wireless: connect by itself when a car Gearslip has connected to before comes up over Bluetooth

gearslip/src/main/java/app/seb3thehacker/gearslip/GearslipActivity.kt

@@ -117,6 +117,17 @@ class GearslipActivity : ComponentActivity(), Projection {
         }
     }
 
+    /** Android's one-time "Allow" for a car to connect by itself; see [WirelessAuto]. */
+    private var approvingCar: String? = null
+    private val carApproval = registerForActivityResult(
+        androidx.activity.result.contract.ActivityResultContracts.StartIntentSenderForResult(),
+    ) { result ->
+        val address = approvingCar ?: return@registerForActivityResult
+        approvingCar = null
+        if (result.resultCode == RESULT_OK) app.seb3thehacker.gearslip.wireless.WirelessAuto.approved(this, address)
+        else GearslipLog.w("auto-connect: declined in Android's dialog")
+    }
+
     /** Setting Gearslip as the phone's caller ID and spam app - what lets it decline a ringing call. */
     private val callScreeningRole = registerForActivityResult(StartActivityForResult()) { result ->
         if (result.resultCode != RESULT_OK) GearslipLog.w("calls: call screening role declined")
@@ -138,6 +149,12 @@ class GearslipActivity : ComponentActivity(), Projection {
         app.seb3thehacker.gearslip.wireless.WirelessLink.onConnected = { socket ->
             runOnUiThread { startWireless(socket) }
         }
+        app.seb3thehacker.gearslip.wireless.WirelessAuto.showApproval = { chooser, address ->
+            runOnUiThread {
+                approvingCar = address
+                carApproval.launch(androidx.activity.result.IntentSenderRequest.Builder(chooser).build())
+            }
+        }
         CarSettings.init(this)
         AppSettings.applyGearslipEnabled(this)
         // A capture that died without tidying up would leave notifications exposed to every
@@ -216,6 +233,7 @@ class GearslipActivity : ComponentActivity(), Projection {
     override fun onDestroy() {
         super.onDestroy()
         app.seb3thehacker.gearslip.wireless.WirelessLink.onConnected = null
+        app.seb3thehacker.gearslip.wireless.WirelessAuto.showApproval = null
         runCatching { unregisterReceiver(detachReceiver) }
         PhoneMirror.onStartRequested = null
         PhoneMirror.onTokenReady = null
@@ -304,6 +322,10 @@ class GearslipActivity : ComponentActivity(), Projection {
     }
 
     private fun handleIntent(intent: Intent?) {
+        if (intent?.action == app.seb3thehacker.gearslip.wireless.WirelessAuto.ACTION_CAR_NEARBY) {
+            connectToNearbyCar(intent.getStringExtra(app.seb3thehacker.gearslip.wireless.WirelessAuto.EXTRA_ADDRESS))
+            return
+        }
         if (intent?.action != UsbManager.ACTION_USB_ACCESSORY_ATTACHED) return
         // Switched off in Settings: the system shouldn't route the car here at all, but if it
         // does, leave the accessory alone.
@@ -321,6 +343,23 @@ class GearslipActivity : ComponentActivity(), Projection {
         start(accessory)
     }
 
+    /** A known car came up over Bluetooth: connect wirelessly, unless USB or another try is already on it. */
+    private fun connectToNearbyCar(address: String?) {
+        if (address == null || !AppSettings.gearslipEnabled(this)) return
+        if (descriptor != null) {
+            GearslipLog.i("auto-connect: the car is on USB already - staying on USB")
+            return
+        }
+        if (runner != null || app.seb3thehacker.gearslip.wireless.WirelessLink.busy) return
+        if (checkSelfPermission(android.Manifest.permission.BLUETOOTH_CONNECT) != android.content.pm.PackageManager.PERMISSION_GRANTED) {
+            GearslipLog.w("auto-connect: needs the Nearby devices permission")
+            return
+        }
+        val adapter = getSystemService(android.bluetooth.BluetoothManager::class.java)?.adapter ?: return
+        val device = runCatching { adapter.getRemoteDevice(address) }.getOrNull() ?: return
+        app.seb3thehacker.gearslip.wireless.WirelessLink.start(this, device)
+    }
+
     private fun start(accessory: UsbAccessory) {
         // A fresh ATTACHED intent means the system wants a new session, whatever state the old
         // one is in - closing first guarantees openAccessory() below never fights a descriptor

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/WirelessButton.kt

@@ -109,6 +109,8 @@ internal fun WirelessButton() {
                                 .clickable {
                                     devices = null
                                     WirelessLink.start(context, device)
+                                    // Next time this car connects, Gearslip does this by itself.
+                                    app.seb3thehacker.gearslip.wireless.WirelessAuto.connectedByHand(context, device)
                                 }
                                 .padding(vertical = 14.dp),
                         )

gearslip/src/main/java/app/seb3thehacker/gearslip/wireless/CarPresenceService.kt

@@ -0,0 +1,15 @@
+package app.seb3thehacker.gearslip.wireless
+
+import android.companion.CompanionDeviceService
+
+/** Android calls this when a car approved in [WirelessAuto] connects over Bluetooth. */
+class CarPresenceService : CompanionDeviceService() {
+
+    @Deprecated("Deprecated in Java")
+    override fun onDeviceAppeared(address: String) {
+        WirelessAuto.carAppeared(applicationContext, address)
+    }
+
+    @Deprecated("Deprecated in Java")
+    override fun onDeviceDisappeared(address: String) {}
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/wireless/WirelessAuto.kt

