feat: delta sync (#18428)

* feat: delta sync

* fix: ignore iCloud assets

* feat: dev logs

* add full sync button

* remove photo_manager dep for sync

* misc logs and fix

* add time taken to DLog

* fix: build release iOS

* ios sync go brrr

* rename local sync service

* update isar fork

* rename to platform assets / albums

* fix ci check

---------

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>
Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/android/app/build.gradle

@@ -1,103 +1,106 @@
 plugins {
-    id "com.android.application"
-    id "kotlin-android"
-    id "dev.flutter.flutter-gradle-plugin"
-    id 'com.google.devtools.ksp'
+  id "com.android.application"
+  id "kotlin-android"
+  id "dev.flutter.flutter-gradle-plugin"
+  id 'com.google.devtools.ksp'
 }
 
 def localProperties = new Properties()
 def localPropertiesFile = rootProject.file('local.properties')
 if (localPropertiesFile.exists()) {
-    localPropertiesFile.withInputStream { localProperties.load(it) }
+  localPropertiesFile.withInputStream { localProperties.load(it) }
 }
 
 def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
 if (flutterVersionCode == null) {
-    flutterVersionCode = '1'
+  flutterVersionCode = '1'
 }
 
 def flutterVersionName = localProperties.getProperty('flutter.versionName')
 if (flutterVersionName == null) {
-    flutterVersionName = '1.0'
+  flutterVersionName = '1.0'
 }
 
 def keystoreProperties = new Properties()
 def keystorePropertiesFile = rootProject.file('key.properties')
 if (keystorePropertiesFile.exists()) {
-    keystorePropertiesFile.withInputStream { keystoreProperties.load(it) }
+  keystorePropertiesFile.withInputStream { keystoreProperties.load(it) }
 }
 
 android {
-    compileSdkVersion 35
+  compileSdkVersion 35
 
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_17
-        targetCompatibility JavaVersion.VERSION_17
-        coreLibraryDesugaringEnabled true
+  compileOptions {
+    sourceCompatibility JavaVersion.VERSION_17
+    targetCompatibility JavaVersion.VERSION_17
+    coreLibraryDesugaringEnabled true
+  }
+
+  kotlinOptions {
+    jvmTarget = '17'
+  }
+
+  sourceSets {
+    main.java.srcDirs += 'src/main/kotlin'
+  }
+
+  defaultConfig {
+    applicationId "app.alextran.immich"
+    minSdkVersion 26
+    targetSdkVersion 35
+    versionCode flutterVersionCode.toInteger()
+    versionName flutterVersionName
+  }
+
+  signingConfigs {
+    release {
+      def keyAliasVal = System.getenv("ALIAS")
+      def keyPasswordVal = System.getenv("ANDROID_KEY_PASSWORD")
+      def storePasswordVal = System.getenv("ANDROID_STORE_PASSWORD")
+
+      keyAlias keyAliasVal ? keyAliasVal : keystoreProperties['keyAlias']
+      keyPassword keyPasswordVal ? keyPasswordVal : keystoreProperties['keyPassword']
+      storeFile file("../key.jks") ? file("../key.jks") : file(keystoreProperties['storeFile'])
+      storePassword storePasswordVal ? storePasswordVal : keystoreProperties['storePassword']
+    }
+  }
+
+  buildTypes {
+    debug {
+      applicationIdSuffix '.debug'
+      versionNameSuffix '-DEBUG'
     }
 
