# User Container Event System - Implementation Guide

This document provides detailed implementation guidance for the dual-channel event system between user containers and the gateway. See `doc/protocol.md` for the protocol specification.

## Overview

User containers emit events that must reach users through various channels:
- **Active session** (WebSocket, Telegram webhook)
- **External delivery** (Telegram API, email, push notifications)

Two ZMQ patterns handle different delivery requirements:
1. **XPUB/SUB**: Fast path for active sessions (fire-and-forget)
2. **DEALER/ROUTER**: Guaranteed delivery for critical events (with ack)

## Architecture Decision: Why Two Channels?

**Problem**: A single pattern can't satisfy both requirements:
- PUB/SUB drops messages if no subscriber (unacceptable for order confirmations)
- DEALER/ROUTER adds latency and requires ack handling (overkill for chart updates)

**Solution**: Container decides routing based on:
1. Event priority (INFORMATIONAL vs CRITICAL)
2. Whether an active session exists (tracked via XPUB subscriptions)

```
┌─────────────────────────────────────────────────────────────────┐
│                         Decision Tree                            │
│                                                                  │
│  Event arrives                                                   │
│      │                                                           │
│      ▼                                                           │
│  ┌───────────────────┐                                          │
│  │ Priority ==       │                                          │
│  │ INFORMATIONAL?    │                                          │
│  └─────────┬─────────┘                                          │
│       Yes  │   No                                                │
│       │    │                                                     │
│       │    ▼                                                     │
│       │  ┌───────────────────┐                                  │
│       │  │ has_active_       │                                  │
│       │  │ subscriber()?     │                                  │
│       │  └─────────┬─────────┘                                  │
│       │       Yes  │   No                                        │
│       │       │    │                                             │
│       ▼       ▼    ▼                                             │
│  ┌─────────────┐  ┌─────────────┐                               │
│  │ XPUB        │  │ DEALER      │                               │
│  │ (fast path) │  │ (guaranteed)│                               │
│  └─────────────┘  └─────────────┘                               │
└─────────────────────────────────────────────────────────────────┘
```

## Container Implementation (Python)

### File Structure

```
client-py/dexorder/
├── events/
│   ├── __init__.py
│   ├── publisher.py      # EventPublisher class
│   ├── types.py          # UserEvent, DeliverySpec, etc.
│   └── pending_store.py  # Disk persistence for critical events
```

