From 30ba7411107ec1014f785d4d1d09bafe67d211c4 Mon Sep 17 00:00:00 2001
From: Tangem <git@tangem.com>
Date: Sun, 4 Jan 2026 14:42:00 +0300
Subject: [PATCH] Updated on 2026-08-14

---
 .../gasless/GetAvailableFeeTokensUseCase.kt   | 84 +++++++++++++++++--
 1 file changed, 79 insertions(+), 5 deletions(-)

diff --git a/domain/transaction/src/main/java/com/tangem/domain/transaction/usecase/gasless/GetAvailableFeeTokensUseCase.kt b/domain/transaction/src/main/java/com/tangem/domain/transaction/usecase/gasless/GetAvailableFeeTokensUseCase.kt
index 7d57316d91..019d021363 100644
--- a/domain/transaction/src/main/java/com/tangem/domain/transaction/usecase/gasless/GetAvailableFeeTokensUseCase.kt
+++ b/domain/transaction/src/main/java/com/tangem/domain/transaction/usecase/gasless/GetAvailableFeeTokensUseCase.kt
@@ -1,15 +1,89 @@
 package com.tangem.domain.transaction.usecase.gasless
 
 import arrow.core.Either
-import arrow.core.left
+import arrow.core.raise.Raise
+import arrow.core.raise.catch
+import arrow.core.raise.either
+import com.tangem.domain.models.currency.CryptoCurrency
 import com.tangem.domain.models.currency.CryptoCurrencyStatus
 import com.tangem.domain.models.network.Network
-import com.tangem.domain.models.wallet.UserWalletId
+import com.tangem.domain.models.wallet.UserWallet
+import com.tangem.domain.tokens.GetMultiCryptoCurrencyStatusUseCase
+import com.tangem.domain.tokens.repository.CurrenciesRepository
+import com.tangem.domain.transaction.GaslessTransactionRepository
 import com.tangem.domain.transaction.error.GetFeeError
+import java.math.BigDecimal
 
-class GetAvailableFeeTokensUseCase {
+class GetAvailableFeeTokensUseCase(
+    private val gaslessTransactionRepository: GaslessTransactionRepository,
+    private val currenciesRepository: CurrenciesRepository,
+    private val getMultiCryptoCurrencyStatusUseCase: GetMultiCryptoCurrencyStatusUseCase,
+) {
 
-    operator fun invoke(userWalletId: UserWalletId, network: Network): Either<GetFeeError, List<CryptoCurrencyStatus>> {
-        return GetFeeError.UnknownError.left()
+    /**
+     * Retrieves available tokens for gasless fee payment.
+     *
+     * @return List where first element is always native currency (for fallback)
+     */
+    suspend operator fun invoke(
+        userWallet: UserWallet,
+        network: Network,
+    ): Either<GetFeeError, List<CryptoCurrencyStatus>> {
+        return either {
+            catch(
+                block = {
+                    val userCurrenciesStatuses = getMultiCryptoCurrencyStatusUseCase.invokeMultiWalletSync(
+                        userWallet.walletId,
+                    ).getOrNull()
+                        ?: raiseIllegalStateError("currencies list is null for userWalletId=${userWallet.walletId}")
+
+                    val nativeCurrencyStatus = getNativeCurrencyStatus(userWallet, network, userCurrenciesStatuses)
+
+                    if (!gaslessTransactionRepository.isNetworkSupported(network)) {
+                        return@either listOf(nativeCurrencyStatus)
+                    }
+
+                    val gaslessTokens = getGaslessTokens(userCurrenciesStatuses)
+                    buildList {
+                        add(nativeCurrencyStatus)
+                        addAll(gaslessTokens)
+                    }
+                },
+                catch = {
+                    raise(GetFeeError.DataError(it))
+                },
+            )
+        }
+    }
+
+    private suspend fun Raise<GetFeeError>.getNativeCurrencyStatus(
+        userWallet: UserWallet,
+        network: Network,
+        userCurrenciesStatuses: List<CryptoCurrencyStatus>,
+    ): CryptoCurrencyStatus {
+        val nativeCurrency = currenciesRepository.getNetworkCoin(
+            userWalletId = userWallet.walletId,
+            networkId = network.id,
+            derivationPath = network.derivationPath,
+        )
+        return userCurrenciesStatuses.find {
+            it.currency.id == nativeCurrency.id
+        } ?: raiseIllegalStateError("no native currency found")
+    }
+
+    private fun getGaslessTokens(userCurrenciesStatuses: List<CryptoCurrencyStatus>): List<CryptoCurrencyStatus> {
+        val supportedGaslessTokens = gaslessTransactionRepository.getSupportedTokens()
+        return userCurrenciesStatuses
+            .asSequence()
+            .filter { currencyStatus ->
+                currencyStatus.currency is CryptoCurrency.Token &&
+                    currencyStatus.value.amount?.let { amount -> amount > BigDecimal.ZERO } == true &&
+                    supportedGaslessTokens.contains(currencyStatus.currency)
+            }
+            .toList()
+    }
+
+    private fun Raise<GetFeeError>.raiseIllegalStateError(error: String): Nothing {
+        raise(GetFeeError.DataError(IllegalStateException(error)))
     }
 }
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