(android) Use unsigned tx to infer amount/index in swap-in signer

Index may not be 0. We can also remove the amount field in the UI.

Author: dpad85

phoenix-android/src/main/kotlin/fr/acinq/phoenix/android/settings/walletinfo/SwapInSignerView.kt

@@ -67,7 +67,7 @@ fun SwapInSignerView(
     onBackClick: () -> Unit,
 ) {
     val context = LocalContext.current
-    val vm = viewModel<SwapInSignerViewModel>(factory = SwapInSignerViewModel.Factory(business.walletManager))
+    val vm = viewModel<SwapInSignerViewModel>(factory = SwapInSignerViewModel.Factory(business.walletManager, business.electrumClient))
 
     var amountInput by remember { mutableStateOf<MilliSatoshi?>(null) }
     var txInput by remember { mutableStateOf("") }
@@ -82,18 +82,6 @@ fun SwapInSignerView(
             val state = vm.state.value
             Text(text = stringResource(id = R.string.swapin_signer_instructions))
             Spacer(modifier = Modifier.height(16.dp))
-            AmountInput(
-                amount = amountInput,
-                onAmountChange = {
-                    amountInput = it?.amount
-                    if (state != SwapInSignerState.Init) vm.state.value = SwapInSignerState.Init
-                },
-                staticLabel = stringResource(id = R.string.swapin_signer_amount),
-                enabled = state !is SwapInSignerState.Signing,
-                modifier = Modifier.fillMaxWidth(),
-                forceUnit = BitcoinUnit.Sat,
-            )
-            Spacer(modifier = Modifier.height(8.dp))
             TextInput(
                 text = txInput,
                 onTextChange = {
@@ -116,7 +104,7 @@ fun SwapInSignerView(
                         icon = R.drawable.ic_check,
                         onClick = {
                             if (amountInput != null && txInput.isNotBlank()) {
-                                vm.sign(unsignedTx = txInput, amount = amountInput!!.truncateToSatoshi())
+                                vm.sign(unsignedTx = txInput)
                                 keyboardManager?.hide()
                             }
                         },

phoenix-android/src/main/kotlin/fr/acinq/phoenix/android/settings/walletinfo/SwapInSignerViewModel.kt

@@ -20,16 +20,8 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.viewModelScope
-import fr.acinq.bitcoin.ByteVector
-import fr.acinq.bitcoin.Satoshi
 import fr.acinq.bitcoin.Transaction
-import fr.acinq.bitcoin.TxOut
-import fr.acinq.lightning.MilliSatoshi
-import fr.acinq.lightning.crypto.KeyManager
-import fr.acinq.lightning.crypto.LocalKeyManager
-import fr.acinq.lightning.transactions.Transactions
-import fr.acinq.phoenix.managers.NodeParamsManager
-import fr.acinq.phoenix.managers.PeerManager
+import fr.acinq.lightning.blockchain.electrum.ElectrumClient
 import fr.acinq.phoenix.managers.WalletManager
 import kotlinx.coroutines.CoroutineExceptionHandler
 import kotlinx.coroutines.Dispatchers
@@ -42,7 +34,6 @@ sealed class SwapInSignerState {
     object Init : SwapInSignerState()
     object Signing : SwapInSignerState()
     data class Signed(
-        val amount: Satoshi,
         val txId: String,
         val userSig: String,
     ) : SwapInSignerState()
@@ -53,39 +44,40 @@ sealed class SwapInSignerState {
 }
 
 class SwapInSignerViewModel(
-    val walletManager: WalletManager,
+    private val walletManager: WalletManager,
+    private val electrumClient: ElectrumClient,
 ) : ViewModel() {
 
-    val log = LoggerFactory.getLogger(this::class.java)
+    private val log = LoggerFactory.getLogger(this::class.java)
     val state = mutableStateOf<SwapInSignerState>(SwapInSignerState.Init)
 
     fun sign(
         unsignedTx: String,
-        amount: Satoshi,
     ) {
         if (state.value == SwapInSignerState.Signing) return
         state.value = SwapInSignerState.Signing
 
         viewModelScope.launch(Dispatchers.Default + CoroutineExceptionHandler { _, e ->
-            log.error("failed to sign tx=$unsignedTx for amount=$amount : ", e)
+            log.error("failed to sign tx=$unsignedTx: ", e)
             state.value = SwapInSignerState.Failed.Error(e)
         }) {
-            log.debug("signing tx=$unsignedTx amount=$amount")
+            log.debug("signing tx=$unsignedTx")
             val tx = try {
                 Transaction.read(unsignedTx)
             } catch (e: Exception) {
                 log.error("invalid transaction input: ", e)
                 state.value = SwapInSignerState.Failed.InvalidTxInput(e)
                 return@launch
             }
+            val input = if (tx.txIn.size == 1) tx.txIn.first() else throw RuntimeException("tx has ${tx.txIn.size} inputs")
+            val prevTx = electrumClient.getTx(input.outPoint.txid) ?: throw RuntimeException("parent tx not found by electrum")
             val keyManager = walletManager.keyManager.filterNotNull().first()
             val userSig = keyManager.swapInOnChainWallet.signSwapInputUserLegacy(
                 fundingTx = tx,
-                index = 0,
-                parentTxOuts = listOf(TxOut(amount, ByteVector.empty)),
+                index = input.outPoint.index.toInt(),
+                parentTxOuts = prevTx.txOut,
             )
             state.value = SwapInSignerState.Signed(
-                amount = amount,
                 txId = tx.txid.toString(),
                 userSig = userSig.toString(),
             )
@@ -94,10 +86,11 @@ class SwapInSignerViewModel(
 
     class Factory(
         private val walletManager: WalletManager,
+        private val electrumClient: ElectrumClient,
     ) : ViewModelProvider.Factory {
         override fun <T : ViewModel> create(modelClass: Class<T>): T {
             @Suppress("UNCHECKED_CAST")
-            return SwapInSignerViewModel(walletManager) as T
+            return SwapInSignerViewModel(walletManager, electrumClient) as T
         }
     }
 }

phoenix-android/src/main/res/values/strings.xml

@@ -775,7 +775,6 @@
 
     <string name="swapin_signer_title">Swap-in signer</string>
     <string name="swapin_signer_instructions">This debugging tool lets you sign swap-in inputs. Only use if you understand what it does.</string>
-    <string name="swapin_signer_amount">Amount</string>
     <string name="swapin_signer_tx">Unsigned tx</string>
     <string name="swapin_signer_sign">Sign</string>
     <string name="swapin_signer_signing">Signing…</string>