Add support for NFC write in FrontendScreen

app/src/main/kotlin/io/homeassistant/companion/android/frontend/FrontendViewModel.kt

@@ -13,8 +13,10 @@ import io.homeassistant.companion.android.frontend.download.DownloadResult
 import io.homeassistant.companion.android.frontend.download.FrontendDownloadManager
 import io.homeassistant.companion.android.frontend.error.FrontendConnectionError
 import io.homeassistant.companion.android.frontend.error.FrontendConnectionErrorStateProvider
+import io.homeassistant.companion.android.frontend.externalbus.FrontendExternalBusRepository
 import io.homeassistant.companion.android.frontend.externalbus.WebViewScript
 import io.homeassistant.companion.android.frontend.externalbus.incoming.HapticType
+import io.homeassistant.companion.android.frontend.externalbus.outgoing.ResultMessage
 import io.homeassistant.companion.android.frontend.handler.FrontendBusObserver
 import io.homeassistant.companion.android.frontend.handler.FrontendHandlerEvent
 import io.homeassistant.companion.android.frontend.js.BridgeState
@@ -67,6 +69,7 @@ internal class FrontendViewModel @VisibleForTesting constructor(
     initialPath: String?,
     webViewClientFactory: HAWebViewClientFactory,
     private val frontendBusObserver: FrontendBusObserver,
+    private val externalBusRepository: FrontendExternalBusRepository,
     private val urlManager: FrontendUrlManager,
     private val connectivityCheckRepository: ConnectivityCheckRepository,
     private val permissionManager: PermissionManager,
@@ -80,6 +83,7 @@ internal class FrontendViewModel @VisibleForTesting constructor(
         savedStateHandle: SavedStateHandle,
         webViewClientFactory: HAWebViewClientFactory,
         frontendBusObserver: FrontendBusObserver,
+        externalBusRepository: FrontendExternalBusRepository,
         urlManager: FrontendUrlManager,
         connectivityCheckRepository: ConnectivityCheckRepository,
         permissionManager: PermissionManager,
@@ -90,6 +94,7 @@ internal class FrontendViewModel @VisibleForTesting constructor(
         initialPath = savedStateHandle.toRoute<FrontendRoute>().path,
         webViewClientFactory = webViewClientFactory,
         frontendBusObserver = frontendBusObserver,
+        externalBusRepository = externalBusRepository,
         urlManager = urlManager,
         connectivityCheckRepository = connectivityCheckRepository,
         permissionManager = permissionManager,
@@ -322,6 +327,24 @@ internal class FrontendViewModel @VisibleForTesting constructor(
         permissionManager.clearPendingPermissionRequest()
     }
 
+    /**
+     * Called by the host after the NFC tag-write flow completes.
+     *
+     * Sends a `result` response back to the frontend correlated by [messageId]. Matches the legacy
+     * behavior of always reporting `success = true` with an empty payload: the underlying
+     * `NfcSetupActivity` only returns a non-zero result code on successful write, and the frontend
+     * silently ignores responses whose id it no longer tracks.
+     *
+     * @param messageId The correlation id received back from the activity result. Corresponds to
+     *   the id of the originating `tag/write` request on success, or `0` (`RESULT_CANCELED`) on
+     *   cancellation.
+     */
+    fun onNfcWriteCompleted(messageId: Int) {
+        viewModelScope.launch {
+            externalBusRepository.send(ResultMessage.success(messageId))
+        }
+    }
+
     private fun loadServer() {
         urlFlowJob?.cancel()
         urlFlowJob = viewModelScope.launch {
@@ -396,6 +419,10 @@ internal class FrontendViewModel @VisibleForTesting constructor(
                 handleDownloadResult(result.result)
             }
 
+            is FrontendHandlerEvent.WriteNfcTag -> {
+                _events.tryEmit(FrontendEvent.LaunchNfcWrite(messageId = result.messageId, tagId = result.tagId))
+            }
+
             is FrontendHandlerEvent.ConfigSent,
             is FrontendHandlerEvent.UnknownMessage,
             -> {

app/src/main/kotlin/io/homeassistant/companion/android/frontend/externalbus/incoming/IncomingExternalBusMessage.kt

