feat: add nfc step 2 - receive with invoice

app/src/main/AndroidManifest.xml

@@ -7,11 +7,12 @@
     <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.FOREGROUND_SERVICE_SPECIAL_USE" />
     <uses-permission android:name="android.permission.NFC" />
 
-
     <uses-feature android:name="android.hardware.camera" android:required="false" />
     <uses-feature android:name="android.hardware.nfc" android:required="false" />
+    <uses-feature android:name="android.hardware.nfc.hce" android:required="false" />
 
     <application
         android:allowBackup="true"
@@ -55,8 +56,24 @@
 
         <service
             android:name=".service.WalletNotificationService"
-            android:foregroundServiceType="dataSync"
+            android:foregroundServiceType="specialUse"
-            android:exported="false" />
+            android:exported="false">
+            <property
+                android:name="android.app.PROPERTY_SPECIAL_USE_FGS_SUBTYPE"
+                android:value="Maintains a persistent Lightning Network connection to receive payment notifications" />
+        </service>
+
+        <service
+            android:name=".ui.nfc.NdefHceService"
+            android:exported="true"
+            android:permission="android.permission.BIND_NFC_SERVICE">
+            <intent-filter>
+                <action android:name="android.nfc.cardemulation.action.HOST_APDU_SERVICE" />
+            </intent-filter>
+            <meta-data
+                android:name="android.nfc.cardemulation.host_apdu_service"
+                android:resource="@xml/apduservice" />
+        </service>
 
     </application>
 

app/src/main/java/com/bitcointxoko/gudariwallet/MainActivity.kt

@@ -1,8 +1,11 @@
 package com.bitcointxoko.gudariwallet
 
 import android.Manifest
+import android.app.PendingIntent
 import android.content.ActivityNotFoundException
 import android.content.Intent
+import android.nfc.NfcAdapter
+import android.nfc.Tag
 import android.os.Build
 import android.os.Bundle
 import android.os.PowerManager
@@ -25,6 +28,7 @@ import com.bitcointxoko.gudariwallet.ui.OnboardingScreen
 import com.bitcointxoko.gudariwallet.ui.WalletScreen
 import com.bitcointxoko.gudariwallet.ui.WalletViewModel
 import com.bitcointxoko.gudariwallet.ui.WalletViewModelFactory
+import com.bitcointxoko.gudariwallet.ui.nfc.NfcViewModel
 import com.bitcointxoko.gudariwallet.ui.theme.GudariWalletTheme
 import com.bitcointxoko.gudariwallet.util.NotificationHelper
 import com.bitcointxoko.gudariwallet.util.IntentUtils
@@ -40,6 +44,23 @@ class MainActivity : AppCompatActivity() {
         WalletViewModelFactory(application)
     }
 
+    // ── NFC ──────────────────────────────────────────────────────────────────
+
+    val nfcVm: NfcViewModel by viewModels()
+
+    private var nfcAdapter: NfcAdapter? = null
+
+    /** Pending intent used by foreground dispatch — routes tag intents back here. */
+    private val nfcPendingIntent: PendingIntent by lazy {
+        PendingIntent.getActivity(
+            this, 0,
+            Intent(this, javaClass).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),
+            PendingIntent.FLAG_MUTABLE
+        )
+    }
+
+    // ── Existing state ───────────────────────────────────────────────────────
+
     // Holds a paymentHash that arrived via notification tap.
     // WalletScreen observes this and navigates to the detail screen.
     // MutableState so Compose recomposes when it changes.
@@ -73,10 +94,14 @@ class MainActivity : AppCompatActivity() {
         NotificationHelper.createChannels(applicationContext)
 
         // Read hash from the intent that launched the activity (cold start from notification)
-        pendingPaymentHash.value = intent.getStringExtra(NotificationHelper.EXTRA_PAYMENT_HASH)
+        pendingPaymentHash.value =
+            intent.getStringExtra(NotificationHelper.EXTRA_PAYMENT_HASH)
         // Read payment URI from the intent that launched the activity (cold start from deep link)
         pendingPaymentUri.value = IntentUtils.extractPaymentUri(intent)
 
+        // Initialise NFC adapter (null on devices without NFC — handled gracefully)
+        nfcAdapter = NfcAdapter.getDefaultAdapter(this)
+
         enableEdgeToEdge()
 
         setContent {
@@ -94,6 +119,7 @@ class MainActivity : AppCompatActivity() {
                     }
                     WalletScreen(
                         vm                 = vm,
+                        nfcVm              = nfcVm,
                         pendingPaymentHash = pendingPaymentHash,
                         pendingPaymentUri  = pendingPaymentUri
                     )
@@ -105,25 +131,54 @@ class MainActivity : AppCompatActivity() {
                 }
             }
         }
-
     }
 
-    // Called when the activity is already running and a notification is tapped
+    // ── NFC foreground dispatch ───────────────────────────────────────────────
+
+    override fun onResume() {
+        super.onResume()
+        // Give this activity first pick of all NFC tag intents while foregrounded.
+        // Passing null for techLists and intentFilters means we intercept every tag type.
+        nfcAdapter?.enableForegroundDispatch(
+            this,
+            nfcPendingIntent,
+            null,   // intercept all intent filters
+            null    // intercept all tech lists
+        )
+    }
+
+    override fun onPause() {
+        super.onPause()
+        nfcAdapter?.disableForegroundDispatch(this)
+    }
+
+    // ── Intent routing ────────────────────────────────────────────────────────
+
+    // Called when the activity is already running and a notification is tapped,
+    // a deep link arrives, or an NFC tag is discovered while foregrounded.
     // (FLAG_ACTIVITY_SINGLE_TOP prevents a new instance being created)
     override fun onNewIntent(intent: Intent) {
         super.onNewIntent(intent)
         setIntent(intent)
+
+        // Notification tap → navigate to payment detail
         val hash = intent.getStringExtra(NotificationHelper.EXTRA_PAYMENT_HASH)
         if (hash != null) {
             pendingPaymentHash.value = hash
         }
+
+        // Deep link / external app URI
         val uri = IntentUtils.extractPaymentUri(intent)
         if (uri != null) {
             pendingPaymentUri.value = uri
         }
+
+        // NFC tag discovered → hand off to NfcViewModel for reading
+        val tag = intent.getParcelableExtra<Tag>(NfcAdapter.EXTRA_TAG)
+        if (tag != null) {
+            nfcVm.onTagDiscovered(tag)
+        }
     }
-
-
 
     // ── Permission / battery helpers (unchanged) ──────────────────────────────
 
@@ -154,7 +209,8 @@ class MainActivity : AppCompatActivity() {
     }
 
     private fun openBatterySettings() {
-        val appDetailsIntent = Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
+        val appDetailsIntent =
+            Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
                 data = "package:$packageName".toUri()
             }
         if (tryStartActivity(appDetailsIntent)) return

app/src/main/java/com/bitcointxoko/gudariwallet/service/WalletNotificationService.kt

