# Agent L: Notifications + Background Service

## Phase: 4 (Feature Completion)
## Depends on: Agent A (Manifest), Agent I (DI)

## Context
The app needs a persistent TCP connection to receive real-time push notifications from the server.
On Android, this requires a Foreground Service to keep the connection alive when the app is backgrounded.
Additionally, local notifications are shown when messages arrive while the app is not in focus.

## Task
Create foreground service for TCP connection, notification channels, and app lifecycle handling.

## Files to Create

### 1. core/ChatService.kt
Android Foreground Service:
```kotlin
package com.kecalek.chat.core

import android.app.Notification
import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.app.Service
import android.content.Intent
import android.os.Build
import android.os.IBinder
import androidx.core.app.NotificationCompat
import com.kecalek.chat.MainActivity
import com.kecalek.chat.R
import dagger.hilt.android.AndroidEntryPoint
import javax.inject.Inject

@AndroidEntryPoint
class ChatService : Service() {

    // TODO: @Inject ChatClient or ConnectionManager

    companion object {
        const val CHANNEL_ID_SERVICE = "kecalek_service"
        const val CHANNEL_ID_MESSAGES = "kecalek_messages"
        const val CHANNEL_ID_GROUPS = "kecalek_groups"
        const val CHANNEL_ID_SYSTEM = "kecalek_system"
        const val NOTIFICATION_ID_SERVICE = 1
    }

    override fun onCreate() {
        super.onCreate()
        createNotificationChannels()
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        startForeground(NOTIFICATION_ID_SERVICE, buildServiceNotification())
        // TODO: Start TCP connection listener
        // TODO: Handle incoming notifications and show local notifications
        return START_STICKY
    }

    override fun onBind(intent: Intent?): IBinder? = null

    override fun onDestroy() {
        // TODO: Disconnect from server
        super.onDestroy()
    }

    private fun createNotificationChannels() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val manager = getSystemService(NotificationManager::class.java)

            // Service channel (silent, low priority)
            manager.createNotificationChannel(
                NotificationChannel(
                    CHANNEL_ID_SERVICE,
                    "Connection Service",
                    NotificationManager.IMPORTANCE_LOW,
                ).apply {
                    description = "Keeps the encrypted connection alive"
                    setShowBadge(false)
                }
            )

            // Message notifications (high priority, sound)
            manager.createNotificationChannel(
                NotificationChannel(
                    CHANNEL_ID_MESSAGES,
                    "Messages",
                    NotificationManager.IMPORTANCE_HIGH,
                ).apply {
                    description = "New message notifications"
                    enableVibration(true)
                }
            )

            // Group notifications
            manager.createNotificationChannel(
                NotificationChannel(
                    CHANNEL_ID_GROUPS,
                    "Groups",
                    NotificationManager.IMPORTANCE_DEFAULT,
                ).apply {
                    description = "Group activity notifications"
                }
            )

            // System notifications (key changes, connection)
            manager.createNotificationChannel(
                NotificationChannel(
                    CHANNEL_ID_SYSTEM,
                    "System",
                    NotificationManager.IMPORTANCE_LOW,
                ).apply {
                    description = "Connection and security notifications"
                }
            )
        }
    }

    private fun buildServiceNotification(): Notification {
        val intent = Intent(this, MainActivity::class.java)
        val pendingIntent = PendingIntent.getActivity(
            this, 0, intent,
            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT,
        )

        return NotificationCompat.Builder(this, CHANNEL_ID_SERVICE)
            .setContentTitle("Kecalek")
            .setContentText("Connected securely")
            .setSmallIcon(android.R.drawable.ic_lock_lock) // TODO: Custom icon
            .setContentIntent(pendingIntent)
            .setOngoing(true)
            .setSilent(true)
            .build()
    }
}
```

