feat: add WIF QR sweep flow

Author: otaliptus

BDKSwiftExampleWallet.xcodeproj/project.pbxproj

@@ -38,6 +38,7 @@
 		AE2B8C1D2A9678C900815B2F /* FeeService.swift in Sources */ = {isa = PBXBuildFile; fileRef = AE2B8C1C2A9678C900815B2F /* FeeService.swift */; };
 		AE2B8C1F2A96797300815B2F /* RecommendedFees.swift in Sources */ = {isa = PBXBuildFile; fileRef = AE2B8C1E2A96797300815B2F /* RecommendedFees.swift */; };
 		AE2F255D2BED0BFB002A9AC6 /* AppError.swift in Sources */ = {isa = PBXBuildFile; fileRef = AE2F255C2BED0BFB002A9AC6 /* AppError.swift */; };
+		4F4D7EDC0B4EB26402929104 /* WifParser.swift in Sources */ = {isa = PBXBuildFile; fileRef = FC190D44F8616C5DC06AD853 /* WifParser.swift */; };
 		AE34DDAC2B6B31ED00F04AD4 /* WalletRecoveryView.swift in Sources */ = {isa = PBXBuildFile; fileRef = AE34DDAB2B6B31ED00F04AD4 /* WalletRecoveryView.swift */; };
 		AE34DDAE2B6B320F00F04AD4 /* WalletRecoveryViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = AE34DDAD2B6B320F00F04AD4 /* WalletRecoveryViewModel.swift */; };
 		AE3646262BEDB01200B04E25 /* FileManager+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = AE3646252BEDB01200B04E25 /* FileManager+Extensions.swift */; };
@@ -145,6 +146,7 @@
 		AE2B8C1C2A9678C900815B2F /* FeeService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FeeService.swift; sourceTree = "<group>"; };
 		AE2B8C1E2A96797300815B2F /* RecommendedFees.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RecommendedFees.swift; sourceTree = "<group>"; };
 		AE2F255C2BED0BFB002A9AC6 /* AppError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppError.swift; sourceTree = "<group>"; };
+		FC190D44F8616C5DC06AD853 /* WifParser.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WifParser.swift; sourceTree = "<group>"; };
 		AE34DDAB2B6B31ED00F04AD4 /* WalletRecoveryView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WalletRecoveryView.swift; sourceTree = "<group>"; };
 		AE34DDAD2B6B320F00F04AD4 /* WalletRecoveryViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WalletRecoveryViewModel.swift; sourceTree = "<group>"; };
 		AE3646252BEDB01200B04E25 /* FileManager+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "FileManager+Extensions.swift"; sourceTree = "<group>"; };
@@ -308,6 +310,7 @@
 			children = (
 				AE79538D2A2D59F000CCB277 /* Constants.swift */,
 				AE2F255C2BED0BFB002A9AC6 /* AppError.swift */,
+				FC190D44F8616C5DC06AD853 /* WifParser.swift */,
 			);
 			path = Utilities;
 			sourceTree = "<group>";
@@ -722,6 +725,7 @@
 				AE18E9382A9528200019D2A4 /* Bundle+Extensions.swift in Sources */,
 				AE79538E2A2D59F000CCB277 /* Constants.swift in Sources */,
 				AE2F255D2BED0BFB002A9AC6 /* AppError.swift in Sources */,
+				4F4D7EDC0B4EB26402929104 /* WifParser.swift in Sources */,
 				AEE6C74F2ABCBA4600442ADD /* WalletSyncState.swift in Sources */,
 				AE1C34242A424456008F807A /* ReceiveView.swift in Sources */,
 				AE91CEED2C0FDB70000AAD20 /* SentAndReceivedValues+Extensions.swift in Sources */,

BDKSwiftExampleWallet/Service/BDK Service/BDKService.swift

@@ -555,6 +555,94 @@ final class BDKService {
         try await signAndBroadcast(psbt: psbt)
     }
 
