Merge pull request #173 from ultrasonic/persistent-cache

Persistent cache

.circleci/config.yml

@@ -22,7 +22,7 @@ jobs:
       - run:
           name: unit-tests
           command: |
-            ./gradlew :subsonic-api:test :ultrasonic:testDebugUnitTest
+            ./gradlew :subsonic-api:test :cache:test :ultrasonic:testDebugUnitTest
             ./gradlew jacocoFullReport
             bash <(curl -s https://codecov.io/bash)
       - run:

cache/build.gradle

@@ -0,0 +1,46 @@
+apply plugin: 'java-library'
+apply plugin: 'kotlin'
+apply plugin: 'jacoco'
+apply from: '../gradle_scripts/code_quality.gradle'
+
+dependencies {
+    api project(':domain')
+    api other.kotlinStdlib
+    api other.twitterSerial
+
+    testImplementation testing.junit
+    testImplementation testing.kotlinJunit
+    testImplementation testing.mockito
+    testImplementation testing.mockitoInline
+    testImplementation testing.mockitoKotlin
+    testImplementation testing.kluent
+}
+
+jacoco {
+    toolVersion(versions.jacoco)
+}
+
+ext {
+    jacocoExclude = []
+}
+
+jacocoTestReport {
+    reports {
+        html.enabled true
+        csv.enabled false
+        xml.enabled true
+    }
+
+    afterEvaluate {
+        classDirectories = files(classDirectories.files.collect {
+            fileTree(dir: it, excludes: jacocoExclude)
+        })
+    }
+}
+
+test.finalizedBy jacocoTestReport
+test {
+    jacoco {
+        excludes += jacocoExclude
+    }
+}

cache/src/main/kotlin/org/moire/ultrasonic/cache/Directories.kt

@@ -0,0 +1,14 @@
+package org.moire.ultrasonic.cache
+
+import java.io.File
+
+/**
+ * Provides access to generic directories:
+ * - for temporary caches
+ * - for permanent data storage
+ */
+interface Directories {
+    fun getInternalCacheDir(): File
+    fun getInternalDataDir(): File
+    fun getExternalCacheDir(): File?
+}

cache/src/main/kotlin/org/moire/ultrasonic/cache/PermanentFileStorage.kt

@@ -0,0 +1,75 @@
+package org.moire.ultrasonic.cache
+
+import com.twitter.serial.serializer.SerializationContext
+import com.twitter.serial.serializer.Serializer
+import com.twitter.serial.stream.Serial
+import com.twitter.serial.stream.bytebuffer.ByteBufferSerial
+import java.io.File
+
+typealias DomainEntitySerializer<T> = Serializer<T>
+
+internal const val STORAGE_DIR_NAME = "persistent_storage"
+
+/**
+ * Provides access to permanent file based storage.
+ *
+ * [serverId] is currently active server. Should be unique per server so stored data will not
+ * interfere with other server data.
+ *
+ * Look at [org.moire.ultrasonic.cache.serializers] package for available [DomainEntitySerializer]s.
+ */
+class PermanentFileStorage(
+        private val directories: Directories,
+        private val serverId: String,
+        private val debug: Boolean = false
+) {
+    private val serializationContext = object : SerializationContext {
+        override fun isDebug(): Boolean = debug
+        override fun isRelease(): Boolean = !debug
+    }
+
+    private val serializer: Serial = ByteBufferSerial(serializationContext)
+
+    /**
+     * Stores given [objectToStore] using [name] as a key and [objectSerializer] as serializer.
+     */
+    fun <T> store(
+            name: String,
+            objectToStore: T,
+            objectSerializer: DomainEntitySerializer<T>
+    ) {
+        val storeFile = getFile(name)
+        if (!storeFile.exists()) storeFile.createNewFile()
+        storeFile.writeBytes(serializer.toByteArray(objectToStore, objectSerializer))
+    }
+
+    /**
+     * Loads object with [name] key using [objectDeserializer] deserializer.
+     */
+    fun <T> load(
+            name: String,
+            objectDeserializer: DomainEntitySerializer<T>
+    ): T? {
+        val storeFile = getFile(name)
+        if (!storeFile.exists()) return null
+
+        return serializer.fromByteArray(storeFile.readBytes(), objectDeserializer)
+    }
+
+    /**
+     * Clear all files in storage.
+     */
+    fun clearAll() {
+        val storageDir = getStorageDir()
+        storageDir.listFiles().forEach { it.deleteRecursively() }
+    }
+
+    private fun getFile(name: String) = File(getStorageDir(), "$name.ser")
+
+    private fun getStorageDir(): File {
+        val mainDir = File(directories.getInternalDataDir(), STORAGE_DIR_NAME)
+        val serverDir = File(mainDir, serverId)
+        if (!serverDir.exists()) serverDir.mkdirs()
+        return serverDir
+    }
+}