@@ -104,17 +104,12 @@ class WalletNotificationService : Service() {
     override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
         // Step 1: Call startForeground immediately — Android requires this within
         // 5 seconds of startForegroundService() or the app is ANR'd.
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE) { // API 34
-            startForeground(
+            startForeground(NotificationConstants.NOTIF_ID_SERVICE, NotificationHelper.buildServiceNotification(this), ServiceInfo.FOREGROUND_SERVICE_TYPE_SPECIAL_USE)
-                NotificationConstants.NOTIF_ID_SERVICE,
+        } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-                NotificationHelper.buildServiceNotification(this),
+            startForeground(NotificationConstants.NOTIF_ID_SERVICE, NotificationHelper.buildServiceNotification(this), ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC)
-                ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC
-            )
         } else {
-            startForeground(
+            startForeground(NotificationConstants.NOTIF_ID_SERVICE, NotificationHelper.buildServiceNotification(this))
-                NotificationConstants.NOTIF_ID_SERVICE,
-                NotificationHelper.buildServiceNotification(this)
-            )
         }
 
         // Step 2: Open the WebSocket. If already open (e.g. service restarted

app/src/main/java/com/bitcointxoko/gudariwallet/ui/WalletScreen.kt

@@ -58,6 +58,7 @@ import com.bitcointxoko.gudariwallet.ui.history.HistoryScreen
 import com.bitcointxoko.gudariwallet.ui.history.HistoryViewModel
 import com.bitcointxoko.gudariwallet.ui.history.HistoryViewModelFactory
 import com.bitcointxoko.gudariwallet.ui.history.PaymentDetailScreen
+import com.bitcointxoko.gudariwallet.ui.nfc.NfcViewModel
 import com.bitcointxoko.gudariwallet.ui.receive.ReceiveScreen
 import com.bitcointxoko.gudariwallet.ui.send.SendScreen
 import com.bitcointxoko.gudariwallet.util.SendInputType
@@ -78,6 +79,7 @@ private const val ROUTE_PAYMENT_DETAIL = "payment_detail/{checkingId}"
 @Composable
 fun WalletScreen(
     vm                : WalletViewModel,
+    nfcVm             : NfcViewModel,          // ← new
     pendingPaymentHash: MutableState<String?>,
     pendingPaymentUri : MutableState<String?>
 ) {
@@ -143,7 +145,7 @@ fun WalletScreen(
     LaunchedEffect(intentUri) {
         if (intentUri != null) {
             Log.d("WalletScreen", "INTENT [URI] deep link received: $intentUri")
-            pendingPaymentUri.value = null          // consume immediately
+            pendingPaymentUri.value = null
             vm.scan(intentUri)
             navController.navigate(TabItem.Send.route) {
                 launchSingleTop = true
@@ -151,9 +153,9 @@ fun WalletScreen(
         }
     }
 
+    // ── Clipboard offer ───────────────────────────────────────────────────────
     val clipboardOffer by vm.clipboardOfferState.collectAsStateWithLifecycle()
 
-    // Auto-dismiss banner after 8 seconds
     LaunchedEffect(clipboardOffer) {
         if (clipboardOffer is ClipboardOfferState.Detected) {
             delay(8_000)
@@ -161,33 +163,13 @@ fun WalletScreen(
         }
     }
 
-    // ── NFC reader mode — register on composition, unregister on disposal ────────
+    // ── NFC offer (tag read while app is foregrounded) ────────────────────────
-    val nfcAdapter = remember {
+    val nfcOffer by nfcVm.nfcOfferState.collectAsStateWithLifecycle()
-        android.nfc.NfcAdapter.getDefaultAdapter(context)
-    }
 
-    DisposableEffect(Unit) {
-        val activity = context as MainActivity
-        nfcAdapter?.enableReaderMode(
-            activity,
-            { tag -> vm.onNfcTagDiscovered(tag) },   // runs on NFC binder thread
-            android.nfc.NfcAdapter.FLAG_READER_NFC_A or
-                    android.nfc.NfcAdapter.FLAG_READER_NFC_B or
-                    android.nfc.NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK.inv(),  // keep NDEF
-            null
-        )
-        onDispose {
-            nfcAdapter?.disableReaderMode(activity)
-        }
-    }
-
-    val nfcOffer by vm.nfcOfferState.collectAsStateWithLifecycle()
-
-    // Auto-dismiss NFC banner after 8 seconds (same as clipboard)
     LaunchedEffect(nfcOffer) {
         if (nfcOffer is NfcOfferState.Detected) {
             delay(8_000)
-            vm.dismissNfcOffer()
+            nfcVm.dismissNfcOffer()
         }
     }
 
@@ -304,7 +286,8 @@ fun WalletScreen(
                 }
                 composable(TabItem.Receive.route) {
                     ReceiveScreen(
-                        vm,
+                        vm    = vm,
+                        nfcVm = nfcVm,          // ← new
                         onNavigateToPaymentDetail = { checkingId ->
                             navController.navigate("payment_detail/$checkingId")
                         }
@@ -341,7 +324,6 @@ fun WalletScreen(
                     ROUTE_HISTORY,
                     enterTransition    = { fadeIn(animationSpec = tween(150)) },
                     popExitTransition  = { fadeOut(animationSpec = tween(150)) }
-
                 ) {
                     HistoryScreen(
                         vm = historyVm,
@@ -393,7 +375,7 @@ fun WalletScreen(
                 exit     = slideOutVertically(targetOffsetY = { -it }),
                 modifier = Modifier
                     .align(Alignment.TopCenter)
-                    .zIndex(1f)
+                    .zIndex(2f)                 // above NFC banner
                     .fillMaxWidth()
                     .statusBarsPadding()
             ) {
@@ -445,18 +427,19 @@ fun WalletScreen(
                     }
                 }
             }
-            // ── NFC banner — floats below clipboard banner, slides in from top ────────────
+
+            // ── NFC banner — floats over content, slides in from top ──────────
+            // Shown when an NFC tag is tapped while the app is foregrounded.
+            // Mirrors the clipboard banner pattern exactly.
             AnimatedVisibility(
                 visible  = nfcOffer is NfcOfferState.Detected,
                 enter    = slideInVertically(initialOffsetY = { -it }),
                 exit     = slideOutVertically(targetOffsetY = { -it }),
                 modifier = Modifier
                     .align(Alignment.TopCenter)
-                    .zIndex(1f)
+                    .zIndex(1f)                 // below clipboard banner if both show
                     .fillMaxWidth()
                     .statusBarsPadding()
-                    // push down if clipboard banner is also showing
-                    .padding(top = if (clipboardOffer is ClipboardOfferState.Detected) 64.dp else 0.dp)
             ) {
                 if (nfcOffer is NfcOfferState.Detected) {
                     val offer    = nfcOffer as NfcOfferState.Detected
@@ -471,15 +454,12 @@ fun WalletScreen(
                         else                   -> "Tap to pay"
                     }
                     Surface(
-                        color    = MaterialTheme.colorScheme.secondaryContainer,  // distinct from clipboard's primaryContainer
+                        color    = MaterialTheme.colorScheme.secondaryContainer,
                         modifier = Modifier
                             .fillMaxWidth()
                             .clickable {
-                                vm.dismissNfcOffer()
+                                nfcVm.dismissNfcOffer()
                                 vm.scan(offer.raw)
-                                // scan() already emits navigateToReceive for LNURL-withdraw,
-                                // so we only need to navigate to Send for everything else.
-                                // The existing navigateToReceive LaunchedEffect handles BoltCard.
                                 navController.navigate(TabItem.Send.route) {
                                     launchSingleTop = true
                                 }
@@ -489,7 +469,7 @@ fun WalletScreen(
                             modifier          = Modifier.padding(horizontal = 16.dp, vertical = 10.dp),
                             verticalAlignment = Alignment.CenterVertically
                         ) {
-                            Icon(Icons.Filled.Nfc, contentDescription = null)
+                            Icon(Icons.Default.Nfc, contentDescription = null)
                             Spacer(Modifier.width(12.dp))
                             Column(Modifier.weight(1f)) {
                                 Text(
@@ -502,7 +482,7 @@ fun WalletScreen(
                                     color = MaterialTheme.colorScheme.onSecondaryContainer.copy(alpha = 0.7f)
                                 )
                             }
-                            IconButton(onClick = { vm.dismissNfcOffer() }) {
+                            IconButton(onClick = { nfcVm.dismissNfcOffer() }) {
                                 Icon(Icons.Default.Close, contentDescription = "Dismiss")
                             }
                         }