### Event Publisher Class

```python
# client-py/dexorder/events/publisher.py

import asyncio
import time
import uuid
from dataclasses import dataclass, field
from typing import Optional
import zmq
import zmq.asyncio

from .types import UserEvent, Priority, EventAck, AckStatus
from .pending_store import PendingStore


@dataclass
class PendingEvent:
    event: UserEvent
    sent_at: float
    retries: int = 0


class EventPublisher:
    """
    Publishes user events via dual ZMQ channels:
    - XPUB for informational/active-session events
    - DEALER for critical/guaranteed-delivery events
    """

    def __init__(
        self,
        user_id: str,
        xpub_port: int = 5570,
        gateway_router_endpoint: str = "tcp://gateway:5571",
        ack_timeout: float = 30.0,
        max_retries: int = 3,
        pending_store_path: Optional[str] = None,
    ):
        self.user_id = user_id
        self.xpub_port = xpub_port
        self.gateway_router_endpoint = gateway_router_endpoint
        self.ack_timeout = ack_timeout
        self.max_retries = max_retries

        self.ctx = zmq.asyncio.Context()

        # XPUB socket for informational events
        self.xpub_socket = self.ctx.socket(zmq.XPUB)
        self.xpub_socket.setsockopt(zmq.XPUB_VERBOSE, 1)
        self.xpub_socket.bind(f"tcp://*:{xpub_port}")

        # DEALER socket for critical events
        self.dealer_socket = self.ctx.socket(zmq.DEALER)
        self.dealer_socket.setsockopt_string(zmq.IDENTITY, f"container-{user_id}")
        self.dealer_socket.connect(gateway_router_endpoint)

        # Track active subscriptions (gateway sessions)
        self.active_subscriptions: set[str] = set()

        # Track pending critical events awaiting ack
        self.pending_events: dict[str, PendingEvent] = {}

        # Persistent store for crash recovery
        self.pending_store = PendingStore(pending_store_path) if pending_store_path else None

        # Background tasks
        self._subscription_task: Optional[asyncio.Task] = None
        self._ack_task: Optional[asyncio.Task] = None
        self._retry_task: Optional[asyncio.Task] = None
        self._running = False

    async def start(self):
        """Start background tasks for subscription tracking and ack handling."""
        self._running = True

        # Reload any persisted pending events
        if self.pending_store:
            for event in await self.pending_store.load_pending():
                self.pending_events[event.event_id] = PendingEvent(event, time.time())

        self._subscription_task = asyncio.create_task(self._subscription_loop())
        self._ack_task = asyncio.create_task(self._ack_loop())
        self._retry_task = asyncio.create_task(self._retry_loop())

    async def stop(self):
        """Stop background tasks and persist pending events."""
        self._running = False

        # Cancel background tasks
        for task in [self._subscription_task, self._ack_task, self._retry_task]:
            if task:
                task.cancel()
                try:
                    await task
                except asyncio.CancelledError:
                    pass

        # Persist pending critical events
        if self.pending_store and self.pending_events:
            await self.pending_store.save_pending(
                [pe.event for pe in self.pending_events.values()]
            )

        # Close sockets
        self.xpub_socket.close()
        self.dealer_socket.close()
        self.ctx.term()

    def has_active_subscriber(self) -> bool:
        """Check if any gateway is subscribed to this user's events."""
        topic = f"USER:{self.user_id}"
        return topic in self.active_subscriptions

    async def publish(self, event: UserEvent):
        """
        Publish event via appropriate channel based on priority and session state.
        """
        # Ensure event has required fields
        if not event.event_id:
            event.event_id = str(uuid.uuid4())
        if not event.user_id:
            event.user_id = self.user_id
        if not event.timestamp:
            event.timestamp = int(time.time() * 1000)

        topic = f"USER:{self.user_id}"
        priority = event.delivery.priority if event.delivery else Priority.NORMAL

        if priority == Priority.INFORMATIONAL:
            # Fire and forget - only send if someone's listening
            if self.has_active_subscriber():
                await self._send_xpub(topic, event)
            # else: silently drop (by design)

        elif self.has_active_subscriber():
            # Active session exists - use fast path
            await self._send_xpub(topic, event)

        else:
            # No active session - use guaranteed delivery
            await self._send_dealer(event)

    async def _send_xpub(self, topic: str, event: UserEvent):
        """Send event via XPUB (fire-and-forget)."""
        payload = event.serialize()  # Protobuf serialization
        await self.xpub_socket.send_multipart([topic.encode(), payload])

    async def _send_dealer(self, event: UserEvent):
        """Send event via DEALER (with ack tracking)."""
        self.pending_events[event.event_id] = PendingEvent(
            event=event,
            sent_at=time.time(),
            retries=0,
        )

        payload = event.serialize()
        await self.dealer_socket.send(payload)

    async def _subscription_loop(self):
        """Process XPUB subscription/unsubscription messages."""
        while self._running:
            try:
                if await self.xpub_socket.poll(100):
                    msg = await self.xpub_socket.recv()
                    # First byte: 1 = subscribe, 0 = unsubscribe
                    # Remaining bytes: topic
                    is_subscribe = msg[0] == 1
                    topic = msg[1:].decode()

                    if is_subscribe:
                        self.active_subscriptions.add(topic)
                    else:
                        self.active_subscriptions.discard(topic)
            except asyncio.CancelledError:
                break
            except Exception as e:
                # Log error but continue
                print(f"Subscription loop error: {e}")

    async def _ack_loop(self):
        """Process EventAck messages from gateway."""
        while self._running:
            try:
                if await self.dealer_socket.poll(100):
                    payload = await self.dealer_socket.recv()
                    ack = EventAck.deserialize(payload)

                    if ack.event_id in self.pending_events:
                        pending = self.pending_events.pop(ack.event_id)

                        if ack.status == AckStatus.ERROR:
                            # Gateway couldn't deliver - log for now
                            # Could implement escalation logic here
                            print(f"Event {ack.event_id} delivery failed: {ack.error_message}")
                        # else: DELIVERED or QUEUED - we're done

            except asyncio.CancelledError:
                break
            except Exception as e:
                print(f"Ack loop error: {e}")

    async def _retry_loop(self):
        """Retry pending events that haven't been acked."""
        while self._running:
            try:
                await asyncio.sleep(5)  # Check every 5 seconds

                now = time.time()
                for event_id, pending in list(self.pending_events.items()):
                    if now - pending.sent_at > self.ack_timeout:
                        if pending.retries >= self.max_retries:
                            # Give up - log and remove
                            print(f"Event {event_id} exceeded max retries, dropping")
                            del self.pending_events[event_id]
                        else:
                            # Retry
                            pending.retries += 1
                            pending.sent_at = now
                            payload = pending.event.serialize()
                            await self.dealer_socket.send(payload)

            except asyncio.CancelledError:
                break
            except Exception as e:
                print(f"Retry loop error: {e}")
```