+    func sweepWif(wif: String, feeRate: UInt64) async throws -> [Txid] {
+        // Keep sweep minimal and predictable across signet/testnet/testnet4 in this example:
+        // use the Esplora path only.
+        guard self.clientType == .esplora else {
+            throw WalletError.sweepEsploraOnly
+        }
+
+        let candidates = [
+            "pkh(\(wif))",
+            "wpkh(\(wif))",
+            "sh(wpkh(\(wif)))",
+            "tr(\(wif))",
+        ]
+
+        var sweptTxids: [Txid] = []
+        var lastWIFOperationError: Error?
+        
+        var destinationScript: Script?
+        
+        for descriptorString in candidates {
+            guard
+                let descriptor = try? Descriptor(
+                    descriptor: descriptorString,
+                    network: self.network
+                )
+            else {
+                continue
+            }
+
+            let tempDir = FileManager.default.temporaryDirectory
+                .appendingPathComponent("bdk-sweep-\(UUID().uuidString)", isDirectory: true)
+            try? FileManager.default.createDirectory(at: tempDir, withIntermediateDirectories: true)
+            defer { try? FileManager.default.removeItem(at: tempDir) }
+
+            let tempPath = tempDir.appendingPathComponent("wallet.sqlite").path
+            let sweepPersister = try Persister.newSqlite(path: tempPath)
+            let sweepWallet = try Wallet.createSingle(
+                descriptor: descriptor,
+                network: self.network,
+                persister: sweepPersister
+            )
+
+            let _ = sweepWallet.revealNextAddress(keychain: .external)
+            let syncRequest = try sweepWallet.startSyncWithRevealedSpks().build()
+            let update = try await self.blockchainClient.sync(syncRequest, UInt64(5))
+            try sweepWallet.applyUpdate(update: update)
+
+            if sweepWallet.balance().total.toSat() == 0 {
+                continue
+            }
+
+            if destinationScript == nil {
+                let destinationAddress = try getAddress()
+                destinationScript = try Address(address: destinationAddress, network: self.network)
+                    .scriptPubkey()
+            }
+
+            guard let destinationScript else {
+                throw WalletError.noSweepableFunds
+            }
+
+            do {
+                let psbt = try TxBuilder()
+                    .drainTo(script: destinationScript)
+                    .drainWallet()
+                    .feeRate(feeRate: FeeRate.fromSatPerVb(satVb: feeRate))
+                    .finish(wallet: sweepWallet)
+
+                guard try sweepWallet.sign(psbt: psbt) else {
+                    continue
+                }
+
+                let tx = try psbt.extractTx()
+                try await self.blockchainClient.broadcast(tx)
+                sweptTxids.append(tx.computeTxid())
+            } catch {
+                lastWIFOperationError = error
+                continue
+            }
+        }
+
+        guard !sweptTxids.isEmpty else {
+            throw lastWIFOperationError ?? WalletError.noSweepableFunds
+        }
+
+        return sweptTxids
+    }
+
     func buildTransaction(address: String, amount: UInt64, feeRate: UInt64) throws
         -> Psbt
     {
@@ -768,6 +856,7 @@ struct BDKClient {
     let fullScanWithInspector: (FullScanScriptInspector) async throws -> Void
     let getAddress: () throws -> String
     let send: (String, UInt64, UInt64) throws -> Void
+    let sweepWif: (String, UInt64) async throws -> [Txid]
     let calculateFee: (Transaction) throws -> Amount
     let calculateFeeRate: (Transaction) throws -> UInt64
     let sentAndReceived: (Transaction) throws -> SentAndReceivedValues
@@ -812,6 +901,9 @@ extension BDKClient {
                 try await BDKService.shared.send(address: address, amount: amount, feeRate: feeRate)
             }
         },
+        sweepWif: { (wif, feeRate) in
+            try await BDKService.shared.sweepWif(wif: wif, feeRate: feeRate)
+        },
         calculateFee: { tx in try BDKService.shared.calculateFee(tx: tx) },
         calculateFeeRate: { tx in try BDKService.shared.calculateFeeRate(tx: tx) },
         sentAndReceived: { tx in try BDKService.shared.sentAndReceived(tx: tx) },
@@ -874,6 +966,7 @@ extension BDKClient {
             fullScanWithInspector: { _ in },
             getAddress: { "tb1pd8jmenqpe7rz2mavfdx7uc8pj7vskxv4rl6avxlqsw2u8u7d4gfs97durt" },
             send: { _, _, _ in },
+            sweepWif: { _, _ in [] },
             calculateFee: { _ in Amount.mock },
             calculateFeeRate: { _ in UInt64(6.15) },
             sentAndReceived: { _ in

