Improved type safety, local auth support, and better error handling

Sources/KeychainKit/Protocols/KeychainAccountProtocol.swift

@@ -0,0 +1,47 @@
+import Foundation
+
+/// A protocol that defines the required properties for a keychain account descriptor.
+///
+/// Types conforming to this protocol provide metadata for configuring secure storage
+/// and access behavior for keychain items.
+public protocol KeychainAccountProtocol {
+    /// A unique string used to identify the keychain account.
+    var identifier: String { get }
+    
+    /// The keychain data protection level for the account.
+    ///
+    /// Defaults to `kSecAttrAccessibleAfterFirstUnlock`. You may override it to use other
+    /// accessibility levels, such as `kSecAttrAccessibleWhenUnlocked`
+    /// or `kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly`.
+    var protection: CFString { get }
+    
+    /// The access control flags used to define authentication requirements.
+    ///
+    /// Defaults to `[]` (no additional access control). Can be overridden to specify
+    /// constraints such as `.userPresence`, `.biometryAny`, or `.devicePasscode`.
+    var accessFlags: SecAccessControlCreateFlags { get }
+    
+    /// Whether the item should be marked as synchronizable via iCloud Keychain.
+    ///
+    /// Defaults to `false`. Set to `true` if the item should sync across devices.
+    var synchronizable: Bool { get }
+}
+
+public extension KeychainAccountProtocol {
+    /// Default value for `protection`: accessible after first unlock.
+    var protection: CFString { kSecAttrAccessibleAfterFirstUnlock }
+    
+    /// Default value for `accessFlags`: no access control constraints.
+    var accessFlags: SecAccessControlCreateFlags { [] }
+    
+    /// Default value for `synchronizable`: not synchronized across devices.
+    var synchronizable: Bool { false }
+}
+
+public extension KeychainAccountProtocol where Self: RawRepresentable, Self.RawValue == String {
+    /// Provides a default `identifier` implementation for `RawRepresentable` types
+    /// whose `RawValue` is `String`.
+    ///
+    /// The `identifier` is derived from the raw string value.
+    var identifier: String { rawValue }
+}