### Event Types

```python
# client-py/dexorder/events/types.py

from dataclasses import dataclass, field
from enum import IntEnum
from typing import Optional
import struct

# Message type IDs (match protocol.md)
MSG_TYPE_USER_EVENT = 0x20
MSG_TYPE_EVENT_ACK = 0x21


class Priority(IntEnum):
    INFORMATIONAL = 0  # Drop if no active session
    NORMAL = 1         # Best effort
    CRITICAL = 2       # Must deliver


class ChannelType(IntEnum):
    ACTIVE_SESSION = 0
    WEB = 1
    TELEGRAM = 2
    EMAIL = 3
    PUSH = 4


class EventType(IntEnum):
    ORDER_PLACED = 0
    ORDER_FILLED = 1
    ORDER_CANCELLED = 2
    ALERT_TRIGGERED = 3
    POSITION_UPDATED = 4
    WORKSPACE_CHANGED = 5
    STRATEGY_LOG = 6


class AckStatus(IntEnum):
    DELIVERED = 0
    QUEUED = 1
    ERROR = 2


@dataclass
class ChannelPreference:
    channel: ChannelType
    only_if_active: bool = False


@dataclass
class DeliverySpec:
    priority: Priority = Priority.NORMAL
    channels: list[ChannelPreference] = field(default_factory=list)

    @staticmethod
    def informational() -> "DeliverySpec":
        """Drop if no active session."""
        return DeliverySpec(
            priority=Priority.INFORMATIONAL,
            channels=[ChannelPreference(ChannelType.ACTIVE_SESSION, only_if_active=True)]
        )

    @staticmethod
    def active_or_telegram() -> "DeliverySpec":
        """Active session preferred, fallback to Telegram."""
        return DeliverySpec(
            priority=Priority.NORMAL,
            channels=[
                ChannelPreference(ChannelType.ACTIVE_SESSION, only_if_active=True),
                ChannelPreference(ChannelType.TELEGRAM, only_if_active=False),
            ]
        )

    @staticmethod
    def critical() -> "DeliverySpec":
        """Must deliver through any available channel."""
        return DeliverySpec(
            priority=Priority.CRITICAL,
            channels=[
                ChannelPreference(ChannelType.ACTIVE_SESSION, only_if_active=True),
                ChannelPreference(ChannelType.TELEGRAM, only_if_active=False),
                ChannelPreference(ChannelType.PUSH, only_if_active=False),
                ChannelPreference(ChannelType.EMAIL, only_if_active=False),
            ]
        )


@dataclass
class UserEvent:
    user_id: str = ""
    event_id: str = ""
    timestamp: int = 0  # Unix millis
    event_type: EventType = EventType.STRATEGY_LOG
    payload: bytes = b""  # JSON or nested protobuf
    delivery: DeliverySpec = field(default_factory=DeliverySpec)

    def serialize(self) -> bytes:
        """Serialize to protobuf wire format."""
        # TODO: Replace with actual protobuf serialization
        # For now, use a simple format for illustration
        import json
        data = {
            "user_id": self.user_id,
            "event_id": self.event_id,
            "timestamp": self.timestamp,
            "event_type": self.event_type,
            "payload": self.payload.decode() if self.payload else "",
            "delivery": {
                "priority": self.delivery.priority,
                "channels": [
                    {"channel": c.channel, "only_if_active": c.only_if_active}
                    for c in self.delivery.channels
                ]
            }
        }
        return bytes([MSG_TYPE_USER_EVENT]) + json.dumps(data).encode()

    @classmethod
    def deserialize(cls, data: bytes) -> "UserEvent":
        """Deserialize from protobuf wire format."""
        import json
        msg_type = data[0]
        assert msg_type == MSG_TYPE_USER_EVENT
        obj = json.loads(data[1:])
        return cls(
            user_id=obj["user_id"],
            event_id=obj["event_id"],
            timestamp=obj["timestamp"],
            event_type=EventType(obj["event_type"]),
            payload=obj.get("payload", "").encode(),
            delivery=DeliverySpec(
                priority=Priority(obj["delivery"]["priority"]),
                channels=[
                    ChannelPreference(ChannelType(c["channel"]), c["only_if_active"])
                    for c in obj["delivery"]["channels"]
                ]
            )
        )


@dataclass
class EventAck:
    event_id: str
    status: AckStatus
    error_message: str = ""

    def serialize(self) -> bytes:
        import json
        data = {
            "event_id": self.event_id,
            "status": self.status,
            "error_message": self.error_message,
        }
        return bytes([MSG_TYPE_EVENT_ACK]) + json.dumps(data).encode()

    @classmethod
    def deserialize(cls, data: bytes) -> "EventAck":
        import json
        msg_type = data[0]
        assert msg_type == MSG_TYPE_EVENT_ACK
        obj = json.loads(data[1:])
        return cls(
            event_id=obj["event_id"],
            status=AckStatus(obj["status"]),
            error_message=obj.get("error_message", ""),
        )
```

