Add Android client support and unify cross-platform builds

android/app/build.gradle.kts

@@ -0,0 +1,48 @@
+plugins {
+    id("com.android.application")
+    id("org.jetbrains.kotlin.android")
+}
+
+android {
+    namespace = "com.gotunnel.android"
+    compileSdk = 34
+
+    defaultConfig {
+        applicationId = "com.gotunnel.android"
+        minSdk = 24
+        targetSdk = 34
+        versionCode = 1
+        versionName = "0.1.0"
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro",
+            )
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+
+    buildFeatures {
+        viewBinding = true
+    }
+}
+
+dependencies {
+    implementation("androidx.appcompat:appcompat:1.7.0")
+    implementation("androidx.core:core-ktx:1.13.1")
+    implementation("androidx.activity:activity-ktx:1.9.2")
+    implementation("com.google.android.material:material:1.12.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1")
+}

android/app/proguard-rules.pro

@@ -0,0 +1,2 @@
+# Placeholder rules for the Android host shell.
+# Add Go bridge / native binding rules here when the core integration is introduced.

android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,47 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
+
+    <application
+        android:name=".GoTunnelApp"
+        android:allowBackup="true"
+        android:icon="@drawable/ic_gotunnel_app"
+        android:label="@string/app_name"
+        android:roundIcon="@drawable/ic_gotunnel_app"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.GoTunnel">
+
+        <activity
+            android:name=".MainActivity"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <service
+            android:name=".service.TunnelService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync"
+            android:stopWithTask="false" />
+
+        <receiver
+            android:name=".service.BootReceiver"
+            android:enabled="true"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.BOOT_COMPLETED" />
+                <action android:name="android.intent.action.MY_PACKAGE_REPLACED" />
+            </intent-filter>
+        </receiver>
+    </application>
+
+</manifest>

android/app/src/main/java/com/gotunnel/android/GoTunnelApp.kt

@@ -0,0 +1,11 @@
+package com.gotunnel.android
+
+import android.app.Application
+import com.gotunnel.android.service.NotificationHelper
+
+class GoTunnelApp : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        NotificationHelper.ensureChannel(this)
+    }
+}

