feat: add nfc step 1

app/src/main/AndroidManifest.xml

@@ -7,8 +7,11 @@
     <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.NFC" />
+
 
     <uses-feature android:name="android.hardware.camera" android:required="false" />
+    <uses-feature android:name="android.hardware.nfc" android:required="false" />
 
     <application
         android:allowBackup="true"

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

@@ -142,6 +142,15 @@ sealed interface ClipboardOfferState {
     ) : ClipboardOfferState
 }
 
+
+sealed interface NfcOfferState {
+    data object None : NfcOfferState
+    data class Detected(
+        val raw      : String,
+        val inputType: SendInputType
+    ) : NfcOfferState
+}
+
 /**
  * Shared interface for send states that represent a fully decoded invoice
  * ready for user confirmation. Allows ConfirmCardContent to accept either

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

@@ -25,6 +25,7 @@ import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.Send
 import androidx.compose.material.icons.filled.Close
 import androidx.compose.material.icons.filled.ContentPaste
+import androidx.compose.material.icons.filled.Nfc
 import androidx.compose.material.icons.filled.QrCode
 import androidx.compose.material.icons.filled.QrCodeScanner
 import androidx.compose.material3.CircularProgressIndicator
@@ -160,6 +161,36 @@ fun WalletScreen(
         }
     }
 
+    // ── NFC reader mode — register on composition, unregister on disposal ────────
+    val nfcAdapter = remember {
+        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()
+        }
+    }
+
     Scaffold(
         bottomBar = {
             if (showBottomBar) {
@@ -414,6 +445,70 @@ fun WalletScreen(
                     }
                 }
             }
+            // ── NFC banner — floats below clipboard banner, slides in from top ────────────
+            AnimatedVisibility(
+                visible  = nfcOffer is NfcOfferState.Detected,
+                enter    = slideInVertically(initialOffsetY = { -it }),
+                exit     = slideOutVertically(targetOffsetY = { -it }),
+                modifier = Modifier
+                    .align(Alignment.TopCenter)
+                    .zIndex(1f)
+                    .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
+                    val label = when (offer.inputType) {
+                        is SendInputType.Bolt11           -> "Invoice"
+                        is SendInputType.Lnurl            -> "LNURL"
+                        is SendInputType.LightningAddress -> "Lightning Address"
+                        else                              -> "Payment"
+                    }
+                    val subLabel = when (offer.inputType) {
+                        is SendInputType.Lnurl -> "Tap to open"
+                        else                   -> "Tap to pay"
+                    }
+                    Surface(
+                        color    = MaterialTheme.colorScheme.secondaryContainer,  // distinct from clipboard's primaryContainer
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .clickable {
+                                vm.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
+                                }
+                            }
+                    ) {
+                        Row(
+                            modifier          = Modifier.padding(horizontal = 16.dp, vertical = 10.dp),
+                            verticalAlignment = Alignment.CenterVertically
+                        ) {
+                            Icon(Icons.Filled.Nfc, contentDescription = null)
+                            Spacer(Modifier.width(12.dp))
+                            Column(Modifier.weight(1f)) {
+                                Text(
+                                    "$label detected via NFC",
+                                    style = MaterialTheme.typography.bodyMedium
+                                )
+                                Text(
+                                    subLabel,
+                                    style = MaterialTheme.typography.bodySmall,
+                                    color = MaterialTheme.colorScheme.onSecondaryContainer.copy(alpha = 0.7f)
+                                )
+                            }
+                            IconButton(onClick = { vm.dismissNfcOffer() }) {
+                                Icon(Icons.Default.Close, contentDescription = "Dismiss")
+                            }
+                        }
+                    }
+                }
+            }
         }
     }
 }

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

@@ -1,6 +1,7 @@
 package com.bitcointxoko.gudariwallet.ui
 
 import android.util.Log
+import androidx.annotation.VisibleForTesting
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.bitcointxoko.gudariwallet.api.LnurlScanResponse
@@ -16,6 +17,7 @@ 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
@@ -33,7 +35,8 @@ 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
@@ -62,9 +65,7 @@ class WalletViewModel(
     fun requestPayment(activity: FragmentActivity, subtitle: String, pay: () -> Unit) =
         sendVm.requestPayment(activity, subtitle, pay)
     fun resetSendState() = sendVm.resetSendState()
-    val clipboardOfferState: StateFlow<ClipboardOfferState> get() = clipboardVm.clipboardOfferState
+
-    fun checkClipboard(text: String?)  = clipboardVm.checkClipboard(text)
-    fun dismissClipboardOffer()        = clipboardVm.dismissClipboardOffer()
     val lightningAddress: StateFlow<String?> = lnAddressStore.lightningAddressFlow
         .stateIn(
             scope        = viewModelScope,
@@ -72,6 +73,21 @@ class WalletViewModel(
             initialValue = null
         )
 
+    val clipboardOfferState: StateFlow<ClipboardOfferState> get() = clipboardVm.clipboardOfferState
+    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

@@ -17,6 +17,7 @@ import com.bitcointxoko.gudariwallet.service.NodeAliasService
 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
 
@@ -45,12 +46,14 @@ class WalletViewModelFactory(private val app: Application) : ViewModelProvider.F
             }
         )
 