-    kotlinOptions {
-        jvmTarget = '17'
+    release {
+      signingConfig signingConfigs.release
     }
-
-    sourceSets {
-        main.java.srcDirs += 'src/main/kotlin'
-    }
-
-    defaultConfig {
-        applicationId "app.alextran.immich"
-        minSdkVersion 26
-        targetSdkVersion 35
-        versionCode flutterVersionCode.toInteger()
-        versionName flutterVersionName
-    }
-
-   signingConfigs {
-       release {
-            def keyAliasVal = System.getenv("ALIAS")
-            def keyPasswordVal = System.getenv("ANDROID_KEY_PASSWORD")
-            def storePasswordVal = System.getenv("ANDROID_STORE_PASSWORD")
-
-            keyAlias keyAliasVal ? keyAliasVal : keystoreProperties['keyAlias']
-            keyPassword keyPasswordVal ? keyPasswordVal : keystoreProperties['keyPassword']
-            storeFile file("../key.jks") ? file("../key.jks") : file(keystoreProperties['storeFile'])
-            storePassword storePasswordVal ? storePasswordVal : keystoreProperties['storePassword']
-       }
-   }
-
-    buildTypes {
-        debug {
-            applicationIdSuffix '.debug'
-            versionNameSuffix '-DEBUG'
-        }
-
-        release {
-            signingConfig signingConfigs.release
-        }
-    }
-    namespace 'app.alextran.immich'
+  }
+  namespace 'app.alextran.immich'
 }
 
 flutter {
-    source '../..'
+  source '../..'
 }
 
 dependencies {
-    def kotlin_version = '2.0.20'
-    def kotlin_coroutines_version = '1.9.0'
-    def work_version = '2.9.1'
-    def concurrent_version = '1.2.0'
-    def guava_version = '33.3.1-android'
-    def glide_version = '4.16.0'
+  def kotlin_version = '2.0.20'
+  def kotlin_coroutines_version = '1.9.0'
+  def work_version = '2.9.1'
+  def concurrent_version = '1.2.0'
+  def guava_version = '33.3.1-android'
+  def glide_version = '4.16.0'
+  def serialization_version = '1.8.1'
 
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
-    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$kotlin_coroutines_version"
-    implementation "androidx.work:work-runtime-ktx:$work_version"
-    implementation "androidx.concurrent:concurrent-futures:$concurrent_version"
-    implementation "com.google.guava:guava:$guava_version"
-    implementation "com.github.bumptech.glide:glide:$glide_version"
-    ksp "com.github.bumptech.glide:ksp:$glide_version"
-    coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.1.2'
+  implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+  implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$kotlin_coroutines_version"
+  implementation "androidx.work:work-runtime-ktx:$work_version"
+  implementation "androidx.concurrent:concurrent-futures:$concurrent_version"
+  implementation "com.google.guava:guava:$guava_version"
+  implementation "com.github.bumptech.glide:glide:$glide_version"
+  implementation "org.jetbrains.kotlinx:kotlinx-serialization-json:$serialization_version"
+
+  ksp "com.github.bumptech.glide:ksp:$glide_version"
+  coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.1.2'
 }
 
 // This is uncommented in F-Droid build script

mobile/android/app/src/main/kotlin/app/alextran/immich/MainActivity.kt

@@ -1,6 +1,11 @@
 package app.alextran.immich
 
+import android.os.Build
+import android.os.ext.SdkExtensions
 import androidx.annotation.NonNull
+import app.alextran.immich.sync.NativeSyncApi
+import app.alextran.immich.sync.NativeSyncApiImpl26
+import app.alextran.immich.sync.NativeSyncApiImpl30
 import io.flutter.embedding.android.FlutterFragmentActivity
 import io.flutter.embedding.engine.FlutterEngine
 
@@ -10,5 +15,13 @@ class MainActivity : FlutterFragmentActivity() {
     flutterEngine.plugins.add(BackgroundServicePlugin())
     flutterEngine.plugins.add(HttpSSLOptionsPlugin())
     // No need to set up method channel here as it's now handled in the plugin
+
+    val nativeSyncApiImpl =
+      if (Build.VERSION.SDK_INT < Build.VERSION_CODES.R || SdkExtensions.getExtensionVersion(Build.VERSION_CODES.R) < 1) {
+        NativeSyncApiImpl26(this)
+      } else {
+        NativeSyncApiImpl30(this)
+      }
+    NativeSyncApi.setUp(flutterEngine.dartExecutor.binaryMessenger, nativeSyncApiImpl)
   }
 }