android/app/src/main/java/com/gotunnel/android/MainActivity.kt

@@ -0,0 +1,153 @@
+package com.gotunnel.android
+
+import android.Manifest
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.net.Uri
+import android.os.Bundle
+import android.os.PowerManager
+import android.provider.Settings
+import android.widget.Toast
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
+import com.gotunnel.android.bridge.TunnelStatus
+import com.gotunnel.android.config.AppConfig
+import com.gotunnel.android.config.ConfigStore
+import com.gotunnel.android.config.ServiceStateStore
+import com.gotunnel.android.databinding.ActivityMainBinding
+import com.gotunnel.android.service.TunnelService
+import java.text.DateFormat
+import java.util.Date
+
+class MainActivity : AppCompatActivity() {
+    private lateinit var binding: ActivityMainBinding
+    private lateinit var configStore: ConfigStore
+    private lateinit var stateStore: ServiceStateStore
+    private val notificationPermissionLauncher =
+        registerForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
+            if (!granted) {
+                Toast.makeText(this, R.string.notification_permission_denied, Toast.LENGTH_SHORT).show()
+            }
+        }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        requestNotificationPermissionIfNeeded()
+
+        binding = ActivityMainBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+
+        configStore = ConfigStore(this)
+        stateStore = ServiceStateStore(this)
+
+        populateForm(configStore.load())
+        renderState()
+
+        binding.saveButton.setOnClickListener {
+            val config = readForm()
+            configStore.save(config)
+            renderState()
+            Toast.makeText(this, R.string.config_saved, Toast.LENGTH_SHORT).show()
+        }
+
+        binding.startButton.setOnClickListener {
+            val config = readForm()
+            configStore.save(config)
+            renderState()
+            ContextCompat.startForegroundService(
+                this,
+                TunnelService.createStartIntent(this, "manual-start"),
+            )
+            Toast.makeText(this, R.string.service_start_requested, Toast.LENGTH_SHORT).show()
+        }
+
+        binding.stopButton.setOnClickListener {
+            ContextCompat.startForegroundService(
+                this,
+                TunnelService.createStopIntent(this, "manual-stop"),
+            )
+            Toast.makeText(this, R.string.service_stop_requested, Toast.LENGTH_SHORT).show()
+        }
+
+        binding.batteryButton.setOnClickListener {
+            openBatteryOptimizationSettings()
+        }
+    }
+
+    override fun onResume() {
+        super.onResume()
+        renderState()
+    }
+
+    private fun populateForm(config: AppConfig) {
+        binding.serverAddressInput.setText(config.serverAddress)
+        binding.tokenInput.setText(config.token)
+        binding.autoStartSwitch.isChecked = config.autoStart
+        binding.autoReconnectSwitch.isChecked = config.autoReconnect
+        binding.useTlsSwitch.isChecked = config.useTls
+    }
+
+    private fun readForm(): AppConfig {
+        return AppConfig(
+            serverAddress = binding.serverAddressInput.text?.toString().orEmpty().trim(),
+            token = binding.tokenInput.text?.toString().orEmpty().trim(),
+            autoStart = binding.autoStartSwitch.isChecked,
+            autoReconnect = binding.autoReconnectSwitch.isChecked,
+            useTls = binding.useTlsSwitch.isChecked,
+        )
+    }
+
+    private fun renderState() {
+        val state = stateStore.load()
+        val timestamp = if (state.updatedAt > 0L) {
+            DateFormat.getDateTimeInstance().format(Date(state.updatedAt))
+        } else {
+            getString(R.string.state_never_updated)
+        }
+
+        binding.stateValue.text = getString(
+            R.string.state_format,
+            state.status.name,
+            state.detail.ifBlank { getString(R.string.state_no_detail) },
+        )
+        binding.stateMeta.text = getString(R.string.state_meta_format, timestamp)
+
+        val hint = when (state.status) {
+            TunnelStatus.RUNNING -> R.string.state_hint_running
+            TunnelStatus.STARTING -> R.string.state_hint_starting
+            TunnelStatus.RECONNECTING -> R.string.state_hint_reconnecting
+            TunnelStatus.ERROR -> R.string.state_hint_error
+            TunnelStatus.STOPPED -> R.string.state_hint_stopped
+        }
+        binding.stateHint.text = getString(hint)
+    }
+
+    private fun requestNotificationPermissionIfNeeded() {
+        if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.TIRAMISU) {
+            return
+        }
+
+        val granted = ContextCompat.checkSelfPermission(
+            this,
+            Manifest.permission.POST_NOTIFICATIONS,
+        ) == PackageManager.PERMISSION_GRANTED
+        if (!granted) {
+            notificationPermissionLauncher.launch(Manifest.permission.POST_NOTIFICATIONS)
+        }
+    }
+
+    private fun openBatteryOptimizationSettings() {
+        val powerManager = getSystemService(PowerManager::class.java)
+        if (powerManager != null && powerManager.isIgnoringBatteryOptimizations(packageName)) {
+            Toast.makeText(this, R.string.battery_optimization_already_disabled, Toast.LENGTH_SHORT).show()
+            return
+        }
+
+        val intent = Intent(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS).apply {
+            data = Uri.parse("package:$packageName")
+        }
+        startActivity(intent)
+    }
+}

android/app/src/main/java/com/gotunnel/android/bridge/GoTunnelBridge.kt

@@ -0,0 +1,10 @@
+package com.gotunnel.android.bridge
+
+import android.content.Context
+
+object GoTunnelBridge {
+    fun create(context: Context): TunnelController {
+        // Stub bridge for the Android shell. Replace with a native Go binding later.
+        return StubTunnelController(context.applicationContext)
+    }
+}

