import FungibleToken from 0xf233dcee88fe0abe import FiatToken from 0xb19436aae4d94622 pub contract TeleportCustodyEthereum { // Event that is emitted when new tokens are teleported in from Ethereum (from: Ethereum Address, 20 bytes) pub event TokensTeleportedIn(amount: UFix64, from: [UInt8], hash: String) // Event that is emitted when tokens are destroyed and teleported to Ethereum (to: Ethereum Address, 20 bytes) pub event TokensTeleportedOut(amount: UFix64, to: [UInt8]) // Event that is emitted when teleport fee is collected (type 0: out, 1: in) pub event FeeCollected(amount: UFix64, type: UInt8) // Event that is emitted when a new burner resource is created pub event TeleportAdminCreated(allowedAmount: UFix64) // The storage path for the admin resource (equivalent to root) pub let AdminStoragePath: StoragePath // The storage path for the teleport-admin resource (less priviledged than admin) pub let TeleportAdminStoragePath: StoragePath // The private path for the teleport-admin resource pub let TeleportAdminPrivatePath: PrivatePath // The public path for the teleport user pub let TeleportUserPublicPath: PublicPath // Frozen flag controlled by Admin pub var isFrozen: Bool // Record teleported Ethereum hashes access(contract) var teleported: {String: Bool} // Controls USDC vault access(contract) let usdcVault: @FiatToken.Vault pub resource Allowance { pub var balance: UFix64 // initialize the balance at resource creation time init(balance: UFix64) { self.balance = balance } } pub resource Administrator { // createNewTeleportAdmin // // Function that creates and returns a new teleport admin resource // pub fun createNewTeleportAdmin(allowedAmount: UFix64): @TeleportAdmin { emit TeleportAdminCreated(allowedAmount: allowedAmount) return <- create TeleportAdmin(allowedAmount: allowedAmount) } pub fun freeze() { TeleportCustodyEthereum.isFrozen = true } pub fun unfreeze() { TeleportCustodyEthereum.isFrozen = false } pub fun createAllowance(allowedAmount: UFix64): @Allowance { return <- create Allowance(balance: allowedAmount) } // deposit // // Function that deposits USDC token into the contract controlled // vault. // pub fun depositFiatToken(from: @FiatToken.Vault) { TeleportCustodyEthereum.usdcVault.deposit(from: <- from) } pub fun withdrawFiatToken(amount: UFix64): @FungibleToken.Vault { return <- TeleportCustodyEthereum.usdcVault.withdraw(amount: amount) } } pub resource interface TeleportUser { // fee collected when token is teleported from Ethereum to Flow pub var inwardFee: UFix64 // fee collected when token is teleported from Flow to Ethereum pub var outwardFee: UFix64 // the amount of tokens that the admin is allowed to teleport pub var allowedAmount: UFix64 // corresponding controller account on Ethereum pub var ethereumAdminAccount: [UInt8] pub fun teleportOut(from: @FiatToken.Vault, to: [UInt8]) pub fun depositAllowance(from: @Allowance) pub fun getFeeAmount(): UFix64 } pub resource interface TeleportControl { pub fun teleportIn(amount: UFix64, from: [UInt8], hash: String): @FungibleToken.Vault pub fun withdrawFee(amount: UFix64): @FungibleToken.Vault pub fun updateInwardFee(fee: UFix64) pub fun updateOutwardFee(fee: UFix64) pub fun updateEthereumAdminAccount(account: [UInt8]) } // TeleportAdmin resource // // Resource object that has the capability to teleport tokens // upon receiving teleport request from Ethereum side // pub resource TeleportAdmin: TeleportUser, TeleportControl { // the amount of tokens that the admin is allowed to teleport pub var allowedAmount: UFix64 // receiver reference to collect teleport fee pub let