### Pending Event Persistence

```python
# client-py/dexorder/events/pending_store.py

import json
import aiofiles
from pathlib import Path
from .types import UserEvent


class PendingStore:
    """
    Persists pending critical events to disk for crash recovery.
    """

    def __init__(self, path: str):
        self.path = Path(path)
        self.path.parent.mkdir(parents=True, exist_ok=True)

    async def save_pending(self, events: list[UserEvent]):
        """Save pending events to disk."""
        data = [
            {
                "user_id": e.user_id,
                "event_id": e.event_id,
                "timestamp": e.timestamp,
                "event_type": e.event_type,
                "payload": e.payload.decode() if e.payload else "",
                "delivery": {
                    "priority": e.delivery.priority,
                    "channels": [
                        {"channel": c.channel, "only_if_active": c.only_if_active}
                        for c in e.delivery.channels
                    ]
                }
            }
            for e in events
        ]
        async with aiofiles.open(self.path, "w") as f:
            await f.write(json.dumps(data))

    async def load_pending(self) -> list[UserEvent]:
        """Load pending events from disk."""
        if not self.path.exists():
            return []

        try:
            async with aiofiles.open(self.path, "r") as f:
                content = await f.read()
            data = json.loads(content)

            events = []
            for obj in data:
                from .types import DeliverySpec, ChannelPreference, Priority, ChannelType, EventType
                events.append(UserEvent(
                    user_id=obj["user_id"],
                    event_id=obj["event_id"],
                    timestamp=obj["timestamp"],
                    event_type=EventType(obj["event_type"]),
                    payload=obj.get("payload", "").encode(),
                    delivery=DeliverySpec(
                        priority=Priority(obj["delivery"]["priority"]),
                        channels=[
                            ChannelPreference(ChannelType(c["channel"]), c["only_if_active"])
                            for c in obj["delivery"]["channels"]
                        ]
                    )
                ))

            # Clear the file after loading
            self.path.unlink()
            return events

        except Exception:
            return []
```

### Integration with Strategy Engine

```python
# Example usage in strategy engine

from dexorder.events import EventPublisher, UserEvent, EventType, DeliverySpec

class StrategyEngine:
    def __init__(self, user_id: str):
        self.user_id = user_id
        self.event_publisher = EventPublisher(
            user_id=user_id,
            pending_store_path=f"/data/users/{user_id}/pending_events.json"
        )

    async def start(self):
        await self.event_publisher.start()

    async def stop(self):
        await self.event_publisher.stop()

    async def on_order_filled(self, order):
        """Called when an order is filled - CRITICAL delivery."""
        event = UserEvent(
            event_type=EventType.ORDER_FILLED,
            payload=json.dumps({
                "order_id": order.id,
                "symbol": order.symbol,
                "side": order.side,
                "price": str(order.fill_price),
                "quantity": str(order.quantity),
            }).encode(),
            delivery=DeliverySpec.critical(),
        )
        await self.event_publisher.publish(event)

    async def on_indicator_update(self, indicator_name: str, value: float):
        """Called on indicator update - INFORMATIONAL (only if watching)."""
        event = UserEvent(
            event_type=EventType.STRATEGY_LOG,
            payload=json.dumps({
                "indicator": indicator_name,
                "value": value,
            }).encode(),
            delivery=DeliverySpec.informational(),
        )
        await self.event_publisher.publish(event)

    async def on_alert_triggered(self, alert):
        """Called when price alert triggers - active session or Telegram."""
        event = UserEvent(
            event_type=EventType.ALERT_TRIGGERED,
            payload=json.dumps({
                "alert_id": alert.id,
                "condition": alert.condition,
                "triggered_price": str(alert.triggered_price),
            }).encode(),
            delivery=DeliverySpec.active_or_telegram(),
        )
        await self.event_publisher.publish(event)
```

## Gateway Implementation (TypeScript)

### File Structure

```
gateway/src/
├── events/
│   ├── index.ts
│   ├── event-subscriber.ts    # SUB socket for informational events
│   ├── event-router.ts        # ROUTER socket for critical events
│   ├── delivery-service.ts    # Telegram, email, push delivery
│   └── types.ts
```