cache/src/main/kotlin/org/moire/ultrasonic/cache/serializers/ArtistSerializer.kt

@@ -0,0 +1,65 @@
+@file:JvmMultifileClass
+@file:JvmName("DomainSerializers")
+package org.moire.ultrasonic.cache.serializers
+
+import com.twitter.serial.serializer.CollectionSerializers
+import com.twitter.serial.serializer.ObjectSerializer
+import com.twitter.serial.serializer.SerializationContext
+import com.twitter.serial.stream.SerializerDefs
+import com.twitter.serial.stream.SerializerInput
+import com.twitter.serial.stream.SerializerOutput
+import org.moire.ultrasonic.cache.DomainEntitySerializer
+import org.moire.ultrasonic.domain.Artist
+
+private const val SERIALIZER_VERSION = 1
+
+private val artistSerializer get() = object : ObjectSerializer<Artist>(SERIALIZER_VERSION) {
+    override fun serializeObject(
+            context: SerializationContext,
+            output: SerializerOutput<out SerializerOutput<*>>,
+            item: Artist
+    ) {
+        output.writeString(item.id)
+                .writeString(item.name)
+                .writeString(item.index)
+                .writeString(item.coverArt)
+                .apply {
+                    val albumCount = item.albumCount
+                    if (albumCount != null) writeLong(albumCount) else writeNull()
+                }
+                .writeInt(item.closeness)
+    }
+
+    override fun deserializeObject(
+            context: SerializationContext,
+            input: SerializerInput,
+            versionNumber: Int
+    ): Artist? {
+        if (versionNumber != SERIALIZER_VERSION) return null
+
+        val id = input.readString()
+        val name = input.readString()
+        val index = input.readString()
+        val coverArt = input.readString()
+        val albumCount = if (input.peekType() == SerializerDefs.TYPE_NULL) {
+            input.readNull()
+            null
+        } else {
+            input.readLong()
+        }
+        val closeness = input.readInt()
+        return Artist(id, name, index, coverArt, albumCount, closeness)
+    }
+}
+
+/**
+ * Serializer/deserializer for [Artist] domain entity.
+ */
+fun getArtistsSerializer(): DomainEntitySerializer<Artist> = artistSerializer
+
+private val artistListSerializer = CollectionSerializers.getListSerializer(artistSerializer)
+
+/**
+ * Serializer/deserializer for list of [Artist] domain entities.
+ */
+fun getArtistListSerializer(): DomainEntitySerializer<List<Artist>> = artistListSerializer

cache/src/main/kotlin/org/moire/ultrasonic/cache/serializers/IndexesSerializer.kt

@@ -0,0 +1,48 @@
+@file:JvmMultifileClass
+@file:JvmName("DomainSerializers")
+package org.moire.ultrasonic.cache.serializers
+
+import com.twitter.serial.serializer.ObjectSerializer
+import com.twitter.serial.serializer.SerializationContext
+import com.twitter.serial.stream.SerializerInput
+import com.twitter.serial.stream.SerializerOutput
+import org.moire.ultrasonic.cache.DomainEntitySerializer
+import org.moire.ultrasonic.domain.Artist
+import org.moire.ultrasonic.domain.Indexes
+
+private const val SERIALIZATION_VERSION = 1
+
+private val indexesSerializer get() = object : ObjectSerializer<Indexes>(SERIALIZATION_VERSION) {
+    override fun serializeObject(
+            context: SerializationContext,
+            output: SerializerOutput<out SerializerOutput<*>>,
+            item: Indexes
+    ) {
+        val artistListSerializer = getArtistListSerializer()
+        output.writeLong(item.lastModified)
+                .writeString(item.ignoredArticles)
+                .writeObject<MutableList<Artist>>(context, item.shortcuts, artistListSerializer)
+                .writeObject<MutableList<Artist>>(context, item.artists, artistListSerializer)
+    }
+
+    override fun deserializeObject(
+            context: SerializationContext,
+            input: SerializerInput,
+            versionNumber: Int
+    ): Indexes? {
+        if (versionNumber != SERIALIZATION_VERSION) return null
+
+        val artistListDeserializer = getArtistListSerializer()
+        val lastModified = input.readLong()
+        val ignoredArticles = input.readString() ?: return null
+        val shortcutsList = input.readObject(context, artistListDeserializer) ?: return null
+        val artistsList = input.readObject(context, artistListDeserializer) ?: return null
+        return Indexes(lastModified, ignoredArticles, shortcutsList.toMutableList(),
+                artistsList.toMutableList())
+    }
+}
+
+/**
+ * Get serializer/deserializer for [Indexes] entity.
+ */
+fun getIndexesSerializer(): DomainEntitySerializer<Indexes> = indexesSerializer

cache/src/main/kotlin/org/moire/ultrasonic/cache/serializers/MusicFolderSerializer.kt

