feat: enhance text-to-speech functionality with markdown support

- Integrated markdown conversion in TextToSpeechController to clean text before speech synthesis, ensuring only valid content is spoken.
- Updated VoiceCallService to utilize markdown conversion for responses, improving the clarity of spoken content.
- Enhanced VoiceCallPage to display cleaned text from markdown, providing a better user experience during voice interactions.

lib/core/utils/markdown_to_text.dart

@@ -0,0 +1,118 @@
+/// Converts markdown text to plain text suitable for text-to-speech.
+///
+/// Strips formatting while preserving the semantic meaning and readability
+/// of the content for audio consumption.
+class MarkdownToText {
+  const MarkdownToText._();
+
+  static final _codeBlockRegex = RegExp(
+    r'```[^\n]*\n(.*?)```',
+    multiLine: true,
+    dotAll: true,
+  );
+  static final _inlineCodeRegex = RegExp(r'`([^`]+)`');
+  static final _boldItalicRegex = RegExp(r'\*\*\*([^*]+)\*\*\*');
+  static final _boldRegex = RegExp(r'\*\*([^*]+)\*\*');
+  static final _italicRegex = RegExp(r'\*([^*]+)\*|_([^_]+)_');
+  static final _strikethroughRegex = RegExp(r'~~([^~]+)~~');
+  static final _linkRegex = RegExp(r'\[([^\]]+)\]\([^)]+\)');
+  static final _imageRegex = RegExp(r'!\[([^\]]*)\]\([^)]+\)');
+  static final _headingRegex = RegExp(r'^#{1,6}\s+(.+)$', multiLine: true);
+  static final _listItemRegex = RegExp(r'^[\s]*[-*+]\s+(.+)$', multiLine: true);
+  static final _orderedListRegex = RegExp(
+    r'^[\s]*\d+\.\s+(.+)$',
+    multiLine: true,
+  );
+  static final _blockquoteRegex = RegExp(r'^>\s*(.+)$', multiLine: true);
+  static final _horizontalRuleRegex = RegExp(
+    r'^[\s]*[-*_]{3,}[\s]*$',
+    multiLine: true,
+  );
+  static final _htmlTagRegex = RegExp(r'<[^>]+>');
+  static final _multipleNewlinesRegex = RegExp(r'\n{3,}');
+  static final _multipleSpacesRegex = RegExp(r' {2,}');
+
+  /// Converts markdown text to plain text suitable for TTS.
+  ///
+  /// - Removes code blocks (replaces with descriptive text)
+  /// - Strips all formatting (bold, italic, strikethrough)
+  /// - Converts links to just their text
+  /// - Removes images (or converts to alt text)
+  /// - Simplifies headings
+  /// - Preserves list structure with natural pauses
+  /// - Removes HTML tags
+  /// - Normalizes whitespace
+  static String convert(String markdown) {
+    if (markdown.trim().isEmpty) {
+      return '';
+    }
+
+    var text = markdown;
+
+    // Remove or replace code blocks with descriptive text
+    text = text.replaceAllMapped(_codeBlockRegex, (match) {
+      final code = match[1]?.trim() ?? '';
+      if (code.isEmpty) {
+        return '';
+      }
+      // For TTS, skip code blocks or use a brief description
+      return ' (code block) ';
+    });
+
+    // Remove inline code backticks but keep the content
+    text = text.replaceAllMapped(_inlineCodeRegex, (match) => match[1] ?? '');
+
+    // Strip bold/italic/strikethrough formatting
+    text = text.replaceAllMapped(_boldItalicRegex, (match) => match[1] ?? '');
+    text = text.replaceAllMapped(_boldRegex, (match) => match[1] ?? '');
+    text = text.replaceAllMapped(
+      _italicRegex,
+      (match) => match[1] ?? match[2] ?? '',
+    );
+    text = text.replaceAllMapped(
+      _strikethroughRegex,
+      (match) => match[1] ?? '',
+    );
+
+    // Convert links to just their text
+    text = text.replaceAllMapped(_linkRegex, (match) => match[1] ?? '');
+
+    // Remove images (or use alt text if available)
+    text = text.replaceAllMapped(_imageRegex, (match) {
+      final alt = match[1]?.trim() ?? '';
+      return alt.isNotEmpty ? ' ($alt image) ' : '';
+    });
+
+    // Simplify headings (remove # symbols)
+    text = text.replaceAllMapped(_headingRegex, (match) {
+      final heading = match[1] ?? '';
+      // Add a pause after headings for natural speech flow
+      return '$heading.\n';
+    });
+
+    // Preserve list items with natural pauses
+    text = text.replaceAllMapped(_listItemRegex, (match) => '${match[1]}. ');
+    text = text.replaceAllMapped(_orderedListRegex, (match) => '${match[1]}. ');
+
+    // Remove blockquote markers
+    text = text.replaceAllMapped(_blockquoteRegex, (match) => match[1] ?? '');
+
+    // Remove horizontal rules
+    text = text.replaceAll(_horizontalRuleRegex, '');
+
+    // Remove HTML tags
+    text = text.replaceAll(_htmlTagRegex, '');
+
+    // Normalize whitespace
+    text = text.replaceAll(_multipleNewlinesRegex, '\n\n');
+    text = text.replaceAll(_multipleSpacesRegex, ' ');
+
+    // Convert newlines to spaces for natural speech flow
+    text = text.replaceAll('\n', ' ');
+
+    // Final cleanup
+    text = text.trim();
+
+    return text;
+  }
+}