### Event Subscriber (Informational Events)

```typescript
// gateway/src/events/event-subscriber.ts

import * as zmq from 'zeromq';
import type { FastifyBaseLogger } from 'fastify';
import type { UserEvent } from './types.js';
import { deserializeUserEvent } from './types.js';

interface SessionRegistry {
  get(userId: string): WebSocket | undefined;
  has(userId: string): boolean;
}

/**
 * Subscribes to user container XPUB sockets for informational events.
 * One SUB socket connects to multiple containers (all containers for active sessions).
 */
export class EventSubscriber {
  private socket: zmq.Subscriber;
  private sessions: SessionRegistry;
  private logger: FastifyBaseLogger;
  private containerEndpoints: Map<string, string> = new Map(); // userId -> endpoint
  private running = false;

  constructor(sessions: SessionRegistry, logger: FastifyBaseLogger) {
    this.socket = new zmq.Subscriber();
    this.sessions = sessions;
    this.logger = logger;
  }

  async start(): Promise<void> {
    this.running = true;
    this.processMessages();
  }

  async stop(): Promise<void> {
    this.running = false;
    this.socket.close();
  }

  /**
   * Called when a user session connects.
   * Connects to the user's container and subscribes to their events.
   */
  async onSessionConnect(userId: string, containerEndpoint: string): Promise<void> {
    const topic = `USER:${userId}`;

    // Connect to container's XPUB socket if not already connected
    if (!this.containerEndpoints.has(userId)) {
      this.socket.connect(containerEndpoint);
      this.containerEndpoints.set(userId, containerEndpoint);
      this.logger.info({ userId, containerEndpoint }, 'Connected to container XPUB');
    }

    // Subscribe to user's topic
    this.socket.subscribe(topic);
    this.logger.info({ userId, topic }, 'Subscribed to user events');
  }

  /**
   * Called when a user session disconnects.
   * Unsubscribes from their events (but keeps connection for potential reconnect).
   */
  async onSessionDisconnect(userId: string): Promise<void> {
    const topic = `USER:${userId}`;
    this.socket.unsubscribe(topic);
    this.logger.info({ userId, topic }, 'Unsubscribed from user events');

    // Optionally disconnect from container after timeout
    // (in case user reconnects quickly)
  }

  private async processMessages(): Promise<void> {
    for await (const [topicBuf, payloadBuf] of this.socket) {
      if (!this.running) break;

      try {
        const topic = topicBuf.toString();
        const userId = topic.replace('USER:', '');
        const event = deserializeUserEvent(payloadBuf);

        // Forward to active WebSocket session
        const ws = this.sessions.get(userId);
        if (ws) {
          ws.send(JSON.stringify({
            type: 'event',
            eventType: event.eventType,
            eventId: event.eventId,
            timestamp: event.timestamp,
            payload: JSON.parse(event.payload.toString()),
          }));
        }
      } catch (error) {
        this.logger.error({ error }, 'Error processing informational event');
      }
    }
  }
}
```