@@ -0,0 +1,50 @@
+@file:JvmMultifileClass
+@file:JvmName("DomainSerializers")
+package org.moire.ultrasonic.cache.serializers
+
+import com.twitter.serial.serializer.CollectionSerializers
+import com.twitter.serial.serializer.ObjectSerializer
+import com.twitter.serial.serializer.SerializationContext
+import com.twitter.serial.stream.SerializerInput
+import com.twitter.serial.stream.SerializerOutput
+import org.moire.ultrasonic.cache.DomainEntitySerializer
+import org.moire.ultrasonic.domain.MusicFolder
+
+private const val SERIALIZATION_VERSION = 1
+
+private val musicFolderSerializer = object : ObjectSerializer<MusicFolder>(SERIALIZATION_VERSION) {
+
+    override fun serializeObject(
+            context: SerializationContext,
+            output: SerializerOutput<out SerializerOutput<*>>,
+            item: MusicFolder
+    ) {
+        output.writeString(item.id).writeString(item.name)
+    }
+
+    override fun deserializeObject(
+            context: SerializationContext,
+            input: SerializerInput,
+            versionNumber: Int
+    ): MusicFolder? {
+        if (versionNumber != SERIALIZATION_VERSION) return null
+
+        val id = input.readString() ?: return null
+        val name = input.readString() ?: return null
+        return MusicFolder(id, name)
+    }
+}
+
+/**
+ * Serializer/deserializer for [MusicFolder] domain entity.
+ */
+fun getMusicFolderSerializer(): DomainEntitySerializer<MusicFolder> = musicFolderSerializer
+
+private val musicFolderListSerializer =
+        CollectionSerializers.getListSerializer(musicFolderSerializer)
+
+/**
+ * Serializer/deserializer for [List] of [MusicFolder] items.
+ */
+fun getMusicFolderListSerializer(): DomainEntitySerializer<List<MusicFolder>> =
+        musicFolderListSerializer

cache/src/test/kotlin/org/moire/ultrasonic/cache/BaseStorageTest.kt

@@ -0,0 +1,42 @@
+package org.moire.ultrasonic.cache
+
+import com.nhaarman.mockito_kotlin.mock
+import com.twitter.serial.util.SerializationUtils
+import org.amshove.kluent.`it returns`
+import org.junit.Before
+import org.junit.Rule
+import org.junit.rules.TemporaryFolder
+import java.io.File
+
+internal const val INTERNAL_DATA_FOLDER = "data"
+internal const val INTERNAL_CACHE_FOLDER = "cache"
+internal const val EXTERNAL_CACHE_FOLDER = "external_cache"
+
+/**
+ * Base test class that inits the storage
+ */
+abstract class BaseStorageTest {
+    @get:Rule val tempFileRule = TemporaryFolder()
+
+    protected lateinit var mockDirectories: Directories
+    protected lateinit var storage: PermanentFileStorage
+
+    open val serverId: String = ""
+
+    @Before
+    fun setUp() {
+        mockDirectories = mock<Directories> {
+            on { getInternalDataDir() } `it returns` tempFileRule.newFolder(INTERNAL_DATA_FOLDER)
+            on { getInternalCacheDir() } `it returns` tempFileRule.newFolder(INTERNAL_CACHE_FOLDER)
+            on { getExternalCacheDir() } `it returns` tempFileRule.newFolder(EXTERNAL_CACHE_FOLDER)
+        }
+        storage = PermanentFileStorage(mockDirectories, serverId, true)
+    }
+
+    protected val storageDir get() = File(mockDirectories.getInternalDataDir(), STORAGE_DIR_NAME)
+
+    protected fun validateSerializedData(index: Int = 0) {
+        val serializedFileBytes = storageDir.listFiles()[index].readBytes()
+        SerializationUtils.validateSerializedData(serializedFileBytes)
+    }
+}