android/app/src/main/java/com/gotunnel/android/bridge/StubTunnelController.kt

@@ -0,0 +1,64 @@
+package com.gotunnel.android.bridge
+
+import android.content.Context
+import com.gotunnel.android.config.AppConfig
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
+
+class StubTunnelController(
+    @Suppress("unused") private val context: Context,
+) : TunnelController {
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
+    private var listener: TunnelController.Listener? = null
+    private var config: AppConfig = AppConfig()
+    private var job: Job? = null
+
+    override val isRunning: Boolean
+        get() = job?.isActive == true
+
+    override fun setListener(listener: TunnelController.Listener?) {
+        this.listener = listener
+    }
+
+    override fun updateConfig(config: AppConfig) {
+        this.config = config
+    }
+
+    override fun start(config: AppConfig) {
+        updateConfig(config)
+        if (isRunning) {
+            listener?.onLog("Stub tunnel already running")
+            return
+        }
+
+        job = scope.launch {
+            listener?.onStatusChanged(TunnelStatus.STARTING, "Preparing tunnel session")
+            delay(400)
+            listener?.onLog("Stub tunnel prepared for ${config.serverAddress}")
+            listener?.onStatusChanged(TunnelStatus.RUNNING, "Waiting for native Go core")
+
+            while (isActive) {
+                delay(30_000)
+                listener?.onLog("Stub keepalive tick for ${this@StubTunnelController.config.serverAddress}")
+            }
+        }
+    }
+
+    override fun stop(reason: String) {
+        listener?.onLog("Stub tunnel stop requested: $reason")
+        job?.cancel()
+        job = null
+        listener?.onStatusChanged(TunnelStatus.STOPPED, reason)
+    }
+
+    override fun restart(reason: String) {
+        listener?.onStatusChanged(TunnelStatus.RECONNECTING, reason)
+        stop(reason)
+        start(config)
+    }
+}

android/app/src/main/java/com/gotunnel/android/bridge/TunnelController.kt

@@ -0,0 +1,26 @@
+package com.gotunnel.android.bridge
+
+import com.gotunnel.android.config.AppConfig
+
+enum class TunnelStatus {
+    STOPPED,
+    STARTING,
+    RUNNING,
+    RECONNECTING,
+    ERROR,
+}
+
+interface TunnelController {
+    interface Listener {
+        fun onStatusChanged(status: TunnelStatus, detail: String = "")
+        fun onLog(message: String)
+    }
+
+    val isRunning: Boolean
+
+    fun setListener(listener: Listener?)
+    fun updateConfig(config: AppConfig)
+    fun start(config: AppConfig)
+    fun stop(reason: String = "manual")
+    fun restart(reason: String = "manual")
+}

android/app/src/main/java/com/gotunnel/android/config/AppConfig.kt

@@ -0,0 +1,9 @@
+package com.gotunnel.android.config
+
+data class AppConfig(
+    val serverAddress: String = "",
+    val token: String = "",
+    val autoStart: Boolean = true,
+    val autoReconnect: Boolean = true,
+    val useTls: Boolean = true,
+)

android/app/src/main/java/com/gotunnel/android/config/ConfigStore.kt

@@ -0,0 +1,36 @@
+package com.gotunnel.android.config
+
+import android.content.Context
+
+class ConfigStore(context: Context) {
+    private val prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
+
+    fun load(): AppConfig {
+        return AppConfig(
+            serverAddress = prefs.getString(KEY_SERVER_ADDRESS, "") ?: "",
+            token = prefs.getString(KEY_TOKEN, "") ?: "",
+            autoStart = prefs.getBoolean(KEY_AUTO_START, true),
+            autoReconnect = prefs.getBoolean(KEY_AUTO_RECONNECT, true),
+            useTls = prefs.getBoolean(KEY_USE_TLS, true),
+        )
+    }
+
+    fun save(config: AppConfig) {
+        prefs.edit()
+            .putString(KEY_SERVER_ADDRESS, config.serverAddress)
+            .putString(KEY_TOKEN, config.token)
+            .putBoolean(KEY_AUTO_START, config.autoStart)
+            .putBoolean(KEY_AUTO_RECONNECT, config.autoReconnect)
+            .putBoolean(KEY_USE_TLS, config.useTls)
+            .apply()
+    }
+
+    companion object {
+        private const val PREFS_NAME = "gotunnel_config"
+        private const val KEY_SERVER_ADDRESS = "server_address"
+        private const val KEY_TOKEN = "token"
+        private const val KEY_AUTO_START = "auto_start"
+        private const val KEY_AUTO_RECONNECT = "auto_reconnect"
+        private const val KEY_USE_TLS = "use_tls"
+    }
+}