BDKSwiftExampleWallet/Service/BDK Service/BDKSwiftExampleWalletError.swift

@@ -14,6 +14,8 @@ enum WalletError: Error {
     case walletNotFound
     case fullScanUnsupported
     case backendNotImplemented
+    case sweepEsploraOnly
+    case noSweepableFunds
 }
 
 extension WalletError: LocalizedError {
@@ -31,6 +33,10 @@ extension WalletError: LocalizedError {
             return "Full scan is not supported by the selected blockchain client"
         case .backendNotImplemented:
             return "The selected blockchain backend is not yet implemented"
+        case .sweepEsploraOnly:
+            return "Sweep is available only with Esplora in this example app"
+        case .noSweepableFunds:
+            return "No sweepable funds found for this WIF"
         }
     }
 }

BDKSwiftExampleWallet/Utilities/WifParser.swift

@@ -0,0 +1,57 @@
+//
+//  WifParser.swift
+//  BDKSwiftExampleWallet
+//
+//  Created by otaliptus on 3/3/26.
+//
+
+import Foundation
+
+// Note: this parser is just a pretty simple heuristic for the simple wallet
+enum WifParser {
+    static func extract(from value: String) -> String? {
+        var candidates = [value]
+
+        if let components = URLComponents(string: value),
+            let queryItems = components.queryItems
+        {
+            for item in queryItems {
+                let key = item.name.lowercased()
+                if key == "wif" || key == "privkey" || key == "private_key" || key == "privatekey",
+                    let itemValue = item.value
+                {
+                    candidates.append(itemValue)
+                }
+            }
+        }
+
+        for candidate in candidates {
+            var token = candidate.trimmingCharacters(in: .whitespacesAndNewlines)
+
+            if token.lowercased().hasPrefix("wif:") {
+                token = String(token.dropFirst(4))
+            }
+
+            if isLikelyWif(token) {
+                return token
+            }
+        }
+
+        return nil
+    }
+
+    static func isLikelyWif(_ value: String) -> Bool {
+        guard value.count == 51 || value.count == 52 else {
+            return false
+        }
+
+        guard let first = value.first, "5KL9c".contains(first) else {
+            return false
+        }
+
+        let base58Charset = CharacterSet(
+            charactersIn: "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
+        )
+        return value.unicodeScalars.allSatisfy { base58Charset.contains($0) }
+    }
+}

BDKSwiftExampleWallet/View Model/OnboardingViewModel.swift

@@ -145,6 +145,12 @@ class OnboardingViewModel: ObservableObject {
 
         Task {
             do {
+                if WifParser.extract(from: self.words) != nil {
+                    throw AppError.generic(
+                        message:
+                            "WIF is for sweep, not wallet creation. Open an existing wallet and use Send > Scan/Paste to sweep it."
+                    )
+                }
                 if self.isDescriptor {
                     try self.bdkClient.createWalletFromDescriptor(self.words)
                 } else if self.isXPub {
@@ -162,6 +168,11 @@ class OnboardingViewModel: ObservableObject {
                     self.isCreatingWallet = false
                     self.createWithPersistError = error
                 }
+            } catch let error as AppError {
+                DispatchQueue.main.async {
+                    self.isCreatingWallet = false
+                    self.onboardingViewError = error
+                }
             } catch {
                 DispatchQueue.main.async {
                     self.isCreatingWallet = false

BDKSwiftExampleWallet/View/OnboardingView.swift

@@ -225,6 +225,7 @@ struct OnboardingView: View {
                 message: Text(viewModel.onboardingViewError?.description ?? "Unknown"),
                 dismissButton: .default(Text("OK")) {
                     viewModel.onboardingViewError = nil
+                    showingOnboardingViewErrorAlert = false
                 }
             )
         }
@@ -251,6 +252,9 @@ struct OnboardingView: View {
                 animateContent = true
             }
         }
+        .onReceive(viewModel.$onboardingViewError) { error in
+            showingOnboardingViewErrorAlert = (error != nil)
+        }
     }
 }
 