@@ -143,6 +143,21 @@ data class OpenAssistPayload(
 @SerialName("haptic")
 data class HapticMessage(override val id: Int? = null, val payload: HapticType) : IncomingExternalBusMessage
 
+/**
+ * Message requesting the app to open the NFC tag-write flow.
+ *
+ * The optional [TagWritePayload.tag] is a pre-filled tag identifier. When null or missing, the
+ * user is prompted to enter/scan a tag manually. The response is a [ResultMessage] correlated via
+ * [id] once the user completes or cancels the flow.
+ */
+@Serializable
+@SerialName("tag/write")
+data class TagWriteMessage(override val id: Int? = null, val payload: TagWritePayload = TagWritePayload()) :
+    IncomingExternalBusMessage
+
+@Serializable
+data class TagWritePayload(val tag: String? = null)
+
 /**
  * Message carrying blob data for a file download initiated by the frontend.
  *

app/src/main/kotlin/io/homeassistant/companion/android/frontend/externalbus/outgoing/OutgoingExternalBusMessage.kt

@@ -7,6 +7,7 @@ import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonNull
+import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.encodeToJsonElement
 
 /**
@@ -39,6 +40,13 @@ data class ResultMessage(
 
     companion object {
 
+        fun success(id: Int?): ResultMessage {
+            return ResultMessage(
+                id = id,
+                result = JsonObject(emptyMap()),
+            )
+        }
+
         /**
          * Creates a config response with app capabilities.
          *

app/src/main/kotlin/io/homeassistant/companion/android/frontend/handler/FrontendHandlerEvent.kt

@@ -70,4 +70,13 @@ sealed interface FrontendHandlerEvent {
      * The ViewModel should process the [result] to emit appropriate UI feedback.
      */
     data class DownloadCompleted(val result: DownloadResult) : FrontendHandlerEvent
+
+    /**
+     * Frontend requested the NFC tag-write flow to be launched.
+     *
+     * @param messageId The correlation id from the incoming `tag/write` message; used to respond back
+     *   to the frontend once the flow completes.
+     * @param tagId Optional pre-filled tag identifier. When null, the user is prompted to enter one.
+     */
+    data class WriteNfcTag(val messageId: Int, val tagId: String?) : FrontendHandlerEvent
 }

app/src/main/kotlin/io/homeassistant/companion/android/frontend/handler/FrontendMessageHandler.kt

@@ -15,6 +15,7 @@ import io.homeassistant.companion.android.frontend.externalbus.incoming.Incoming
 import io.homeassistant.companion.android.frontend.externalbus.incoming.OpenAssistMessage
 import io.homeassistant.companion.android.frontend.externalbus.incoming.OpenAssistSettingsMessage
 import io.homeassistant.companion.android.frontend.externalbus.incoming.OpenSettingsMessage
+import io.homeassistant.companion.android.frontend.externalbus.incoming.TagWriteMessage
 import io.homeassistant.companion.android.frontend.externalbus.incoming.ThemeUpdateMessage
 import io.homeassistant.companion.android.frontend.externalbus.incoming.UnknownIncomingMessage
 import io.homeassistant.companion.android.frontend.externalbus.outgoing.ConfigResult
@@ -163,6 +164,14 @@ class FrontendMessageHandler @Inject constructor(
 
             is HapticMessage -> FrontendHandlerEvent.PerformHaptic(message.payload)
 
+            is TagWriteMessage -> {
+                Timber.d("Tag write request received with id: ${message.id}")
+                FrontendHandlerEvent.WriteNfcTag(
+                    messageId = message.id ?: -1,
+                    tagId = message.payload.tag,
+                )
+            }
+
             is HandleBlobMessage -> {
                 Timber.d("handleBlob called with filename=${message.filename}")
                 val result = downloadManager.handleBlob(data = message.data, filename = message.filename)

app/src/main/kotlin/io/homeassistant/companion/android/frontend/navigation/FrontendEvent.kt

@@ -33,4 +33,15 @@ sealed interface FrontendEvent {
 
     /** Open a URI externally using the host-provided external link handler. */
     data class OpenExternalLink(val uri: Uri) : FrontendEvent
+
+    /**
+     * Launch the NFC tag-write flow.
+     *
+     * The host is responsible for launching the corresponding activity contract and forwarding the
+     * result back to the ViewModel via [FrontendViewModel.onNfcWriteCompleted].
+     *
+     * @param messageId Correlation id from the originating `tag/write` request.
+     * @param tagId Optional pre-filled tag identifier.
+     */
+    data class LaunchNfcWrite(val messageId: Int, val tagId: String?) : FrontendEvent
 }

app/src/main/kotlin/io/homeassistant/companion/android/frontend/navigation/FrontendNavigation.kt