cache/src/test/kotlin/org/moire/ultrasonic/cache/PermanentFileStorageTest.kt

@@ -0,0 +1,81 @@
+package org.moire.ultrasonic.cache
+
+import org.amshove.kluent.`should contain`
+import org.amshove.kluent.`should equal to`
+import org.amshove.kluent.`should equal`
+import org.junit.Test
+import org.moire.ultrasonic.cache.serializers.getMusicFolderSerializer
+import org.moire.ultrasonic.domain.MusicFolder
+import java.io.File
+
+/**
+ * Integration test for [PermanentFileStorage].
+ */
+class PermanentFileStorageTest : BaseStorageTest() {
+    override val serverId: String
+        get() = "some-server-id"
+
+    @Test
+    fun `Should create storage dir if it is not exist`() {
+        val item = MusicFolder("1", "2")
+        storage.store("test", item, getMusicFolderSerializer())
+
+        storageDir.exists() `should equal to` true
+        getServerStorageDir().exists() `should equal to` true
+    }
+
+    @Test
+    fun `Should serialize to file`() {
+        val item = MusicFolder("1", "23")
+        val name = "some-name"
+
+        storage.store(name, item, getMusicFolderSerializer())
+
+        val storageFiles = getServerStorageDir().listFiles()
+        storageFiles.size `should equal to` 1
+        storageFiles[0].name `should contain` name
+    }
+
+    @Test
+    fun `Should deserialize stored object`() {
+        val item = MusicFolder("some", "nice")
+        val name = "some-name"
+        storage.store(name, item, getMusicFolderSerializer())
+
+        val loadedItem = storage.load(name, getMusicFolderSerializer())
+
+        loadedItem `should equal` item
+    }
+
+    @Test
+    fun `Should overwrite existing stored object`() {
+        val name = "some-nice-name"
+        val item1 = MusicFolder("1", "1")
+        val item2 = MusicFolder("2", "2")
+        storage.store(name, item1, getMusicFolderSerializer())
+        storage.store(name, item2, getMusicFolderSerializer())
+
+        val loadedItem = storage.load(name, getMusicFolderSerializer())
+
+        loadedItem `should equal` item2
+    }
+
+    @Test
+    fun `Should clear all files when clearAll is called`() {
+        storage.store("name1", MusicFolder("1", "1"), getMusicFolderSerializer())
+        storage.store("name2", MusicFolder("2", "2"), getMusicFolderSerializer())
+
+        storage.clearAll()
+
+        getServerStorageDir().listFiles().size `should equal to` 0
+    }
+
+    @Test
+    fun `Should return null if serialized file not available`() {
+        val loadedItem = storage.load("some-name", getMusicFolderSerializer())
+
+        loadedItem `should equal` null
+    }
+
+    private fun getServerStorageDir() = File(storageDir, serverId)
+}

cache/src/test/kotlin/org/moire/ultrasonic/cache/serializers/ArtistSerializerTest.kt

@@ -0,0 +1,57 @@
+package org.moire.ultrasonic.cache.serializers
+
+import org.amshove.kluent.`should equal`
+import org.junit.Test
+import org.moire.ultrasonic.cache.BaseStorageTest
+import org.moire.ultrasonic.domain.Artist
+
+/**
+ * [Artist] serializers test.
+ */
+class ArtistSerializerTest : BaseStorageTest() {
+    @Test
+    fun `Should correctly serialize Artist object`() {
+        val item = Artist("id", "name", "index", "coverArt", 1, 0)
+
+        storage.store("some-name", item, getArtistsSerializer())
+
+        validateSerializedData()
+    }
+
+    @Test
+    fun `Should correctly deserialize Artist object`() {
+        val itemName = "some-name"
+        val item = Artist("id", "name", "index", "coverArt", null, 0)
+        storage.store(itemName, item, getArtistsSerializer())
+
+        val loadedItem = storage.load(itemName, getArtistsSerializer())
+
+        loadedItem `should equal` item
+    }
+
+    @Test
+    fun `Should correctly serialize list of Artists`() {
+        val itemsList = listOf(
+                Artist(id = "1"),
+                Artist(id = "2", name = "some")
+        )
+
+        storage.store("some-name", itemsList, getArtistListSerializer())
+
+        validateSerializedData()
+    }
+
+    @Test
+    fun `Should correctly deserialize list of Artists`() {
+        val name = "some-name"
+        val itemsList = listOf(
+                Artist(id = "1"),
+                Artist(id = "2", name = "some")
+        )
+        storage.store(name, itemsList, getArtistListSerializer())
+
+        val loadedItems = storage.load(name, getArtistListSerializer())
+
+        loadedItems `should equal` itemsList
+    }
+}

cache/src/test/kotlin/org/moire/ultrasonic/cache/serializers/IndexesSerializerTest.kt

@@ -0,0 +1,40 @@
+package org.moire.ultrasonic.cache.serializers
+
+import org.amshove.kluent.`should equal`
+import org.junit.Test
+import org.moire.ultrasonic.cache.BaseStorageTest
+import org.moire.ultrasonic.domain.Artist
+import org.moire.ultrasonic.domain.Indexes
+
+/**
+ * Test [Indexes] domain entity serializer.
+ */
+class IndexesSerializerTest : BaseStorageTest() {
+    @Test
+    fun `Should correctly serialize Indexes object`() {
+        val item = Indexes(220L, "", mutableListOf(
+                Artist("12")
+        ), mutableListOf(
+                Artist("233", "some")
+        ))
+
+        storage.store("some-name", item, getIndexesSerializer())
+
+        validateSerializedData()
+    }
+
+    @Test
+    fun `Should correctly deserialize Indexes object`() {
+        val name = "some-name"
+        val item = Indexes(220L, "", mutableListOf(
+                Artist("12")
+        ), mutableListOf(
+                Artist("233", "some")
+        ))
+        storage.store(name, item, getIndexesSerializer())
+
+        val loadedItem = storage.load(name, getIndexesSerializer())
+
+        loadedItem `should equal` item
+    }
+}

cache/src/test/kotlin/org/moire/ultrasonic/cache/serializers/MusicFolderSerializerTest.kt

