Allow custom LCP device identifiers (#661)

Author: dewantawsif

CHANGELOG.md

@@ -11,6 +11,12 @@ All notable changes to this project will be documented in this file. Take a look
 * Added `VisualNavigatorDelegate.navigatorContentInset(_:)` to customize the content and safe-area insets used by the navigator.
     * By default, the navigator uses the window's `safeAreaInsets`, which can cause content to shift when the status bar is shown or hidden (since those insets change). To avoid this, implement `navigatorContentInset(_:)` and return insets that remain stable across status bar visibility changes — for example, a top inset large enough to accommodate the maximum expected status bar height.
 
+#### LCP
+
+* Added an initializer parameter for providing a custom device identifier (contributed by [@dewantawsif](https://github.com/readium/swift-toolkit/pull/661)).
+    * You must ensure the identifier is unique and stable for the device (persist and reuse across app launches).
+    * Recommended: generate an app-scoped UUID and store it securely (e.g., in the Keychain); avoid hardware or advertising identifiers.
+
 ### Changed
 
 #### Navigator

Sources/LCP/LCPService.swift

@@ -23,13 +23,18 @@ public final class LCPService: Loggable {
 
     /// - Parameter deviceName: Device name used when registering a license to an LSD server.
     ///   If not provided, the device name will be the default `UIDevice.current.name`.
+    /// - Parameter deviceId: Device ID used when registering a license to an LSD server.
+    ///   You must ensure the identifier is unique and stable for the device (persist and
+    ///   reuse across app launches). If not provided, the device ID will be generated as
+    ///   a random UUID.
     public init(
         client: LCPClient,
         licenseRepository: LCPLicenseRepository,
         passphraseRepository: LCPPassphraseRepository,
         assetRetriever: AssetRetriever,
         httpClient: HTTPClient,
-        deviceName: String? = nil
+        deviceName: String? = nil,
+        deviceId: String? = nil
     ) {
         // Determine whether the embedded liblcp.a is in production mode, by attempting to open a production license.
         let isProduction: Bool = {
@@ -50,6 +55,7 @@ public final class LCPService: Loggable {
             crl: CRLService(httpClient: httpClient),
             device: DeviceService(
                 deviceName: deviceName ?? UIDevice.current.name,
+                deviceId: deviceId,
                 repository: licenseRepository,
                 httpClient: httpClient
             ),

Sources/LCP/Services/DeviceService.swift

@@ -12,27 +12,30 @@ final class DeviceService {
     private let httpClient: HTTPClient
 
     /// Returns the device's name.
-    var name: String
+    let name: String
+    /// Returns the device's ID
+    let id: String
 
     init(
         deviceName: String,
+        deviceId: String?,
         repository: LCPLicenseRepository,
         httpClient: HTTPClient
     ) {
         name = deviceName
-        self.repository = repository
-        self.httpClient = httpClient
-    }
 
-    /// Returns the device ID, creates it if needed.
-    var id: String {
-        let defaults = UserDefaults.standard
-        guard let deviceId = defaults.string(forKey: "lcp_device_id") else {
-            let deviceId = UUID().description
-            defaults.set(deviceId.description, forKey: "lcp_device_id")
-            return deviceId.description
+        if let providedId = deviceId {
+            id = providedId
+        } else if let savedId = UserDefaults.standard.string(forKey: "lcp_device_id") {
+            id = savedId
+        } else {
+            let generatedId = UUID().uuidString
+            UserDefaults.standard.set(generatedId, forKey: "lcp_device_id")
+            id = generatedId
         }
-        return deviceId
+
+        self.repository = repository
+        self.httpClient = httpClient
     }
 
     // Device ID and name as query parameters for HTTP requests.