Add ExoPlayerDataSourceProvider to offer support for caching in media3 audio navigator (readium#539)

Author: qnga

readium/adapters/exoplayer/audio/src/main/java/org/readium/adapter/exoplayer/audio/DefaultExoPlayerDataSourceProvider.kt

@@ -0,0 +1,11 @@
+package org.readium.adapter.exoplayer.audio
+
+import androidx.media3.datasource.DataSource
+import org.readium.r2.shared.publication.Publication
+
+public class DefaultExoPlayerDataSourceProvider : ExoPlayerDataSourceProvider {
+
+    override fun createDataSourceFactory(publication: Publication): DataSource.Factory {
+        return PublicationExoPlayerDataSource.Factory(publication)
+    }
+}

readium/adapters/exoplayer/audio/src/main/java/org/readium/adapter/exoplayer/audio/ExoPlayerDataSourceProvider.kt

@@ -0,0 +1,9 @@
+package org.readium.adapter.exoplayer.audio
+
+import androidx.media3.datasource.DataSource
+import org.readium.r2.shared.publication.Publication
+
+public fun interface ExoPlayerDataSourceProvider {
+
+    public fun createDataSourceFactory(publication: Publication): DataSource.Factory
+}

readium/adapters/exoplayer/audio/src/main/java/org/readium/adapter/exoplayer/audio/ExoPlayerEngineProvider.kt

@@ -9,7 +9,6 @@
 package org.readium.adapter.exoplayer.audio
 
 import android.app.Application
-import androidx.media3.datasource.DataSource
 import kotlin.time.Duration
 import kotlin.time.Duration.Companion.seconds
 import org.readium.navigator.media.audio.AudioEngineProvider
@@ -28,12 +27,16 @@ import org.readium.r2.shared.util.Try
  *
  * Provide [ExoPlayerDefaults] to customize the default values that will be used by
  * the navigator for some preferences.
+ *
+ * Pass an [ExoPlayerDataSourceProvider] providing a caching data source with an upstream
+ * [PublicationExoPlayerDataSource] if you need caching.
  */
 @ExperimentalReadiumApi
 @androidx.annotation.OptIn(androidx.media3.common.util.UnstableApi::class)
 public class ExoPlayerEngineProvider(
     private val application: Application,
     private val metadataProvider: MediaMetadataProvider = DefaultMediaMetadataProvider(),
+    private val dataSourceProvider: ExoPlayerDataSourceProvider = DefaultExoPlayerDataSourceProvider(),
     private val defaults: ExoPlayerDefaults = ExoPlayerDefaults(),
     private val configuration: ExoPlayerEngine.Configuration = ExoPlayerEngine.Configuration()
 ) : AudioEngineProvider<ExoPlayerSettings, ExoPlayerPreferences, ExoPlayerPreferencesEditor> {
@@ -45,7 +48,7 @@ public class ExoPlayerEngineProvider(
     ): Try<ExoPlayerEngine, Nothing> {
         val metadataFactory = metadataProvider.createMetadataFactory(publication)
         val settingsResolver = ExoPlayerSettingsResolver(defaults)
-        val dataSourceFactory: DataSource.Factory = ExoPlayerDataSource.Factory(publication)
+        val dataSourceFactory = dataSourceProvider.createDataSourceFactory(publication)
         val initialIndex = publication.readingOrder.indexOfFirstWithHref(initialLocator.href) ?: 0
         val initialPosition = initialLocator.locations.time ?: Duration.ZERO
         val playlist = ExoPlayerEngine.Playlist(

readium/adapters/exoplayer/audio/src/main/java/org/readium/adapter/exoplayer/audio/ExoPlayerDataSource.kt renamed to readium/adapters/exoplayer/audio/src/main/java/org/readium/adapter/exoplayer/audio/PublicationExoPlayerDataSource.kt

@@ -38,17 +38,17 @@ internal sealed class ExoPlayerDataSourceException(message: String, cause: Throw
  * An ExoPlayer's [DataSource] which retrieves resources from a [Publication].
  */
 @androidx.annotation.OptIn(androidx.media3.common.util.UnstableApi::class)
-internal class ExoPlayerDataSource internal constructor(
+public class PublicationExoPlayerDataSource internal constructor(
     private val publication: Publication
 ) : BaseDataSource(/* isNetwork = */ true) {
 
-    class Factory(
+    public class Factory(
         private val publication: Publication,
         private val transferListener: TransferListener? = null
     ) : DataSource.Factory {
 
         override fun createDataSource(): DataSource =
-            ExoPlayerDataSource(publication).apply {
+            PublicationExoPlayerDataSource(publication).apply {
                 if (transferListener != null) {
                     addTransferListener(transferListener)
                 }