@@ -0,0 +1,57 @@
+package org.moire.ultrasonic.cache.serializers
+
+import org.amshove.kluent.`should equal`
+import org.junit.Test
+import org.moire.ultrasonic.cache.BaseStorageTest
+import org.moire.ultrasonic.domain.MusicFolder
+
+/**
+ * [MusicFolder] serializers test.
+ */
+class MusicFolderSerializerTest : BaseStorageTest() {
+    @Test
+    fun `Should correctly serialize MusicFolder object`() {
+        val item = MusicFolder("Music", "Folder")
+
+        storage.store("some-name", item, getMusicFolderSerializer())
+
+        validateSerializedData()
+    }
+
+    @Test
+    fun `Should correctly deserialize MusicFolder object`() {
+        val name = "name"
+        val item = MusicFolder("some", "none")
+        storage.store(name, item, getMusicFolderSerializer())
+
+        val loadedItem = storage.load(name, getMusicFolderSerializer())
+
+        loadedItem `should equal` item
+    }
+
+    @Test
+    fun `Should correctly serialize list of MusicFolders objects`() {
+        val itemsList = listOf(
+                MusicFolder("1", "1"),
+                MusicFolder("2", "2")
+        )
+
+        storage.store("some-name", itemsList, getMusicFolderListSerializer())
+
+        validateSerializedData()
+    }
+
+    @Test
+    fun `Should correctly deserialize list of MusicFolder objects`() {
+        val name = "some-name"
+        val itemsList = listOf(
+                MusicFolder("1", "1"),
+                MusicFolder("2", "2")
+        )
+        storage.store(name, itemsList, getMusicFolderListSerializer())
+
+        val loadedItem = storage.load(name, getMusicFolderListSerializer())
+
+        loadedItem `should equal` itemsList
+    }
+}

dependencies.gradle

@@ -22,6 +22,7 @@ ext.versions = [
         jackson              : "2.9.0",
         okhttp               : "3.9.0",
         semver               : "1.0.0",
+        twitterSerial        : "0.1.6",
 
         junit                : "4.12",
         mockito              : "2.12.0",
@@ -52,6 +53,7 @@ ext.other = [
         jacksonKotlin      : "com.fasterxml.jackson.module:jackson-module-kotlin:$versions.jackson",
         okhttpLogging      : "com.squareup.okhttp3:logging-interceptor:$versions.okhttp",
         semver             : "net.swiftzer.semver:semver:$versions.semver",
+        twitterSerial      : "com.twitter.serial:serial:$versions.twitterSerial",
 ]
 
 ext.testing = [

domain/build.gradle

@@ -0,0 +1,38 @@
+apply plugin: 'java-library'
+apply plugin: 'kotlin'
+apply plugin: 'jacoco'
+apply from: '../gradle_scripts/code_quality.gradle'
+
+dependencies {
+    api other.kotlinStdlib
+    api other.semver
+}
+
+jacoco {
+    toolVersion(versions.jacoco)
+}
+
+ext {
+    jacocoExclude = []
+}
+
+jacocoTestReport {
+    reports {
+        html.enabled true
+        csv.enabled false
+        xml.enabled true
+    }
+
+    afterEvaluate {
+        classDirectories = files(classDirectories.files.collect {
+            fileTree(dir: it, excludes: jacocoExclude)
+        })
+    }
+}
+
+test.finalizedBy jacocoTestReport
+test {
+    jacoco {
+        excludes += jacocoExclude
+    }
+}

domain/src/main/kotlin/org/moire/ultrasonic/domain/SearchResult.kt

@@ -1,10 +1,12 @@
 package org.moire.ultrasonic.domain
 
+import org.moire.ultrasonic.domain.MusicDirectory.Entry
+
 /**
  * The result of a search.  Contains matching artists, albums and songs.
  */
 data class SearchResult(
         val artists: List<Artist>,
-        val albums: List<MusicDirectory.Entry>,
+        val albums: List<Entry>,
-        val songs: List<MusicDirectory.Entry>
+        val songs: List<Entry>
 )

gradle_scripts/jacoco.gradle

@@ -6,9 +6,11 @@ task jacocoMergeReports(type: JacocoMerge) {
 
     def subsonicApi = project.findProject("subsonic-api")
     def ultrasonicApp = project.findProject("ultrasonic")
+    def cache = project.findProject("cache")
     executionData(
             "${subsonicApi.buildDir}/jacoco/test.exec",
             "${ultrasonicApp.buildDir}/jacoco/testDebugUnitTest.exec",
+            "${cache.buildDir}/jacoco/test.exec"
     )
     destinationFile(file("${project.buildDir}/jacoco/jacoco.exec"))
 }
@@ -20,6 +22,7 @@ def createJacocoFullReportTask() {
 
         def subsonicApi = project.findProject("subsonic-api")
         def ultrasonicApp = project.findProject("ultrasonic")
+        def cache = project.findProject("cache")
 
