import FungibleToken from 0xa0225e7000ac82a9 import ViewResolver from 0xb6763b4399a888c8 import FungibleTokenMetadataViews from 0xa0225e7000ac82a9 import FlowToken from 0x4445e7ad11568276 import ScopedFTProviders from 0x715c57f7a59bc39b import EVM from 0xb6763b4399a888c8 import FlowEVMBridge from 0x715c57f7a59bc39b import FlowEVMBridgeConfig from 0x715c57f7a59bc39b import FlowEVMBridgeUtils from 0x715c57f7a59bc39b /// Bridges a Vault from the signer's storage to the signer's COA in EVM.Account. /// /// NOTE: This transaction also onboards the Vault to the bridge if necessary which may incur additional fees /// than bridging an asset that has already been onboarded. /// /// @param tokenContractAddress: The Flow account address hosting the FT-defining Cadence contract /// @param tokenContractName: The name of the Vault-defining Cadence contract /// @param amount: The amount of tokens to bridge from EVM /// transaction(tokenContractAddress: Address, tokenContractName: String, amount: UFix64) { let sentVault: @{FungibleToken.Vault} let coa: auth(EVM.Bridge) &EVM.CadenceOwnedAccount let requiresOnboarding: Bool let scopedProvider: @ScopedFTProviders.ScopedFTProvider prepare(signer: auth(CopyValue, BorrowValue, IssueStorageCapabilityController, PublishCapability, SaveValue) &Account) { /* --- Reference the signer's CadenceOwnedAccount --- */ // // Borrow a reference to the signer's COA self.coa = signer.storage.borrow(from: /storage/evm) ?? panic("Could not borrow COA from provided gateway address") /* --- Retrieve the funds --- */ // // Borrow a reference to the FungibleToken Vault let viewResolver = getAccount(tokenContractAddress).contracts.borrow<&{ViewResolver}>(name: tokenContractName) ?? panic("Could not borrow ViewResolver from FungibleToken contract") let vaultData = viewResolver.resolveContractView( resourceType: nil, viewType: Type() ) as! FungibleTokenMetadataViews.FTVaultData? ?? panic("Could not resolve FTVaultData view") let vault = signer.storage.borrow( from: vaultData.storagePath ) ?? panic("Could not access signer's FungibleToken Vault") // Withdraw the requested balance & calculate the approximate bridge fee based on storage usage let currentStorageUsage = signer.storage.used self.sentVault <- vault.withdraw(amount: amount) let withdrawnStorageUsage = signer.storage.used // Approximate the bridge fee based on the difference in storage usage with some buffer var approxFee = FlowEVMBridgeUtils.calculateBridgeFee( bytes: currentStorageUsage - withdrawnStorageUsage ) * 1.10 // Determine if the Vault requires onboarding - this impacts the fee required self.requiresOnboarding = FlowEVMBridge.typeRequiresOnboarding(self.sentVault.getType()) ?? panic("Bridge does not support this asset type") if self.requiresOnboarding { approxFee = approxFee + FlowEVMBridgeConfig.onboardFee } /* --- Configure a ScopedFTProvider --- */ // // 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( /storage/flowTokenVault ) signer.storage.save(providerCap, to: FlowEVMBridgeConfig.providerCapabilityStoragePath) } // Copy the stored Provider capability and create a ScopedFTProvider let providerCapCopy = signer.storage.copy>( from: FlowEVMBridgeConfig.providerCapabilityStoragePath ) ?? panic("Invalid Provider Capability found in storage.") let providerFilter = ScopedFTProviders.AllowanceFilter(approxFee) self.scopedProvider <- ScopedFTProviders.createScopedFTProvider( provider: providerCapCopy, filters: [ providerFilter ], expiration: getCurrentBlock().timestamp + 1.0 ) } execute { if self.requiresOnboarding { // Onboard the Vault to the bridge FlowEVMBridge.onboardByType( self.sentVault.getType(), feeProvider: &self.scopedProvider as auth(FungibleToken.Withdraw) &{FungibleToken.Provider} ) } // Execute the bridge self.coa.depositTokens( vault: <-self.sentVault, feeProvider: &self.scopedProvider as auth(FungibleToken.Withdraw) &{FungibleToken.Provider} ) // Destroy the ScopedFTProvider destroy self.scopedProvider } }

🎶Happy diving into the flow

Transaction

🎶Happy diving into the flow