websocket_handler.py

"""
WebSocket Handler for Real-time STT/TTS with Barge-in Support
"""
from fastapi import WebSocket, WebSocketDisconnect
from typing import Dict, Any, Optional
import json
import asyncio
import base64
from datetime import datetime
from collections import deque
from enum import Enum
import numpy as np
import traceback

from session import Session, session_store
from config_provider import ConfigProvider
from chat_handler import handle_new_message, handle_parameter_followup
from stt_factory import STTFactory
from tts_factory import TTSFactory
from logger import log_info, log_error, log_debug, log_warning

# ========================= CONSTANTS =========================
# Default values - will be overridden by config
DEFAULT_SILENCE_THRESHOLD_MS = 2000
DEFAULT_AUDIO_CHUNK_SIZE = 4096
DEFAULT_ENERGY_THRESHOLD = 0.0005 # 0.01
DEFAULT_AUDIO_BUFFER_MAX_SIZE = 1000

# ========================= ENUMS =========================
class ConversationState(Enum):
    IDLE = "idle"
    LISTENING = "listening"
    PROCESSING_STT = "processing_stt"
    PROCESSING_LLM = "processing_llm"
    PROCESSING_TTS = "processing_tts"
    PLAYING_AUDIO = "playing_audio"

# ========================= CLASSES =========================
class AudioBuffer:
    """Thread-safe circular buffer for audio chunks"""
    def __init__(self, max_size: int = DEFAULT_AUDIO_BUFFER_MAX_SIZE):
        self.buffer = deque(maxlen=max_size)
        self.lock = asyncio.Lock()
        
    async def add_chunk(self, chunk_data: str):
        """Add base64 encoded audio chunk"""
        async with self.lock:
            decoded = base64.b64decode(chunk_data)
            self.buffer.append(decoded)
            
    async def get_all_audio(self) -> bytes:
        """Get all audio data concatenated"""
        async with self.lock:
            return b''.join(self.buffer)
    
    async def clear(self):
        """Clear buffer"""
        async with self.lock:
            self.buffer.clear()
    
    def size(self) -> int:
        """Get current buffer size"""
        return len(self.buffer)


class SilenceDetector:
    """Detect silence in audio stream"""
    def __init__(self, threshold_ms: int = DEFAULT_SILENCE_THRESHOLD_MS, energy_threshold: float = DEFAULT_ENERGY_THRESHOLD):
        self.threshold_ms = threshold_ms
        self.energy_threshold = energy_threshold
        self.silence_start = None
        self.sample_rate = 16000
        
    def update(self, audio_chunk: bytes) -> int:
        """Update with new audio chunk and return silence duration in ms"""
        if self.is_silence(audio_chunk):
            if self.silence_start is None:
                self.silence_start = datetime.now()
            silence_duration = (datetime.now() - self.silence_start).total_seconds() * 1000
            return int(silence_duration)
        else:
            self.silence_start = None
            return 0
    
    def is_silence(self, audio_chunk: bytes) -> bool:
        """Check if audio chunk is silence"""
        try:
            # Convert bytes to numpy array (assuming 16-bit PCM)
            audio_data = np.frombuffer(audio_chunk, dtype=np.int16)
            
            # Calculate RMS energy
            if len(audio_data) == 0:
                return True
                
            rms = np.sqrt(np.mean(audio_data.astype(float) ** 2))
            normalized_rms = rms / 32768.0  # Normalize for 16-bit audio
    
            # Audio energy log'unu kaldırdık
            
            return normalized_rms < self.energy_threshold
        except Exception as e:
            log_warning(f"Silence detection error: {e}")
            return False
    
    def reset(self):
        """Reset silence detection"""
        self.silence_start = None


class BargeInHandler:
    """Handle user interruptions during TTS playback"""
    def __init__(self):
        self.active_tts_task: Optional[asyncio.Task] = None
        self.is_interrupting = False
        self.lock = asyncio.Lock()
    
    async def start_tts_task(self, coro):
        """Start a cancellable TTS task"""
        async with self.lock:
            # Cancel any existing task
            if self.active_tts_task and not self.active_tts_task.done():
                self.active_tts_task.cancel()
                try:
                    await self.active_tts_task
                except asyncio.CancelledError:
                    pass
            