app/src/main/java/com/bitcointxoko/gudariwallet/ui/WalletViewModel.kt

@@ -17,7 +17,6 @@ import com.bitcointxoko.gudariwallet.data.LightningAddressStore
 import com.bitcointxoko.gudariwallet.ui.balance.BalanceViewModel
 import com.bitcointxoko.gudariwallet.ui.clipboard.ClipboardViewModel
 import com.bitcointxoko.gudariwallet.ui.fiat.FiatViewModel
-import com.bitcointxoko.gudariwallet.ui.nfc.NfcViewModel
 import com.bitcointxoko.gudariwallet.ui.receive.ReceiveViewModel
 import com.bitcointxoko.gudariwallet.ui.send.SendViewModel
 import kotlinx.coroutines.flow.SharingStarted
@@ -35,8 +34,7 @@ class WalletViewModel(
     val         fiatVm      : FiatViewModel,
     val         receiveVm   : ReceiveViewModel,
     val         sendVm      : SendViewModel,
-    val         clipboardVm : ClipboardViewModel,
+    val         clipboardVm : ClipboardViewModel
-    val         nfcVm       : NfcViewModel
 ) : ViewModel() {
     val balanceState: StateFlow<BalanceState> get() = balanceVm.balanceState
     val balanceHidden: StateFlow<Boolean>   get() = fiatVm.balanceHidden
@@ -77,17 +75,6 @@ class WalletViewModel(
     fun checkClipboard(text: String?)  = clipboardVm.checkClipboard(text)
     fun dismissClipboardOffer()        = clipboardVm.dismissClipboardOffer()
 
-    val nfcOfferState: StateFlow<NfcOfferState> = nfcVm.nfcOfferState
-
-    fun onNfcTagDiscovered(tag: android.nfc.Tag) = nfcVm.onTagDiscovered(tag)
-    @VisibleForTesting
-    fun onNfcTagRead(text: String?)              = nfcVm.onNfcTagRead(text)
-    fun dismissNfcOffer()                        = nfcVm.dismissNfcOffer()
-    val nfcBroadcastState: StateFlow<NfcViewModel.NfcBroadcastState> get() = nfcVm.broadcastState
-    fun startNfcBroadcast(payload: String) = nfcVm.startBroadcast(payload)
-    fun cancelNfcBroadcast()               = nfcVm.cancelBroadcast()
-    fun dismissNfcBroadcastResult()        = nfcVm.dismissBroadcastResult()
-
     init {
         observePaymentEvents()
         fetchLightningAddress()

app/src/main/java/com/bitcointxoko/gudariwallet/ui/WalletViewModelFactory.kt

@@ -50,10 +50,6 @@ class WalletViewModelFactory(private val app: Application) : ViewModelProvider.F
             ownInvoice = { (receiveVm.receiveState.value as? ReceiveState.InvoiceReady)?.bolt11 },
             ownAddress = { lnAddressStore.currentAddress }
         )
-        val nfcVm = NfcViewModel(
-            ownInvoice = { (receiveVm.receiveState.value as? ReceiveState.InvoiceReady)?.bolt11 },
-            ownAddress = { lnAddressStore.currentAddress }
-        )
 
         balanceVm.onBalanceRefreshed = { fiatVm.onBalanceRefreshed() }
 
@@ -68,7 +64,6 @@ class WalletViewModelFactory(private val app: Application) : ViewModelProvider.F
             receiveVm = receiveVm,
             sendVm = sendVm,
             clipboardVm      = clipboardVm,
-            nfcVm = nfcVm,
             lnAddressStore = lnAddressStore,
         ) as T
     }

app/src/main/java/com/bitcointxoko/gudariwallet/ui/clipboard/ClipboardViewModel.kt

@@ -3,12 +3,10 @@ package com.bitcointxoko.gudariwallet.ui.clipboard
 import android.util.Log
 import androidx.lifecycle.ViewModel
 import com.bitcointxoko.gudariwallet.ui.ClipboardOfferState
-import com.bitcointxoko.gudariwallet.ui.ReceiveState
 import com.bitcointxoko.gudariwallet.util.SendInputDetector
 import com.bitcointxoko.gudariwallet.util.SendInputType
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
-import kotlinx.coroutines.flow.StateFlow as SF
 
 private const val TAG = "ClipboardViewModel"
 

