feat: add sending by nfc

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

@@ -296,6 +296,7 @@ fun WalletScreen(
                 composable(TabItem.Send.route) {
                     SendScreen(
                         vm = vm,
+                        nfcVm = nfcVm,
                         onViewDetails = { checkingId ->
                             historyVm.refresh()
                             navController.navigate("payment_detail/$checkingId") {

app/src/main/java/com/bitcointxoko/gudariwallet/ui/send/SendScreen.kt

@@ -7,6 +7,7 @@ import androidx.compose.foundation.text.KeyboardActions
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.ContentPaste
+import androidx.compose.material.icons.filled.Nfc
 import androidx.compose.material3.*
 import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
@@ -21,8 +22,10 @@ import androidx.compose.ui.unit.dp
 import androidx.fragment.app.FragmentActivity
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.bitcointxoko.gudariwallet.ui.BalanceState
+import com.bitcointxoko.gudariwallet.ui.NfcOfferState
 import com.bitcointxoko.gudariwallet.ui.SendState
 import com.bitcointxoko.gudariwallet.ui.WalletViewModel
+import com.bitcointxoko.gudariwallet.ui.nfc.NfcViewModel
 import com.bitcointxoko.gudariwallet.util.SendInputDetector
 import com.bitcointxoko.gudariwallet.util.feePpm
 import com.bitcointxoko.gudariwallet.util.formatFiat
@@ -30,21 +33,38 @@ import com.bitcointxoko.gudariwallet.util.satsToFiat
 import kotlinx.coroutines.launch
 
 @Composable
-fun SendScreen(vm: WalletViewModel, onViewDetails: (paymentHash: String) -> Unit = {}) {
-    val sendState: SendState by vm.sendState.collectAsStateWithLifecycle()
-    var input by remember { mutableStateOf("") }
-    val context  = LocalContext.current
-    val activity = context as FragmentActivity
-    val clipboard = LocalClipboard.current
-    val scope     = rememberCoroutineScope()
-    val balanceState by vm.balanceState.collectAsStateWithLifecycle()
-    val fiatRate     = (balanceState as? BalanceState.Success)?.let { s ->
+fun SendScreen(
+    vm           : WalletViewModel,
+    nfcVm        : NfcViewModel,
+    onViewDetails: (paymentHash: String) -> Unit = {}
+) {
+    val sendState    : SendState by vm.sendState.collectAsStateWithLifecycle()
+    var input        by remember { mutableStateOf("") }
+    val context       = LocalContext.current
+    val activity      = context as FragmentActivity
+    val clipboard     = LocalClipboard.current
+    val scope         = rememberCoroutineScope()
+    val balanceState  by vm.balanceState.collectAsStateWithLifecycle()
+    val fiatRate      = (balanceState as? BalanceState.Success)?.let { s ->
         s.fiatAmount?.let { if (s.sats > 0) s.sats.toDouble() / it else null }
     }
-    val fiatCurrency = (balanceState as? BalanceState.Success)?.fiatCurrency
+    val fiatCurrency  = (balanceState as? BalanceState.Success)?.fiatCurrency
+
+    // ── Collect NFC offer at top level — never inside a conditional ───────────
+    val nfcOffer by nfcVm.nfcOfferState.collectAsStateWithLifecycle()
 
     DisposableEffect(Unit) { onDispose { vm.resetSendState() } }
 
+    // ── Auto-trigger scan when NFC offer arrives ──────────────────────────────
+    LaunchedEffect(nfcOffer) {
+        val offer = nfcOffer
+        if (offer is NfcOfferState.Detected && sendState is SendState.Idle) {
+            input = offer.raw
+            vm.scan(offer.raw)
+            nfcVm.dismissNfcOffer()
+        }
+    }
+
     Column(
         modifier = Modifier
             .fillMaxSize()
@@ -55,13 +75,31 @@ fun SendScreen(vm: WalletViewModel, onViewDetails: (paymentHash: String) -> Unit
     ) {
         Spacer(Modifier.height(32.dp))
 
-        // ── Header row (matches ReceiveIdleContent) ──────────────────────────
+        // ── Header row ────────────────────────────────────────────────────────
         Row(
             modifier              = Modifier.fillMaxWidth(),
             verticalAlignment     = Alignment.CenterVertically,
             horizontalArrangement = Arrangement.SpaceBetween
         ) {
             Text("Send", style = MaterialTheme.typography.headlineSmall)
+
+            // NFC indicator — only visible in Idle/Error, lights up when offer pending
+            if (sendState is SendState.Idle || sendState is SendState.Error) {
+                FilledTonalIconButton(
+                    onClick  = { /* passive indicator */ },
+                    modifier = Modifier.size(40.dp)
+                ) {
+                    Icon(
+                        imageVector        = Icons.Filled.Nfc,
+                        contentDescription = "Tap NFC device to receive invoice",
+                        tint               = if (nfcOffer is NfcOfferState.Detected)
+                            MaterialTheme.colorScheme.primary
+                        else
+                            MaterialTheme.colorScheme.onSurfaceVariant,
+                        modifier           = Modifier.size(20.dp)
+                    )
+                }
+            }
         }
 
         if (sendState !is SendState.PaymentSent) {