            # Start new task
            self.active_tts_task = asyncio.create_task(coro)
            return self.active_tts_task
    
    async def handle_interruption(self, current_state: ConversationState):
        """Handle barge-in interruption"""
        async with self.lock:
            self.is_interrupting = True
            
            # Cancel TTS if active
            if self.active_tts_task and not self.active_tts_task.done():
                log_info("Barge-in: Cancelling active TTS")
                self.active_tts_task.cancel()
                try:
                    await self.active_tts_task
                except asyncio.CancelledError:
                    pass
            
            # Reset flag after short delay
            await asyncio.sleep(0.5)
            self.is_interrupting = False


class RealtimeSession:
    """Manage a real-time conversation session"""
    def __init__(self, session: Session):
        self.session = session
        self.state = ConversationState.IDLE
        self.is_websocket_active = True  # Yeni flag
        
        # Get settings from config
        config = ConfigProvider.get().global_config.stt_provider.settings
        
        # Initialize with config values or defaults
        silence_threshold = config.get("speech_timeout_ms", DEFAULT_SILENCE_THRESHOLD_MS)
        energy_threshold = config.get("energy_threshold", DEFAULT_ENERGY_THRESHOLD)
        buffer_max_size = config.get("audio_buffer_max_size", DEFAULT_AUDIO_BUFFER_MAX_SIZE)
        
        self.audio_buffer = AudioBuffer(max_size=buffer_max_size)
        self.silence_detector = SilenceDetector(
            threshold_ms=silence_threshold,
            energy_threshold=energy_threshold
        )
        self.barge_in_handler = BargeInHandler()
        self.stt_manager = None
        self.current_transcription = ""
        self.is_streaming = False
        self.lock = asyncio.Lock()
        
        # Store config for later use
        self.audio_chunk_size = config.get("audio_chunk_size", DEFAULT_AUDIO_CHUNK_SIZE)
        self.silence_threshold_ms = silence_threshold
        
    async def initialize_stt(self):
        """Initialize STT provider"""
        try:
            self.stt_manager = STTFactory.create_provider()
            if not self.stt_manager:
                log_error("❌ STT manager is None - STTFactory.create_provider() returned None", session_id=self.session.session_id)
                return False
                
            log_info(f"✅ STT manager created: {type(self.stt_manager).__name__}", session_id=self.session.session_id)
            
            # Get STT config from provider settings
            config = ConfigProvider.get().global_config.stt_provider.settings
            
            # Get language from session locale
            session_locale = getattr(self.session, 'locale', 'tr')  # Default to 'tr' if not set
            
            # Import LocaleManager to get proper locale tag
            from locale_manager import LocaleManager
            locale_data = LocaleManager.get_locale(session_locale)
            
            # Get proper locale tag for STT (e.g., tr -> tr-TR)
            language_code = locale_data.get('locale_tag', 'tr-TR')
            
            log_info(f"🌍 Session locale: {session_locale}, STT language: {language_code}", session_id=self.session.session_id)
            
            stt_config = {
                "language": language_code,
                "interim_results": config.get("interim_results", True),
                "single_utterance": False,
                "enable_punctuation": config.get("enable_punctuation", True),
                "sample_rate": 16000,
                "encoding": "WEBM_OPUS"
            }
            
            log_info(f"🎤 Starting STT streaming with config: {stt_config}", session_id=self.session.session_id)
            
