fix: server side tts on ios

lib/core/services/sse_stream_parser.dart

@@ -4,15 +4,15 @@ import 'package:dio/dio.dart';
 import '../utils/debug_logger.dart';
 
 /// Parser for Server-Sent Events (SSE) streaming responses.
-/// 
+///
 /// This matches the web client's EventSourceParserStream behavior,
 /// parsing SSE data chunks and extracting OpenAI-compatible deltas.
 class SSEStreamParser {
   /// Parse an SSE response stream from Dio into text chunks.
-  /// 
+  ///
   /// Returns a stream of content strings extracted from OpenAI-style
   /// completion chunks.
-  /// 
+  ///
   /// [heartbeatTimeout] - Maximum time without data before considering
   /// the connection stale (default: 2 minutes)
   /// [onHeartbeat] - Callback invoked when any data is received
@@ -24,46 +24,43 @@ class SSEStreamParser {
   }) async* {
     DateTime lastDataReceived = DateTime.now();
     Timer? heartbeatTimer;
-    
+
     // Set up heartbeat monitoring
     if (heartbeatTimeout.inMilliseconds > 0) {
-      heartbeatTimer = Timer.periodic(
-        const Duration(seconds: 30),
-        (timer) {
-          final timeSinceLastData = DateTime.now().difference(lastDataReceived);
-          if (timeSinceLastData > heartbeatTimeout) {
-            DebugLogger.warning(
-              'SSE stream heartbeat timeout: No data received for ${timeSinceLastData.inSeconds}s',
-              data: {'timeout': heartbeatTimeout.inSeconds},
-            );
-            timer.cancel();
-          }
-        },
-      );
+      heartbeatTimer = Timer.periodic(const Duration(seconds: 30), (timer) {
+        final timeSinceLastData = DateTime.now().difference(lastDataReceived);
+        if (timeSinceLastData > heartbeatTimeout) {
+          DebugLogger.warning(
+            'SSE stream heartbeat timeout: No data received for ${timeSinceLastData.inSeconds}s',
+            data: {'timeout': heartbeatTimeout.inSeconds},
+          );
+          timer.cancel();
+        }
+      });
     }
-    
+
     try {
       // Buffer for accumulating incomplete SSE messages
       String buffer = '';
-      
+
       await for (final chunk in responseBody.stream) {
         // Update last data timestamp and invoke heartbeat callback
         lastDataReceived = DateTime.now();
         onHeartbeat?.call();
-        
+
         // Convert bytes to string (Dio ResponseBody.stream always emits Uint8List)
         final text = utf8.decode(chunk as List<int>, allowMalformed: true);
         buffer += text;
-        
+
         // Process complete SSE messages (delimited by double newline)
         final messages = buffer.split('\n\n');
-        
+
         // Keep the last (potentially incomplete) message in the buffer
         buffer = messages.removeLast();
-        
+
         for (final message in messages) {
           if (message.trim().isEmpty) continue;
-          
+
           // Parse SSE message
           final content = _parseSSEMessage(message);
           if (content != null) {
@@ -72,7 +69,7 @@ class SSEStreamParser {
               DebugLogger.stream('SSE stream completed with [DONE] signal');
               return;
             }
-            
+
             // Split large deltas into smaller chunks for smoother UI updates
             if (splitLargeDeltas && content.length > 5) {
               yield* _splitIntoChunks(content);
@@ -82,7 +79,7 @@ class SSEStreamParser {
           }
         }
       }
-      
+
       // Process any remaining buffered data
       if (buffer.trim().isNotEmpty) {
         final content = _parseSSEMessage(buffer);
@@ -103,34 +100,34 @@ class SSEStreamParser {
       heartbeatTimer?.cancel();
     }
   }
-  
+
   /// Parse a single SSE message and extract content.
   static String? _parseSSEMessage(String message) {
     try {
       // SSE format: "data: <json>\n" or just the JSON
       String dataLine = message.trim();
-      
+
       // Remove "data: " prefix if present
       if (dataLine.startsWith('data: ')) {
         dataLine = dataLine.substring(6).trim();
       } else if (dataLine.startsWith('data:')) {
         dataLine = dataLine.substring(5).trim();
       }
-      
+
       // Handle [DONE] signal
       if (dataLine == '[DONE]' || dataLine == 'DONE') {
         return '[DONE]';
       }
-      
+
       // Skip empty data
       if (dataLine.isEmpty) {
         return null;
       }
-      
+
       // Parse JSON
       try {
         final json = jsonDecode(dataLine) as Map<String, dynamic>;
-        
+
         // Handle errors
         if (json['error'] != null) {
           DebugLogger.error(
@@ -140,7 +137,7 @@ class SSEStreamParser {
           );
           return null;
         }
-        
+
         // Extract content from OpenAI-style response
         // Format: { choices: [{ delta: { content: "..." } }] }
         final choices = json['choices'];
@@ -156,13 +153,13 @@ class SSEStreamParser {
             }
           }
         }
-        
+
         // Alternative format: { content: "..." }
         final directContent = json['content'];
         if (directContent is String && directContent.isNotEmpty) {
           return directContent;
         }
-        
+
         return null;
       } on FormatException catch (e) {
         DebugLogger.warning(
@@ -181,24 +178,24 @@ class SSEStreamParser {
       return null;
     }
   }
-  
+
   /// Split large content into smaller chunks for smoother streaming.
   /// This matches the web client's streamLargeDeltasAsRandomChunks behavior.
   static Stream<String> _splitIntoChunks(String content) async* {
     var remaining = content;
-    
+
     while (remaining.isNotEmpty) {
       // Random chunk size between 1-3 characters
       final chunkSize = (remaining.length < 3)
           ? remaining.length
           : 1 + (DateTime.now().millisecond % 3);
-      
+
       final chunk = remaining.substring(0, chunkSize);
       yield chunk;
-      
+
       // Small delay for smoother visual effect (matching web client)
       await Future.delayed(const Duration(milliseconds: 5));
-      
+
       remaining = remaining.substring(chunkSize);
     }
   }