android/app/src/main/java/com/gotunnel/android/config/ServiceStateStore.kt

@@ -0,0 +1,40 @@
+package com.gotunnel.android.config
+
+import android.content.Context
+import com.gotunnel.android.bridge.TunnelStatus
+
+data class ServiceState(
+    val status: TunnelStatus = TunnelStatus.STOPPED,
+    val detail: String = "",
+    val updatedAt: Long = 0L,
+)
+
+class ServiceStateStore(context: Context) {
+    private val prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
+
+    fun load(): ServiceState {
+        val statusName = prefs.getString(KEY_STATUS, TunnelStatus.STOPPED.name) ?: TunnelStatus.STOPPED.name
+        val status = runCatching { TunnelStatus.valueOf(statusName) }.getOrDefault(TunnelStatus.STOPPED)
+
+        return ServiceState(
+            status = status,
+            detail = prefs.getString(KEY_DETAIL, "") ?: "",
+            updatedAt = prefs.getLong(KEY_UPDATED_AT, 0L),
+        )
+    }
+
+    fun save(status: TunnelStatus, detail: String) {
+        prefs.edit()
+            .putString(KEY_STATUS, status.name)
+            .putString(KEY_DETAIL, detail)
+            .putLong(KEY_UPDATED_AT, System.currentTimeMillis())
+            .apply()
+    }
+
+    companion object {
+        private const val PREFS_NAME = "gotunnel_state"
+        private const val KEY_STATUS = "status"
+        private const val KEY_DETAIL = "detail"
+        private const val KEY_UPDATED_AT = "updated_at"
+    }
+}

android/app/src/main/java/com/gotunnel/android/service/BootReceiver.kt

@@ -0,0 +1,26 @@
+package com.gotunnel.android.service
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import androidx.core.content.ContextCompat
+import com.gotunnel.android.config.ConfigStore
+
+class BootReceiver : BroadcastReceiver() {
+    override fun onReceive(context: Context, intent: Intent) {
+        val action = intent.action ?: return
+        if (action != Intent.ACTION_BOOT_COMPLETED && action != Intent.ACTION_MY_PACKAGE_REPLACED) {
+            return
+        }
+
+        val config = ConfigStore(context).load()
+        if (!config.autoStart) {
+            return
+        }
+
+        ContextCompat.startForegroundService(
+            context,
+            TunnelService.createStartIntent(context, action.lowercase()),
+        )
+    }
+}

android/app/src/main/java/com/gotunnel/android/service/NetworkMonitor.kt

@@ -0,0 +1,52 @@
+package com.gotunnel.android.service
+
+import android.content.Context
+import android.net.ConnectivityManager
+import android.net.Network
+import android.net.NetworkCapabilities
+
+class NetworkMonitor(
+    context: Context,
+    private val onAvailable: () -> Unit,
+    private val onLost: () -> Unit = {},
+) {
+    private val connectivityManager =
+        context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+
+    private var registered = false
+
+    private val callback = object : ConnectivityManager.NetworkCallback() {
+        override fun onAvailable(network: Network) {
+            onAvailable()
+        }
+
+        override fun onLost(network: Network) {
+            onLost()
+        }
+    }
+
+    fun start() {
+        if (registered) {
+            return
+        }
+        connectivityManager.registerDefaultNetworkCallback(callback)
+        registered = true
+    }
+
+    fun isConnected(): Boolean {
+        val network = connectivityManager.activeNetwork ?: return false
+        val capabilities = connectivityManager.getNetworkCapabilities(network) ?: return false
+        return capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) &&
+            capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED)
+    }
+
+    fun stop() {
+        if (!registered) {
+            return
+        }
+        runCatching {
+            connectivityManager.unregisterNetworkCallback(callback)
+        }
+        registered = false
+    }
+}

