refactor: remove server audio transcription and related fallback logic, retaining only on-device speech-to-text functionality

lib/features/chat/services/voice_input_service.dart

@@ -3,8 +3,7 @@ import 'package:record/record.dart';
 import 'package:flutter/widgets.dart';
 import 'dart:async';
 import 'dart:io' show Platform;
-import 'package:path_provider/path_provider.dart';
-import 'package:path/path.dart' as p;
+// Removed path imports as server transcription fallback was removed
 import 'package:stts/stts.dart';
 
 // Lightweight replacement for previous stt.LocaleName used across the UI
@@ -175,16 +174,9 @@ class VoiceInputService {
         try {
           final isStillAvailable = await _speech.isSupported();
           if (!isStillAvailable && _isListening) {
-            // speech recognition no longer available, fallback to recording
+            // Speech recognition no longer available; stop listening
             _localSttAvailable = false;
-            // Restart with fallback method
-            _startRecordingProxyIntensity();
-            _autoStopTimer?.cancel();
-            _autoStopTimer = Timer(const Duration(seconds: 30), () {
-              if (_isListening) {
-                _stopListening();
-              }
-            });
+            _stopListening();
             return;
           }
         } catch (e) {
@@ -218,24 +210,17 @@ class VoiceInputService {
         }
         // Start recognition (no await blocking the sync flow)
         _speech.start(SttRecognitionOptions(punctuation: true)).catchError((_) {
-          // fallback to recording
+          // On-device STT failed; stop listening entirely as server transcription is removed
           _localSttAvailable = false;
-          _startRecordingProxyIntensity();
+          _stopListening();
         });
       } catch (e) {
         _localSttAvailable = false;
-        _startRecordingProxyIntensity();
+        _stopListening();
       }
     } else {
-      // Fallback: record audio and signal file path for server transcription
-      // Local STT not available, falling back to recording
-      _startRecordingProxyIntensity();
-      _autoStopTimer?.cancel();
-      _autoStopTimer = Timer(const Duration(seconds: 30), () {
-        if (_isListening) {
-          _stopListening();
-        }
-      });
+      // No local STT available; stop immediately since server transcription is removed
+      _stopListening();
     }
 
     return _textStreamController!.stream;
@@ -262,9 +247,6 @@ class VoiceInputService {
         _sttStateSub?.cancel();
       } catch (_) {}
       _sttStateSub = null;
-    } else {
-      // Also stop recorder if active
-      await _stopRecording();
     }
 
     _autoStopTimer?.cancel();
@@ -284,84 +266,12 @@ class VoiceInputService {
 
   void dispose() {
     stopListening();
-    _stopRecording(force: true);
     try {
       _speech.dispose().catchError((_) {});
     } catch (_) {}
   }
 
-  // --- Recording and intensity proxy for server transcription path ---
-  Future<void> _startRecordingProxyIntensity() async {
-    try {
-      final hasMic = await _recorder.hasPermission();
-      if (!hasMic) {
-        _textStreamController?.addError('Microphone permission not granted');
-        _stopListening();
-        return;
-      }
-
-      // Start recording in a portable format (WAV/PCM) for best compatibility with server
-      final tmpDir = await getTemporaryDirectory();
-      final filePath = p.join(
-        tmpDir.path,
-        'conduit_voice_${DateTime.now().millisecondsSinceEpoch}.wav',
-      );
-      await _recorder.start(
-        const RecordConfig(
-          encoder: AudioEncoder.wav,
-          numChannels: 1,
-          sampleRate: 16000,
-          bitRate: 128000,
-        ),
-        path: filePath,
-      );
-      // recording started at filePath
-
-      // Drive intensity from amplitude stream and detect silence
-      // Consider amplitude less than threshold as silence; stop after ~3s of continuous silence
-      const silenceThresholdDb = -45.0; // dBFS threshold
-      const silenceWindow = Duration(seconds: 3);
-      DateTime lastNonSilent = DateTime.now();
-
-      _ampSub = _recorder
-          .onAmplitudeChanged(const Duration(milliseconds: 125))
-          .listen((amp) {
-            if (!_isListening) return;
-            // Normalize peak power (dBFS) into 0-10 bar scale
-            final db = amp.current;
-            // Map dB [-60..0] -> [0..10]
-            final clamped = db.clamp(-60.0, 0.0);
-            final norm = ((clamped + 60.0) / 60.0) * 10.0;
-            _intensityController?.add(norm.round().clamp(0, 10));
-
-            if (db > silenceThresholdDb) {
-              lastNonSilent = DateTime.now();
-            } else {
-              if (DateTime.now().difference(lastNonSilent) >= silenceWindow) {
-                _stopListening();
-              }
-            }
-          });
-    } catch (e) {
-      _textStreamController?.addError('Audio recording failed: $e');
-      _stopListening();
-    }
-  }
-
-  Future<void> _stopRecording({bool force = false}) async {
-    try {
-      if (!await _recorder.isRecording() && !force) return;
-      final path = await _recorder.stop();
-      if (path == null) {
-        _textStreamController?.addError('Recording failed: no file path');
-        return;
-      }
-      // Hand off recorded file path to listeners as a special token; UI layer will upload for transcription
-      _textStreamController?.add('[[AUDIO_FILE_PATH]]:$path');
-    } catch (e) {
-      _textStreamController?.addError('Stop recording error: $e');
-    }
-  }
+  // Recording fallback removed; only on-device STT is supported now
 
   // Native locales not used in server transcription mode
 }