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/Messages.g.kt

@@ -0,0 +1,393 @@
+// Autogenerated from Pigeon (v25.3.2), do not edit directly.
+// See also: https://pub.dev/packages/pigeon
+@file:Suppress("UNCHECKED_CAST", "ArrayInDataClass")
+
+package app.alextran.immich.sync
+
+import android.util.Log
+import io.flutter.plugin.common.BasicMessageChannel
+import io.flutter.plugin.common.BinaryMessenger
+import io.flutter.plugin.common.EventChannel
+import io.flutter.plugin.common.MessageCodec
+import io.flutter.plugin.common.StandardMethodCodec
+import io.flutter.plugin.common.StandardMessageCodec
+import java.io.ByteArrayOutputStream
+import java.nio.ByteBuffer
+private object MessagesPigeonUtils {
+
+  fun wrapResult(result: Any?): List<Any?> {
+    return listOf(result)
+  }
+
+  fun wrapError(exception: Throwable): List<Any?> {
+    return if (exception is FlutterError) {
+      listOf(
+        exception.code,
+        exception.message,
+        exception.details
+      )
+    } else {
+      listOf(
+        exception.javaClass.simpleName,
+        exception.toString(),
+        "Cause: " + exception.cause + ", Stacktrace: " + Log.getStackTraceString(exception)
+      )
+    }
+  }
+  fun deepEquals(a: Any?, b: Any?): Boolean {
+    if (a is ByteArray && b is ByteArray) {
+        return a.contentEquals(b)
+    }
+    if (a is IntArray && b is IntArray) {
+        return a.contentEquals(b)
+    }
+    if (a is LongArray && b is LongArray) {
+        return a.contentEquals(b)
+    }
+    if (a is DoubleArray && b is DoubleArray) {
+        return a.contentEquals(b)
+    }
+    if (a is Array<*> && b is Array<*>) {
+      return a.size == b.size &&
+          a.indices.all{ deepEquals(a[it], b[it]) }
+    }
+    if (a is List<*> && b is List<*>) {
+      return a.size == b.size &&
+          a.indices.all{ deepEquals(a[it], b[it]) }
+    }
+    if (a is Map<*, *> && b is Map<*, *>) {
+      return a.size == b.size && a.all {
+          (b as Map<Any?, Any?>).containsKey(it.key) &&
+          deepEquals(it.value, b[it.key])
+      }
+    }
+    return a == b
+  }
+      
+}
+
+/**
+ * Error class for passing custom error details to Flutter via a thrown PlatformException.
+ * @property code The error code.
+ * @property message The error message.
+ * @property details The error details. Must be a datatype supported by the api codec.
+ */
+class FlutterError (
+  val code: String,
+  override val message: String? = null,
+  val details: Any? = null
+) : Throwable()
+
+/** Generated class from Pigeon that represents data sent in messages. */
+data class PlatformAsset (
+  val id: String,
+  val name: String,
+  val type: Long,
+  val createdAt: Long? = null,
+  val updatedAt: Long? = null,
+  val durationInSeconds: Long
+)
+ {
+  companion object {
+    fun fromList(pigeonVar_list: List<Any?>): PlatformAsset {
+      val id = pigeonVar_list[0] as String
+      val name = pigeonVar_list[1] as String
+      val type = pigeonVar_list[2] as Long
+      val createdAt = pigeonVar_list[3] as Long?
+      val updatedAt = pigeonVar_list[4] as Long?
+      val durationInSeconds = pigeonVar_list[5] as Long
+      return PlatformAsset(id, name, type, createdAt, updatedAt, durationInSeconds)
+    }
+  }
+  fun toList(): List<Any?> {
+    return listOf(
+      id,
+      name,
+      type,
+      createdAt,
+      updatedAt,
+      durationInSeconds,
+    )
+  }
+  override fun equals(other: Any?): Boolean {
+    if (other !is PlatformAsset) {
+      return false
+    }