android/app/src/main/java/com/gotunnel/android/service/NotificationHelper.kt

@@ -0,0 +1,96 @@
+package com.gotunnel.android.service
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import androidx.core.app.NotificationCompat
+import com.gotunnel.android.MainActivity
+import com.gotunnel.android.R
+import com.gotunnel.android.bridge.TunnelStatus
+import com.gotunnel.android.config.AppConfig
+
+object NotificationHelper {
+    const val CHANNEL_ID = "gotunnel_tunnel"
+    const val NOTIFICATION_ID = 2001
+
+    fun ensureChannel(context: Context) {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
+            return
+        }
+
+        val manager = context.getSystemService(NotificationManager::class.java) ?: return
+        if (manager.getNotificationChannel(CHANNEL_ID) != null) {
+            return
+        }
+
+        val channel = NotificationChannel(
+            CHANNEL_ID,
+            context.getString(R.string.notification_channel_name),
+            NotificationManager.IMPORTANCE_LOW,
+        ).apply {
+            description = context.getString(R.string.notification_channel_description)
+        }
+        manager.createNotificationChannel(channel)
+    }
+
+    fun build(
+        context: Context,
+        status: TunnelStatus,
+        detail: String,
+        config: AppConfig,
+    ): Notification {
+        val baseText = when {
+            detail.isNotBlank() -> detail
+            config.serverAddress.isNotBlank() -> context.getString(
+                R.string.notification_text_configured,
+                config.serverAddress,
+            )
+            else -> context.getString(R.string.notification_text_unconfigured)
+        }
+
+        val contentIntent = PendingIntent.getActivity(
+            context,
+            0,
+            Intent(context, MainActivity::class.java),
+            pendingIntentFlags(),
+        )
+
+        val stopIntent = PendingIntent.getService(
+            context,
+            1,
+            TunnelService.createStopIntent(context, "notification-stop"),
+            pendingIntentFlags(),
+        )
+
+        val restartIntent = PendingIntent.getService(
+            context,
+            2,
+            TunnelService.createRestartIntent(context, "notification-restart"),
+            pendingIntentFlags(),
+        )
+
+        return NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_gotunnel_notification)
+            .setContentTitle(context.getString(R.string.notification_title, status.name))
+            .setContentText(baseText)
+            .setStyle(NotificationCompat.BigTextStyle().bigText(baseText))
+            .setOngoing(status != TunnelStatus.STOPPED)
+            .setOnlyAlertOnce(true)
+            .setContentIntent(contentIntent)
+            .addAction(android.R.drawable.ic_popup_sync, context.getString(R.string.notification_action_restart), restartIntent)
+            .addAction(android.R.drawable.ic_menu_close_clear_cancel, context.getString(R.string.notification_action_stop), stopIntent)
+            .build()
+    }
+
+    private fun pendingIntentFlags(): Int {
+        return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
+        } else {
+            PendingIntent.FLAG_UPDATE_CURRENT
+        }
+    }
+}