app/src/main/java/com/bitcointxoko/gudariwallet/ui/nfc/NdefHceService.kt

@@ -0,0 +1,152 @@
+package com.bitcointxoko.gudariwallet.ui.nfc
+
+import android.nfc.cardemulation.HostApduService
+import android.os.Bundle
+import android.util.Log
+
+/**
+ * HCE service that emulates an NFC Forum Type 4 Tag containing an NDEF
+ * message. The NDEF message holds a URI record (lightning: or bitcoin: URI)
+ * set by NfcViewModel via the companion-object singleton slot.
+ *
+ * Protocol reference: NFC Forum Type 4 Tag Operation Specification.
+ * The reader performs:
+ *   1. SELECT NDEF Application  (AID D2760000850101)
+ *   2. SELECT Capability Container file (file ID 0xE103)
+ *   3. READ BINARY of CC file
+ *   4. SELECT NDEF file (file ID from CC)
+ *   5. READ BINARY of NDEF file (length prefix + NDEF message bytes)
+ */
+class NdefHceService : HostApduService() {
+
+    companion object {
+        private const val TAG = "NdefHceService"
+
+        // ── APDU status words ────────────────────────────────────────────────
+        private val SW_OK               = byteArrayOf(0x90.toByte(), 0x00)
+        private val SW_FILE_NOT_FOUND   = byteArrayOf(0x6A.toByte(), 0x82.toByte())
+        private val SW_UNKNOWN          = byteArrayOf(0x6F.toByte(), 0x00)
+
+        // ── File IDs ─────────────────────────────────────────────────────────
+        private val CC_FILE_ID   = byteArrayOf(0xE1.toByte(), 0x03.toByte())
+        private val NDEF_FILE_ID = byteArrayOf(0xE1.toByte(), 0x04.toByte())
+
+        // ── NDEF Application AID ─────────────────────────────────────────────
+        private val NDEF_AID = byteArrayOf(
+            0xD2.toByte(), 0x76.toByte(), 0x00.toByte(), 0x00.toByte(),
+            0x85.toByte(), 0x01.toByte(), 0x01.toByte()
+        )
+
+        // ── Capability Container (CC) file ───────────────────────────────────
+        // Standard 15-byte CC for a Type 4 Tag:
+        //   Bytes 0-1 : CC length (0x000F = 15)
+        //   Byte  2   : Mapping version (0x20 = v2.0)
+        //   Bytes 3-4 : Max R-APDU data size (0x007F = 127)
+        //   Bytes 5-6 : Max C-APDU data size (0x007F = 127)
+        //   Bytes 7-8 : NDEF File Control TLV tag+length (0x04, 0x06)
+        //   Bytes 9-10: NDEF file ID (0xE104)
+        //   Bytes 11-12: Max NDEF file size (0x0400 = 1024)
+        //   Byte  13  : Read access (0x00 = open)
+        //   Byte  14  : Write access (0xFF = no write)
+        private val CC_FILE = byteArrayOf(
+            0x00, 0x0F,
+            0x20,
+            0x00, 0x7F,
+            0x00, 0x7F,
+            0x04, 0x06,
+            0xE1.toByte(), 0x04,
+            0x04, 0x00,
+            0x00,
+            0xFF.toByte()
+        )
+
+        // ── Shared NDEF payload slot ─────────────────────────────────────────
+        // Written by NfcViewModel, read by processCommandApdu().
+        // Volatile is sufficient — single writer, single reader on binder thread.
+        @Volatile
+        var ndefFileBytes: ByteArray? = null
+    }
+
+    // Which file is currently selected (null = NDEF app selected, no file yet)
+    private var selectedFileId: ByteArray? = null
+
+    override fun processCommandApdu(apdu: ByteArray, extras: Bundle?): ByteArray {
+        Log.d(TAG, "APDU IN: ${apdu.toHex()}")
+
+        if (apdu.size < 4) return SW_UNKNOWN
+
+        val ins = apdu[1]
+
+        return when {
+            // ── SELECT (INS = 0xA4) ──────────────────────────────────────────
+            ins == 0xA4.toByte() -> handleSelect(apdu)
+
+            // ── READ BINARY (INS = 0xB0) ─────────────────────────────────────
+            ins == 0xB0.toByte() -> handleReadBinary(apdu)
+
+            else -> SW_UNKNOWN
+        }.also { Log.d(TAG, "APDU OUT: ${it.toHex()}") }
+    }
+
+    private fun handleSelect(apdu: ByteArray): ByteArray {
+        if (apdu.size < 5) return SW_UNKNOWN
+        val dataLen = apdu[4].toInt() and 0xFF
+        if (apdu.size < 5 + dataLen) return SW_UNKNOWN
+        val data = apdu.copyOfRange(5, 5 + dataLen)
+
+        return when {
+            data.contentEquals(NDEF_AID) -> {
+                selectedFileId = null          // app selected, no file yet
+                Log.d(TAG, "SELECT NDEF Application OK")
+                SW_OK
+            }
+            data.contentEquals(CC_FILE_ID) -> {
+                selectedFileId = CC_FILE_ID
+                Log.d(TAG, "SELECT CC file OK")
+                SW_OK
+            }
+            data.contentEquals(NDEF_FILE_ID) -> {
+                selectedFileId = NDEF_FILE_ID
+                Log.d(TAG, "SELECT NDEF file OK")
+                SW_OK
+            }
+            else -> {
+                Log.w(TAG, "SELECT unknown file: ${data.toHex()}")
+                SW_FILE_NOT_FOUND
+            }
+        }
+    }
+
+    private fun handleReadBinary(apdu: ByteArray): ByteArray {
+        if (apdu.size < 5) return SW_UNKNOWN
+        val offset = ((apdu[2].toInt() and 0xFF) shl 8) or (apdu[3].toInt() and 0xFF)
+        val length = apdu[4].toInt() and 0xFF
+
+        val fileData: ByteArray = when {
+            selectedFileId != null && selectedFileId!!.contentEquals(CC_FILE_ID) ->
+                CC_FILE
+            selectedFileId != null && selectedFileId!!.contentEquals(NDEF_FILE_ID) -> {
+                ndefFileBytes ?: run {
+                    Log.w(TAG, "READ BINARY: no NDEF data loaded")
+                    return SW_FILE_NOT_FOUND
+                }
+            }
+            else -> return SW_FILE_NOT_FOUND
+        }
+
+        if (offset >= fileData.size) return SW_FILE_NOT_FOUND
+        val end   = minOf(offset + length, fileData.size)
+        val chunk = fileData.copyOfRange(offset, end)
+        return chunk + SW_OK
+    }
+
+    override fun onDeactivated(reason: Int) {
+        Log.d(TAG, "HCE deactivated, reason=$reason")
+        selectedFileId = null
+    }
+
+    // ── Helper ───────────────────────────────────────────────────────────────
+    private fun ByteArray.toHex(): String =
+        joinToString("") { "%02X".format(it) }
+}
+

app/src/main/java/com/bitcointxoko/gudariwallet/ui/nfc/NfcViewModel.kt

@@ -1,13 +1,17 @@
-// ui/nfc/NfcViewModel.kt
 package com.bitcointxoko.gudariwallet.ui.nfc
 
+import android.content.ComponentName
+import android.content.Context
+import android.nfc.NfcAdapter
 import android.nfc.NdefMessage
 import android.nfc.NdefRecord
 import android.nfc.Tag
+import android.nfc.tech.IsoDep
 import android.nfc.tech.Ndef
 import android.nfc.tech.NdefFormatable
 import android.util.Log
 import androidx.lifecycle.ViewModel
+import com.bitcointxoko.gudariwallet.ui.nfc.NdefHceService
 import com.bitcointxoko.gudariwallet.ui.NfcOfferState
 import com.bitcointxoko.gudariwallet.util.SendInputDetector
 import com.bitcointxoko.gudariwallet.util.SendInputType
@@ -16,129 +20,60 @@ import kotlinx.coroutines.flow.StateFlow
 
 private const val TAG = "NfcViewModel"
 
-class NfcViewModel(
+class NfcViewModel : ViewModel() {
-    // Same lambda pattern as ClipboardViewModel — no peer VM dependencies.
-    private val ownInvoice : () -> String?,
-    private val ownAddress : () -> String?,
-) : ViewModel() {
 
-    // ── Broadcast state ───────────────────────────────────────────────────────────
+    // ── NFC receive (HCE emulation) ──────────────────────────────────────────
 
-    sealed interface NfcBroadcastState {
+    private val _isNfcEmulating = MutableStateFlow(false)
-        data object Idle        : NfcBroadcastState
+    val isNfcEmulating: StateFlow<Boolean> = _isNfcEmulating
-        data object WaitingForTap : NfcBroadcastState   // button pressed, awaiting tag
-        data object Success     : NfcBroadcastState
-        data class  Error(val message: String) : NfcBroadcastState
-    }
-    private val _nfcOfferState = MutableStateFlow<NfcOfferState>(NfcOfferState.None)
-    val nfcOfferState: StateFlow<NfcOfferState> = _nfcOfferState
 
-    private val _broadcastState = MutableStateFlow<NfcBroadcastState>(NfcBroadcastState.Idle)
+    /**
-    val broadcastState: StateFlow<NfcBroadcastState> = _broadcastState
+     * Start emulating an NFC tag containing [uri] (e.g. "lightning:lnbc...").
-    private var pendingBroadcastPayload: String? = null
+     * Builds the NDEF file bytes and loads them into NdefHceService.
-
+     */
-    fun startBroadcast(payload: String) {
+    fun startEmulating(uri: String) {
-        pendingBroadcastPayload = payload
+        Log.d(TAG, "startEmulating: $uri")
-        _broadcastState.value = NfcBroadcastState.WaitingForTap
+        NdefHceService.ndefFileBytes = buildNdefFileBytes(uri)
-        Log.d(TAG, "startBroadcast: waiting for tag tap, payload=$payload")
+        _isNfcEmulating.value = true
-    }
-
-    fun cancelBroadcast() {
-        pendingBroadcastPayload = null
-        _broadcastState.value = NfcBroadcastState.Idle
-    }
-
-    fun dismissBroadcastResult() {
-        _broadcastState.value = NfcBroadcastState.Idle
     }
 