### Event Router (Critical Events)

```typescript
// gateway/src/events/event-router.ts

import * as zmq from 'zeromq';
import type { FastifyBaseLogger } from 'fastify';
import type { UserEvent, EventAck, AckStatus } from './types.js';
import { deserializeUserEvent, serializeEventAck } from './types.js';
import type { DeliveryService } from './delivery-service.js';

interface SessionRegistry {
  get(userId: string): WebSocket | undefined;
  has(userId: string): boolean;
}

/**
 * ROUTER socket that receives critical events from all containers.
 * Delivers events and sends acks back to containers.
 */
export class EventRouter {
  private socket: zmq.Router;
  private sessions: SessionRegistry;
  private delivery: DeliveryService;
  private logger: FastifyBaseLogger;
  private running = false;

  // Deduplication: track recently processed event IDs
  private processedEvents: Map<string, number> = new Map();
  private readonly DEDUP_TTL_MS = 5 * 60 * 1000; // 5 minutes

  constructor(
    sessions: SessionRegistry,
    delivery: DeliveryService,
    logger: FastifyBaseLogger,
    bindEndpoint: string = 'tcp://*:5571'
  ) {
    this.socket = new zmq.Router();
    this.sessions = sessions;
    this.delivery = delivery;
    this.logger = logger;

    this.socket.bind(bindEndpoint);
    this.logger.info({ bindEndpoint }, 'Event router bound');
  }

  async start(): Promise<void> {
    this.running = true;
    this.processMessages();
    this.cleanupDedup();
  }

  async stop(): Promise<void> {
    this.running = false;
    this.socket.close();
  }

  private async processMessages(): Promise<void> {
    for await (const [identity, payload] of this.socket) {
      if (!this.running) break;

      try {
        const event = deserializeUserEvent(payload);

        // Deduplication check
        if (this.processedEvents.has(event.eventId)) {
          // Already processed - send success ack
          await this.sendAck(identity, event.eventId, 'DELIVERED');
          continue;
        }

        this.logger.info(
          { eventId: event.eventId, userId: event.userId, eventType: event.eventType },
          'Processing critical event'
        );

        // Deliver through channel preferences
        const status = await this.deliverEvent(event);

        // Mark as processed
        this.processedEvents.set(event.eventId, Date.now());

        // Send ack back to container
        await this.sendAck(identity, event.eventId, status);

      } catch (error) {
        this.logger.error({ error }, 'Error processing critical event');
        // Don't ack - let container retry
      }
    }
  }

  private async deliverEvent(event: UserEvent): Promise<AckStatus> {
    for (const pref of event.delivery.channels) {
      // Skip if channel requires active session but none exists
      if (pref.onlyIfActive && !this.sessions.has(event.userId)) {
        continue;
      }

      try {
        switch (pref.channel) {
          case 'ACTIVE_SESSION': {
            const ws = this.sessions.get(event.userId);
            if (ws) {
              ws.send(JSON.stringify({
                type: 'event',
                eventType: event.eventType,
                eventId: event.eventId,
                timestamp: event.timestamp,
                payload: JSON.parse(event.payload.toString()),
              }));
              return 'DELIVERED';
            }
            break;
          }

          case 'TELEGRAM':
            await this.delivery.sendTelegram(event.userId, event);
            return 'DELIVERED';

          case 'EMAIL':
            await this.delivery.sendEmail(event.userId, event);
            return 'DELIVERED';

          case 'PUSH':
            await this.delivery.sendPush(event.userId, event);
            return 'DELIVERED';
        }
      } catch (error) {
        this.logger.warn(
          { error, channel: pref.channel, eventId: event.eventId },
          'Channel delivery failed, trying next'
        );
        // Continue to next channel preference
      }
    }

    // All channels failed
    return 'ERROR';
  }

  private async sendAck(
    identity: Buffer,
    eventId: string,
    status: AckStatus,
    errorMessage?: string
  ): Promise<void> {
    const ack: EventAck = { eventId, status, errorMessage: errorMessage || '' };
    await this.socket.send([identity, serializeEventAck(ack)]);
  }

  private cleanupDedup(): void {
    setInterval(() => {
      const now = Date.now();
      for (const [eventId, timestamp] of this.processedEvents) {
        if (now - timestamp > this.DEDUP_TTL_MS) {
          this.processedEvents.delete(eventId);
        }
      }
    }, 60000); // Cleanup every minute
  }
}
```