android/app/src/main/java/com/gotunnel/android/service/TunnelService.kt

@@ -0,0 +1,177 @@
+package com.gotunnel.android.service
+
+import android.app.Service
+import android.content.Context
+import android.content.Intent
+import android.os.IBinder
+import androidx.core.app.NotificationManagerCompat
+import com.gotunnel.android.bridge.GoTunnelBridge
+import com.gotunnel.android.bridge.TunnelController
+import com.gotunnel.android.bridge.TunnelStatus
+import com.gotunnel.android.config.AppConfig
+import com.gotunnel.android.config.ConfigStore
+import com.gotunnel.android.config.ServiceStateStore
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
+
+class TunnelService : Service() {
+    private val serviceScope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
+    private lateinit var configStore: ConfigStore
+    private lateinit var stateStore: ServiceStateStore
+    private lateinit var controller: TunnelController
+    private lateinit var networkMonitor: NetworkMonitor
+    private var currentConfig: AppConfig = AppConfig()
+    private var networkMonitorPrimed = false
+
+    override fun onCreate() {
+        super.onCreate()
+        configStore = ConfigStore(this)
+        stateStore = ServiceStateStore(this)
+        controller = GoTunnelBridge.create(applicationContext)
+        controller.setListener(object : TunnelController.Listener {
+            override fun onStatusChanged(status: TunnelStatus, detail: String) {
+                stateStore.save(status, detail)
+                updateNotification(status, detail)
+            }
+
+            override fun onLog(message: String) {
+                val current = stateStore.load()
+                stateStore.save(current.status, message)
+                updateNotification(current.status, message)
+            }
+        })
+        networkMonitor = NetworkMonitor(
+            this,
+            onAvailable = {
+                if (networkMonitorPrimed) {
+                    networkMonitorPrimed = false
+                } else {
+                    val config = configStore.load()
+                    if (config.autoReconnect && controller.isRunning) {
+                        controller.restart("network-restored")
+                    }
+                }
+            },
+            onLost = {
+                val detail = getString(com.gotunnel.android.R.string.network_lost)
+                stateStore.save(TunnelStatus.RECONNECTING, detail)
+                updateNotification(TunnelStatus.RECONNECTING, detail)
+            },
+        )
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        ensureForeground()
+
+        when (intent?.action) {
+            ACTION_STOP -> {
+                stopServiceInternal(intent.getStringExtra(EXTRA_REASON) ?: "stop")
+                return START_NOT_STICKY
+            }
+
+            ACTION_RESTART -> {
+                controller.restart(intent.getStringExtra(EXTRA_REASON) ?: "restart")
+            }
+
+            else -> {
+                startOrRefreshTunnel(intent?.getStringExtra(EXTRA_REASON) ?: "start")
+            }
+        }
+
+        return START_STICKY
+    }
+
+    override fun onDestroy() {
+        runCatching { networkMonitor.stop() }
+        runCatching { controller.stop("service-destroyed") }
+        serviceScope.cancel()
+        super.onDestroy()
+    }
+
+    override fun onBind(intent: Intent?): IBinder? = null
+
+    private fun ensureForeground() {
+        val state = stateStore.load()
+        val config = configStore.load()
+        NotificationHelper.ensureChannel(this)
+        startForeground(
+            NotificationHelper.NOTIFICATION_ID,
+            NotificationHelper.build(
+                this,
+                state.status,
+                state.detail,
+                config,
+            ),
+        )
+    }
+
+    private fun startOrRefreshTunnel(reason: String) {
+        currentConfig = configStore.load()
+        controller.updateConfig(currentConfig)
+        stateStore.save(TunnelStatus.STARTING, reason)
+        updateNotification(TunnelStatus.STARTING, reason)
+
+        if (!isConfigReady(currentConfig)) {
+            val detail = getString(com.gotunnel.android.R.string.config_missing)
+            stateStore.save(TunnelStatus.STOPPED, detail)
+            updateNotification(TunnelStatus.STOPPED, detail)
+            return
+        }
+
+        networkMonitorPrimed = networkMonitor.isConnected()
+        controller.start(currentConfig)
+        runCatching { networkMonitor.start() }
+    }
+
+    private fun stopServiceInternal(reason: String) {
+        runCatching { networkMonitor.stop() }
+        networkMonitorPrimed = false
+        controller.stop(reason)
+        stateStore.save(TunnelStatus.STOPPED, reason)
+        updateNotification(TunnelStatus.STOPPED, reason)
+        stopForeground(STOP_FOREGROUND_REMOVE)
+        stopSelf()
+    }
+
+    private fun updateNotification(status: TunnelStatus, detail: String) {
+        val config = currentConfig.takeIf { it.serverAddress.isNotBlank() } ?: configStore.load()
+        NotificationManagerCompat.from(this).notify(
+            NotificationHelper.NOTIFICATION_ID,
+            NotificationHelper.build(this, status, detail, config),
+        )
+    }
+
+    private fun isConfigReady(config: AppConfig): Boolean {
+        return config.serverAddress.isNotBlank() && config.token.isNotBlank()
+    }
+
+    companion object {
+        const val ACTION_START = "com.gotunnel.android.service.action.START"
+        const val ACTION_STOP = "com.gotunnel.android.service.action.STOP"
+        const val ACTION_RESTART = "com.gotunnel.android.service.action.RESTART"
+        const val EXTRA_REASON = "extra_reason"
+
+        fun createStartIntent(context: Context, reason: String): Intent {
+            return Intent(context, TunnelService::class.java).apply {
+                action = ACTION_START
+                putExtra(EXTRA_REASON, reason)
+            }
+        }
+
+        fun createStopIntent(context: Context, reason: String): Intent {
+            return Intent(context, TunnelService::class.java).apply {
+                action = ACTION_STOP
+                putExtra(EXTRA_REASON, reason)
+            }
+        }
+
+        fun createRestartIntent(context: Context, reason: String): Intent {
+            return Intent(context, TunnelService::class.java).apply {
+                action = ACTION_RESTART
+                putExtra(EXTRA_REASON, reason)
+            }
+        }
+    }
+}