@@ -1,6 +1,7 @@
 package io.homeassistant.companion.android.frontend.navigation
 
 import android.net.Uri
+import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.annotation.VisibleForTesting
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
@@ -18,6 +19,7 @@ import io.homeassistant.companion.android.common.data.servers.ServerManager.Comp
 import io.homeassistant.companion.android.frontend.FrontendScreen
 import io.homeassistant.companion.android.frontend.FrontendViewModel
 import io.homeassistant.companion.android.launch.HAStartDestinationRoute
+import io.homeassistant.companion.android.nfc.WriteNfcTag
 import io.homeassistant.companion.android.settings.SettingsActivity
 import io.homeassistant.companion.android.util.getActivity
 import io.homeassistant.companion.android.webview.WebViewActivity
@@ -71,6 +73,10 @@ internal fun NavGraphBuilder.frontendScreen(
         composable<FrontendRoute> {
             val viewModel: FrontendViewModel = hiltViewModel()
 
+            val nfcWriteLauncher = rememberLauncherForActivityResult(WriteNfcTag()) { resultCode ->
+                viewModel.onNfcWriteCompleted(resultCode)
+            }
+
             FrontendEventHandler(
                 events = viewModel.events,
                 onShowSnackbar = onShowSnackbar,
@@ -86,6 +92,9 @@ internal fun NavGraphBuilder.frontendScreen(
                     )
                 },
                 onOpenExternalLink = onOpenExternalLink,
+                onLaunchNfcWrite = { messageId, tagId ->
+                    nfcWriteLauncher.launch(WriteNfcTag.Input(tagId = tagId, messageId = messageId))
+                },
             )
 
             FrontendScreen(
@@ -126,6 +135,7 @@ internal fun FrontendEventHandler(
     onNavigateToSettings: (SettingsActivity.Deeplink?) -> Unit,
     onNavigateToAssist: (serverId: Int, pipelineId: String?, startListening: Boolean) -> Unit,
     onOpenExternalLink: suspend (Uri) -> Unit,
+    onLaunchNfcWrite: (messageId: Int, tagId: String?) -> Unit,
 ) {
     val resources = LocalResources.current
     LaunchedEffect(Unit) {
@@ -150,6 +160,10 @@ internal fun FrontendEventHandler(
                 is FrontendEvent.OpenExternalLink -> {
                     onOpenExternalLink(event.uri)
                 }
+
+                is FrontendEvent.LaunchNfcWrite -> {
+                    onLaunchNfcWrite(event.messageId, event.tagId)
+                }
             }
         }
     }

app/src/test/kotlin/io/homeassistant/companion/android/frontend/FrontendViewModelTest.kt

@@ -9,7 +9,9 @@ import io.homeassistant.companion.android.common.data.connectivity.ConnectivityC
 import io.homeassistant.companion.android.frontend.download.DownloadResult
 import io.homeassistant.companion.android.frontend.download.FrontendDownloadManager
 import io.homeassistant.companion.android.frontend.error.FrontendConnectionError
+import io.homeassistant.companion.android.frontend.externalbus.FrontendExternalBusRepository
 import io.homeassistant.companion.android.frontend.externalbus.incoming.HapticType
+import io.homeassistant.companion.android.frontend.externalbus.outgoing.ResultMessage
 import io.homeassistant.companion.android.frontend.handler.FrontendBusObserver
 import io.homeassistant.companion.android.frontend.handler.FrontendHandlerEvent
 import io.homeassistant.companion.android.frontend.js.FrontendJsBridgeFactory
@@ -38,6 +40,7 @@ import kotlinx.coroutines.test.UnconfinedTestDispatcher
 import kotlinx.coroutines.test.advanceTimeBy
 import kotlinx.coroutines.test.advanceUntilIdle
 import kotlinx.coroutines.test.runTest
+import kotlinx.serialization.json.JsonObject
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.BeforeEach
@@ -54,6 +57,7 @@ class FrontendViewModelTest {
 