+    if (this === other) {
+      return true
+    }
+    return MessagesPigeonUtils.deepEquals(toList(), other.toList())  }
+
+  override fun hashCode(): Int = toList().hashCode()
+}
+
+/** Generated class from Pigeon that represents data sent in messages. */
+data class PlatformAlbum (
+  val id: String,
+  val name: String,
+  val updatedAt: Long? = null,
+  val isCloud: Boolean,
+  val assetCount: Long
+)
+ {
+  companion object {
+    fun fromList(pigeonVar_list: List<Any?>): PlatformAlbum {
+      val id = pigeonVar_list[0] as String
+      val name = pigeonVar_list[1] as String
+      val updatedAt = pigeonVar_list[2] as Long?
+      val isCloud = pigeonVar_list[3] as Boolean
+      val assetCount = pigeonVar_list[4] as Long
+      return PlatformAlbum(id, name, updatedAt, isCloud, assetCount)
+    }
+  }
+  fun toList(): List<Any?> {
+    return listOf(
+      id,
+      name,
+      updatedAt,
+      isCloud,
+      assetCount,
+    )
+  }
+  override fun equals(other: Any?): Boolean {
+    if (other !is PlatformAlbum) {
+      return false
+    }
+    if (this === other) {
+      return true
+    }
+    return MessagesPigeonUtils.deepEquals(toList(), other.toList())  }
+
+  override fun hashCode(): Int = toList().hashCode()
+}
+
+/** Generated class from Pigeon that represents data sent in messages. */
+data class SyncDelta (
+  val hasChanges: Boolean,
+  val updates: List<PlatformAsset>,
+  val deletes: List<String>,
+  val assetAlbums: Map<String, List<String>>
+)
+ {
+  companion object {
+    fun fromList(pigeonVar_list: List<Any?>): SyncDelta {
+      val hasChanges = pigeonVar_list[0] as Boolean
+      val updates = pigeonVar_list[1] as List<PlatformAsset>
+      val deletes = pigeonVar_list[2] as List<String>
+      val assetAlbums = pigeonVar_list[3] as Map<String, List<String>>
+      return SyncDelta(hasChanges, updates, deletes, assetAlbums)
+    }
+  }
+  fun toList(): List<Any?> {
+    return listOf(
+      hasChanges,
+      updates,
+      deletes,
+      assetAlbums,
+    )
+  }
+  override fun equals(other: Any?): Boolean {
+    if (other !is SyncDelta) {
+      return false
+    }
+    if (this === other) {
+      return true
+    }
+    return MessagesPigeonUtils.deepEquals(toList(), other.toList())  }
+
+  override fun hashCode(): Int = toList().hashCode()
+}
+private open class MessagesPigeonCodec : StandardMessageCodec() {
+  override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
+    return when (type) {
+      129.toByte() -> {
+        return (readValue(buffer) as? List<Any?>)?.let {
+          PlatformAsset.fromList(it)
+        }
+      }
+      130.toByte() -> {
+        return (readValue(buffer) as? List<Any?>)?.let {
+          PlatformAlbum.fromList(it)
+        }
+      }
+      131.toByte() -> {
+        return (readValue(buffer) as? List<Any?>)?.let {
+          SyncDelta.fromList(it)
+        }
+      }
+      else -> super.readValueOfType(type, buffer)
+    }
+  }
+  override fun writeValue(stream: ByteArrayOutputStream, value: Any?)   {
+    when (value) {
+      is PlatformAsset -> {
+        stream.write(129)
+        writeValue(stream, value.toList())
+      }
+      is PlatformAlbum -> {
+        stream.write(130)
+        writeValue(stream, value.toList())
+      }
+      is SyncDelta -> {
+        stream.write(131)
+        writeValue(stream, value.toList())
+      }
+      else -> super.writeValue(stream, value)
+    }
+  }
+}
+
+/** Generated interface from Pigeon that represents a handler of messages from Flutter. */