android/app/src/main/res/drawable/ic_gotunnel_app.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#0EA5A8"
+        android:pathData="M54,10a44,44 0 1,0 0,88a44,44 0 1,0 0,-88z" />
+    <path
+        android:fillColor="#0F172A"
+        android:pathData="M39,35h30c4.4,0 8,3.6 8,8v22c0,4.4 -3.6,8 -8,8H39c-4.4,0 -8,-3.6 -8,-8V43c0,-4.4 3.6,-8 8,-8z" />
+    <path
+        android:fillColor="#E5E7EB"
+        android:pathData="M44,43h20c2.2,0 4,1.8 4,4v14c0,2.2 -1.8,4 -4,4H44c-2.2,0 -4,-1.8 -4,-4V47c0,-2.2 1.8,-4 4,-4z" />
+    <path
+        android:fillColor="#38BDF8"
+        android:pathData="M52,49l10,6l-10,6z" />
+</vector>

android/app/src/main/res/drawable/ic_gotunnel_notification.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M12,2a10,10 0 1,0 0,20a10,10 0 1,0 0,-20z" />
+    <path
+        android:fillColor="#0EA5A8"
+        android:pathData="M8,8h8c1.1,0 2,0.9 2,2v4c0,1.1 -0.9,2 -2,2H8c-1.1,0 -2,-0.9 -2,-2v-4c0,-1.1 0.9,-2 2,-2z" />
+    <path
+        android:fillColor="#0F172A"
+        android:pathData="M10,10l4,2l-4,2z" />
+</vector>

android/app/src/main/res/layout/activity_main.xml

@@ -0,0 +1,125 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:fillViewport="true">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:padding="24dp">
+
+        <TextView
+            android:id="@+id/titleText"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/app_name"
+            android:textAppearance="?attr/textAppearanceHeadlineMedium" />
+
+        <TextView
+            android:id="@+id/subtitleText"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            android:text="@string/main_subtitle"
+            android:textAppearance="?attr/textAppearanceBodyMedium" />
+
+        <EditText
+            android:id="@+id/serverAddressInput"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="24dp"
+            android:hint="@string/server_address_hint"
+            android:inputType="textUri"
+            android:padding="12dp" />
+
+        <EditText
+            android:id="@+id/tokenInput"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:hint="@string/token_hint"
+            android:inputType="textPassword"
+            android:padding="12dp" />
+
+        <com.google.android.material.switchmaterial.SwitchMaterial
+            android:id="@+id/autoStartSwitch"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="20dp"
+            android:text="@string/auto_start_label" />
+
+        <com.google.android.material.switchmaterial.SwitchMaterial
+            android:id="@+id/autoReconnectSwitch"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/auto_reconnect_label" />
+
+        <com.google.android.material.switchmaterial.SwitchMaterial
+            android:id="@+id/useTlsSwitch"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/use_tls_label" />
+
+        <TextView
+            android:id="@+id/stateHint"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="20dp"
+            android:text="@string/state_hint_stopped"
+            android:textAppearance="?attr/textAppearanceBodyMedium" />
+
+        <TextView
+            android:id="@+id/stateValue"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            android:textAppearance="?attr/textAppearanceBodyLarge" />
+
+        <TextView
+            android:id="@+id/stateMeta"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="4dp"
+            android:textAppearance="?attr/textAppearanceBodySmall" />
+
+        <com.google.android.material.button.MaterialButton
+            android:id="@+id/batteryButton"
+            style="?attr/materialButtonOutlinedStyle"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="20dp"
+            android:text="@string/battery_button" />
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="24dp"
+            android:orientation="horizontal">
+
+            <com.google.android.material.button.MaterialButton
+                android:id="@+id/saveButton"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:text="@string/save_button" />
+
+            <com.google.android.material.button.MaterialButton
+                android:id="@+id/startButton"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_marginStart="12dp"
+                android:layout_weight="1"
+                android:text="@string/start_button" />
+
+            <com.google.android.material.button.MaterialButton
+                android:id="@+id/stopButton"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_marginStart="12dp"
+                android:layout_weight="1"
+                android:text="@string/stop_button" />
+        </LinearLayout>
+    </LinearLayout>
+</ScrollView>