            # Start streaming
            await self.stt_manager.start_streaming(stt_config)
            self.is_streaming = True
            
            log_info("✅ STT streaming started successfully", session_id=self.session.session_id)
            return True
            
        except Exception as e:
            log_error(f"❌ Failed to initialize STT", error=str(e), traceback=traceback.format_exc(), session_id=self.session.session_id)
            self.stt_manager = None
            self.is_streaming = False
            return False
    
    async def change_state(self, new_state: ConversationState):
        """Change conversation state"""
        async with self.lock:
            old_state = self.state
            self.state = new_state
            log_debug(
                f"State change: {old_state.value} → {new_state.value}",
                session_id=self.session.session_id
            )
    
    async def handle_barge_in(self):
        """Handle user interruption"""
        await self.barge_in_handler.handle_interruption(self.state)
        await self.change_state(ConversationState.LISTENING)
    
    async def reset_for_new_utterance(self):
        """Reset for new user utterance"""
        await self.audio_buffer.clear()
        self.silence_detector.reset()
        self.current_transcription = ""
        if hasattr(self, 'speech_started'):
            delattr(self, 'speech_started')  # Speech started flag'ini sıfırla
    
    async def cleanup(self):
        """Clean up resources"""
        try:
            self.is_websocket_active = False  # WebSocket kapanıyor
            if self.stt_manager:
                await self.stt_manager.stop_streaming()
            log_info(f"Cleaned up realtime session", session_id=self.session.session_id)
        except Exception as e:
            log_warning(f"Cleanup error", error=str(e), session_id=self.session.session_id)

# ========================= MAIN HANDLER =========================
async def websocket_endpoint(websocket: WebSocket, session_id: str):
    """Main WebSocket endpoint for real-time conversation"""
    log_info(f"🔌 WebSocket connection attempt", session_id=session_id)
    
    await websocket.accept()
    log_info(f"✅ WebSocket accepted", session_id=session_id)
    
    # Get session
    session = session_store.get_session(session_id)
    if not session:
        log_error(f"❌ Session not found", session_id=session_id)
        await websocket.send_json({
            "type": "error",
            "message": "Session not found"
        })
        await websocket.close()
        return
    
    log_info(f"✅ Session found", session_id=session_id, project=session.project_name)
    
    # Mark as realtime session
    session.is_realtime = True
    session_store.update_session(session)
    
    # Initialize conversation
    realtime_session = RealtimeSession(session)
    
    # Initialize STT
    log_info(f"🎤 Initializing STT...", session_id=session_id)
    stt_initialized = await realtime_session.initialize_stt()
    if not stt_initialized:
        log_error(f"❌ STT initialization failed", session_id=session_id)
        await websocket.send_json({
            "type": "error",
            "message": "STT initialization failed"
        })
    else:
        log_info(f"✅ STT initialized", session_id=session_id)
    
    # Send session started confirmation
    await websocket.send_json({
        "type": "session_started",
        "session_id": session_id,
        "stt_initialized": stt_initialized
    })
    
    # Send welcome message from session history
    log_info(f"📋 Checking for welcome message in session history...", session_id=session_id)
    
    # chat_history değişkenini session'dan al
    chat_history = session.chat_history
    
    if chat_history and len(chat_history) > 0:
        log_info(f"📋 Found {len(chat_history)} messages in history", session_id=session_id)
        
        # Get the last assistant message (welcome message)
        for i, msg in enumerate(reversed(chat_history)):
            log_debug(f"📋 Message {i}: role={msg.get('role', 'unknown')}, content_preview={msg.get('content', '')[:50]}...", session_id=session_id)
            
            if msg.get('role') == 'assistant':
                welcome_text = msg.get('content', '')
                log_info(f"📢 Found welcome message: {welcome_text[:50]}...", session_id=session_id)
                
                # Send text first
                try:
                    await websocket.send_json({
                        "type": "assistant_response",
                        "text": welcome_text,
                        "is_welcome": True
                    })
                    log_info(f"✅ Welcome text sent via WebSocket", session_id=session_id)
                except Exception as e:
                    log_error(f"❌ Failed to send welcome text", error=str(e), session_id=session_id)
                
