import FungibleToken from 0xf233dcee88fe0abe import NonFungibleToken from 0x1d7e57aa55817448 import DapperUtilityCoin from 0xead892083b3e2c6c import Genies from 0x12450e4bb3b7666e import NFTStorefront from 0x4eb8a10cb9f87357 transaction(storefrontAddress: Address, listingResourceID: UInt64, expectedPrice: UFix64) { let paymentVault: @FungibleToken.Vault let buyerNFTCollection: &Genies.Collection{NonFungibleToken.Receiver} let storefront: &NFTStorefront.Storefront{NFTStorefront.StorefrontPublic} let listing: &NFTStorefront.Listing{NFTStorefront.ListingPublic} let geniesAuthAccount: AuthAccount let mainDUCVault: &DapperUtilityCoin.Vault let balanceBeforeTransfer: UFix64 prepare(genies: AuthAccount, dapper: AuthAccount, buyer: AuthAccount) { if buyer.borrow<&Genies.Collection>(from: Genies.CollectionStoragePath) == nil { buyer.save(<-Genies.createEmptyCollection(), to: Genies.CollectionStoragePath) buyer.link<&Genies.Collection{Genies.GeniesNFTCollectionPublic, NonFungibleToken.Receiver}>( Genies.CollectionPublicPath, target: Genies.CollectionStoragePath ) } self.geniesAuthAccount = genies // Although the Storefront is available as a public capability, we want to borrow // from storage so that we can enforce the need for Genies to sign this transaction self.storefront = genies.borrow<&NFTStorefront.Storefront{NFTStorefront.StorefrontPublic}>(from: NFTStorefront.StorefrontStoragePath) ?? panic("Could not borrow a reference to the storefront") self.listing = self.storefront.borrowListing(listingResourceID: listingResourceID) ?? panic("No Listing with that ID in Storefront") let salePrice = self.listing.getDetails().salePrice if expectedPrice != salePrice { panic("Sale price not expected value") } self.mainDUCVault = dapper.borrow<&DapperUtilityCoin.Vault>(from: /storage/dapperUtilityCoinVault) ?? panic("Could not borrow reference to Dapper Utility Coin vault") self.balanceBeforeTransfer = self.mainDUCVault.balance self.paymentVault <- self.mainDUCVault.withdraw(amount: salePrice) self.buyerNFTCollection = buyer .getCapability<&Genies.Collection{NonFungibleToken.Receiver}>( Genies.CollectionPublicPath ) .borrow() ?? panic("Cannot borrow Genies collection receiver from buyerAddress") } // The pre phase is executed after the prepare phase, // and is used for checking if explicit conditions hold before executing the remainder of the transaction pre { self.geniesAuthAccount.address == storefrontAddress && self.geniesAuthAccount.address == 0x12450e4bb3b7666e: "Requires valid authorizing signature" } execute { let item <- self.listing.purchase( payment: <-self.paymentVault ) self.buyerNFTCollection.deposit(token: <-item) } post { // Ensure there is no DUC leakage self.mainDUCVault.balance == self.balanceBeforeTransfer: "transaction would leak DUC" } }

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Transaction