android/app/src/main/res/values/colors.xml

@@ -0,0 +1,7 @@
+<resources>
+    <color name="gotunnel_background">#0F172A</color>
+    <color name="gotunnel_surface">#111827</color>
+    <color name="gotunnel_primary">#0EA5A8</color>
+    <color name="gotunnel_secondary">#38BDF8</color>
+    <color name="gotunnel_text">#E5E7EB</color>
+</resources>

android/app/src/main/res/values/strings.xml

@@ -0,0 +1,36 @@
+<resources>
+    <string name="app_name">GoTunnel</string>
+    <string name="main_subtitle">Android host shell for the GoTunnel client core.</string>
+    <string name="server_address_hint">Server address, for example 10.0.2.2:7000</string>
+    <string name="token_hint">Authentication token</string>
+    <string name="auto_start_label">Start on boot</string>
+    <string name="auto_reconnect_label">Restart on network restore</string>
+    <string name="use_tls_label">Use TLS</string>
+    <string name="save_button">Save</string>
+    <string name="start_button">Start</string>
+    <string name="stop_button">Stop</string>
+    <string name="battery_button">Battery optimization</string>
+    <string name="config_saved">Configuration saved</string>
+    <string name="service_start_requested">Service start requested</string>
+    <string name="service_stop_requested">Service stop requested</string>
+    <string name="battery_optimization_already_disabled">Battery optimization is already disabled for GoTunnel.</string>
+    <string name="notification_permission_denied">Notification permission was denied. Foreground service notifications may be limited.</string>
+    <string name="state_never_updated">Never updated</string>
+    <string name="state_no_detail">No detail</string>
+    <string name="state_format">State: %1$s\nDetail: %2$s</string>
+    <string name="state_meta_format">Updated: %1$s</string>
+    <string name="state_hint_stopped">The foreground service is idle until a configuration is saved and started.</string>
+    <string name="state_hint_starting">The host shell is preparing a tunnel session.</string>
+    <string name="state_hint_running">The host shell is ready. The native Go tunnel core can be attached here later.</string>
+    <string name="state_hint_reconnecting">The host shell is waiting for connectivity to return.</string>
+    <string name="state_hint_error">The last session reported an error. Check the configuration and service notification.</string>
+    <string name="notification_channel_name">GoTunnel service</string>
+    <string name="notification_channel_description">Keeps the Android host shell running in the foreground</string>
+    <string name="notification_title">GoTunnel - %1$s</string>
+    <string name="notification_text_configured">Configured for %1$s</string>
+    <string name="notification_text_unconfigured">No server configured yet</string>
+    <string name="notification_action_restart">Restart</string>
+    <string name="notification_action_stop">Stop</string>
+    <string name="config_missing">Server address and token are required</string>
+    <string name="network_lost">Network lost</string>
+</resources>

android/app/src/main/res/values/themes.xml

@@ -0,0 +1,13 @@
+<resources xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+    <style name="Theme.GoTunnel" parent="Theme.Material3.DayNight.NoActionBar">
+        <item name="colorPrimary">@color/gotunnel_primary</item>
+        <item name="colorSecondary">@color/gotunnel_secondary</item>
+        <item name="colorBackground">@color/gotunnel_background</item>
+        <item name="colorSurface">@color/gotunnel_surface</item>
+        <item name="android:textColorPrimary">@color/gotunnel_text</item>
+        <item name="android:textColorSecondary">@color/gotunnel_text</item>
+        <item name="android:statusBarColor" tools:targetApi="l">@color/gotunnel_background</item>
+        <item name="android:navigationBarColor" tools:targetApi="l">@color/gotunnel_background</item>
+    </style>
+</resources>