### 2. core/NotificationHelper.kt
Helper for showing local notifications:
```kotlin
package com.kecalek.chat.core

import android.app.NotificationManager
import android.app.PendingIntent
import android.content.Context
import android.content.Intent
import androidx.core.app.NotificationCompat
import com.kecalek.chat.MainActivity
import dagger.hilt.android.qualifiers.ApplicationContext
import javax.inject.Inject
import javax.inject.Singleton

@Singleton
class NotificationHelper @Inject constructor(
    @ApplicationContext private val context: Context,
) {
    private val notificationManager =
        context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager

    private var nextNotificationId = 100

    fun showMessageNotification(
        senderName: String,
        conversationId: String,
        messagePreview: String?,
    ) {
        // E2EE: Never show plaintext in notification if app is locked
        val displayText = messagePreview ?: "New encrypted message"

        val intent = Intent(context, MainActivity::class.java).apply {
            putExtra("conversationId", conversationId)
            flags = Intent.FLAG_ACTIVITY_SINGLE_TOP
        }
        val pendingIntent = PendingIntent.getActivity(
            context, conversationId.hashCode(), intent,
            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT,
        )

        val notification = NotificationCompat.Builder(context, ChatService.CHANNEL_ID_MESSAGES)
            .setContentTitle(senderName)
            .setContentText(displayText)
            .setSmallIcon(android.R.drawable.ic_dialog_email) // TODO: Custom icon
            .setContentIntent(pendingIntent)
            .setAutoCancel(true)
            .setGroup("messages")
            .build()

        notificationManager.notify(nextNotificationId++, notification)
    }

    fun showGroupNotification(
        groupName: String,
        action: String, // "invited you", "member joined", etc.
    ) {
        val notification = NotificationCompat.Builder(context, ChatService.CHANNEL_ID_GROUPS)
            .setContentTitle(groupName)
            .setContentText(action)
            .setSmallIcon(android.R.drawable.ic_dialog_info) // TODO: Custom icon
            .setAutoCancel(true)
            .build()

        notificationManager.notify(nextNotificationId++, notification)
    }

    fun showSystemNotification(title: String, text: String) {
        val notification = NotificationCompat.Builder(context, ChatService.CHANNEL_ID_SYSTEM)
            .setContentTitle(title)
            .setContentText(text)
            .setSmallIcon(android.R.drawable.ic_lock_lock) // TODO: Custom icon
            .setAutoCancel(true)
            .build()

        notificationManager.notify(nextNotificationId++, notification)
    }

    fun cancelAll() {
        notificationManager.cancelAll()
    }
}
```

### 3. core/AppLifecycleObserver.kt
```kotlin
package com.kecalek.chat.core

import androidx.lifecycle.DefaultLifecycleObserver
import androidx.lifecycle.LifecycleOwner
import javax.inject.Inject
import javax.inject.Singleton

/**
 * Observes app lifecycle to manage TCP connection state.
 * - Foreground: ensure connection is active
 * - Background: keep connection via foreground service
 */
@Singleton
class AppLifecycleObserver @Inject constructor(
    // TODO: Inject ChatClient or ConnectionManager
) : DefaultLifecycleObserver {

    var isInForeground: Boolean = false
        private set

    override fun onStart(owner: LifecycleOwner) {
        isInForeground = true
        // TODO: Reconnect if disconnected, health check
    }

    override fun onStop(owner: LifecycleOwner) {
        isInForeground = false
        // TODO: Connection stays alive via foreground service
    }
}
```

### 4. Update AndroidManifest.xml
Add service declaration:
```xml
<service
    android:name=".core.ChatService"
    android:foregroundServiceType="dataSync"
    android:exported="false" />
```

## Notification Types to Handle
These 17 server push notification types must trigger appropriate local notifications:

| Server Type | Notification Channel | Display |
|-------------|---------------------|---------|
| `new_message` | Messages | "Sender: message preview" |
| `messages_read` | (none) | Silent — update UI only |
| `message_deleted` | (none) | Silent — update UI only |
| `message_reacted` | (none) | Silent — update UI only |
| `message_pinned` | (none) | Silent — update UI only |
| `message_unpinned` | (none) | Silent — update UI only |
| `conversation_created` | Groups | "New conversation created" |
| `conversation_renamed` | Groups | "Group renamed to X" |
| `member_added` | Groups | "X joined the group" |
| `member_removed` | Groups | "X was removed" |
| `group_invitation` | Groups | "X invited you to Y" |
| `user_online` | (none) | Silent — update UI only |
| `user_offline` | (none) | Silent — update UI only |
| `online_users` | (none) | Silent — update UI only |
| `session_reset` | System | "Session reset by X" |
| `keys_updated` | System | "Security keys updated" |

## Constraints
- Foreground service with `FOREGROUND_SERVICE_DATA_SYNC` type
- `START_STICKY` to restart if killed
- Notification channels required for Android O+
- E2EE consideration: don't show plaintext in notifications when app is locked
- Group notifications by conversation for notification stacking
- Use PendingIntent.FLAG_IMMUTABLE (Android 12+ requirement)

## DO NOT
- Implement actual TCP connection management
- Handle message decryption
- Implement Firebase Cloud Messaging (future enhancement)
- Store messages or update database directly (delegate to ChatClient)