@@ -0,0 +1,102 @@
+package app.seb3thehacker.gearslip.wireless
+
+import android.annotation.SuppressLint
+import android.bluetooth.BluetoothDevice
+import android.companion.AssociationRequest
+import android.companion.BluetoothDeviceFilter
+import android.companion.CompanionDeviceManager
+import android.content.Context
+import android.content.Intent
+import android.content.IntentSender
+import android.os.Handler
+import android.os.Looper
+import app.seb3thehacker.gearslip.GearslipLog
+import app.seb3thehacker.gearslip.GearslipActivity
+
+/**
+ * Starts wireless Android Auto by itself when a car Gearslip has connected to before comes up
+ * over Bluetooth.
+ *
+ * Android only lets an app wake up and open its screen from the background for a device it
+ * manages as a companion, so the first wireless connection to a car also asks Android to make
+ * that car Gearslip's companion. Android shows its own one-time "Allow" for it; after that it
+ * tells [CarPresenceService] whenever the car connects, and Gearslip connects to it.
+ */
+object WirelessAuto {
+
+    /** Action on the activity's intent when the car came up on its own. */
+    const val ACTION_CAR_NEARBY = "app.seb3thehacker.gearslip.CAR_NEARBY"
+    const val EXTRA_ADDRESS = "address"
+
+    private const val PREFS = "gearslip_wireless_auto"
+
+    private val log = GearslipLog.tagged("AAW")
+
+    /** Set by the activity: shows Android's companion dialog, which only an activity can do. */
+    @Volatile var showApproval: ((IntentSender, String) -> Unit)? = null
+
+    /**
+     * Called whenever the driver connects to [device] by hand. Asks Android once per car; a car
+     * already approved only has its presence watched again, in case Android forgot.
+     */
+    @SuppressLint("MissingPermission")
+    fun connectedByHand(context: Context, device: BluetoothDevice) {
+        val manager = context.getSystemService(CompanionDeviceManager::class.java) ?: return
+        val address = device.address
+        if (isCompanion(manager, address)) {
+            watch(context, address)
+            return
+        }
+        val prefs = context.getSharedPreferences(PREFS, Context.MODE_PRIVATE)
+        if (prefs.getBoolean(address, false)) return
+        prefs.edit().putBoolean(address, true).apply()
+
+        val request = AssociationRequest.Builder()
+            .addDeviceFilter(BluetoothDeviceFilter.Builder().setAddress(address).build())
+            .setSingleDevice(true)
+            .build()
+        log.i("auto-connect: asking Android to let Gearslip watch for ${WirelessLink.name(device)}")
+        @Suppress("DEPRECATION")
+        manager.associate(request, object : CompanionDeviceManager.Callback() {
+            @Deprecated("Deprecated in Java")
+            override fun onDeviceFound(chooser: IntentSender) {
+                showApproval?.invoke(chooser, address) ?: log.w("auto-connect: no screen to ask on")
+            }
+
+            override fun onFailure(error: CharSequence?) {
+                log.w("auto-connect: Android wouldn't ask ($error)")
+            }
+        }, Handler(Looper.getMainLooper()))
+    }
+
+    /** The driver allowed it in Android's dialog. */
+    fun approved(context: Context, address: String) {
+        log.i("auto-connect: allowed")
+        watch(context, address)
+    }
+
+    @SuppressLint("MissingPermission")
+    private fun watch(context: Context, address: String) {
+        val manager = context.getSystemService(CompanionDeviceManager::class.java) ?: return
+        @Suppress("DEPRECATION")
+        runCatching { manager.startObservingDevicePresence(address) }
+            .onFailure { log.w("auto-connect: couldn't watch for the car (${it.message})") }
+    }
+
+    @Suppress("DEPRECATION")
+    private fun isCompanion(manager: CompanionDeviceManager, address: String): Boolean =
+        runCatching { manager.associations.any { it.equals(address, ignoreCase = true) } }.getOrDefault(false)
+
+    /** From [CarPresenceService]: the car is here, so bring Gearslip up to connect to it. */
+    fun carAppeared(context: Context, address: String) {
+        log.i("auto-connect: a car Gearslip knows connected over Bluetooth")
+        runCatching {
+            context.startActivity(
+                Intent(context, GearslipActivity::class.java)
+                    .setAction(ACTION_CAR_NEARBY)
+                    .putExtra(EXTRA_ADDRESS, address)
+                    .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
+            )
+        }.onFailure { log.w("auto-connect: couldn't open Gearslip (${it.message})") }
+    }
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/wireless/WirelessLink.kt

@@ -82,6 +82,9 @@ object WirelessLink {
     @Volatile private var tcp: Socket? = null
     @Volatile private var network: ConnectivityManager.NetworkCallback? = null
     @Volatile private var worker: Thread? = null
+
+    /** A start-up or a session's Bluetooth channel is under way. */
+    val busy: Boolean get() = worker?.isAlive == true
     /** Set when Android drops the car's network mid-try, so the rest don't bind to a dead one. */
     @Volatile private var lostNetwork: Network? = null
     /** Bumped on each Wi-Fi join and on stop, so an older run of TCP tries ends instead of racing the new one. */