                # Generate and send TTS if available
                tts_provider = TTSFactory.create_provider()
                if tts_provider:
                    try:
                        log_info(f"🎤 Generating welcome TTS...", session_id=session_id)
                        
                        # TTS preprocessor kullan
                        from tts_preprocessor import TTSPreprocessor
                        preprocessor = TTSPreprocessor(language=session.locale)
                        processed_text = preprocessor.preprocess(
                            welcome_text,
                            tts_provider.get_preprocessing_flags()
                        )
                        
                        # TTS oluştur
                        audio_data = await tts_provider.synthesize(processed_text)
                        
                        if audio_data:
                            # Audio'yu base64'e çevir ve chunk'lara böl
                            audio_base64 = base64.b64encode(audio_data).decode('utf-8')
                            chunk_size = 16384
                            total_length = len(audio_base64)
                            total_chunks = (total_length + chunk_size - 1) // chunk_size
                            
                            log_info(f"📤 Sending welcome TTS in {total_chunks} chunks", session_id=session_id)
                            
                            for i in range(0, total_length, chunk_size):
                                chunk = audio_base64[i:i + chunk_size]
                                chunk_index = i // chunk_size
                                is_last = chunk_index == total_chunks - 1
                                
                                await websocket.send_json({
                                    "type": "tts_audio",
                                    "data": chunk,
                                    "chunk_index": chunk_index,
                                    "total_chunks": total_chunks,
                                    "is_last": is_last,
                                    "mime_type": "audio/mpeg"
                                })
                            
                            log_info(f"✅ Welcome TTS sent", session_id=session_id)
                    except Exception as e:
                        log_error(f"❌ Failed to send welcome TTS", error=str(e), traceback=traceback.format_exc(), session_id=session_id)
                else:
                    log_warning(f"⚠️ No TTS provider available", session_id=session_id)
                
                break
        else:
            log_warning(f"⚠️ No assistant message found in history", session_id=session_id)
    else:
        log_warning(f"⚠️ No messages in session history", session_id=session_id)
    
    log_info(f"💬 Ready for conversation", session_id=session_id)

    try:
        while True:
            try:
                # Receive message with timeout
                message = await asyncio.wait_for(
                    websocket.receive_json(), 
                    timeout=60.0  # 60 second timeout
                )
                
                message_type = message.get("type")
                # Debug log'u kaldırdık
                
                if message_type == "audio_chunk":
                    await handle_audio_chunk(websocket, realtime_session, message)
                    
                elif message_type == "control":
                    await handle_control_message(websocket, realtime_session, message)
                    
                elif message_type == "ping":
                    # Keep-alive ping - log yapmadan
                    await websocket.send_json({"type": "pong"})
                    
            except asyncio.TimeoutError:
                # Timeout log'unu da azaltalım - her timeout'ta değil
                await websocket.send_json({"type": "ping"})
                
    except WebSocketDisconnect as e:
        log_info(f"🔌 WebSocket disconnected", session_id=session_id, code=e.code, reason=e.reason)
    except Exception as e:
        log_error(
            f"❌ WebSocket error",
            error=str(e),
            traceback=traceback.format_exc(),
            session_id=session_id
        )
        await websocket.send_json({
            "type": "error",
            "message": str(e)
        })
    finally:
            log_info(f"🧹 Cleaning up WebSocket connection", session_id=session_id)
            await realtime_session.cleanup()
            
            # WebSocket'in açık olup olmadığını kontrol et
            try:
                if websocket.client_state.value == 1:  # 1 = CONNECTED state
                    await websocket.close()
            except Exception as e:
                log_debug(f"WebSocket already closed or error during close: {e}", session_id=session_id)
        