BDKSwiftExampleWallet/View/Send/AddressView.swift

@@ -14,7 +14,11 @@ struct AddressView: View {
     @Binding var navigationPath: NavigationPath
     @State var address: String = ""
     @State private var isShowingAlert = false
+    @State private var alertTitle = "Error"
     @State private var alertMessage = ""
+    @State private var isSweeping = false
+    private let bdkClient: BDKClient = .live
+    private let sweepFeeRate: UInt64 = 2
     let pasteboard = UIPasteboard.general
 
     var body: some View {
@@ -29,7 +33,7 @@ struct AddressView: View {
             )
             .alert(isPresented: $isShowingAlert) {
                 Alert(
-                    title: Text("Error"),
+                    title: Text(alertTitle),
                     message: Text(alertMessage),
                     dismissButton: .default(Text("OK"))
                 )
@@ -45,7 +49,14 @@ extension AddressView {
     func handleScan(result: Result<ScanResult, ScanError>) {
         switch result {
         case .success(let result):
-            let scannedAddress = result.string.lowercased().replacingOccurrences(
+            let scannedValue = result.string.trimmingCharacters(in: .whitespacesAndNewlines)
+
+            if let wif = WifParser.extract(from: scannedValue) {
+                sweep(wif: wif)
+                return
+            }
+
+            let scannedAddress = scannedValue.lowercased().replacingOccurrences(
                 of: "bitcoin:",
                 with: ""
             )
@@ -54,10 +65,12 @@ extension AddressView {
                 address = bitcoinAddress
                 navigationPath.append(NavigationDestination.amount(address: bitcoinAddress))
             } else {
+                alertTitle = "Error"
                 alertMessage = "The scanned QR code did not contain a valid Bitcoin address."
                 isShowingAlert = true
             }
         case .failure(let error):
+            alertTitle = "Error"
             alertMessage = "Scanning failed: \(error.localizedDescription)"
             isShowingAlert = true
         }
@@ -66,24 +79,68 @@ extension AddressView {
     private func pasteAddress() {
         if let pasteboardContent = UIPasteboard.general.string {
             if pasteboardContent.isEmpty {
+                alertTitle = "Error"
                 alertMessage = "The pasteboard is empty."
                 isShowingAlert = true
                 return
             }
             let trimmedContent = pasteboardContent.trimmingCharacters(in: .whitespacesAndNewlines)
             if trimmedContent.isEmpty {
+                alertTitle = "Error"
                 alertMessage = "The pasteboard contains only whitespace."
                 isShowingAlert = true
                 return
             }
+
+            if let wif = WifParser.extract(from: trimmedContent) {
+                sweep(wif: wif)
+                return
+            }
+
             let lowercaseAddress = trimmedContent.lowercased()
             address = lowercaseAddress
             navigationPath.append(NavigationDestination.amount(address: address))
         } else {
+            alertTitle = "Error"
             alertMessage = "Unable to access the pasteboard. Please try copying the address again."
             isShowingAlert = true
         }
     }
+
+    private func sweep(wif: String) {
+        guard !isSweeping else { return }
+        isSweeping = true
+
+        Task {
+            defer {
+                Task { @MainActor in
+                    isSweeping = false
+                }
+            }
+
+            do {
+                let txids = try await bdkClient.sweepWif(wif, sweepFeeRate)
+                let txidText = txids.map { "\($0)" }.joined(separator: ", ")
+
+                await MainActor.run {
+                    alertTitle = "Success"
+                    alertMessage = "Sweep broadcasted: \(txidText)"
+                    isShowingAlert = true
+                    NotificationCenter.default.post(
+                        name: Notification.Name("TransactionSent"),
+                        object: nil
+                    )
+                }
+            } catch {
+                await MainActor.run {
+                    alertTitle = "Error"
+                    alertMessage = "Sweep failed: \(error.localizedDescription)"
+                    isShowingAlert = true
+                }
+            }
+        }
+    }
+
 }
 
 struct CustomScannerView: View {