app/api/streaming.py

"""
WebSocket streaming endpoint for real-time ECG monitoring.

Supports:
- Live ECG signal streaming
- Real-time gating, inference, and rule evaluation
- Multi-patient concurrent monitoring
"""
import asyncio
import json
from typing import Any, Dict, List, Optional
from datetime import datetime

from fastapi import APIRouter, WebSocket, WebSocketDisconnect, Depends
from sqlalchemy.orm import Session

from app.db.session import get_session
from app.ml.gating import gate_signal
from app.ml.inference import infer_ecg
from app.rules.engine import evaluate_ecg_rules
from app.models.ecg import ECGSample

router = APIRouter()


class ConnectionManager:
    """Manages WebSocket connections for multiple patients."""

    def __init__(self):
        self.active_connections: Dict[str, WebSocket] = {}

    async def connect(self, patient_id: str, websocket: WebSocket):
        await websocket.accept()
        self.active_connections[patient_id] = websocket

    def disconnect(self, patient_id: str):
        if patient_id in self.active_connections:
            del self.active_connections[patient_id]

    async def send_message(self, patient_id: str, message: Dict[str, Any]):
        if patient_id in self.active_connections:
            await self.active_connections[patient_id].send_json(message)

    def get_active_patients(self) -> List[str]:
        return list(self.active_connections.keys())


manager = ConnectionManager()


@router.websocket("/ws/ecg/{patient_id}")
async def ecg_stream(websocket: WebSocket, patient_id: str):
    """
    WebSocket endpoint for streaming ECG data.

    Protocol:
    - Client sends: {"signal": [float, ...], "patient_context": {...}}
    - Server responds: {"status": "ok", "result": {...}, "timestamp": "..."}

    The server runs gating → inference → rules and streams back results.
    """
    await manager.connect(patient_id, websocket)

    try:
        while True:
            # Receive signal chunk from client
            data = await websocket.receive_json()

            signal = data.get("signal", [])
            patient_context = data.get("patient_context", {})
            patient_context["patient_id"] = patient_id

            if not signal:
                await websocket.send_json({
                    "status": "error",
                    "message": "Empty signal",
                    "timestamp": datetime.utcnow().isoformat()
                })
                continue

            # Process signal through pipeline
            try:
                # Step 1: Gating
                gated, gating_meta = gate_signal(signal)

                # Step 2: Inference
                model_output = infer_ecg(gated, original_len=len(signal), gating_meta=gating_meta)

                # Step 3: Rules
                rules_result = evaluate_ecg_rules(patient_context, model_output)

                # Build response
                result = {
                    "patient_id": patient_id,
                    "label": model_output.get("label"),
                    "score": round(float(model_output.get("score", 0.0)), 3),
                    "hr": model_output.get("hr"),
                    "alert_level": rules_result.get("alert_level"),
                    "explanations": rules_result.get("explanations", []),
                    "gating": {
                        "ratio": round(gating_meta.get("ratio", 1.0), 3),
                        "selected_windows": gating_meta.get("selected_windows", 0),
                        "total_windows": gating_meta.get("total_windows", 0),
                        "energy_saved_pct": round((1 - gating_meta.get("ratio", 1.0)) * 100, 1),
                    },
                    "timestamp": datetime.utcnow().isoformat(),
                }

                await websocket.send_json({
                    "status": "ok",
                    "result": result,
                    "timestamp": datetime.utcnow().isoformat(),
                })

            except Exception as e:
                await websocket.send_json({
                    "status": "error",
                    "message": str(e),
                    "timestamp": datetime.utcnow().isoformat(),
                })

    except WebSocketDisconnect:
        manager.disconnect(patient_id)
        print(f"Patient {patient_id} disconnected")


@router.get("/active-streams")
async def get_active_streams() -> Dict[str, Any]:
    """Get list of active patient streams."""
    return {
        "active_patients": manager.get_active_patients(),
        "count": len(manager.get_active_patients()),
    }


@router.post("/broadcast-alert")
async def broadcast_alert(alert: Dict[str, Any]):
    """
    Broadcast an alert to all connected patients (admin use).

    Example: System-wide maintenance notification.
    """
    for patient_id in manager.get_active_patients():
        await manager.send_message(patient_id, {
            "type": "system_alert",
            "message": alert.get("message", ""),
            "timestamp": datetime.utcnow().isoformat(),
        })

    return {"status": "ok", "recipients": len(manager.get_active_patients())}