Allow custom LCP device identifiers (#720)

Author: dewantawsif

.gitignore

@@ -49,6 +49,7 @@ captures/
 .idea/jarRepositories.xml
 .idea/misc.xml
 .idea/migrations.xml
+.idea/markdown.xml
 # Android Studio 3 in .gitignore file.
 .idea/caches
 .idea/modules.xml

CHANGELOG.md

@@ -13,6 +13,12 @@ All notable changes to this project will be documented in this file. Take a look
 * New experimental positioning of EPUB decorations that places highlights behind text to improve legibility with opaque decorations (contributed by [@ddfreiling](https://github.com/readium/kotlin-toolkit/pull/721)).
     * To opt-in, initialize the `EpubNavigatorFragment.Configuration` object with `decorationTemplates = HtmlDecorationTemplates.defaultTemplates(alpha = 1.0, experimentalPositioning = true)`.
 
+#### LCP
+
+* Added an initializer parameter for providing a custom device identifier (contributed by [@dewantawsif](https://github.com/readium/kotlin-toolkit/pull/720)).
+    * 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. Avoid hardware or advertising identifiers.
+
 
 ## [3.1.2]
 

readium/lcp/src/main/java/org/readium/r2/lcp/LcpService.kt

@@ -135,11 +135,15 @@ public interface LcpService {
          * @param deviceName Device name used when registering a license to an LSD server.
          * If not provided, the device name will be generated from the device's manufacturer and
          * model.
+         * @param deviceId Device ID used when registering a license to an LSD server.
+         * If not provided, the device ID will be generated as a random UUID and persisted for
+         * future sessions.
          */
         public operator fun invoke(
             context: Context,
             assetRetriever: AssetRetriever,
             deviceName: String? = null,
+            deviceId: String? = null,
         ): LcpService? {
             if (!LcpClient.isAvailable()) {
                 return null
@@ -152,6 +156,7 @@ public interface LcpService {
             val network = NetworkService()
             val device = DeviceService(
                 deviceName = deviceName,
+                deviceId = deviceId,
                 repository = deviceRepository,
                 network = network,
                 context = context

readium/lcp/src/main/java/org/readium/r2/lcp/service/DeviceService.kt

@@ -10,31 +10,34 @@
 package org.readium.r2.lcp.service
 
 import android.content.Context
-import android.content.SharedPreferences
 import android.os.Build
-import java.io.Serializable
+import androidx.core.content.edit
 import java.util.UUID
 import org.readium.r2.lcp.license.model.LicenseDocument
 import org.readium.r2.lcp.license.model.components.Link
 
 internal class DeviceService(
     deviceName: String?,
+    deviceId: String?,
     private val repository: DeviceRepository,
     private val network: NetworkService,
     val context: Context,
-) : Serializable {
-
-    private val preferences: SharedPreferences = context.getSharedPreferences(
-        "org.readium.r2.settings",
-        Context.MODE_PRIVATE
-    )
-
-    val id: String
-        get() {
-            val deviceId = preferences.getString("lcp_device_id", UUID.randomUUID().toString())!!
-            preferences.edit().putString("lcp_device_id", deviceId).apply()
-            return deviceId
-        }
+) {
+
+    val id: String = deviceId ?: generatedId
+
+    private val generatedId: String get() {
+        val key = "lcp_device_id"
+
+        val preferences = context.getSharedPreferences("org.readium.r2.settings", Context.MODE_PRIVATE)
+
+        preferences.getString(key, null)
+            ?.let { return it }
+
+        val id = UUID.randomUUID().toString()
+        preferences.edit { putString(key, id) }
+        return id
+    }
 
     val name: String =
         deviceName ?: "${Build.MANUFACTURER} ${Build.MODEL}"