Swift Keychain

import SwiftUI

struct ContentView: View {
    @State private var service: String = ""
    @State private var account: String = ""
    @State private var secret: String = ""
    
    @State var message: String = ""
    @State var show: Bool = false
    
    var body: some View {
        Grid {
            GridRow {
                Text("service")
                TextField("service, e.g. https://github.com", text: $service)
            }
            GridRow {
                Text("account")
                TextField("account, e.g. john", text: $account)
            }
            GridRow {
                Text("secret")
                SecureField("secret, e.g. P@ssword!", text: $secret)
            }
        }.padding()
        
        VStack {
            HStack {
                
                Button("get") {
                    let (status, secret) = KeychainManager.get(service: service, account: account)
                    message = String(SecCopyErrorMessageString(status, nil) ?? "unknown" as CFString)
                    self.secret = secret ?? ""
                    if status == errSecSuccess {
                        message = "Success\n\n\(message)\n\nSecret: \(self.secret)"
                    } else {
                        message = "Failure\n\n\(message)"
                    }
                    show = true
                }.alert(message, isPresented: $show) {
                    Button("OK") {}
                }
                
                Button("insert") {
                    Task {
                        let status = await KeychainManager.insert(service: service, account: account, secret: secret)
                        message = String(SecCopyErrorMessageString(status, nil) ?? "unknown" as CFString)
                        if status == errSecSuccess {
                            message = "Success\n\n\(message)"
                        } else {
                            message = "Failure\n\n\(message)"
                        }
                        show = true
                    }
                }.alert(message, isPresented: $show) {
                    Button("OK") { }
                }
                
                Button("update") {
                    Task {
                        let status = KeychainManager.update(service: service, account: account, secret: secret)
                        message = String(SecCopyErrorMessageString(status, nil) ?? "unknown" as CFString)
                        if status == errSecSuccess {
                            message = "Success\n\n\(message)"
                        } else {
                            message = "Failure\n\n\(message)"
                        }
                        show = true
                    }
                }.alert(message, isPresented: $show) {
                    Button("OK") { }
                }
                
                Button("delete") {
                    Task {
                        let status = await KeychainManager.delete(service: service, account: account)
                        message = String(SecCopyErrorMessageString(status, nil) ?? "unknown" as CFString)
                        if status == errSecSuccess {
                            message = "Success\n\n\(message)"
                        } else {
                            message = "Failure\n\n\(message)"
                        }
                        show = true
                    }
                }.alert(message, isPresented: $show) {
                    Button("OK") {}
                }
                
                Button("save") {
                    Task {
                        let status = await KeychainManager.save(service: service, account: account, secret: secret)
                        message = String(SecCopyErrorMessageString(status, nil) ?? "unknown" as CFString)
                        if status == errSecSuccess {
                            message = "Success\n\n\(message)"
                        } else {
                            message = "Failure\n\n\(message)"
                        }
                        show = true
                    }
                }.alert(message, isPresented: $show) {
                    Button("OK") {}
                }
                
            }
            Text("Secrets saved to iCloud Keychain, try fill form, then save, get, update, delete").foregroundStyle(.secondary).padding()
        }
    }
}

// https://www.youtube.com/watch?v=cQjgBIJtMbw
class KeychainManager {
    /// Retrieve secret for given `account` in `service`.
    ///
    /// ```
    /// let (status, secret) = KeychainManager.get(service: "https://github.com", account: "john")
    /// if status == errSecSuccess && secret != nil {
    ///     print("secret: \(secret)")
    /// }
    /// ```
    ///
    /// - Parameters:
    ///     - service: can by any string, but usually is an url, e.g.: https://github.com/
    ///     - account: our username, e.g.: john
    ///
    /// - Returns: tuple with `status` and `secret`.
    static func get(service: String, account: String) -> (status: OSStatus, secret: String?) {
        var result: CFTypeRef?
        let status = SecItemCopyMatching([
            kSecClass: kSecClassGenericPassword,
            kSecAttrService: service,
            kSecAttrAccount: account,
            kSecReturnData: kCFBooleanTrue as Any,
            kSecMatchLimit: kSecMatchLimitOne
        ] as CFDictionary, &result)
        guard let data = result as? Data else {
            return (status, nil)
        }
        let secret = String(decoding: data, as: UTF8.self)
        return (status, secret)
    }
    
    static func insert(service: String, account: String, secret: String) async -> OSStatus {
        guard let data = secret.data(using: .utf8) else {
            return errSecBadReq
        }
        return SecItemAdd([
            kSecClass: kSecClassGenericPassword,
            kSecAttrService: service,
            kSecAttrAccount: account,
            kSecValueData: data
        ] as CFDictionary, nil)
    }
    
    static func update(service: String, account: String, secret: String) -> OSStatus {
        guard let data = secret.data(using: .utf8) else {
            return errSecBadReq
        }
        return SecItemUpdate([
            kSecClass: kSecClassGenericPassword,
            kSecAttrService: service,
            kSecAttrAccount: account
        ] as CFDictionary, [
            kSecValueData: data
        ] as CFDictionary)
    }
    
    /// Deletes secret from keychain
    ///
    /// ```
    ///  Task {
    ///     let status = await Keychain.delete(service: "https://github.com/", "john")
    ///     if status != errSecSuccess {
    ///         message = String(SecCopyErrorMessageString(status, nil) ?? "unknown error" as CFString)
    ///         print("unable delete secret because of \(message)")
    ///     }
    /// }
    /// ```
    ///
    /// - Parameters:
    ///     - service: can by any string, but usually is an url, e.g.: https://github.com/
    ///     - account: our username, e.g.: john
    static func delete(service: String, account: String) async -> OSStatus {
        return SecItemDelete([
            kSecClass: kSecClassGenericPassword,
            kSecAttrService: service,
            kSecAttrAccount: account
        ] as CFDictionary)
    }
    
    /// Saves secret to keychain
    ///
    /// ```
    ///  Task {
    ///     let status = await Keychain.save(service: "https://github.com/", "john", secret: "P@ssword!")
    ///     if status != errSecSuccess {
    ///         message = String(SecCopyErrorMessageString(status, nil) ?? "unknown error" as CFString)
    ///         print("failure: \(message)")
    ///     }
    /// }
    /// ```
    ///
    /// - Parameters:
    ///     - service: can by any string, but usually is an url, e.g.: https://github.com/
    ///     - account: our username, e.g.: john
    ///     - secret: password to be saved
    static func save(service: String, account: String, secret: String) async -> OSStatus {
        let status = update(service: service, account: account, secret: secret)
        if status == errSecItemNotFound {
            return await insert(service: service, account: account, secret: secret)
        }
        return status
    }
}

#Preview {
    ContentView()
}