batch.map((att, idx) => ({
-                            type: 'document',
-                            media: { source: Buffer.from(att.content), filename: att.filename },
-                            ...(i === 0 && idx === 0 ? { caption } : {}),
-                        }));
-                        await bot.telegram.sendMediaGroup(targetUserId, mediaGroup);
-                    } catch (e) {
-                        console.error(`Failed to send attachment batch ${i / batchSize + 1}:`, e);
-                    }
-                }
-            }
+            await sendTelegramAttachments(c.env.TELEGRAM_BOT_TOKEN, targetUserId, attachments, caption);
         }
     };
 

worker/src/telegram_api/tg_file_upload.ts

@@ -0,0 +1,49 @@
+const TG_MAX_FILE_SIZE = 50 * 1024 * 1024; // 50MB Telegram Bot API limit
+
+export async function sendTelegramAttachments(
+    botToken: string,
+    chatId: string,
+    attachments: ParsedEmailAttachment[],
+    caption: string
+) {
+    try {
+        const validAttachments = attachments.filter(att => {
+            if (att.content.byteLength > TG_MAX_FILE_SIZE) {
+                console.log(`Skipping attachment ${att.filename}: ${(att.content.byteLength / 1024 / 1024).toFixed(1)}MB exceeds 50MB limit`);
+                return false;
+            }
+            return true;
+        });
+        if (validAttachments.length === 0) return;
+
+        const batchSize = 6;
+        for (let i = 0; i < validAttachments.length; i += batchSize) {
+            const batch = validAttachments.slice(i, i + batchSize);
+            const formData = new FormData();
+            const media: { type: string; media: string; caption?: string }[] = [];
+            for (let j = 0; j < batch.length; j++) {
+                const att = batch[j];
+                const attachKey = `file${j}`;
+                media.push({
+                    type: 'document',
+                    media: `attach://${attachKey}`,
+                    ...(i === 0 && j === 0 ? { caption } : {}),
+                });
+                const blob = new Blob([att.content], { type: 'application/octet-stream' });
+                formData.append(attachKey, blob, att.filename || `attachment_${j}`);
+            }
+            formData.append('chat_id', chatId);
+            formData.append('media', JSON.stringify(media));
+            const res = await fetch(
+                `https://api.telegram.org/bot${botToken}/sendMediaGroup`,
+                { method: 'POST', body: formData }
+            );
+            if (!res.ok) {
+                const text = await res.text();
+                console.error(`Failed to send attachment batch ${i / batchSize + 1}: ${res.status} ${text.substring(0, 200)}`);
+            }
+        }
+    } catch (e) {
+        console.error("Failed to send telegram attachments:", e);
+    }
+}