### Delivery Service

```typescript
// gateway/src/events/delivery-service.ts

import type { FastifyBaseLogger } from 'fastify';
import type { UserEvent } from './types.js';

interface UserChannelConfig {
  telegramChatId?: string;
  email?: string;
  pushToken?: string;
}

/**
 * Handles actual delivery to external channels.
 * Owns credentials for Telegram bot, email service, push notifications.
 */
export class DeliveryService {
  private telegramBotToken: string;
  private emailServiceKey: string;
  private pushServiceKey: string;
  private logger: FastifyBaseLogger;

  // User channel configs (loaded from DB)
  private userConfigs: Map<string, UserChannelConfig> = new Map();

  constructor(config: {
    telegramBotToken: string;
    emailServiceKey: string;
    pushServiceKey: string;
    logger: FastifyBaseLogger;
  }) {
    this.telegramBotToken = config.telegramBotToken;
    this.emailServiceKey = config.emailServiceKey;
    this.pushServiceKey = config.pushServiceKey;
    this.logger = config.logger;
  }

  async loadUserConfig(userId: string): Promise<UserChannelConfig> {
    // TODO: Load from database
    // For now, return cached or empty
    return this.userConfigs.get(userId) || {};
  }

  async sendTelegram(userId: string, event: UserEvent): Promise<void> {
    const config = await this.loadUserConfig(userId);
    if (!config.telegramChatId) {
      throw new Error('User has no Telegram chat ID configured');
    }

    const message = this.formatEventMessage(event);

    const response = await fetch(
      `https://api.telegram.org/bot${this.telegramBotToken}/sendMessage`,
      {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          chat_id: config.telegramChatId,
          text: message,
          parse_mode: 'Markdown',
        }),
      }
    );

    if (!response.ok) {
      const error = await response.text();
      throw new Error(`Telegram API error: ${error}`);
    }

    this.logger.info({ userId, eventId: event.eventId }, 'Sent Telegram notification');
  }

  async sendEmail(userId: string, event: UserEvent): Promise<void> {
    const config = await this.loadUserConfig(userId);
    if (!config.email) {
      throw new Error('User has no email configured');
    }

    // TODO: Implement email sending via SendGrid/SES/etc.
    this.logger.info({ userId, eventId: event.eventId }, 'Sent email notification');
  }

  async sendPush(userId: string, event: UserEvent): Promise<void> {
    const config = await this.loadUserConfig(userId);
    if (!config.pushToken) {
      throw new Error('User has no push token configured');
    }

    // TODO: Implement push notification via Firebase/APNs
    this.logger.info({ userId, eventId: event.eventId }, 'Sent push notification');
  }

  private formatEventMessage(event: UserEvent): string {
    const payload = JSON.parse(event.payload.toString());

    switch (event.eventType) {
      case 'ORDER_FILLED':
        return `🟢 *Order Filled*\n` +
          `Symbol: ${payload.symbol}\n` +
          `Side: ${payload.side}\n` +
          `Price: ${payload.price}\n` +
          `Quantity: ${payload.quantity}`;

      case 'ALERT_TRIGGERED':
        return `🔔 *Alert Triggered*\n` +
          `Condition: ${payload.condition}\n` +
          `Price: ${payload.triggered_price}`;

      case 'POSITION_UPDATED':
        return `📊 *Position Updated*\n` +
          `Symbol: ${payload.symbol}\n` +
          `Size: ${payload.size}\n` +
          `PnL: ${payload.unrealized_pnl}`;

      default:
        return `📌 *Notification*\n${JSON.stringify(payload, null, 2)}`;
    }
  }
}
```

### Integration in Gateway Main

```typescript
// gateway/src/main.ts (additions)

import { EventSubscriber } from './events/event-subscriber.js';
import { EventRouter } from './events/event-router.js';
import { DeliveryService } from './events/delivery-service.js';

// In main setup:

const sessionRegistry = new Map<string, WebSocket>();

const deliveryService = new DeliveryService({
  telegramBotToken: process.env.TELEGRAM_BOT_TOKEN!,
  emailServiceKey: process.env.EMAIL_SERVICE_KEY!,
  pushServiceKey: process.env.PUSH_SERVICE_KEY!,
  logger: app.log,
});

const eventSubscriber = new EventSubscriber(sessionRegistry, app.log);
const eventRouter = new EventRouter(sessionRegistry, deliveryService, app.log);

await eventSubscriber.start();
await eventRouter.start();

// In WebSocket handler:

websocket.on('connection', async (ws, req) => {
  const authContext = await authenticate(req);
  const userId = authContext.userId;
  const containerEndpoint = authContext.license.containerEventEndpoint;

  // Register session
  sessionRegistry.set(userId, ws);

  // Subscribe to informational events
  await eventSubscriber.onSessionConnect(userId, containerEndpoint);

  ws.on('close', async () => {
    sessionRegistry.delete(userId);
    await eventSubscriber.onSessionDisconnect(userId);
  });
});
```

## Protobuf Definitions

Add to `proto/user_events.proto`:

```protobuf
syntax = "proto3";

package dexorder.events;

message UserEvent {
  string user_id = 1;
  string event_id = 2;
  int64 timestamp = 3;
  EventType event_type = 4;
  bytes payload = 5;
  DeliverySpec delivery = 6;
}

enum EventType {
  ORDER_PLACED = 0;
  ORDER_FILLED = 1;
  ORDER_CANCELLED = 2;
  ALERT_TRIGGERED = 3;
  POSITION_UPDATED = 4;
  WORKSPACE_CHANGED = 5;
  STRATEGY_LOG = 6;
}

message DeliverySpec {
  Priority priority = 1;
  repeated ChannelPreference channels = 2;
}

enum Priority {
  INFORMATIONAL = 0;
  NORMAL = 1;
  CRITICAL = 2;
}

message ChannelPreference {
  ChannelType channel = 1;
  bool only_if_active = 2;
}

enum ChannelType {
  ACTIVE_SESSION = 0;
  WEB = 1;
  TELEGRAM = 2;
  EMAIL = 3;
  PUSH = 4;
}

message EventAck {
  string event_id = 1;
  AckStatus status = 2;
  string error_message = 3;
}

enum AckStatus {
  DELIVERED = 0;
  QUEUED = 1;
  ERROR = 2;
}
```