# ========================= MESSAGE HANDLERS =========================
async def handle_audio_chunk(websocket: WebSocket, session: RealtimeSession, message: Dict[str, Any]):
    """Handle incoming audio chunk with barge-in support"""
    try:
        # WebSocket kapandıysa işlem yapma
        if not session.is_websocket_active:
            return
            
        audio_data = message.get("data")
        if not audio_data:
            log_warning(f"⚠️ Empty audio chunk received", session_id=session.session.session_id)
            return
        
        # Check for barge-in during TTS/audio playback
        if session.state in [ConversationState.PLAYING_AUDIO, ConversationState.PROCESSING_TTS]:
            await session.handle_barge_in()
            await websocket.send_json({
                "type": "control",
                "action": "stop_playback"
            })
            log_info(f"🛑 Barge-in detected", session_id=session.session.session_id, state=session.state.value)
        
        # Change state to listening if idle
        if session.state == ConversationState.IDLE:
            await session.change_state(ConversationState.LISTENING)
            await websocket.send_json({
                "type": "state_change",
                "from": "idle",
                "to": "listening"
            })
        
        # Add to buffer
        await session.audio_buffer.add_chunk(audio_data)
        
        # Decode for processing
        decoded_audio = base64.b64decode(audio_data)
        
        # Check silence - LOGLAMA YAPMA
        silence_duration = session.silence_detector.update(decoded_audio)
        
        # Stream to STT if available
        if session.stt_manager and session.state == ConversationState.LISTENING:
            # Ensure streaming is active
            if not session.is_streaming:
                log_warning(f"⚠️ STT manager exists but streaming not active", session_id=session.session.session_id)
                # Try to restart streaming
                stt_initialized = await session.initialize_stt()
                if not stt_initialized:
                    await websocket.send_json({
                        "type": "error",
                        "error_type": "stt_error",
                        "message": "STT streaming not available"
                    })
                    return
            
            try:
                # Chunk counter - sadece önemli milestone'larda logla
                if not hasattr(session, 'chunk_counter'):
                    session.chunk_counter = 0
                session.chunk_counter += 1
                
                if session.chunk_counter == 1:
                    log_info(f"🎤 Started streaming audio to STT", session_id=session.session.session_id)
                elif session.chunk_counter % 100 == 0:
                    log_info(f"📊 Sent {session.chunk_counter} chunks to STT so far...", session_id=session.session.session_id)
                
                # STT'ye gönder ve sonuçları bekle
                async for result in session.stt_manager.stream_audio(decoded_audio):
                    # SADECE FINAL RESULT'LARI LOGLA VE GÖNDER
                    if result.is_final:
                        log_info(f"✅ FINAL TRANSCRIPTION: '{result.text}'", session_id=session.session.session_id)
                        
                        # Send ONLY final transcription to frontend
                        await websocket.send_json({
                            "type": "transcription",
                            "text": result.text,
                            "is_final": True,
                            "confidence": result.confidence
                        })
                        
                        session.current_transcription = result.text
                        
                        # Final transcription geldiğinde hemen işle
                        if session.current_transcription:
                            # State'i değiştir ve user input'u işle
                            await session.change_state(ConversationState.PROCESSING_STT)
                            await websocket.send_json({
                                "type": "state_change",
                                "from": "listening",
                                "to": "processing_stt"
                            })
                            
                            # Process user input
                            await process_user_input(websocket, session)
                            
                            # STT'den final result geldiğinde audio buffer'ı ve transcription'ı resetle
                            await session.reset_for_new_utterance()
                            return  # Bu audio chunk için işlem tamamlandı
                    