feeCollector: @FiatToken.Vault // fee collected when token is teleported from Ethereum to Flow pub var inwardFee: UFix64 // fee collected when token is teleported from Flow to Ethereum pub var outwardFee: UFix64 // corresponding controller account on Ethereum pub var ethereumAdminAccount: [UInt8] // teleportIn // // Function that release USDC tokens from custody, // and returns them to the calling context. // pub fun teleportIn(amount: UFix64, from: [UInt8], hash: String): @FungibleToken.Vault { pre { !TeleportCustodyEthereum.isFrozen: "Teleport service is frozen" amount <= self.allowedAmount: "Amount teleported must be less than the allowed amount" amount > self.inwardFee: "Amount teleported must be greater than inward teleport fee" from.length == 20: "Ethereum address should be 20 bytes" hash.length == 64: "Ethereum tx hash should be 32 bytes" !(TeleportCustodyEthereum.teleported[hash] ?? false): "Same hash already teleported" } self.allowedAmount = self.allowedAmount - amount TeleportCustodyEthereum.teleported[hash] = true emit TokensTeleportedIn(amount: amount, from: from, hash: hash) let vault <- TeleportCustodyEthereum.usdcVault.withdraw(amount: amount) let fee <- vault.withdraw(amount: self.inwardFee) self.feeCollector.deposit(from: <-fee) emit FeeCollected(amount: self.inwardFee, type: 1) return <- vault } // teleportOut // // Function that destroys a Vault instance, effectively burning the tokens. // // Note: the burned tokens are automatically subtracted from the // total supply in the Vault destructor. // pub fun teleportOut(from: @FiatToken.Vault, to: [UInt8]) { pre { !TeleportCustodyEthereum.isFrozen: "Teleport service is frozen" to.length == 20: "Ethereum address should be 20 bytes" } let vault <- from as! @FiatToken.Vault let fee <- vault.withdraw(amount: self.outwardFee) self.feeCollector.deposit(from: <-fee) emit FeeCollected(amount: self.outwardFee, type: 0) let amount = vault.balance TeleportCustodyEthereum.usdcVault.deposit(from: <- vault) emit TokensTeleportedOut(amount: amount, to: to) } pub fun withdrawFee(amount: UFix64): @FungibleToken.Vault { return <- self.feeCollector.withdraw(amount: amount) } pub fun updateInwardFee(fee: UFix64) { self.inwardFee = fee } pub fun updateOutwardFee(fee: UFix64) { self.outwardFee = fee } pub fun updateEthereumAdminAccount(account: [UInt8]) { pre { account.length == 20: "Ethereum address should be 20 bytes" } self.ethereumAdminAccount = account } pub fun getFeeAmount(): UFix64 { return self.feeCollector.balance } pub fun depositAllowance(from: @Allowance) { self.allowedAmount = self.allowedAmount + from.balance destroy from } init(allowedAmount: UFix64) { self.allowedAmount = allowedAmount self.feeCollector <- FiatToken.createEmptyVault() as! @FiatToken.Vault self.inwardFee = 0.01 self.outwardFee = 10.0 self.ethereumAdminAccount = [] } destroy() { destroy self.feeCollector } } pub fun getLockedVaultBalance(): UFix64 { return TeleportCustodyEthereum.usdcVault.balance } init() { // Initialize the path fields self.AdminStoragePath = /storage/usdcTeleportCustodyEthereumAdmin self.TeleportAdminStoragePath = /storage/usdcTeleportCustodyEthereumTeleportAdmin self.TeleportUserPublicPath = /public/usdcTeleportCustodyEthereumTeleportUser self.TeleportAdminPrivatePath = /private/usdcTeleportCustodyEthereumTeleportAdmin // Initialize contract variables self.isFrozen = false self.teleported = {} // Setup internal USDC vault self.usdcVault <- FiatToken.createEmptyVault() as! @FiatToken.Vault let admin <- create Administrator() self.account.save(<-admin, to: self.AdminStoragePath) } }

Contract

Contract