     /**
-     * Called from onTagDiscovered. If a broadcast is pending, write to the tag
+     * Stop emulating — clears the NDEF payload from the HCE service.
-     * instead of treating it as an incoming payment offer.
-     * Returns true if the tag was consumed for writing (caller should not process
-     * it as an incoming offer).
      */
-    fun tryWriteToTag(tag: Tag): Boolean {
+    fun stopEmulating() {
-        val payload = pendingBroadcastPayload ?: return false
+        Log.d(TAG, "stopEmulating")
-
+        NdefHceService.ndefFileBytes = null
-        val record = if (payload.startsWith("http://") || payload.startsWith("https://")
+        _isNfcEmulating.value = false
-            || payload.startsWith("lnurl") || payload.startsWith("bitcoin:")
-        ) {
-            // URI record
-            NdefRecord.createUri(payload)
-        } else {
-            // Text record (bolt11, lightning address, etc.)
-            NdefRecord.createTextRecord("en", payload)
     }
 
-        val message = NdefMessage(arrayOf(record))
+    override fun onCleared() {
-
+        super.onCleared()
-        return try {
+        stopEmulating()
-            val ndef = Ndef.get(tag)
-            if (ndef != null) {
-                ndef.connect()
-                if (!ndef.isWritable) {
-                    _broadcastState.value = NfcBroadcastState.Error("Tag is read-only")
-                    return true
-                }
-                if (ndef.maxSize < message.toByteArray().size) {
-                    _broadcastState.value = NfcBroadcastState.Error("Tag too small")
-                    return true
-                }
-                ndef.writeNdefMessage(message)
-                ndef.close()
-            } else {
-                // Try to format an unformatted tag
-                val formatable = NdefFormatable.get(tag)
-                    ?: run {
-                        _broadcastState.value = NfcBroadcastState.Error("Tag not NDEF compatible")
-                        return true
-                    }
-                formatable.connect()
-                formatable.format(message)
-                formatable.close()
-            }
-            pendingBroadcastPayload = null
-            _broadcastState.value = NfcBroadcastState.Success
-            Log.d(TAG, "tryWriteToTag: write successful")
-            true
-        } catch (e: Exception) {
-            Log.e(TAG, "tryWriteToTag: write failed", e)
-            _broadcastState.value = NfcBroadcastState.Error(e.message ?: "Write failed")
-            true
-        }
     }
 
-    // ── Called from WalletScreen's NFC reader-mode callback ──────────────────
+    // ── NFC send (tag reading) ───────────────────────────────────────────────
+
+    private val _nfcOfferState = MutableStateFlow<NfcOfferState>(NfcOfferState.None)
+    val nfcOfferState: StateFlow<NfcOfferState> = _nfcOfferState
+
+    /**
+     * Called from MainActivity.onNewIntent when an NFC tag is discovered.
+     * Reads the NDEF message from the tag and checks if it contains a
+     * recognisable payment URI.
+     */
     fun onTagDiscovered(tag: Tag) {
-        // If a broadcast is pending, write to the tag and stop
+        Log.d(TAG, "onTagDiscovered: ${tag.id?.toHex()}")
-        if (tryWriteToTag(tag)) return
-        // Otherwise, decode and offer as incoming payment
-        val raw = decodeNdefTag(tag)
-        Log.d(TAG, "onTagDiscovered decoded: $raw")
-        onNfcTagRead(raw)
-    }
 
-    fun onNfcTagRead(text: String?) {
+        val text = readNdefText(tag) ?: run {
-        val trimmed = text?.trim().takeIf { !it.isNullOrBlank() } ?: return
+            Log.w(TAG, "Could not read NDEF from tag")
-
-        // Guard: ignore our own invoice
-        val invoice = ownInvoice()
-        if (invoice != null && trimmed.equals(invoice, ignoreCase = true)) {
-            Log.d(TAG, "Skipping own invoice")
-            return
-        }
-
-        // Guard: ignore our own lightning address
-        val address = ownAddress()
-        if (address != null && trimmed.equals(address, ignoreCase = true)) {
-            Log.d(TAG, "Skipping own lightning address")
             return
         }
 
+        Log.d(TAG, "Tag NDEF text: $text")
+        val trimmed = text.trim()
         val type = SendInputDetector.detect(trimmed)
         if (type == SendInputType.Unknown) {
-            Log.d(TAG, "Unknown input type, ignoring")
+            Log.d(TAG, "Tag content not a recognised payment URI")
             return
         }
 
@@ -149,55 +84,118 @@ class NfcViewModel(
         _nfcOfferState.value = NfcOfferState.None
     }
 
-    // ── NDEF decoding ─────────────────────────────────────────────────────────
+    // ── NDEF reading ─────────────────────────────────────────────────────────
-    private fun decodeNdefTag(tag: Tag): String? {
+
-        val ndef = Ndef.get(tag) ?: return null
+    private fun readNdefText(tag: Tag): String? {
-        return try {
+        // Try standard NDEF first (covers Type 1–5 tags, NTAG21x, etc.)
+        Ndef.get(tag)?.use { ndef ->
             ndef.connect()
-            val message = ndef.ndefMessage ?: return null
+            val msg = ndef.ndefMessage ?: ndef.cachedNdefMessage ?: return null
-            val record  = message.records.firstOrNull() ?: return null
+            return extractUri(msg)
-            decodeNdefRecord(record)
-        } catch (e: Exception) {
-            Log.e(TAG, "NDEF read failed", e)
-            null
-        } finally {
-            runCatching { ndef.close() }
-        }
         }
 
-    private fun decodeNdefRecord(record: NdefRecord): String? = when (record.tnf) {
+        // Try NdefFormatable (blank tags — nothing to read)
-        NdefRecord.TNF_WELL_KNOWN -> when {
+        // Try IsoDep last (Type 4 / ISO-DEP tags like Bolt Cards)
-            // URI record (https://..., lnurl:..., bitcoin:..., etc.)
+        IsoDep.get(tag)?.use { isoDep ->
-            record.type.contentEquals(NdefRecord.RTD_URI) ->
+            isoDep.connect()
-                record.toUri()?.toString()
+            isoDep.timeout = 3000
-
+            val msg = readNdefFromIsoDep(isoDep) ?: return null
-            // Plain text record (lnbc..., user@domain.com, etc.)
+            return extractUri(msg)
-            record.type.contentEquals(NdefRecord.RTD_TEXT) ->
-                decodeTextRecord(record.payload)
-
-            else -> null
         }
-        // Absolute URI (some tags encode this way)
-        NdefRecord.TNF_ABSOLUTE_URI ->
-            String(record.payload, Charsets.UTF_8)
 
