Merge pull request #255 from synonymdev/fix/transfer-spending-limit

Fix LSP balance calculation

Author: jvsena42

app/src/main/java/to/bitkit/ui/screens/transfer/SpendingAmountScreen.kt

@@ -23,6 +23,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import kotlinx.coroutines.launch
 import to.bitkit.R
 import to.bitkit.models.Toast
@@ -60,6 +61,7 @@ fun SpendingAmountScreen(
     val blocktank = blocktankViewModel ?: return
     val currencies = LocalCurrencies.current
     val resources = LocalContext.current.resources
+    val transferValues by viewModel.transferValues.collectAsStateWithLifecycle()
 
     ScreenColumn {
         AppTopBar(
@@ -78,41 +80,39 @@ fun SpendingAmountScreen(
             var isLoading by remember { mutableStateOf(false) }
 
             val availableAmount = LocalBalances.current.totalOnchainSats - 512u // default tx fee
-
-            var maxClientBalance by remember { mutableStateOf(0uL) }
-            var maxLspBalance by remember { mutableStateOf(0uL) }
             var maxLspFee by remember { mutableStateOf(0uL) }
 
             val feeMaximum = max(0, availableAmount.toLong() - maxLspFee.toLong())
-            val maximum = min(maxClientBalance.toLong(), feeMaximum)
+            val maximum = min(
+                transferValues.maxClientBalance.toLong(),
+                feeMaximum
+            ) // TODO USE MAX AVAILABLE TO TRANSFER INSTEAD OF MAX ONCHAIN BALANCE
 
             // Update maxClientBalance Effect
             LaunchedEffect(satsAmount) {
-                val transferValues = viewModel.calculateTransferValues(satsAmount.toULong())
-                maxClientBalance = transferValues.maxClientBalance
-                Logger.debug("maxClientBalance: $maxClientBalance", context = "SpendingAmountScreen")
-            }
-
-            // Update maxLspBalance Effect
-            LaunchedEffect(availableAmount) {
-                val transferValues = viewModel.calculateTransferValues(availableAmount)
-                maxLspBalance = transferValues.defaultLspBalance
-                Logger.debug("maxLspBalance: $maxLspBalance", context = "SpendingAmountScreen")
+                viewModel.updateTransferValues(satsAmount.toULong())
+                Logger.debug(
+                    "satsAmount changed - maxClientBalance: ${transferValues.maxClientBalance}",
+                    context = "SpendingAmountScreen"
+                )
             }
 
             // Update maxLspFee Effect
-            LaunchedEffect(availableAmount, maxLspBalance) {
+            LaunchedEffect(availableAmount, transferValues.maxLspBalance) { // TODO MOVE TO VIEWMODEL
                 runCatching {
                     val estimate = blocktank.estimateOrderFee(
                         spendingBalanceSats = availableAmount,
-                        receivingBalanceSats = maxLspBalance,
+                        receivingBalanceSats = transferValues.maxLspBalance,
                     )
                     maxLspFee = estimate.feeSat
                 }
             }
 
             Spacer(modifier = Modifier.height(32.dp))
-            Display(text = stringResource(R.string.lightning__spending_amount__title).withAccent(accentColor = Colors.Purple))
+            Display(
+                text = stringResource(R.string.lightning__spending_amount__title)
+                    .withAccent(accentColor = Colors.Purple)
+            )
             Spacer(modifier = Modifier.height(32.dp))
 
             AmountInput(
@@ -167,11 +167,13 @@ fun SpendingAmountScreen(
             PrimaryButton(
                 text = stringResource(R.string.common__continue),
                 onClick = {
-                    if (maxLspBalance == 0uL) {
+                    if (transferValues.maxLspBalance == 0uL) {
                         app.toast(
                             type = Toast.ToastType.ERROR,
                             title = resources.getString(R.string.lightning__spending_amount__error_max__title),
-                            description = resources.getString(R.string.lightning__spending_amount__error_max__description_zero),
+                            description = resources.getString(
+                                R.string.lightning__spending_amount__error_max__description_zero
+                            ),
                         )
                         return@PrimaryButton
                     }

app/src/main/java/to/bitkit/viewmodels/TransferViewModel.kt

@@ -194,12 +194,40 @@ class TransferViewModel @Inject constructor(
 
         // The maximum channel size the user can open including existing channels
         val maxChannelSize2 = if (maxChannelSize1 > channelsSize) maxChannelSize1 - channelsSize else 0u
-        val maxChannelSize = min(maxChannelSize1, maxChannelSize2)
+        val maxChannelSizeAvailableToIncrease = min(maxChannelSize1, maxChannelSize2)
 
         val minLspBalance = getMinLspBalance(clientBalanceSat, minChannelSizeSat)
-        val maxLspBalance = if (maxChannelSize > clientBalanceSat) maxChannelSize - clientBalanceSat else 0u
+        val maxLspBalance = if (maxChannelSizeAvailableToIncrease > clientBalanceSat) {
+            maxChannelSizeAvailableToIncrease - clientBalanceSat
+        } else {
+            0u
+        }
         val defaultLspBalance = getDefaultLspBalance(clientBalanceSat, maxLspBalance)
-        val maxClientBalance = getMaxClientBalance(maxChannelSize)
+        val maxClientBalance = getMaxClientBalance(maxChannelSizeAvailableToIncrease)
+
+        if (maxChannelSizeAvailableToIncrease < clientBalanceSat) { // TODO DISPLAY ERROR
+            Logger.warn(
+                "Amount clientBalanceSat:$clientBalanceSat too large, max possible: $maxChannelSizeAvailableToIncrease",
+                context = TAG
+            )
+        }
+
+        if (defaultLspBalance < minLspBalance || defaultLspBalance > maxLspBalance) {
+            Logger.warn(
+                "Invalid defaultLspBalance:$defaultLspBalance " +
+                    "min possible:$maxLspBalance, " +
+                    "max possible: $minLspBalance",
+                context = TAG
+            )
+        }
+
+        if (maxChannelSizeAvailableToIncrease <= 0u) {
+            Logger.warn("Max channel size reached. current size: $channelsSize sats", context = TAG)
+        }
+
+        if (maxClientBalance <= 0u) {
+            Logger.warn("No liquidity available to purchase $maxClientBalance", context = TAG)
+        }
 
         return TransferValues(
             defaultLspBalance = defaultLspBalance,
@@ -225,16 +253,14 @@ class TransferViewModel @Inject constructor(
             throw ServiceError.CurrencyRateUnavailable
         }
 
-        // Safely calculate lspBalance to avoid arithmetic overflow
-        var lspBalance: ULong = 0u
-        if (defaultLspBalanceSats > clientBalanceSat) {
-            lspBalance = defaultLspBalanceSats - clientBalanceSat
-        }
-        if (lspBalance > threshold1) {
-            lspBalance = clientBalanceSat
-        }
-        if (lspBalance > threshold2) {
-            lspBalance = maxLspBalance
+        val lspBalance = if (clientBalanceSat < threshold1) { // 0-225€: LSP balance = 450€ - client balance
+            defaultLspBalanceSats - clientBalanceSat
+        } else if (clientBalanceSat < threshold2) { // 225-495€: LSP balance = client balance
+            clientBalanceSat
+        } else if (clientBalanceSat < maxLspBalance) { // 495-950€: LSP balance = max - client balance
+            maxLspBalance - clientBalanceSat
+        } else {
+            maxLspBalance
         }
 
         return min(lspBalance, maxLspBalance)