         classDirectories = files(
                 fileTree(
@@ -29,6 +32,10 @@ def createJacocoFullReportTask() {
                 fileTree(
                         dir: "${ultrasonicApp.buildDir}/intermediates/classes/debug/org",
                         excludes: ultrasonicApp.jacocoExclude
+                ),
+                fileTree(
+                        dir: "${cache.buildDir}/classes/kotlin/main",
+                        excludes: cache.jacocoExclude
                 )
         )
         sourceDirectories = files(subsonicApi.sourceSets.main.getAllSource(),

settings.gradle

@@ -1,4 +1,7 @@
-include ':library', ':subsonic-api'
+include ':library'
+include ':domain'
+include ':subsonic-api'
+include ':cache'
 include ':menudrawer'
 include ':pulltorefresh'
 include ':ultrasonic'

ultrasonic/build.gradle

@@ -47,15 +47,15 @@ dependencies {
     implementation project(':menudrawer')
     implementation project(':pulltorefresh')
     implementation project(':library')
+    implementation project(':domain')
     implementation project(':subsonic-api')
+    implementation project(':cache')
 
     implementation androidSupport.support
     implementation androidSupport.design
 
     implementation other.kotlinStdlib
 
-    implementation other.semver
-
     testImplementation other.kotlinReflect
     testImplementation testing.junit
     testImplementation testing.kotlinJunit

ultrasonic/src/main/java/org/moire/ultrasonic/fragment/ServerSettingsFragment.java

@@ -12,7 +12,9 @@ import android.support.annotation.Nullable;
 import android.util.Log;
 import android.view.View;
 
+import org.moire.ultrasonic.BuildConfig;
 import org.moire.ultrasonic.R;
+import org.moire.ultrasonic.cache.PermanentFileStorage;
 import org.moire.ultrasonic.service.MusicService;
 import org.moire.ultrasonic.service.MusicServiceFactory;
 import org.moire.ultrasonic.util.Constants;
@@ -279,6 +281,15 @@ public class ServerSettingsFragment extends PreferenceFragment
         int activeServers = sharedPreferences
                 .getInt(Constants.PREFERENCES_KEY_ACTIVE_SERVERS, 0);
 
+        // Clear permanent storage
+        final String storageServerId = MusicServiceFactory.getServerId(sharedPreferences, serverId);
+        final PermanentFileStorage fileStorage = new PermanentFileStorage(
+                MusicServiceFactory.getDirectories(getActivity()),
+                storageServerId,
+                BuildConfig.DEBUG
+        );
+        fileStorage.clearAll();
+
         // Reset values to null so when we ask for them again they are new
         sharedPreferences.edit()
                 .remove(Constants.PREFERENCES_KEY_SERVER_NAME + serverId)

ultrasonic/src/main/java/org/moire/ultrasonic/service/MusicServiceFactory.java

@@ -22,12 +22,17 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import android.util.Log;
 
+import org.jetbrains.annotations.NotNull;
 import org.moire.ultrasonic.BuildConfig;
 import org.moire.ultrasonic.api.subsonic.SubsonicAPIClient;
 import org.moire.ultrasonic.api.subsonic.SubsonicAPIVersions;
+import org.moire.ultrasonic.cache.Directories;
+import org.moire.ultrasonic.cache.PermanentFileStorage;
 import org.moire.ultrasonic.util.Constants;
 import org.moire.ultrasonic.util.Util;
 
+import java.io.File;
+
 /**
  * @author Sindre Mehus
  * @version $Id$
@@ -44,7 +49,9 @@ public class MusicServiceFactory {
                 synchronized (MusicServiceFactory.class) {
                     if (OFFLINE_MUSIC_SERVICE == null) {
                         Log.d(LOG_TAG, "Creating new offline music service");
-                        OFFLINE_MUSIC_SERVICE = new OfflineMusicService(createSubsonicApiClient(context));
+                        OFFLINE_MUSIC_SERVICE = new OfflineMusicService(
+                                createSubsonicApiClient(context),
+                                getPermanentFileStorage(context));
                     }
                 }
             }
@@ -57,7 +64,8 @@ public class MusicServiceFactory {
                     if (REST_MUSIC_SERVICE == null) {
                         Log.d(LOG_TAG, "Creating new rest music service");
                         REST_MUSIC_SERVICE = new CachedMusicService(new RESTMusicService(
-                                createSubsonicApiClient(context)));
+                                createSubsonicApiClient(context),
+                                getPermanentFileStorage(context)));
                     }
                 }
             }
@@ -104,4 +112,39 @@ public class MusicServiceFactory {
                 Constants.REST_CLIENT_ID, allowSelfSignedCertificate,
                 enableLdapUserSupport, BuildConfig.DEBUG);
     }
+
+    private static PermanentFileStorage getPermanentFileStorage(final Context context) {
+        final SharedPreferences preferences = Util.getPreferences(context);
+        int instance = preferences.getInt(Constants.PREFERENCES_KEY_SERVER_INSTANCE, 1);
+        final String serverId = getServerId(preferences, instance);
+
+        return new PermanentFileStorage(getDirectories(context), serverId, BuildConfig.DEBUG);
+    }
+
+    public static String getServerId(final SharedPreferences sp, final int instance) {
+        String serverUrl = sp.getString(
+                Constants.PREFERENCES_KEY_SERVER_URL + instance, null);
+        return String.valueOf(Math.abs((serverUrl + instance).hashCode()));
+    }
+
+    public static Directories getDirectories(final Context context) {
+        return new Directories() {
+            @NotNull
+            @Override
+            public File getInternalCacheDir() {
+                return context.getCacheDir();
+            }
+
+            @NotNull
+            @Override
+            public File getInternalDataDir() {
+                return context.getFilesDir();
+            }
+
+            @Override
+            public File getExternalCacheDir() {
+                return context.getExternalCacheDir();
+            }
+        };
+    }
 }