## Kubernetes Configuration

### Container Ports

Add to agent deployment template:

```yaml
# deploy/k8s/templates/agent-deployment.yaml

spec:
  containers:
    - name: agent
      ports:
        - containerPort: 3000   # MCP server
          name: mcp
        - containerPort: 5570   # XPUB for informational events
          name: events-xpub
```

### Gateway Configuration

```yaml
# deploy/k8s/base/gateway.yaml

spec:
  containers:
    - name: gateway
      ports:
        - containerPort: 3000   # HTTP/WebSocket
          name: http
        - containerPort: 5571   # ROUTER for critical events
          name: events-router
      env:
        - name: TELEGRAM_BOT_TOKEN
          valueFrom:
            secretKeyRef:
              name: gateway-secrets
              key: telegram-bot-token
        - name: EVENT_ROUTER_BIND
          value: "tcp://*:5571"
```

### Network Policy

Allow containers to connect to gateway ROUTER:

```yaml
# deploy/k8s/base/network-policies.yaml (additions)

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: agent-to-gateway-events
  namespace: dexorder-agents
spec:
  podSelector:
    matchLabels:
      app: agent
  policyTypes:
    - Egress
  egress:
    - to:
        - namespaceSelector:
            matchLabels:
              name: dexorder-system
          podSelector:
            matchLabels:
              app: gateway
      ports:
        - protocol: TCP
          port: 5571  # Critical events ROUTER
```

## Testing

### Unit Tests

```python
# tests/test_event_publisher.py

import pytest
import asyncio
from dexorder.events import EventPublisher, UserEvent, DeliverySpec, EventType

@pytest.mark.asyncio
async def test_informational_dropped_without_subscriber():
    publisher = EventPublisher(user_id="test-user", xpub_port=15570)
    await publisher.start()

    # No subscriber connected
    assert not publisher.has_active_subscriber()

    # Publish informational event - should be silently dropped
    event = UserEvent(
        event_type=EventType.STRATEGY_LOG,
        payload=b'{"test": true}',
        delivery=DeliverySpec.informational(),
    )
    await publisher.publish(event)

    # No pending events (was dropped, not queued)
    assert len(publisher.pending_events) == 0

    await publisher.stop()

@pytest.mark.asyncio
async def test_critical_queued_without_subscriber():
    publisher = EventPublisher(user_id="test-user", xpub_port=15571)
    await publisher.start()

    # No subscriber connected
    assert not publisher.has_active_subscriber()

    # Publish critical event - should go to DEALER
    event = UserEvent(
        event_type=EventType.ORDER_FILLED,
        payload=b'{"order_id": "123"}',
        delivery=DeliverySpec.critical(),
    )
    await publisher.publish(event)

    # Should be in pending queue
    assert len(publisher.pending_events) == 1

    await publisher.stop()
```

### Integration Test

```bash
# Start a mock gateway ROUTER
python -c "
import zmq
ctx = zmq.Context()
router = ctx.socket(zmq.ROUTER)
router.bind('tcp://*:5571')
print('Waiting for events...')
while True:
    identity, payload = router.recv_multipart()
    print(f'Received from {identity}: {payload}')
    # Send ack
    router.send_multipart([identity, b'\x21{\"event_id\":\"test\",\"status\":0}'])
"

# In another terminal, run container with test events
python -c "
import asyncio
from dexorder.events import EventPublisher, UserEvent, DeliverySpec, EventType

async def main():
    pub = EventPublisher('test-user', gateway_router_endpoint='tcp://localhost:5571')
    await pub.start()

    event = UserEvent(
        event_type=EventType.ORDER_FILLED,
        payload=b'{\"test\": true}',
        delivery=DeliverySpec.critical(),
    )
    await pub.publish(event)

    await asyncio.sleep(5)  # Wait for ack
    print(f'Pending events: {len(pub.pending_events)}')

    await pub.stop()

asyncio.run(main())
"
```

## Migration Plan

1. **Phase 1**: Add protobuf definitions, build Python/TypeScript types
2. **Phase 2**: Implement EventPublisher in container (inactive by default)
3. **Phase 3**: Implement EventSubscriber/EventRouter in gateway
4. **Phase 4**: Add DeliveryService with Telegram integration
5. **Phase 5**: Enable in container, test with single user
6. **Phase 6**: Roll out to all users, add email/push support

## Monitoring

Key metrics to track:
- `events_published_total{priority, channel}` - Events published by container
- `events_delivered_total{channel, status}` - Events delivered by gateway
- `events_pending_count` - Current pending critical events per container
- `event_delivery_latency_ms{channel}` - Time from publish to delivery
- `event_retry_total` - Retries due to ack timeout