-        else -> null
+        return null
     }
 
     /**
-     * NDEF Text record payload layout:
+     * Reads an NDEF message from an ISO-DEP (Type 4) tag by replaying the
-     *   byte 0      : status byte (bit7 = UTF-16 flag, bits 5-0 = lang code length)
+     * same APDU sequence our HCE service responds to.
-     *   bytes 1..n  : language code (e.g. "en")
-     *   bytes n+1.. : the actual text
      */
-    private fun decodeTextRecord(payload: ByteArray): String? {
+    private fun readNdefFromIsoDep(isoDep: IsoDep): NdefMessage? {
-        if (payload.isEmpty()) return null
+        fun ByteArray.sw(): Int =
-        val statusByte  = payload[0].toInt() and 0xFF
+            ((this[size - 2].toInt() and 0xFF) shl 8) or (this[size - 1].toInt() and 0xFF)
-        val isUtf16     = (statusByte and 0x80) != 0
+        fun ByteArray.data(): ByteArray = copyOfRange(0, size - 2)
-        val langLength  = statusByte and 0x3F
+        fun ByteArray.isOk() = sw() == 0x9000
-        val textStart   = 1 + langLength
+
-        if (textStart > payload.size) return null
+        // 1. SELECT NDEF Application
-        val charset = if (isUtf16) Charsets.UTF_16 else Charsets.UTF_8
+        val selectApp = byteArrayOf(
-        return String(payload, textStart, payload.size - textStart, charset)
+            0x00, 0xA4.toByte(), 0x04, 0x00, 0x07,
+            0xD2.toByte(), 0x76, 0x00, 0x00, 0x85.toByte(), 0x01, 0x01,
+            0x00
+        )
+        if (!isoDep.transceive(selectApp).isOk()) return null
+
+        // 2. SELECT CC file
+        val selectCc = byteArrayOf(0x00, 0xA4.toByte(), 0x00, 0x0C, 0x02, 0xE1.toByte(), 0x03)
+        if (!isoDep.transceive(selectCc).isOk()) return null
+
+        // 3. READ CC (15 bytes)
+        val readCc = byteArrayOf(0x00, 0xB0.toByte(), 0x00, 0x00, 0x0F)
+        val ccResp = isoDep.transceive(readCc)
+        if (!ccResp.isOk() || ccResp.size < 17) return null
+        val cc = ccResp.data()
+
+        // Parse NDEF file ID and max size from CC
+        val ndefFileId = cc.copyOfRange(9, 11)
+        val maxNdefSize = ((cc[11].toInt() and 0xFF) shl 8) or (cc[12].toInt() and 0xFF)
+
+        // 4. SELECT NDEF file
+        val selectNdef = byteArrayOf(0x00, 0xA4.toByte(), 0x00, 0x0C, 0x02) + ndefFileId
+        if (!isoDep.transceive(selectNdef).isOk()) return null
+
+        // 5. READ NDEF length (first 2 bytes)
+        val readLen = byteArrayOf(0x00, 0xB0.toByte(), 0x00, 0x00, 0x02)
+        val lenResp = isoDep.transceive(readLen)
+        if (!lenResp.isOk()) return null
+        val ndefLen = ((lenResp[0].toInt() and 0xFF) shl 8) or (lenResp[1].toInt() and 0xFF)
+        if (ndefLen == 0 || ndefLen > maxNdefSize) return null
+
+        // 6. READ NDEF data
+        val readData = byteArrayOf(
+            0x00, 0xB0.toByte(),
+            0x00, 0x02,                          // offset 2 (skip the 2-byte length)
+            ndefLen.coerceAtMost(0xFF).toByte()
+        )
+        val dataResp = isoDep.transceive(readData)
+        if (!dataResp.isOk()) return null
+
+        return runCatching { NdefMessage(dataResp.data()) }.getOrNull()
     }
+
+    // ── NDEF helpers ─────────────────────────────────────────────────────────
+
+    private fun extractUri(msg: NdefMessage): String? {
+        for (record in msg.records) {
+            val uri = record.toUri()
+            if (uri != null) return uri.toString()
+
+            // Fallback: plain text record
+            if (record.tnf == NdefRecord.TNF_WELL_KNOWN &&
+                record.type.contentEquals(NdefRecord.RTD_TEXT)
+            ) {
+                val payload = record.payload
+                val langLen = payload[0].toInt() and 0x3F
+                return String(payload, 1 + langLen, payload.size - 1 - langLen, Charsets.UTF_8)
+            }
+        }
+        return null
+    }
+
+    // ── NDEF file builder (for HCE emulation) ────────────────────────────────
+
+    /**
+     * Builds the raw bytes of the NDEF file as served by the HCE service.
+     * Layout: [2-byte NDEF length (big-endian)] [NDEF message bytes]
+     */
+    private fun buildNdefFileBytes(uri: String): ByteArray {
+        val record = NdefRecord.createUri(uri)
+        val ndefMessage = NdefMessage(record)
+        val msgBytes = ndefMessage.toByteArray()
+        val len = msgBytes.size
+        return byteArrayOf(
+            ((len shr 8) and 0xFF).toByte(),
+            (len and 0xFF).toByte()
+        ) + msgBytes
+    }
+
+    private fun ByteArray.toHex(): String = joinToString("") { "%02X".format(it) }
 }

app/src/main/java/com/bitcointxoko/gudariwallet/ui/receive/QrDisplayCard.kt

@@ -2,55 +2,57 @@ package com.bitcointxoko.gudariwallet.ui.receive
 
 import android.content.ClipData
 import android.graphics.Bitmap
+import android.graphics.Color
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.aspectRatio
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.ContentCopy
+import androidx.compose.material.icons.filled.Nfc
 import androidx.compose.material.icons.filled.Share
+import androidx.compose.material.icons.filled.WbSunny
+import androidx.compose.material.icons.outlined.Nfc
+import androidx.compose.material3.FilledTonalIconButton
 import androidx.compose.material3.Icon
-import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.IconButton
-import androidx.compose.material3.Text
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.asImageBitmap
+import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.ClipEntry
 import androidx.compose.ui.platform.LocalClipboard
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.unit.dp
+import androidx.core.graphics.createBitmap
+import androidx.core.graphics.set
 import com.bitcointxoko.gudariwallet.util.IntentUtils
 import com.google.zxing.BarcodeFormat
 import com.google.zxing.qrcode.QRCodeWriter
 import kotlinx.coroutines.launch
-import android.graphics.Color
-import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.aspectRatio
-import androidx.compose.material.icons.filled.Nfc
-import androidx.compose.material3.IconButton
-import androidx.compose.ui.Alignment
-import androidx.compose.ui.layout.ContentScale
-import androidx.core.graphics.createBitmap
-import androidx.core.graphics.set
-
 