+interface NativeSyncApi {
+  fun shouldFullSync(): Boolean
+  fun getMediaChanges(): SyncDelta
+  fun checkpointSync()
+  fun clearSyncCheckpoint()
+  fun getAssetIdsForAlbum(albumId: String): List<String>
+  fun getAlbums(): List<PlatformAlbum>
+  fun getAssetsCountSince(albumId: String, timestamp: Long): Long
+  fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?): List<PlatformAsset>
+
+  companion object {
+    /** The codec used by NativeSyncApi. */
+    val codec: MessageCodec<Any?> by lazy {
+      MessagesPigeonCodec()
+    }
+    /** Sets up an instance of `NativeSyncApi` to handle messages through the `binaryMessenger`. */
+    @JvmOverloads
+    fun setUp(binaryMessenger: BinaryMessenger, api: NativeSyncApi?, messageChannelSuffix: String = "") {
+      val separatedMessageChannelSuffix = if (messageChannelSuffix.isNotEmpty()) ".$messageChannelSuffix" else ""
+      val taskQueue = binaryMessenger.makeBackgroundTaskQueue()
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.shouldFullSync$separatedMessageChannelSuffix", codec)
+        if (api != null) {
+          channel.setMessageHandler { _, reply ->
+            val wrapped: List<Any?> = try {
+              listOf(api.shouldFullSync())
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getMediaChanges$separatedMessageChannelSuffix", codec, taskQueue)
+        if (api != null) {
+          channel.setMessageHandler { _, reply ->
+            val wrapped: List<Any?> = try {
+              listOf(api.getMediaChanges())
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.checkpointSync$separatedMessageChannelSuffix", codec)
+        if (api != null) {
+          channel.setMessageHandler { _, reply ->
+            val wrapped: List<Any?> = try {
+              api.checkpointSync()
+              listOf(null)
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.clearSyncCheckpoint$separatedMessageChannelSuffix", codec)
+        if (api != null) {
+          channel.setMessageHandler { _, reply ->
+            val wrapped: List<Any?> = try {
+              api.clearSyncCheckpoint()
+              listOf(null)
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetIdsForAlbum$separatedMessageChannelSuffix", codec, taskQueue)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val albumIdArg = args[0] as String
+            val wrapped: List<Any?> = try {
+              listOf(api.getAssetIdsForAlbum(albumIdArg))
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAlbums$separatedMessageChannelSuffix", codec, taskQueue)
+        if (api != null) {
+          channel.setMessageHandler { _, reply ->
+            val wrapped: List<Any?> = try {
+              listOf(api.getAlbums())
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsCountSince$separatedMessageChannelSuffix", codec, taskQueue)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val albumIdArg = args[0] as String
+            val timestampArg = args[1] as Long
+            val wrapped: List<Any?> = try {
+              listOf(api.getAssetsCountSince(albumIdArg, timestampArg))
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsForAlbum$separatedMessageChannelSuffix", codec, taskQueue)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val albumIdArg = args[0] as String
+            val updatedTimeCondArg = args[1] as Long?
+            val wrapped: List<Any?> = try {
+              listOf(api.getAssetsForAlbum(albumIdArg, updatedTimeCondArg))
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+    }
+  }
+}

