From 19008ca485355bea295de40e22c7ef6c24e3a71b Mon Sep 17 00:00:00 2001
From: Hoan HL <hoan.h.luu@drachtio.org>
Date: Thu, 27 Nov 2025 15:27:29 +0700
Subject: [PATCH] wip

---
 lib/tasks/gather.js     |  2 +-
 lib/tasks/stt-task.js   |  7 ++++---
 lib/tasks/transcribe.js | 24 +++++++++++++++++++++++-
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/lib/tasks/gather.js b/lib/tasks/gather.js
index 6ccfda36..bc10c2d2 100644
--- a/lib/tasks/gather.js
+++ b/lib/tasks/gather.js
@@ -1161,7 +1161,7 @@ class TaskGather extends SttTask {
   }
 
   async _startFallback(cs, ep, evt) {
-    if (this.canFallback) {
+    if (this.canFallback()) {
       this._stopTranscribing(ep);
       try {
         this.logger.debug('gather:_startFallback');
diff --git a/lib/tasks/stt-task.js b/lib/tasks/stt-task.js
index f02d9776..06cd4992 100644
--- a/lib/tasks/stt-task.js
+++ b/lib/tasks/stt-task.js
@@ -171,7 +171,7 @@ class SttTask extends Task {
       try {
         this.sttCredentials = await this._initSpeechCredentials(this.cs, this.vendor, this.label);
       } catch (error) {
-        if (this.canFallback) {
+        if (this.canFallback()) {
           this.notifyError(
             {
               msg: 'ASR error', details:`Invalid vendor ${this.vendor}, Error: ${error}`,
@@ -340,11 +340,12 @@ class SttTask extends Task {
     return credentials;
   }
 
-  get canFallback() {
+  canFallback() {
     return this.fallbackVendor && this.isHandledByPrimaryProvider && !this.cs.hasFallbackAsr;
   }
 
-  // gather does not need to provide ep, but transcribe does as it might has 2 legs
+  // ep is optional for gather or any verb that have single ep,
+  // but transcribe does need as it might has 2 eps
   async _initFallback(ep) {
     assert(this.fallbackVendor, 'fallback failed without fallbackVendor configuration');
     this.logger.info(`Failed to use primary STT provider, fallback to ${this.fallbackVendor}`);
diff --git a/lib/tasks/transcribe.js b/lib/tasks/transcribe.js
index 2ea6d199..e636d8c4 100644
--- a/lib/tasks/transcribe.js
+++ b/lib/tasks/transcribe.js
@@ -70,6 +70,9 @@ class TaskTranscribe extends SttTask {
     this._bufferedTranscripts = [ [], [] ];  // for channel 1 and 2
     this.bugname_prefix = 'transcribe_';
     this.paused = false;
+    // fallback flags
+    this.isHandledByPrimaryProviderForEp1 = true;
+    this.isHandledByPrimaryProviderForEp2 = true;
   }
 
   get name() { return TaskName.Transcribe; }
@@ -776,7 +779,7 @@ class TaskTranscribe extends SttTask {
   }
 
   async _startFallback(cs, _ep, evt) {
-    if (this.canFallback) {
+    if (this.canFallback(_ep)) {
       _ep.stopTranscription({
         vendor: this.vendor,
         bugname: this.bugname,
@@ -895,6 +898,25 @@ class TaskTranscribe extends SttTask {
     if (this._asrTimer) clearTimeout(this._asrTimer);
     this._asrTimer = null;
   }
+
+  // We need to keep track the fallback is happened for each endpoint
+  // override the canFallback and _initFallback methods to make sure that
+  // we only fallback once per endpoint
+  canFallback(ep) {
+    const isHandledByPrimaryProvider = ep === this.ep ?
+      this.isHandledByPrimaryProviderForEp1 : ep === this.ep2 ?
+        this.isHandledByPrimaryProviderForEp2 : false;
+    return this.fallbackVendor && isHandledByPrimaryProvider && !this.cs.hasFallbackAsr;
+  }
+
+  _initFallback(ep) {
+    if (ep === this.ep) {
+      this.isHandledByPrimaryProviderForEp1 = false;
+    } else if (ep === this.ep2) {
+      this.isHandledByPrimaryProviderForEp2 = false;
+    }
+    return super._initFallback(ep);
+  }
 }
 
 module.exports = TaskTranscribe;