ultrasonic/src/main/java/org/moire/ultrasonic/service/OfflineMusicService.java

@@ -24,6 +24,7 @@ import android.media.MediaMetadataRetriever;
 import android.util.Log;
 
 import org.moire.ultrasonic.api.subsonic.SubsonicAPIClient;
+import org.moire.ultrasonic.cache.PermanentFileStorage;
 import org.moire.ultrasonic.domain.Artist;
 import org.moire.ultrasonic.domain.Genre;
 import org.moire.ultrasonic.domain.Indexes;
@@ -67,8 +68,8 @@ public class OfflineMusicService extends RESTMusicService
 	private static final String TAG = OfflineMusicService.class.getSimpleName();
 	private static final Pattern COMPILE = Pattern.compile(" ");
 
-    public OfflineMusicService(SubsonicAPIClient subsonicAPIClient) {
+    public OfflineMusicService(SubsonicAPIClient subsonicAPIClient, PermanentFileStorage storage) {
-        super(subsonicAPIClient);
+        super(subsonicAPIClient, storage);
     }
 
     @Override

ultrasonic/src/main/java/org/moire/ultrasonic/service/RESTMusicService.java

@@ -61,6 +61,8 @@ import org.moire.ultrasonic.api.subsonic.response.SharesResponse;
 import org.moire.ultrasonic.api.subsonic.response.StreamResponse;
 import org.moire.ultrasonic.api.subsonic.response.SubsonicResponse;
 import org.moire.ultrasonic.api.subsonic.response.VideosResponse;
+import org.moire.ultrasonic.cache.PermanentFileStorage;
+import org.moire.ultrasonic.cache.serializers.DomainSerializers;
 import org.moire.ultrasonic.domain.APIAlbumConverter;
 import org.moire.ultrasonic.domain.APIArtistConverter;
 import org.moire.ultrasonic.domain.APIBookmarkConverter;
@@ -104,7 +106,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Locale;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
@@ -117,10 +118,19 @@ import retrofit2.Response;
 public class RESTMusicService implements MusicService {
     private static final String TAG = RESTMusicService.class.getSimpleName();
 
-    private final SubsonicAPIClient subsonicAPIClient;
+    private static final String MUSIC_FOLDER_STORAGE_NAME = "music_folder";
+    private static final String INDEXES_STORAGE_NAME = "indexes";
+    private static final String ARTISTS_STORAGE_NAME = "artists";
 
-    public RESTMusicService(SubsonicAPIClient subsonicAPIClient) {
+    private final SubsonicAPIClient subsonicAPIClient;
+    private final PermanentFileStorage fileStorage;
+
+    public RESTMusicService(
+            final SubsonicAPIClient subsonicAPIClient,
+            final PermanentFileStorage fileStorage
+    ) {
         this.subsonicAPIClient = subsonicAPIClient;
+        this.fileStorage = fileStorage;
     }
 
     @Override
@@ -146,7 +156,8 @@ public class RESTMusicService implements MusicService {
     public List<MusicFolder> getMusicFolders(boolean refresh,
                                              Context context,
                                              ProgressListener progressListener) throws Exception {
-        List<MusicFolder> cachedMusicFolders = readCachedMusicFolders(context);
+        List<MusicFolder> cachedMusicFolders = fileStorage.load(MUSIC_FOLDER_STORAGE_NAME,
+                DomainSerializers.getMusicFolderListSerializer());
         if (cachedMusicFolders != null && !refresh) {
             return cachedMusicFolders;
         }
@@ -157,31 +168,18 @@ public class RESTMusicService implements MusicService {
 
         List<MusicFolder> musicFolders = APIMusicFolderConverter
                 .toDomainEntityList(response.body().getMusicFolders());
-        writeCachedMusicFolders(context, musicFolders);
+        fileStorage.store(MUSIC_FOLDER_STORAGE_NAME, musicFolders,
+                DomainSerializers.getMusicFolderListSerializer());
         return musicFolders;
     }
 
