fix: prevent topup max from creating invalid transactions (#1442)

* fix: log tx data for debugging

* fix: properly handle max topup

Author: HashEngineering

wallet/src/de/schildbach/wallet/payments/SendCoinsTaskRunner.kt

@@ -463,6 +463,7 @@ class SendCoinsTaskRunner @Inject constructor(
                 metadataProvider.setTransactionService(sendRequest.tx.txId, serviceName)
             }
             log.info("send successful, transaction committed: {}", transaction.txId.toString())
+            log.info("  transaction: {}", transaction.toStringHex())
             walletApplication.broadcastTransaction(transaction)
             logSendTxEvent(transaction, wallet)
             transaction

wallet/src/de/schildbach/wallet/ui/send/BuyCreditsFragment.kt

@@ -131,13 +131,13 @@ class BuyCreditsFragment : SendCoinsFragment() {
                 // TODO: there are no events for Topups
                 // viewModel.logEvent(AnalyticsConstants.Topup.ENTER_AMOUNT_TOPUP)
 
-                if (enterAmountFragment?.maxSelected == true) {
+                val maxSelected = enterAmountFragment?.maxSelected ?: false
+                if (maxSelected) {
                     viewModel.logEvent(AnalyticsConstants.SendReceive.ENTER_AMOUNT_MAX)
                 }
-
                 // buy do an asset lock transaction or we do this in the worker?
-                val topUpKey = viewModel.getNextTopupKey()
-                val tx = viewModel.signAndSendAssetLock(editedAmount, exchangeRate, checkBalance, topUpKey)
+                val topUpKey = viewModel.getNextKey()
+                val tx = viewModel.signAndSendAssetLock(editedAmount, exchangeRate, checkBalance, topUpKey, maxSelected)
                 buyCreditsViewModel.topUpTransaction = tx
 
                 onSignAndSendPaymentSuccess(tx)
@@ -150,6 +150,7 @@ class BuyCreditsFragment : SendCoinsFragment() {
             } catch (ex: InsufficientMoneyException) {
                 showInsufficientMoneyDialog(ex.missing ?: Coin.ZERO)
             } catch (ex: KeyCrypterException) {
+                log.info("send topup failure (encryption)", ex)
                 showFailureDialog(ex)
             } catch (ex: Wallet.CouldNotAdjustDownwards) {
                 showEmptyWalletFailedDialog()

wallet/src/de/schildbach/wallet/ui/send/SendCoinsViewModel.kt

@@ -51,6 +51,7 @@ import org.bitcoinj.core.Context
 import org.bitcoinj.core.ECKey
 import org.bitcoinj.core.InsufficientMoneyException
 import org.bitcoinj.core.Transaction
+import org.bitcoinj.evolution.AssetLockTransaction
 import org.bitcoinj.utils.ExchangeRate
 import org.bitcoinj.wallet.AuthenticationKeyChain
 import org.bitcoinj.wallet.SendRequest
@@ -261,7 +262,8 @@ class SendCoinsViewModel @Inject constructor(
         editedAmount: Coin,
         exchangeRate: ExchangeRate?,
         checkBalance: Boolean,
-        key: ECKey
+        key: ECKey,
+        emptyWallet: Boolean
     ): Transaction {
         _state.value = State.SENDING
         if (!isAssetLock) {
@@ -270,7 +272,7 @@ class SendCoinsViewModel @Inject constructor(
         val finalPaymentIntent = basePaymentIntent.mergeWithEditedValues(editedAmount, null)
 
         val transaction = try {
-            val finalSendRequest = sendCoinsTaskRunner.createAssetLockSendRequest(
+            var finalSendRequest = sendCoinsTaskRunner.createAssetLockSendRequest(
                 basePaymentIntent.mayEditAmount(),
                 finalPaymentIntent,
                 true,
@@ -280,6 +282,25 @@ class SendCoinsViewModel @Inject constructor(
             finalSendRequest.memo = basePaymentIntent.memo
             finalSendRequest.exchangeRate = exchangeRate
 
+            if (emptyWallet) {
+                sendCoinsTaskRunner.signSendRequest(finalSendRequest)
+                wallet.completeTx(finalSendRequest)
+
+                // make sure that the asset lock payload matches the OP_RETURN output
+                val outputValue = finalSendRequest.tx.outputs.first().value
+                val assetLockedValue = (finalSendRequest.tx as AssetLockTransaction).assetLockPayload.creditOutputs.first().value
+                if (assetLockedValue != outputValue) {
+                    val newRequest = SendRequest.assetLock(wallet.params, key, outputValue, true)
+                    newRequest.coinSelector = finalSendRequest.coinSelector
+                    newRequest.returnChange = finalSendRequest.returnChange
+                    newRequest.aesKey = finalSendRequest.aesKey
+                    finalSendRequest = newRequest
+                } else {
+                    // this shouldn't happen
+                    error("The asset lock value is the same as the output though emptying the wallet")
+                }
+            }
+
             sendCoinsTaskRunner.sendCoins(finalSendRequest, checkBalanceConditions = checkBalance)
         } catch (ex: Exception) {
             _state.value = State.FAILED
@@ -534,7 +555,7 @@ class SendCoinsViewModel @Inject constructor(
         }
     }
 
-    fun getNextTopupKey(): ECKey {
+    fun getNextKey(): ECKey {
         val authGroup = wallet.getKeyChainExtension(
             AuthenticationGroupExtension.EXTENSION_ID
         ) as AuthenticationGroupExtension