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImpl26.kt

@@ -0,0 +1,24 @@
+package app.alextran.immich.sync
+
+import android.content.Context
+
+
+class NativeSyncApiImpl26(context: Context) : NativeSyncApiImplBase(context), NativeSyncApi {
+  override fun shouldFullSync(): Boolean {
+    return true
+  }
+
+  // No-op for Android 10 and below
+  override fun checkpointSync() {
+    // Cannot throw exception as this is called from the Dart side
+    // during the full sync process as well
+  }
+
+  override fun clearSyncCheckpoint() {
+    // No-op for Android 10 and below
+  }
+
+  override fun getMediaChanges(): SyncDelta {
+    throw IllegalStateException("Method not supported on this Android version.")
+  }
+}

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImpl30.kt

@@ -0,0 +1,89 @@
+package app.alextran.immich.sync
+
+import android.content.Context
+import android.os.Build
+import android.provider.MediaStore
+import androidx.annotation.RequiresApi
+import androidx.annotation.RequiresExtension
+import kotlinx.serialization.json.Json
+
+@RequiresApi(Build.VERSION_CODES.Q)
+@RequiresExtension(extension = Build.VERSION_CODES.R, version = 1)
+class NativeSyncApiImpl30(context: Context) : NativeSyncApiImplBase(context), NativeSyncApi {
+  private val ctx: Context = context.applicationContext
+  private val prefs = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE)
+
+  companion object {
+    const val SHARED_PREF_NAME = "Immich::MediaManager"
+    const val SHARED_PREF_MEDIA_STORE_VERSION_KEY = "MediaStore::getVersion"
+    const val SHARED_PREF_MEDIA_STORE_GEN_KEY = "MediaStore::getGeneration"
+  }
+
+  private fun getSavedGenerationMap(): Map<String, Long> {
+    return prefs.getString(SHARED_PREF_MEDIA_STORE_GEN_KEY, null)?.let {
+      Json.decodeFromString<Map<String, Long>>(it)
+    } ?: emptyMap()
+  }
+
+  override fun clearSyncCheckpoint() {
+    prefs.edit().apply {
+      remove(SHARED_PREF_MEDIA_STORE_VERSION_KEY)
+      remove(SHARED_PREF_MEDIA_STORE_GEN_KEY)
+      apply()
+    }
+  }
+
+  override fun shouldFullSync(): Boolean =
+    MediaStore.getVersion(ctx) != prefs.getString(SHARED_PREF_MEDIA_STORE_VERSION_KEY, null)
+
+  override fun checkpointSync() {
+    val genMap = MediaStore.getExternalVolumeNames(ctx)
+      .associateWith { MediaStore.getGeneration(ctx, it) }
+
+    prefs.edit().apply {
+      putString(SHARED_PREF_MEDIA_STORE_VERSION_KEY, MediaStore.getVersion(ctx))
+      putString(SHARED_PREF_MEDIA_STORE_GEN_KEY, Json.encodeToString(genMap))
+      apply()
+    }
+  }
+
+  override fun getMediaChanges(): SyncDelta {
+    val genMap = getSavedGenerationMap()
+    val currentVolumes = MediaStore.getExternalVolumeNames(ctx)
+    val changed = mutableListOf<PlatformAsset>()
+    val deleted = mutableListOf<String>()
+    val assetAlbums = mutableMapOf<String, List<String>>()
+    var hasChanges = genMap.keys != currentVolumes
+
+    for (volume in currentVolumes) {
+      val currentGen = MediaStore.getGeneration(ctx, volume)
+      val storedGen = genMap[volume] ?: 0
+      if (currentGen <= storedGen) {
+        continue
+      }
+
+      hasChanges = true
+
+      val selection =
+        "$MEDIA_SELECTION AND (${MediaStore.MediaColumns.GENERATION_MODIFIED} > ? OR ${MediaStore.MediaColumns.GENERATION_ADDED} > ?)"
+      val selectionArgs = arrayOf(
+        *MEDIA_SELECTION_ARGS,
+        storedGen.toString(),
+        storedGen.toString()
+      )
+
+      getAssets(getCursor(volume, selection, selectionArgs)).forEach {
+        when (it) {
+          is AssetResult.ValidAsset -> {
+            changed.add(it.asset)
+            assetAlbums[it.asset.id] = listOf(it.albumId)
+          }
+
+          is AssetResult.InvalidAsset -> deleted.add(it.assetId)
+        }
+      }
+    }
+    // Unmounted volumes are handled in dart when the album is removed
+    return SyncDelta(hasChanges, changed, deleted, assetAlbums)
+  }
+}

