Updated on 2026-08-14

domain/legacy/src/main/java/com/tangem/domain/walletmanager/DefaultWalletManagersFacade.kt

@@ -38,7 +38,7 @@ import timber.log.Timber
 import java.math.BigDecimal
 import java.util.EnumSet
 
-@Suppress("LargeClass")
+@Suppress("LargeClass", "TooManyFunctions")
 // FIXME: Move to its own module and make internal
 @Deprecated("Inject the WalletManagerFacade interface using DI instead")
 class DefaultWalletManagersFacade(
@@ -433,6 +433,20 @@ class DefaultWalletManagersFacade(
         )
     }
 
+    override suspend fun estimateFee(
+        amount: Amount,
+        userWalletId: UserWalletId,
+        network: Network,
+    ): Result<TransactionFee>? {
+        val blockchain = Blockchain.fromId(network.id.value)
+        val walletManager = getOrCreateWalletManager(
+            userWalletId = userWalletId,
+            blockchain = blockchain,
+            derivationPath = network.derivationPath.value,
+        )
+        return (walletManager as? TransactionSender)?.estimateFee(amount = amount)
+    }
+
     override suspend fun validateTransaction(
         amount: Amount,
         fee: Amount?,

domain/legacy/src/main/java/com/tangem/domain/walletmanager/WalletManagersFacade.kt

@@ -25,6 +25,7 @@ import java.util.EnumSet
 /**
  * A facade for managing wallets.
  */
+@Suppress("TooManyFunctions")
 interface WalletManagersFacade {
 
     /**
@@ -166,6 +167,15 @@ interface WalletManagersFacade {
         network: Network,
     ): Result<TransactionFee>?
 
+    /**
+     * Returns estimated fee for transaction
+     *
+     * @param amount of transaction
+     * @param userWalletId selected wallet id
+     * @param network network of currency
+     */
+    suspend fun estimateFee(amount: Amount, userWalletId: UserWalletId, network: Network): Result<TransactionFee>?
+
     /**
      * Validates transaction
      *

domain/transaction/src/main/java/com/tangem/domain/transaction/usecase/EstimateFeeUseCase.kt

@@ -0,0 +1,63 @@
+package com.tangem.domain.transaction.usecase
+
+import arrow.core.Either
+import arrow.core.left
+import arrow.core.right
+import com.tangem.blockchain.common.Amount
+import com.tangem.blockchain.common.AmountType
+import com.tangem.blockchain.common.Token
+import com.tangem.blockchain.common.transaction.TransactionFee
+import com.tangem.blockchain.extensions.Result
+import com.tangem.domain.tokens.model.CryptoCurrency
+import com.tangem.domain.transaction.error.GetFeeError
+import com.tangem.domain.walletmanager.WalletManagersFacade
+import com.tangem.domain.wallets.models.UserWalletId
+import com.tangem.utils.coroutines.CoroutineDispatcherProvider
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOn
+import java.math.BigDecimal
+
+/**
+ * Use case to estimate transaction fee
+ */
+class EstimateFeeUseCase(
+    private val walletManagersFacade: WalletManagersFacade,
+    private val dispatcher: CoroutineDispatcherProvider,
+) {
+    suspend operator fun invoke(
+        amount: BigDecimal,
+        userWalletId: UserWalletId,
+        cryptoCurrency: CryptoCurrency,
+    ): Flow<Either<GetFeeError.DataError, TransactionFee>> {
+        return flow {
+            val result = walletManagersFacade.estimateFee(
+                amount = convertCryptoCurrencyToAmount(cryptoCurrency, amount),
+                userWalletId = userWalletId,
+                network = cryptoCurrency.network,
+            )
+
+            val maybeFee = when (result) {
+                is Result.Success -> result.data.right()
+                else -> GetFeeError.DataError.left()
+            }
+            emit(maybeFee)
+        }.flowOn(dispatcher.io)
+    }
+
+    private fun convertCryptoCurrencyToAmount(cryptoCurrency: CryptoCurrency, amount: BigDecimal) = Amount(
+        currencySymbol = cryptoCurrency.symbol,
+        value = amount,
+        decimals = cryptoCurrency.decimals,
+        type = when (cryptoCurrency) {
+            is CryptoCurrency.Coin -> AmountType.Coin
+            is CryptoCurrency.Token -> AmountType.Token(
+                token = Token(
+                    symbol = cryptoCurrency.symbol,
+                    contractAddress = cryptoCurrency.contractAddress,
+                    decimals = cryptoCurrency.decimals,
+                ),
+            )
+        },
+    )
+}