 /**
- * QR image followed by Copy / Share / Brightness action row.
+ * QR image followed by Share / Copy / Brightness / NFC icon-button row.
  *
- * @param content              What to encode into QR
+ * @param content            What to encode into the QR code.
- * @param contentDescription   Accessibility label for the image.
+ * @param contentDescription Accessibility label for the QR image.
- * @param clipLabel            Label used when writing to the clipboard (e.g. "Lightning Address").
+ * @param clipLabel          Label used when writing to the clipboard.
  * @param shareTitle         Chooser title for the share intent.
  * @param textToCopy         The raw string placed on the clipboard and shared.
  * @param brightnessOn       Current brightness-boost state.
  * @param onToggleBrightness Called when the brightness button is tapped.
+ * @param isNfcEmulating     Current NFC emulation state (null = hide NFC button).
+ * @param onToggleNfc        Called when the NFC button is tapped.
+ * @param nfcEnabled         Whether the NFC button should be interactive (e.g. false when invoice expired).
  */
 @Composable
 internal fun QrDisplayCard(
@@ -62,11 +64,12 @@ internal fun QrDisplayCard(
     textToCopy           : String,
     brightnessOn         : Boolean,
     onToggleBrightness   : () -> Unit,
-    onNfcBroadcast       : (() -> Unit)? = null,
+    isNfcEmulating       : Boolean? = null,   // null → no NFC button shown
+    onToggleNfc          : (() -> Unit)? = null,
+    nfcEnabled           : Boolean = true,
     qrModifier           : Modifier = Modifier.size(260.dp)
 ) {
     val bitmap    = remember(content) { generateQrBitmap(content).asImageBitmap() }
-
     val context   = LocalContext.current
     val clipboard = LocalClipboard.current
     val scope     = rememberCoroutineScope()
@@ -76,6 +79,7 @@ internal fun QrDisplayCard(
         horizontalAlignment = Alignment.CenterHorizontally,
         verticalArrangement = Arrangement.spacedBy(8.dp)
     ) {
+        // ── QR image ─────────────────────────────────────────────────────────
         Image(
             bitmap             = bitmap,
             contentDescription = contentDescription,
@@ -85,39 +89,72 @@ internal fun QrDisplayCard(
                 .clip(RoundedCornerShape(12.dp))
         )
 
+        // ── Action row: Share | Copy | Brightness | NFC ───────────────────────
         Row(
-            horizontalArrangement = Arrangement.spacedBy(8.dp),
+            modifier              = Modifier.fillMaxWidth(),
-            modifier              = Modifier.fillMaxWidth()
+            horizontalArrangement = Arrangement.spacedBy(8.dp, Alignment.CenterHorizontally),
+            verticalAlignment     = Alignment.CenterVertically
         ) {
-            OutlinedButton(
+            // Share
-                onClick  = { IntentUtils.shareText(context, textToCopy, shareTitle) },
+            IconButton(
-                modifier = Modifier.weight(1f)
+                onClick = { IntentUtils.shareText(context, textToCopy, shareTitle) }
             ) {
-                Icon(Icons.Filled.Share, contentDescription = "Share",
+                Icon(
-                    modifier = Modifier.size(18.dp))
+                    imageVector        = Icons.Filled.Share,
-                Spacer(Modifier.width(6.dp))
+                    contentDescription = "Share",
-                Text("Share")
+                    tint               = MaterialTheme.colorScheme.onSurfaceVariant
+                )
             }
-            OutlinedButton(
+
+            // Copy
+            IconButton(
                 onClick = {
                     scope.launch {
                         clipboard.setClipEntry(
                             ClipEntry(ClipData.newPlainText(clipLabel, textToCopy))
                         )
                     }
-                },
-                modifier = Modifier.weight(1f)
-            ) {
-                Icon(Icons.Filled.ContentCopy, contentDescription = "Copy",
-                    modifier = Modifier.size(18.dp))
-                Spacer(Modifier.width(6.dp))
-                Text("Copy")
                 }
-            BrightnessToggleButton(isOn = brightnessOn, onToggle = onToggleBrightness)
+            ) {
+                Icon(
+                    imageVector        = Icons.Filled.ContentCopy,
+                    contentDescription = "Copy",
+                    tint               = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+            }
+
+            // Brightness
+            FilledTonalIconButton(
+                onClick = onToggleBrightness
+            ) {
+                Icon(
+                    imageVector        = Icons.Filled.WbSunny,
+                    contentDescription = if (brightnessOn) "Reduce brightness" else "Boost brightness",
+                    tint               = if (brightnessOn) MaterialTheme.colorScheme.primary
+                    else             MaterialTheme.colorScheme.onSurfaceVariant
+                )
+            }
+
+            // NFC — only shown when caller passes isNfcEmulating
+            if (isNfcEmulating != null && onToggleNfc != null) {
+                FilledTonalIconButton(
+                    onClick  = onToggleNfc,
+                    enabled  = nfcEnabled
+                ) {
+                    Icon(
+                        imageVector        = if (isNfcEmulating) Icons.Filled.Nfc else Icons.Outlined.Nfc,
+                        contentDescription = if (isNfcEmulating) "Stop NFC sharing" else "Share via NFC",
+                        tint               = if (isNfcEmulating) MaterialTheme.colorScheme.primary
+                        else                MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                }
+            }
         }
     }
 }
 
+// ── QR generation ────────────────────────────────────────────────────────────
+
 private const val QR_BITMAP_SIZE = 512
 
 private fun generateQrBitmap(content: String): Bitmap {
@@ -133,4 +170,3 @@ private fun generateQrBitmap(content: String): Bitmap {
                 this[x, y] = if (bits[x, y]) Color.BLACK else Color.WHITE
     }
 }
-

app/src/main/java/com/bitcointxoko/gudariwallet/ui/receive/ReceiveScreen.kt

@@ -21,10 +21,14 @@ import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.CheckCircle
 import androidx.compose.material.icons.filled.Download
+import androidx.compose.material.icons.filled.Nfc
+import androidx.compose.material.icons.filled.QrCode
+import androidx.compose.material.icons.outlined.Nfc
 import androidx.compose.material3.Button
 import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
 import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.FilledTonalIconButton
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.LinearProgressIndicator
@@ -59,13 +63,15 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.bitcointxoko.gudariwallet.ui.ReceiveState
 import com.bitcointxoko.gudariwallet.ui.WalletViewModel
 import com.bitcointxoko.gudariwallet.ui.components.UnitWheelPicker
+import com.bitcointxoko.gudariwallet.ui.nfc.NfcViewModel
 import com.bitcointxoko.gudariwallet.util.fiatLabel
 import kotlinx.coroutines.delay
 
 @Composable
 fun ReceiveScreen(
-    vm: WalletViewModel,
+    vm                       : WalletViewModel,
-    onNavigateToPaymentDetail : (checkingId: String) -> Unit
+    nfcVm                    : NfcViewModel,        // ← new
+    onNavigateToPaymentDetail: (checkingId: String) -> Unit
 ) {
     val receiveState     by vm.receiveState.collectAsStateWithLifecycle()
     val lightningAddress by vm.lightningAddress.collectAsStateWithLifecycle()
@@ -87,15 +93,25 @@ fun ReceiveScreen(
         brightnessOn = !brightnessOn
     }
 
+    // Stop NFC emulation and reset receive state when leaving the screen
     DisposableEffect(Unit) {
         onDispose {
             val lp = window.attributes
             lp.screenBrightness = originalBrightness
             window.attributes = lp
+            nfcVm.stopEmulating()   // ← new: clean up HCE on exit
             vm.resetReceiveState()
         }
     }
 
+    // Also stop emulating if the invoice is reset mid-session
+    // (e.g. user taps "Cancel" or "New Invoice")
+    LaunchedEffect(receiveState) {
+        if (receiveState !is ReceiveState.InvoiceReady) {
+            nfcVm.stopEmulating()
+        }
+    }
+
     Box(modifier = Modifier.fillMaxSize()) {
         if (receiveState !is ReceiveState.InvoiceReady) {
             Column(
@@ -188,11 +204,15 @@ fun ReceiveScreen(
                 fiatCurrency       = fiatCurrency,
                 brightnessOn       = brightnessOn,
                 onToggleBrightness = onToggleBrightness,
+                nfcVm              = nfcVm,             // ← new
                 onReset            = { vm.resetReceiveState() }
             )
         }
     }
 }
+
+// ── LnurlWithdrawSheet (unchanged) ───────────────────────────────────────────
+
 @Composable
 private fun LnurlWithdrawSheet(
     state    : ReceiveState.LnurlWithdrawReady,
@@ -309,8 +329,13 @@ private fun LnurlWithdrawSheet(
         }
     }
 }
+
+// ── AmountUnit (unchanged) ────────────────────────────────────────────────────
+
 private enum class AmountUnit { SATS, FIAT }
 
