Merge 774294d into 9f71d65

src/index.js

@@ -54,9 +54,29 @@ const singleUserHandler = async (
   req,
   type,
   replyToken,
+  timeout,
   userId,
   otherFields
 ) => {
+  // reply before timeout
+  // the reply token becomes invalid after a certain period of time
+  // https://developers.line.biz/en/reference/messaging-api/#send-reply-message
+  let isReplied = false;
+  setTimeout(function() {
+    if (isReplied) return;
+
+    isReplied = true;
+    lineClient('/message/reply', {
+      replyToken,
+      messages: [
+        {
+          type: 'text',
+          text: t`Line bot is busy, or we cannot handle this message. Maybe you can try again a few minutes later.`,
+        },
+      ],
+    });
+  }, timeout);
+
   if (userIdBlacklist.indexOf(userId) !== -1) {
     // User blacklist
     console.log(
@@ -184,6 +204,8 @@ const singleUserHandler = async (
   // Send replies. Does not need to wait for lineClient's callbacks.
   // lineClient's callback does error handling by itself.
   //
+  if (isReplied) return;
+  isReplied = true;
   lineClient('/message/reply', {
     replyToken,
     messages: result.replies,
@@ -208,9 +230,18 @@ router.post('/callback', ctx => {
 
   ctx.request.body.events.forEach(
     async ({ type, replyToken, source, ...otherFields }) => {
+      // set 28s timeout
+      const timeout = 28000;
       let { userId } = source;
       if (source.type === 'user') {
-        singleUserHandler(ctx.request, type, replyToken, userId, otherFields);
+        singleUserHandler(
+          ctx.request,
+          type,
+          replyToken,
+          timeout,
+          userId,
+          otherFields
+        );
       } else if (source.type === 'group') {
         groupHandler(ctx.request, type, replyToken, userId, otherFields);
       }