-//        val lightningAddress = MutableStateFlow<String?>(balancePrefs.lightningAddress)
-
         val clipboardVm = ClipboardViewModel(
             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() }
 
@@ -65,6 +68,7 @@ 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/nfc/NfcViewModel.kt

@@ -0,0 +1,203 @@
+// ui/nfc/NfcViewModel.kt
+package com.bitcointxoko.gudariwallet.ui.nfc
+
+import android.nfc.NdefMessage
+import android.nfc.NdefRecord
+import android.nfc.Tag
+import android.nfc.tech.Ndef
+import android.nfc.tech.NdefFormatable
+import android.util.Log
+import androidx.lifecycle.ViewModel
+import com.bitcointxoko.gudariwallet.ui.NfcOfferState
+import com.bitcointxoko.gudariwallet.util.SendInputDetector
+import com.bitcointxoko.gudariwallet.util.SendInputType
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+
+private const val TAG = "NfcViewModel"
+
+class NfcViewModel(
+    // Same lambda pattern as ClipboardViewModel — no peer VM dependencies.
+    private val ownInvoice : () -> String?,
+    private val ownAddress : () -> String?,
+) : ViewModel() {
+
+    // ── Broadcast state ───────────────────────────────────────────────────────────
+
+    sealed interface NfcBroadcastState {
+        data object Idle        : NfcBroadcastState
+        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
+    private var pendingBroadcastPayload: String? = null
+
+    fun startBroadcast(payload: String) {
+        pendingBroadcastPayload = payload
+        _broadcastState.value = NfcBroadcastState.WaitingForTap
+        Log.d(TAG, "startBroadcast: waiting for tag tap, payload=$payload")
+    }
+
+    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
+     * 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 {
+        val payload = pendingBroadcastPayload ?: return false
+
+        val record = if (payload.startsWith("http://") || payload.startsWith("https://")
+            || 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))
+
+        return try {
+            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 ──────────────────
+    fun onTagDiscovered(tag: Tag) {
+        // If a broadcast is pending, write to the tag and stop
+        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 trimmed = text?.trim().takeIf { !it.isNullOrBlank() } ?: return
+
+        // 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
+        }
+
+        val type = SendInputDetector.detect(trimmed)
+        if (type == SendInputType.Unknown) {
+            Log.d(TAG, "Unknown input type, ignoring")
+            return
+        }
+
+        _nfcOfferState.value = NfcOfferState.Detected(raw = trimmed, inputType = type)
+    }
+
+    fun dismissNfcOffer() {
+        _nfcOfferState.value = NfcOfferState.None
+    }
+
+    // ── NDEF decoding ─────────────────────────────────────────────────────────
+    private fun decodeNdefTag(tag: Tag): String? {
+        val ndef = Ndef.get(tag) ?: return null
+        return try {
+            ndef.connect()
+            val message = ndef.ndefMessage ?: return null
+            val record  = message.records.firstOrNull() ?: return null
+            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) {
+        NdefRecord.TNF_WELL_KNOWN -> when {
+            // URI record (https://..., lnurl:..., bitcoin:..., etc.)
+            record.type.contentEquals(NdefRecord.RTD_URI) ->
+                record.toUri()?.toString()
+
+            // Plain text record (lnbc..., user@domain.com, etc.)
+            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
+    }
+
+    /**
+     * NDEF Text record payload layout:
+     *   byte 0      : status byte (bit7 = UTF-16 flag, bits 5-0 = lang code length)
+     *   bytes 1..n  : language code (e.g. "en")
+     *   bytes n+1.. : the actual text
+     */
+    private fun decodeTextRecord(payload: ByteArray): String? {
+        if (payload.isEmpty()) return null
+        val statusByte  = payload[0].toInt() and 0xFF
+        val isUtf16     = (statusByte and 0x80) != 0
+        val langLength  = statusByte and 0x3F
+        val textStart   = 1 + langLength
+        if (textStart > payload.size) return null
+        val charset = if (isUtf16) Charsets.UTF_16 else Charsets.UTF_8
+        return String(payload, textStart, payload.size - textStart, charset)
+    }
+}

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

@@ -13,7 +13,6 @@ 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.Share
-import androidx.compose.material3.Button
 import androidx.compose.material3.Icon
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
@@ -34,7 +33,8 @@ import kotlinx.coroutines.launch
 import android.graphics.Color
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.aspectRatio
-import androidx.compose.foundation.layout.height
+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
@@ -54,6 +54,7 @@ import androidx.core.graphics.set
  */
 @Composable
 internal fun QrDisplayCard(
+    modifier             : Modifier = Modifier,
     content              : String,
     contentDescription   : String,
     clipLabel            : String,
@@ -61,7 +62,7 @@ internal fun QrDisplayCard(
     textToCopy           : String,
     brightnessOn         : Boolean,
     onToggleBrightness   : () -> Unit,
-    modifier             : Modifier = Modifier,
+    onNfcBroadcast       : (() -> Unit)? = null,
     qrModifier           : Modifier = Modifier.size(260.dp)
 ) {
     val bitmap = remember(content) { generateQrBitmap(content).asImageBitmap() }