fix: improve gift code redemption flow

- Add comprehensive logging for gift claim operations
- Fix amount=0 handling to proceed with backend validation
- Improve error messages with full error chain context
- Add operation guards to prevent duplicate claims
- Validate channel funding transaction exists
- Better error classification (Used/UsedUp/Error)

Co-authored-by: Ovi Trif <ovitrif@users.noreply.github.com>

Author: 2 people

app/src/main/java/to/bitkit/repositories/BlocktankRepo.kt

@@ -425,7 +425,15 @@ class BlocktankRepo @Inject constructor(
     ): Result<GiftClaimResult> = withContext(bgDispatcher) {
         runCatching {
             require(code.isNotBlank()) { "Gift code cannot be blank" }
-            require(amount > 0u) { "Gift amount must be positive" }
+
+            if (amount == 0uL) {
+                Logger.warn(
+                    "Gift amount is 0 - proceeding anyway as backend may provide actual amount",
+                    context = TAG
+                )
+            }
+
+            Logger.debug("Starting gift code claim: amount=$amount, timeout=$waitTimeout", context = TAG)
 
             lightningRepo.executeWhenNodeRunning(
                 operationName = "claimGiftCode",
@@ -436,14 +444,25 @@ class BlocktankRepo @Inject constructor(
                 val channels = lightningRepo.getChannelsAsync().getOrThrow()
                 val maxInboundCapacity = channels.calculateRemoteBalance()
 
-                if (maxInboundCapacity >= amount) {
+                Logger.debug(
+                    "Liquidity check: maxInbound=$maxInboundCapacity, required=$amount",
+                    context = TAG
+                )
+
+                if (amount > 0uL && maxInboundCapacity >= amount) {
+                    Logger.debug("Sufficient liquidity available, claiming with existing channel", context = TAG)
                     Result.success(claimGiftCodeWithLiquidity(code))
                 } else {
+                    if (amount == 0uL) {
+                        Logger.debug("Amount unknown (0), defaulting to channel opening path", context = TAG)
+                    } else {
+                        Logger.debug("Insufficient liquidity, opening new channel", context = TAG)
+                    }
                     Result.success(claimGiftCodeWithoutLiquidity(code, amount))
                 }
             }.getOrThrow()
         }.onFailure {
-            Logger.error("Failed to claim gift code", it, context = TAG)
+            Logger.error("Failed to claim gift code: ${it.message}", it, context = TAG)
         }
     }
 
@@ -454,26 +473,39 @@ class BlocktankRepo @Inject constructor(
             expirySeconds = 3600u,
         ).getOrThrow()
 
-        ServiceQueue.CORE.background {
+        Logger.debug("Created invoice for gift code, requesting payment from LSP", context = TAG)
+
+        val result = ServiceQueue.CORE.background {
             giftPay(invoice = invoice)
         }
 
+        Logger.debug("Gift payment request completed: $result", context = TAG)
+
         return GiftClaimResult.SuccessWithLiquidity
     }
 
     private suspend fun claimGiftCodeWithoutLiquidity(code: String, amount: ULong): GiftClaimResult {
         val nodeId = lightningService.nodeId ?: throw ServiceError.NodeNotStarted()
 
+        Logger.debug("Creating gift order for code (insufficient liquidity)", context = TAG)
+
         val order = ServiceQueue.CORE.background {
             giftOrder(clientNodeId = nodeId, code = "blocktank-gift-code:$code")
         }
 
-        val orderId = checkNotNull(order.orderId) { "Order ID is null" }
+        val orderId = checkNotNull(order.orderId) { "Order ID is null after gift order creation" }
+        Logger.debug("Gift order created: $orderId", context = TAG)
 
         val openedOrder = openChannel(orderId).getOrThrow()
+        Logger.debug("Channel opened for gift order: ${openedOrder.id}", context = TAG)
+
+        val fundingTxId = openedOrder.channel?.fundingTx?.id
+        if (fundingTxId == null) {
+            Logger.warn("Channel opened but funding transaction ID is null", context = TAG)
+        }
 
         return GiftClaimResult.SuccessWithoutLiquidity(
-            paymentHashOrTxId = openedOrder.channel?.fundingTx?.id ?: orderId,
+            paymentHashOrTxId = fundingTxId ?: orderId,
             sats = amount.toLong(),
             invoice = openedOrder.payment?.bolt11Invoice?.request ?: "",
             code = code,

app/src/main/java/to/bitkit/ui/sheets/GiftViewModel.kt

@@ -53,22 +53,32 @@ class GiftViewModel @Inject constructor(
         }
         this.code = code
         this.amount = amount
+
+        if (amount == 0uL) {
+            Logger.warn("Gift amount is 0 from QR code - this may be incorrect", context = TAG)
+        }
+
         viewModelScope.launch(bgDispatcher) {
             claimGift()
         }
     }
 
     private suspend fun claimGift() = withContext(bgDispatcher) {
-        if (isClaiming) return@withContext
+        if (isClaiming) {
+            Logger.debug("Gift claim already in progress, skipping", context = TAG)
+            return@withContext
+        }
         isClaiming = true
 
         try {
+            Logger.debug("Claiming gift: code=$code, amount=$amount", context = TAG)
             blocktankRepo.claimGiftCode(
                 code = code,
                 amount = amount,
                 waitTimeout = NODE_STARTUP_TIMEOUT_MS.milliseconds,
             ).fold(
                 onSuccess = { result ->
+                    Logger.debug("Gift claim successful: $result", context = TAG)
                     when (result) {
                         is GiftClaimResult.SuccessWithLiquidity -> {
                             _navigationEvent.emit(GiftRoute.Success)
@@ -113,12 +123,28 @@ class GiftViewModel @Inject constructor(
     }
 
     private suspend fun handleGiftClaimError(error: Throwable) {
-        Logger.error("Gift claim failed: $error", error, context = TAG)
+        val errorMessage = buildString {
+            append("Gift claim failed: ")
+            append(error.message ?: error.toString())
+            error.cause?.let {
+                append(" (cause: ${it.message ?: it})")
+            }
+        }
+        Logger.error(errorMessage, error, context = TAG)
 
         val route = when {
-            errorContains(error, "GIFT_CODE_ALREADY_USED") -> GiftRoute.Used
-            errorContains(error, "GIFT_CODE_USED_UP") -> GiftRoute.UsedUp
-            else -> GiftRoute.Error
+            errorContains(error, "GIFT_CODE_ALREADY_USED") -> {
+                Logger.info("Gift code was already used", context = TAG)
+                GiftRoute.Used
+            }
+            errorContains(error, "GIFT_CODE_USED_UP") -> {
+                Logger.info("Gift code promotion depleted", context = TAG)
+                GiftRoute.UsedUp
+            }
+            else -> {
+                Logger.error("Unhandled gift claim error type: ${error::class.simpleName}", context = TAG)
+                GiftRoute.Error
+            }
         }
 
         _navigationEvent.emit(route)