+// ── ReceiveIdleContent (unchanged) ───────────────────────────────────────────
+
 @Composable
 private fun ReceiveIdleContent(
     fiatRate           : Double?,
@@ -326,10 +351,8 @@ private fun ReceiveIdleContent(
     val focusManager       = LocalFocusManager.current
     val keyboardController = LocalSoftwareKeyboardController.current
 
-    // Wrap the toggle so that opening the address card always clears focus + keyboard
     val onToggleAddressWithDismiss = {
         if (!showAddress) {
-            // About to show address — dismiss keyboard and clear focus first
             keyboardController?.hide()
             focusManager.clearFocus()
         }
@@ -347,7 +370,6 @@ private fun ReceiveIdleContent(
     ) {
         Spacer(Modifier.height(8.dp))
 
-        // ── Header row ────────────────────────────────────────────────────────
         Row(
             modifier              = Modifier.fillMaxWidth(),
             verticalAlignment     = Alignment.CenterVertically,
@@ -370,7 +392,6 @@ private fun ReceiveIdleContent(
             }
         }
 
-        // ── Lightning address card ────────────────────────────────────────────
         AnimatedVisibility(visible = showAddress && lightningAddress != null) {
             Card(
                 colors   = CardDefaults.cardColors(
@@ -417,7 +438,7 @@ private fun ReceiveIdleContent(
                 fiatRate          = fiatRate,
                 fiatCurrency      = fiatCurrency,
                 addressShowing    = showAddress,
-                onCollapseAddress = onToggleAddressWithDismiss,  // ← consistent: same wrapper
+                onCollapseAddress = onToggleAddressWithDismiss,
                 onNext            = { text, unit ->
                     confirmedAmountText = text
                     confirmedUnit       = unit
@@ -439,6 +460,9 @@ private fun ReceiveIdleContent(
         }
     }
 }
+
+// ── AmountStepContent (unchanged) ────────────────────────────────────────────
+
 @Composable
 private fun AmountStepContent(
     fiatRate          : Double?,
@@ -536,6 +560,9 @@ private fun AmountStepContent(
         }
     }
 }
+
+// ── MemoStepContent (unchanged) ──────────────────────────────────────────────
+
 @Composable
 private fun MemoStepContent(
     confirmedSats   : Long,
@@ -578,6 +605,9 @@ private fun MemoStepContent(
         }
     }
 }
+
+// ── ReceiveInvoiceContent — NFC toggle added ──────────────────────────────────
+
 @Composable
 private fun ReceiveInvoiceContent(
     state              : ReceiveState.InvoiceReady,
@@ -585,8 +615,11 @@ private fun ReceiveInvoiceContent(
     fiatCurrency       : String?,
     brightnessOn       : Boolean,
     onToggleBrightness : () -> Unit,
+    nfcVm              : NfcViewModel,
     onReset            : () -> Unit
 ) {
+    val isEmulating by nfcVm.isNfcEmulating.collectAsStateWithLifecycle()
+
     var secondsLeft by remember {
         mutableLongStateOf(
             (state.expiresAt - System.currentTimeMillis() / 1000L).coerceAtLeast(0L)
@@ -622,9 +655,7 @@ private fun ReceiveInvoiceContent(
             )
         }
 
-        // ── QR — weight(1f) claims all remaining vertical space ───────────────
+        // ── QR + action row (Share / Copy / Brightness / NFC) ─────────────────
-        // modifier targets the QrDisplayCard's outer Column (gives it the height)
-        // qrModifier targets the Image inside (fills that height, stays square)
         QrDisplayCard(
             content            = state.bolt11.uppercase(),
             contentDescription = "Lightning invoice QR code",
@@ -633,23 +664,30 @@ private fun ReceiveInvoiceContent(
             textToCopy         = state.bolt11,
             brightnessOn       = brightnessOn,
             onToggleBrightness = onToggleBrightness,
+            isNfcEmulating     = isEmulating,
+            onToggleNfc        = {
+                if (isEmulating) nfcVm.stopEmulating()
+                else             nfcVm.startEmulating("lightning:${state.bolt11}")
+            },
+            nfcEnabled         = !isExpired,
             modifier           = Modifier
-                .weight(1f)        // outer Column gets all remaining height
+                .weight(1f)
                 .fillMaxWidth(),
             qrModifier         = Modifier
-                .fillMaxWidth()    // Image fills the column width
+                .fillMaxWidth()
-                .weight(1f)        // Image also takes remaining height inside QrDisplayCard's Column
+                .weight(1f)
         )
 
-        // ── Status ────────────────────────────────────────────────────────────
+        // ── Status row — restored to original simple format ───────────────────
         Row(
+            modifier          = Modifier.fillMaxWidth(),
             verticalAlignment = Alignment.CenterVertically,
-            horizontalArrangement = Arrangement.spacedBy(8.dp)
+            horizontalArrangement = Arrangement.spacedBy(8.dp, Alignment.CenterHorizontally)
         ) {
             if (!isExpired) {
                 CircularProgressIndicator(modifier = Modifier.size(16.dp), strokeWidth = 2.dp)
                 Text(
-                    text  = "Waiting for payment…",
+                    text  = "Waiting…",
                     style = MaterialTheme.typography.bodySmall,
                     color = MaterialTheme.colorScheme.onSurfaceVariant
                 )
@@ -676,6 +714,9 @@ private fun ReceiveInvoiceContent(
     }
 }
 
+
+// ── ReceiveSuccessContent (unchanged) ────────────────────────────────────────
+
 @Composable
 private fun ReceiveSuccessContent(
     amountSats   : Long,
@@ -701,7 +742,6 @@ private fun ReceiveSuccessContent(
         Spacer(Modifier.height(16.dp))
         Text("Payment Received!", style = MaterialTheme.typography.headlineSmall)
         Spacer(Modifier.height(8.dp))
-        // AmountDisplay renders both the sats line and the fiat subtitle
         AmountDisplay(amountSats = amountSats, fiatLabel = fiatLabel)
         if (!memo.isNullOrBlank()) {
             Spacer(Modifier.height(4.dp))

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

@@ -1,3 +1,4 @@
 <resources>
     <string name="app_name">Gudari Wallet</string>
+    <string name="nfc_hce_description">Gudari Wallet NFC payment sharing</string>
 </resources>

app/src/main/res/xml/apduservice.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<host-apdu-service
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:description="@string/nfc_hce_description"
+    android:requireDeviceUnlock="false">
+
+    <aid-group
+        android:description="@string/nfc_hce_description"
+        android:category="other">
+        <!--
+            NFC Forum Type 4 Tag AID.
+            Any NFC reader that supports NDEF will SELECT this AID first.
+        -->
+        <aid-filter android:name="D2760000850101" />
+    </aid-group>
+
+</host-apdu-service>