-    private static List<MusicFolder> readCachedMusicFolders(Context context) {
-        String filename = getCachedMusicFoldersFilename(context);
-        return FileUtil.deserialize(context, filename);
-    }
-
-    private static void writeCachedMusicFolders(Context context, List<MusicFolder> musicFolders) {
-        String filename = getCachedMusicFoldersFilename(context);
-        FileUtil.serialize(context, new ArrayList<>(musicFolders), filename);
-    }
-
-    private static String getCachedMusicFoldersFilename(Context context) {
-        String s = Util.getRestUrl(context, null);
-        return String.format(Locale.US, "musicFolders-%d.ser", Math.abs(s.hashCode()));
-    }
-
     @Override
     public Indexes getIndexes(String musicFolderId,
                               boolean refresh,
                               Context context,
                               ProgressListener progressListener) throws Exception {
-        Indexes cachedIndexes = readCachedIndexes(context, musicFolderId);
+        Indexes cachedIndexes = fileStorage.load(INDEXES_STORAGE_NAME,
+                DomainSerializers.getIndexesSerializer());
         if (cachedIndexes != null && !refresh) {
             return cachedIndexes;
         }
@@ -192,59 +190,30 @@ public class RESTMusicService implements MusicService {
         checkResponseSuccessful(response);
 
         Indexes indexes = APIIndexesConverter.toDomainEntity(response.body().getIndexes());
-        writeCachedIndexes(context, indexes, musicFolderId);
+        fileStorage.store(INDEXES_STORAGE_NAME, indexes, DomainSerializers.getIndexesSerializer());
         return indexes;
     }
 
-    private static Indexes readCachedIndexes(Context context, String musicFolderId) {
-        String filename = getCachedIndexesFilename(context, musicFolderId);
-        return FileUtil.deserialize(context, filename);
-    }
-
-    private static void writeCachedIndexes(Context context, Indexes indexes, String musicFolderId) {
-        String filename = getCachedIndexesFilename(context, musicFolderId);
-        FileUtil.serialize(context, indexes, filename);
-    }
-
-    private static String getCachedIndexesFilename(Context context, String musicFolderId) {
-        String s = Util.getRestUrl(context, null) + musicFolderId;
-        return String.format(Locale.US, "indexes-%d.ser", Math.abs(s.hashCode()));
-    }
-
     @Override
     public Indexes getArtists(boolean refresh,
                               Context context,
                               ProgressListener progressListener) throws Exception {
-        Indexes cachedArtists = readCachedArtists(context);
+        Indexes cachedArtists = fileStorage
-        if (cachedArtists != null &&
+                .load(ARTISTS_STORAGE_NAME, DomainSerializers.getIndexesSerializer());
-                !refresh) {
+        if (cachedArtists != null && !refresh) {
             return cachedArtists;
         }
 
         updateProgressListener(progressListener, R.string.parser_reading);
-        Response<GetArtistsResponse> response = subsonicAPIClient.getApi().getArtists(null).execute();
+        Response<GetArtistsResponse> response = subsonicAPIClient.getApi()
+                .getArtists(null).execute();
         checkResponseSuccessful(response);
 
         Indexes indexes = APIIndexesConverter.toDomainEntity(response.body().getIndexes());
-        writeCachedArtists(context, indexes);
+        fileStorage.store(ARTISTS_STORAGE_NAME, indexes, DomainSerializers.getIndexesSerializer());
         return indexes;
     }
 
-    private static Indexes readCachedArtists(Context context) {
-        String filename = getCachedArtistsFilename(context);
-        return FileUtil.deserialize(context, filename);
-    }
-
-    private static void writeCachedArtists(Context context, Indexes artists) {
-        String filename = getCachedArtistsFilename(context);
-        FileUtil.serialize(context, artists, filename);
-    }
-
-    private static String getCachedArtistsFilename(Context context) {
-        String s = Util.getRestUrl(context, null);
-        return String.format(Locale.US, "indexes-%d.ser", Math.abs(s.hashCode()));
-    }
-
     @Override
     public void star(String id,
                      String albumId,

ultrasonic/src/main/java/org/moire/ultrasonic/util/FileUtil.java

@@ -26,7 +26,6 @@ import android.text.TextUtils;
 import android.util.Log;
 
 import org.moire.ultrasonic.activity.SubsonicTabActivity;
-import org.moire.ultrasonic.domain.Artist;
 import org.moire.ultrasonic.domain.MusicDirectory;
 
 import java.io.File;
@@ -300,11 +299,6 @@ public class FileUtil
 		return BitmapFactory.decodeByteArray(bytes, 0, bytes.length, opt);
 	}
 
-	public static File getArtistDirectory(Context context, Artist artist)
-	{
-		return new File(String.format("%s/%s", getMusicDirectory(context).getPath(), fileSystemSafe(artist.getName())));
-	}
-
 	public static File getAlbumArtDirectory()
 	{
 		File albumArtDir = new File(getUltraSonicDirectory(), "artwork");