                    # Interim result'ları SADECE ilk kelimede logla (konuşma başlangıcı)
                    elif result.text.strip() and not hasattr(session, 'speech_started'):
                        session.speech_started = True
                        log_info(f"🎤 User started speaking", session_id=session.session.session_id)
                        
            except Exception as e:
                log_error(f"❌ STT streaming error", error=str(e), traceback=traceback.format_exc(), session_id=session.session.session_id)
                await websocket.send_json({
                    "type": "error",
                    "error_type": "stt_error",
                    "message": f"STT error: {str(e)}"
                })
            
    except Exception as e:
        log_error(
            f"❌ Audio chunk handling error",
            error=str(e),
            traceback=traceback.format_exc(),
            session_id=session.session.session_id
        )
        await websocket.send_json({
            "type": "error",
            "message": f"Audio processing error: {str(e)}"
        })
        
async def handle_control_message(websocket: WebSocket, session: RealtimeSession, message: Dict[str, Any]):
    """Handle control messages"""
    action = message.get("action")
    config = message.get("config", {})
    
    log_debug(f"🎮 Control message", action=action, session_id=session.session.session_id)
    
    if action == "start_session":
        # Session configuration
        await websocket.send_json({
            "type": "session_config",
            "session_id": session.session.session_id,
            "config": {
                "silence_threshold_ms": session.silence_threshold_ms,
                "audio_chunk_size": session.audio_chunk_size,
                "supports_barge_in": True
            }
        })
        
    elif action == "end_session" or action == "stop_session":
        # Clean up and close
        await session.cleanup()
        await websocket.close()
        
    elif action == "interrupt":
        # Handle explicit interrupt
        await session.handle_barge_in()
        await websocket.send_json({
            "type": "control",
            "action": "interrupt_acknowledged"
        })
        
    elif action == "reset":
        # Reset conversation state
        await session.reset_for_new_utterance()
        await session.change_state(ConversationState.IDLE)
        await websocket.send_json({
            "type": "state_change",
            "from": session.state.value,
            "to": "idle"
        })
        
    elif action == "audio_ended":
        # Audio playback ended on client
        if session.state == ConversationState.PLAYING_AUDIO:
            await session.change_state(ConversationState.IDLE)
            await websocket.send_json({
                "type": "state_change",
                "from": "playing_audio",
                "to": "idle"
            })


# ========================= PROCESSING FUNCTIONS =========================
async def process_user_input(websocket: WebSocket, session: RealtimeSession):
    """Process complete user input"""
    try:
        user_text = session.current_transcription
        if not user_text:
            log_warning(f"⚠️ Empty transcription, resetting", session_id=session.session.session_id)
            await session.reset_for_new_utterance()
            await session.change_state(ConversationState.IDLE)
            return
        
        log_info(f"🎯 Processing user input", text=user_text, session_id=session.session.session_id)
        
        # State zaten PROCESSING_STT olarak set edildi, direkt devam et
        
        # Send final transcription
        await websocket.send_json({
            "type": "transcription",
            "text": user_text,
            "is_final": True,
            "confidence": 0.95
        })
        
        # State: LLM Processing
        await session.change_state(ConversationState.PROCESSING_LLM)
        await websocket.send_json({
            "type": "state_change",
            "from": "processing_stt",
            "to": "processing_llm"
        })
        
        # Add to chat history
        session.session.add_message("user", user_text)
        
        # Get LLM response based on session state
        log_info(f"🤖 Getting LLM response", session_state=session.session.state, session_id=session.session.session_id)
        
        if session.session.state == "collect_params":
            response_text = await handle_parameter_followup(session.session, user_text)
        else:
            response_text = await handle_new_message(session.session, user_text)
        
        log_info(f"💬 LLM response: {response_text[:50]}...", session_id=session.session.session_id)
        
        # Add response to history
        session.session.add_message("assistant", response_text)
        
        # Send text response
        await websocket.send_json({
            "type": "assistant_response",
            "text": response_text
        })
        
        # Generate TTS if enabled
        tts_provider = TTSFactory.create_provider()
        if tts_provider:
            await session.change_state(ConversationState.PROCESSING_TTS)
            await websocket.send_json({
                "type": "state_change",
                "from": "processing_llm",
                "to": "processing_tts"
            })
            
