update bridge fee approximation in nft bridging txns

onflow · Oct 25, 2024 · 47f8732 · 47f8732
1 parent a452f91
commit 47f8732
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Showing 4 changed files with 16 additions and 14 deletions.
diff --git a/cadence/transactions/bridge/nft/bridge_nft_from_evm.cdc b/cadence/transactions/bridge/nft/bridge_nft_from_evm.cdc
@@ -64,8 +64,10 @@ transaction(nftIdentifier: String, id: UInt256) {
 
         /* --- Configure a ScopedFTProvider --- */
         //
-        // Calculate the bridge fee - bridging from EVM consumes no storage, so flat fee
-        let approxFee = FlowEVMBridgeUtils.calculateBridgeFee(bytes: 0)
+        // Set a cap on the withdrawable bridge fee
+        var approxFee = FlowEVMBridgeUtils.calculateBridgeFee(
+                bytes: 200_000 // 200 kB as upper bound on movable storage used in a single transaction
+            )
         // Issue and store bridge-dedicated Provider Capability in storage if necessary
         if signer.storage.type(at: FlowEVMBridgeConfig.providerCapabilityStoragePath) == nil {
             let providerCap = signer.capabilities.storage.issue<auth(FungibleToken.Withdraw) &{FungibleToken.Provider}>(

diff --git a/cadence/transactions/bridge/nft/bridge_nft_to_any_cadence_address.cdc b/cadence/transactions/bridge/nft/bridge_nft_to_any_cadence_address.cdc
@@ -67,8 +67,10 @@ transaction(nftIdentifier: String, id: UInt256, recipient: Address) {
 
         /* --- Configure a ScopedFTProvider --- */
         //
-        // Calculate the bridge fee - bridging from EVM consumes no storage, so flat fee
-        let approxFee = FlowEVMBridgeUtils.calculateBridgeFee(bytes: 0)
+        // Set a cap on the withdrawable bridge fee
+        var approxFee = FlowEVMBridgeUtils.calculateBridgeFee(
+                bytes: 200_000 // 200 kB as upper bound on movable storage used in a single transaction
+            )
         // Issue and store bridge-dedicated Provider Capability in storage if necessary
         if signer.storage.type(at: FlowEVMBridgeConfig.providerCapabilityStoragePath) == nil {
             let providerCap = signer.capabilities.storage.issue<auth(FungibleToken.Withdraw) &{FungibleToken.Provider}>(

diff --git a/cadence/transactions/bridge/nft/bridge_nft_to_any_evm_address.cdc b/cadence/transactions/bridge/nft/bridge_nft_to_any_evm_address.cdc
@@ -52,15 +52,14 @@ transaction(nftIdentifier: String, id: UInt64, recipient: String) {
             ) ?? panic("Could not access signer's NFT Collection")
 
         // Withdraw the requested NFT & calculate the approximate bridge fee based on NFT storage usage
-        let currentStorageUsage = signer.storage.used
         self.nft <- collection.withdraw(withdrawID: id)
-        let withdrawnStorageUsage = signer.storage.used
         var approxFee = FlowEVMBridgeUtils.calculateBridgeFee(
-                bytes: currentStorageUsage - withdrawnStorageUsage
-            ) * 1.10
+                bytes: 200_000 // 200 kB as upper bound on movable storage used in a single transaction
+            )
         // Determine if the NFT requires onboarding - this impacts the fee required
         self.requiresOnboarding = FlowEVMBridge.typeRequiresOnboarding(self.nft.getType())
             ?? panic("Bridge does not support this asset type")
+        // Add the onboarding fee if onboarding is necessary
         if self.requiresOnboarding {
             approxFee = approxFee + FlowEVMBridgeConfig.onboardFee
         }
@@ -100,7 +99,7 @@ transaction(nftIdentifier: String, id: UInt64, recipient: String) {
                 feeProvider: &self.scopedProvider as auth(FungibleToken.Withdraw) &{FungibleToken.Provider}
             )
         }
-        // Execute the bridge transaction
+        // Execute the bridge to EVM
         let recipientEVMAddress = EVM.addressFromString(recipient)
         FlowEVMBridge.bridgeNFTToEVM(
             token: <-self.nft,

diff --git a/cadence/transactions/bridge/nft/bridge_nft_to_evm.cdc b/cadence/transactions/bridge/nft/bridge_nft_to_evm.cdc
@@ -58,16 +58,15 @@ transaction(nftIdentifier: String, id: UInt64) {
                 from: collectionData.storagePath
             ) ?? panic("Could not access signer's NFT Collection")
 
-        // Withdraw the requested NFT & calculate the approximate bridge fee based on NFT storage usage
-        let currentStorageUsage = signer.storage.used
+        // Withdraw the requested NFT & set a cap on the withdrawable bridge fee
         self.nft <- collection.withdraw(withdrawID: id)
-        let withdrawnStorageUsage = signer.storage.used
         var approxFee = FlowEVMBridgeUtils.calculateBridgeFee(
-                bytes: currentStorageUsage - withdrawnStorageUsage
-            ) * 1.10
+                bytes: 200_000 // 200 kB as upper bound on movable storage used in a single transaction
+            )
         // Determine if the NFT requires onboarding - this impacts the fee required
         self.requiresOnboarding = FlowEVMBridge.typeRequiresOnboarding(self.nft.getType())
             ?? panic("Bridge does not support this asset type")
+        // Add the onboarding fee if onboarding is necessary
         if self.requiresOnboarding {
             approxFee = approxFee + FlowEVMBridgeConfig.onboardFee
         }