lib/features/chat/providers/text_to_speech_provider.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../../../core/utils/markdown_to_text.dart';
 import '../services/text_to_speech_service.dart';
 
 enum TtsPlaybackStatus { idle, initializing, loading, speaking, paused, error }
@@ -161,7 +162,21 @@ class TextToSpeechController extends Notifier<TextToSpeechState> {
     );
 
     try {
-      await _service.speak(text);
+      // Convert markdown to clean text for TTS
+      final cleanText = MarkdownToText.convert(text);
+      if (cleanText.isEmpty) {
+        // No speakable content
+        if (!ref.mounted) {
+          return;
+        }
+        state = state.copyWith(
+          status: TtsPlaybackStatus.idle,
+          clearActiveMessageId: true,
+        );
+        return;
+      }
+
+      await _service.speak(cleanText);
       if (!ref.mounted) {
         return;
       }

lib/features/chat/services/voice_call_service.dart

@@ -5,6 +5,7 @@ import 'package:wakelock_plus/wakelock_plus.dart';
 
 import '../../../core/providers/app_providers.dart';
 import '../../../core/services/socket_service.dart';
+import '../../../core/utils/markdown_to_text.dart';
 import '../providers/chat_providers.dart';
 import 'text_to_speech_service.dart';
 import 'voice_input_service.dart';
@@ -80,8 +81,8 @@ class VoiceCallService {
     await _notificationService.initialize();
 
     // Request notification permissions if needed
-    final notificationsEnabled =
-        await _notificationService.areNotificationsEnabled();
+    final notificationsEnabled = await _notificationService
+        .areNotificationsEnabled();
     if (!notificationsEnabled) {
       await _notificationService.requestPermissions();
     }
@@ -186,12 +187,10 @@ class VoiceCallService {
       );
 
       // Forward intensity stream for waveform visualization
-      _intensitySubscription = _voiceInput.intensityStream.listen(
-        (intensity) {
+      _intensitySubscription = _voiceInput.intensityStream.listen((intensity) {
         if (_isDisposed) return;
         _intensityController.add(intensity);
-        },
-      );
+      });
     } catch (e) {
       _updateState(VoiceCallState.error);
       rethrow;
@@ -283,7 +282,17 @@ class VoiceCallService {
       await _intensitySubscription?.cancel();
 
       _updateState(VoiceCallState.speaking);
-      await _tts.speak(response);
+
+      // Convert markdown to clean text for TTS
+      final cleanText = MarkdownToText.convert(response);
+      if (cleanText.isEmpty) {
+        // No speakable content, restart listening
+        _isSpeaking = false;
+        await _startListening();
+        return;
+      }
+
+      await _tts.speak(cleanText);
       // After speaking completes, _handleTtsComplete will restart listening
     } catch (e) {
       _isSpeaking = false;

lib/features/chat/views/voice_call_page.dart

@@ -6,6 +6,7 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../../core/providers/app_providers.dart';
+import '../../../core/utils/markdown_to_text.dart';
 import '../services/voice_call_service.dart';
 
 class VoiceCallPage extends ConsumerStatefulWidget {
@@ -239,7 +240,8 @@ class _VoiceCallPageState extends ConsumerState<VoiceCallPage>
               builder: (context, child) {
                 final offset = (index * 0.2) % 1.0;
                 final animation = (_waveController.value + offset) % 1.0;
-                final height = 20.0 +
+                final height =
+                    20.0 +
                     (math.sin(animation * math.pi * 2) * 30.0).abs() +
                     (_currentIntensity * 4.0);
 
@@ -271,10 +273,7 @@ class _VoiceCallPageState extends ConsumerState<VoiceCallPage>
               decoration: BoxDecoration(
                 shape: BoxShape.circle,
                 color: primaryColor.withValues(alpha: 0.2),
-                border: Border.all(
-                  color: primaryColor,
-                  width: 3,
-                ),
+                border: Border.all(color: primaryColor, width: 3),
               ),
               child: Center(
                 child: Icon(
@@ -323,7 +322,8 @@ class _VoiceCallPageState extends ConsumerState<VoiceCallPage>
       displayText = _currentTranscript;
     } else if (_currentState == VoiceCallState.speaking &&
         _currentResponse.isNotEmpty) {
-      displayText = _currentResponse;
+      // Convert markdown to clean text for display
+      displayText = MarkdownToText.convert(_currentResponse);
     }
 
     if (displayText.isEmpty) {
@@ -405,25 +405,12 @@ class _VoiceCallPageState extends ConsumerState<VoiceCallPage>
           child: Container(
             width: 64,
             height: 64,
-            decoration: BoxDecoration(
-              shape: BoxShape.circle,
-              color: color,
-            ),
-            child: Icon(
-              icon,
-              color: Colors.white,
-              size: 32,
-            ),
+            decoration: BoxDecoration(shape: BoxShape.circle, color: color),
+            child: Icon(icon, color: Colors.white, size: 32),
           ),
         ),
         const SizedBox(height: 8),
-        Text(
-          label,
-          style: TextStyle(
-            fontSize: 12,
-            color: color,
-          ),
-        ),
+        Text(label, style: TextStyle(fontSize: 12, color: color)),
       ],
     );
   }