            # Generate TTS with barge-in support
            tts_task = await session.barge_in_handler.start_tts_task(
                generate_and_stream_tts(websocket, session, tts_provider, response_text)
            )
            
            try:
                await tts_task
            except asyncio.CancelledError:
                log_info("⚡ TTS cancelled due to barge-in", session_id=session.session.session_id)
        else:
            # No TTS, go back to idle
            await session.change_state(ConversationState.IDLE)
            await websocket.send_json({
                "type": "state_change",
                "from": "processing_llm",
                "to": "idle"
            })
        
    except Exception as e:
        log_error(
            f"❌ Error processing user input",
            error=str(e),
            traceback=traceback.format_exc(),
            session_id=session.session.session_id
        )
        await websocket.send_json({
            "type": "error",
            "message": f"Processing error: {str(e)}"
        })
        await session.reset_for_new_utterance()
        await session.change_state(ConversationState.IDLE)

async def generate_and_stream_tts(
    websocket: WebSocket,
    session: RealtimeSession,
    tts_provider,
    text: str
):
    """Generate and stream TTS audio with cancellation support"""
    try:
        log_info(f"🎤 Starting TTS generation for text: '{text[:50]}...'", session_id=session.session.session_id)
        
        # Generate audio
        audio_data = await tts_provider.synthesize(text)
        log_info(f"✅ TTS generated: {len(audio_data)} bytes, type: {type(audio_data)}", session_id=session.session.session_id)
        
        # Change state to playing
        await session.change_state(ConversationState.PLAYING_AUDIO)
        await websocket.send_json({
            "type": "state_change",
            "from": "processing_tts",
            "to": "playing_audio"
        })
        
        # Convert entire audio to base64 for transmission
        import base64
        log_debug(f"📦 Converting audio to base64...")
        audio_base64 = base64.b64encode(audio_data).decode('utf-8')
        log_info(f"📊 Base64 conversion complete: {len(audio_base64)} chars from {len(audio_data)} bytes", session_id=session.session.session_id)
        
        # Log first 100 chars of base64 to verify it's valid
        log_debug(f"🔍 Base64 preview: {audio_base64[:100]}...")
        
        # Stream audio in chunks
        chunk_size = 16384  # Larger chunk size for base64
        total_length = len(audio_base64)
        total_chunks = (total_length + chunk_size - 1) // chunk_size
        
        log_info(f"📤 Streaming TTS audio: {len(audio_data)} bytes as {total_length} base64 chars in {total_chunks} chunks", session_id=session.session.session_id)
        
        for i in range(0, total_length, chunk_size):
            # Check for cancellation
            if asyncio.current_task().cancelled():
                log_info(f"⚡ Streaming cancelled at chunk {i//chunk_size}", session_id=session.session.session_id)
                break
                
            chunk = audio_base64[i:i + chunk_size]
            chunk_index = i // chunk_size
            is_last = chunk_index == total_chunks - 1
            
            log_debug(f"📨 Sending chunk {chunk_index}/{total_chunks}, size: {len(chunk)}, is_last: {is_last}")
            
            await websocket.send_json({
                "type": "tts_audio",
                "data": chunk,
                "chunk_index": chunk_index,
                "total_chunks": total_chunks,
                "is_last": is_last,
                "mime_type": "audio/mpeg"
            })
            
            # Small delay to prevent overwhelming the client
            await asyncio.sleep(0.01)
        
        log_info(
            f"✅ TTS streaming completed successfully",
            session_id=session.session.session_id,
            text_length=len(text),
            audio_size=len(audio_data),
            chunks_sent=total_chunks
        )
        
    except asyncio.CancelledError:
        log_info("🛑 TTS streaming cancelled", session_id=session.session.session_id)
        raise
    except Exception as e:
        log_error(
            f"❌ TTS generation error",
            error=str(e),
            traceback=traceback.format_exc(),
            session_id=session.session.session_id
        )
        await websocket.send_json({
            "type": "error",
            "message": f"TTS error: {str(e)}"
        })