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImplBase.kt

@@ -0,0 +1,177 @@
+package app.alextran.immich.sync
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.database.Cursor
+import android.provider.MediaStore
+import java.io.File
+
+sealed class AssetResult {
+  data class ValidAsset(val asset: PlatformAsset, val albumId: String) : AssetResult()
+  data class InvalidAsset(val assetId: String) : AssetResult()
+}
+
+@SuppressLint("InlinedApi")
+open class NativeSyncApiImplBase(context: Context) {
+  private val ctx: Context = context.applicationContext
+
+  companion object {
+    const val MEDIA_SELECTION =
+      "(${MediaStore.Files.FileColumns.MEDIA_TYPE} = ? OR ${MediaStore.Files.FileColumns.MEDIA_TYPE} = ?)"
+    val MEDIA_SELECTION_ARGS = arrayOf(
+      MediaStore.Files.FileColumns.MEDIA_TYPE_IMAGE.toString(),
+      MediaStore.Files.FileColumns.MEDIA_TYPE_VIDEO.toString()
+    )
+    const val BUCKET_SELECTION = "(${MediaStore.Files.FileColumns.BUCKET_ID} = ?)"
+    val ASSET_PROJECTION = arrayOf(
+      MediaStore.MediaColumns._ID,
+      MediaStore.MediaColumns.DATA,
+      MediaStore.MediaColumns.DISPLAY_NAME,
+      MediaStore.MediaColumns.DATE_TAKEN,
+      MediaStore.MediaColumns.DATE_ADDED,
+      MediaStore.MediaColumns.DATE_MODIFIED,
+      MediaStore.Files.FileColumns.MEDIA_TYPE,
+      MediaStore.MediaColumns.BUCKET_ID,
+      MediaStore.MediaColumns.DURATION
+    )
+  }
+
+  protected fun getCursor(
+    volume: String,
+    selection: String,
+    selectionArgs: Array<String>,
+    projection: Array<String> = ASSET_PROJECTION,
+    sortOrder: String? = null
+  ): Cursor? = ctx.contentResolver.query(
+    MediaStore.Files.getContentUri(volume),
+    projection,
+    selection,
+    selectionArgs,
+    sortOrder,
+  )
+
+  protected fun getAssets(cursor: Cursor?): Sequence<AssetResult> {
+    return sequence {
+      cursor?.use { c ->
+        val idColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns._ID)
+        val dataColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.DATA)
+        val nameColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.DISPLAY_NAME)
+        val dateTakenColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.DATE_TAKEN)
+        val dateAddedColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.DATE_ADDED)
+        val dateModifiedColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.DATE_MODIFIED)
+        val mediaTypeColumn = c.getColumnIndexOrThrow(MediaStore.Files.FileColumns.MEDIA_TYPE)
+        val bucketIdColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.BUCKET_ID)
+        val durationColumn = c.getColumnIndexOrThrow(MediaStore.MediaColumns.DURATION)
+
+        while (c.moveToNext()) {
+          val id = c.getLong(idColumn).toString()
+
+          val path = c.getString(dataColumn)
+          if (path.isNullOrBlank() || !File(path).exists()) {
+            yield(AssetResult.InvalidAsset(id))
+            continue
+          }
+
+          val mediaType = c.getInt(mediaTypeColumn)
+          val name = c.getString(nameColumn)
+          // Date taken is milliseconds since epoch, Date added is seconds since epoch
+          val createdAt = (c.getLong(dateTakenColumn).takeIf { it > 0 }?.div(1000))
+            ?: c.getLong(dateAddedColumn)
+          // Date modified is seconds since epoch
+          val modifiedAt = c.getLong(dateModifiedColumn)
+          // Duration is milliseconds