     private val webViewClientFactory: HAWebViewClientFactory = mockk(relaxed = true)
     private val frontendBusObserver: FrontendBusObserver = mockk(relaxed = true)
+    private val externalBusRepository: FrontendExternalBusRepository = mockk(relaxed = true)
     private val urlManager: FrontendUrlManager = mockk(relaxed = true)
     private val connectivityCheckRepository: ConnectivityCheckRepository = mockk(relaxed = true)
     private val permissionManager: PermissionManager = mockk(relaxed = true)
@@ -79,6 +83,7 @@ class FrontendViewModelTest {
             initialPath = path,
             webViewClientFactory = webViewClientFactory,
             frontendBusObserver = frontendBusObserver,
+            externalBusRepository = externalBusRepository,
             urlManager = urlManager,
             connectivityCheckRepository = connectivityCheckRepository,
             permissionManager = permissionManager,
@@ -568,6 +573,44 @@ class FrontendViewModelTest {
             assertTrue(events.any { it is FrontendEvent.NavigateToAssistSettings })
             job.cancel()
         }
+
+        @Test
+        fun `Given WriteNfcTag handler event when collected then LaunchNfcWrite is emitted`() = runTest {
+            val messageFlow = MutableSharedFlow<FrontendHandlerEvent>()
+            every { frontendBusObserver.messageResults() } returns messageFlow
+            every { urlManager.serverUrlFlow(any(), any()) } returns flowOf(
+                UrlLoadResult.Success(url = testUrlWithAuth, serverId = serverId),
+            )
+
+            val viewModel = createViewModel()
+
+            viewModel.events.test {
+                advanceTimeBy(CONNECTION_TIMEOUT - 1.seconds)
+
+                messageFlow.emit(FrontendHandlerEvent.WriteNfcTag(messageId = 42, tagId = "tag-abc"))
+
+                assertEquals(FrontendEvent.LaunchNfcWrite(messageId = 42, tagId = "tag-abc"), awaitItem())
+                cancelAndIgnoreRemainingEvents()
+            }
+        }
+
+        @Test
+        fun `Given onNfcWriteCompleted when called then sends empty-result ResultMessage back to frontend`() = runTest {
+            every { urlManager.serverUrlFlow(any(), any()) } returns flowOf(
+                UrlLoadResult.Success(url = testUrlWithAuth, serverId = serverId),
+            )
+
+            val viewModel = createViewModel()
+
+            viewModel.onNfcWriteCompleted(messageId = 42)
+            advanceUntilIdle()
+
+            coVerify {
+                externalBusRepository.send(
+                    ResultMessage(id = 42, success = true, result = JsonObject(emptyMap())),
+                )
+            }
+        }
     }
 
     @Nested

app/src/test/kotlin/io/homeassistant/companion/android/frontend/externalbus/incoming/IncomingExternalBusMessageTest.kt

@@ -102,6 +102,30 @@ class IncomingExternalBusMessageTest {
         assertEquals("file.pdf", blobMessage.filename)
     }
 
+    @Test
+    fun `Given tag-write JSON with tag then parses to TagWriteMessage with tag`() {
+        val json = """{"type":"tag/write","id":11,"payload":{"tag":"abc-123"}}"""
+
+        val message = frontendExternalBusJson.decodeFromString<IncomingExternalBusMessage>(json)
+
+        assertInstanceOf(TagWriteMessage::class.java, message)
+        val tagMessage = message as TagWriteMessage
+        assertEquals(11, tagMessage.id)
+        assertEquals("abc-123", tagMessage.payload.tag)
+    }
+
+    @Test
+    fun `Given tag-write JSON without payload then parses to TagWriteMessage with null tag`() {
+        val json = """{"type":"tag/write","id":12}"""
+
+        val message = frontendExternalBusJson.decodeFromString<IncomingExternalBusMessage>(json)
+
+        assertInstanceOf(TagWriteMessage::class.java, message)
+        val tagMessage = message as TagWriteMessage
+        assertEquals(12, tagMessage.id)
+        assertNull(tagMessage.payload.tag)
+    }
+
     @Test
     fun `Given unknown type JSON then parses to UnknownIncomingMessage`() {
         val json = """{"type":"future-feature","id":99,"payload":{"data":"something"}}"""