+          val duration = if (mediaType == MediaStore.Files.FileColumns.MEDIA_TYPE_IMAGE) 0
+          else c.getLong(durationColumn) / 1000
+          val bucketId = c.getString(bucketIdColumn)
+
+          val asset = PlatformAsset(id, name, mediaType.toLong(), createdAt, modifiedAt, duration)
+          yield(AssetResult.ValidAsset(asset, bucketId))
+        }
+      }
+    }
+  }
+
+  fun getAlbums(): List<PlatformAlbum> {
+    val albums = mutableListOf<PlatformAlbum>()
+    val albumsCount = mutableMapOf<String, Int>()
+
+    val projection = arrayOf(
+      MediaStore.Files.FileColumns.BUCKET_ID,
+      MediaStore.Files.FileColumns.BUCKET_DISPLAY_NAME,
+      MediaStore.Files.FileColumns.DATE_MODIFIED,
+    )
+    val selection =
+      "(${MediaStore.Files.FileColumns.BUCKET_ID} IS NOT NULL) AND $MEDIA_SELECTION"
+
+    getCursor(
+      MediaStore.VOLUME_EXTERNAL,
+      selection,
+      MEDIA_SELECTION_ARGS,
+      projection,
+      "${MediaStore.Files.FileColumns.DATE_MODIFIED} DESC"
+    )?.use { cursor ->
+      val bucketIdColumn =
+        cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.BUCKET_ID)
+      val bucketNameColumn =
+        cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.BUCKET_DISPLAY_NAME)
+      val dateModified =
+        cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DATE_MODIFIED)
+
+      while (cursor.moveToNext()) {
+        val id = cursor.getString(bucketIdColumn)
+
+        val count = albumsCount.getOrDefault(id, 0)
+        if (count != 0) {
+          albumsCount[id] = count + 1
+          continue
+        }
+
+        val name = cursor.getString(bucketNameColumn)
+        val updatedAt = cursor.getLong(dateModified)
+        albums.add(PlatformAlbum(id, name, updatedAt, false, 0))
+        albumsCount[id] = 1
+      }
+    }
+
+    return albums.map { it.copy(assetCount = albumsCount[it.id]?.toLong() ?: 0) }
+      .sortedBy { it.id }
+  }
+
+  fun getAssetIdsForAlbum(albumId: String): List<String> {
+    val projection = arrayOf(MediaStore.MediaColumns._ID)
+
+    return getCursor(
+      MediaStore.VOLUME_EXTERNAL,
+      "$BUCKET_SELECTION AND $MEDIA_SELECTION",
+      arrayOf(albumId, *MEDIA_SELECTION_ARGS),
+      projection
+    )?.use { cursor ->
+      val idColumn = cursor.getColumnIndexOrThrow(MediaStore.MediaColumns._ID)
+      generateSequence {
+        if (cursor.moveToNext()) cursor.getLong(idColumn).toString() else null
+      }.toList()
+    } ?: emptyList()
+  }
+
+  fun getAssetsCountSince(albumId: String, timestamp: Long): Long =
+    getCursor(
+      MediaStore.VOLUME_EXTERNAL,
+      "$BUCKET_SELECTION AND ${MediaStore.Files.FileColumns.DATE_ADDED} > ? AND $MEDIA_SELECTION",
+      arrayOf(albumId, timestamp.toString(), *MEDIA_SELECTION_ARGS),
+    )?.use { cursor -> cursor.count.toLong() } ?: 0L
+
+
+  fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?): List<PlatformAsset> {
+    var selection = "$BUCKET_SELECTION AND $MEDIA_SELECTION"
+    val selectionArgs = mutableListOf(albumId, *MEDIA_SELECTION_ARGS)
+
+    if (updatedTimeCond != null) {
+      selection += " AND (${MediaStore.Files.FileColumns.DATE_MODIFIED} > ? OR ${MediaStore.Files.FileColumns.DATE_ADDED} > ?)"
+      selectionArgs.addAll(listOf(updatedTimeCond.toString(), updatedTimeCond.toString()))
+    }
+
+    return getAssets(getCursor(MediaStore.VOLUME_EXTERNAL, selection, selectionArgs.toTypedArray()))
+      .mapNotNull { result -> (result as? AssetResult.ValidAsset)?.asset }
+      .toList()
+  }
+}