Fix #386: Add support for local caching of audio & image assets

app/src/main/java/org/oppia/app/application/ApplicationComponent.kt

@@ -13,6 +13,7 @@ import org.oppia.domain.classify.rules.multiplechoiceinput.MultipleChoiceInputMo
 import org.oppia.domain.classify.rules.numberwithunits.NumberWithUnitsRuleModule
 import org.oppia.domain.classify.rules.numericinput.NumericInputRuleModule
 import org.oppia.domain.classify.rules.textinput.TextInputRuleModule
+import org.oppia.util.caching.CachingModule
 import org.oppia.util.gcsresource.GcsResourceModule
 import org.oppia.util.logging.LoggerModule
 import org.oppia.util.parser.GlideImageLoaderModule
@@ -29,7 +30,7 @@ import javax.inject.Singleton
   ContinueModule::class, FractionInputModule::class, ItemSelectionInputModule::class, MultipleChoiceInputModule::class,
   NumberWithUnitsRuleModule::class, NumericInputRuleModule::class, TextInputRuleModule::class,
   InteractionsModule::class, GcsResourceModule::class, GlideImageLoaderModule::class, ImageParsingModule::class,
-  HtmlParserEntityTypeModule::class
+  HtmlParserEntityTypeModule::class, CachingModule::class
 ])
 interface ApplicationComponent {
   @Component.Builder

app/src/main/java/org/oppia/app/home/topiclist/TopicSummaryViewModel.kt

@@ -19,7 +19,7 @@ class TopicSummaryViewModel(
   private val topicSummaryClickListener: TopicSummaryClickListener
 ) : HomeItemViewModel() {
   val name: String = topicSummary.name
-  val canonicalStoryCount: Int = topicSummary.canonicalStoryCount
+  val totalChapterCount: Int = topicSummary.totalChapterCount
   @ColorInt
   val backgroundColor: Int = retrieveBackgroundColor()
   @ColorInt

app/src/main/java/org/oppia/app/topic/overview/TopicOverviewViewModel.kt

@@ -6,12 +6,21 @@ import org.oppia.app.R
 import org.oppia.app.fragment.FragmentScope
 import org.oppia.app.model.Topic
 import org.oppia.app.viewmodel.ObservableViewModel
+import java.text.DecimalFormat
 import javax.inject.Inject
 
 /** [ViewModel] for showing topic overview details. */
 @FragmentScope
 class TopicOverviewViewModel @Inject constructor() : ObservableViewModel() {
+  private val decimalFormat: DecimalFormat = DecimalFormat("#.###")
+
   val topic = ObservableField<Topic>(Topic.getDefaultInstance())
 
-  var downloadStatusIndicatorDrawableResourceId = ObservableField<Int>(R.drawable.ic_available_offline_primary_24dp)
+  var downloadStatusIndicatorDrawableResourceId = ObservableField(R.drawable.ic_available_offline_primary_24dp)
+
+  /** Returns the number of megabytes of disk space this topic requires, formatted for display. */
+  fun getTopicSizeMb(): String {
+    val topicSizeMb: Double = (topic.get()?.diskSizeBytes ?: 0) / (1024.0 * 1024.0)
+    return decimalFormat.format(topicSizeMb)
+  }
 }

app/src/main/res/layout/topic_overview_fragment.xml

@@ -142,7 +142,7 @@
         android:layout_marginTop="12dp"
         android:fontFamily="sans-serif"
         android:gravity="top"
-        android:text="@{String.format(@string/topic_download_text, viewModel.topic.getSerializedSize())}"
+        android:text="@{String.format(@string/topic_download_text, viewModel.getTopicSizeMb())}"
         android:textColor="@color/oppiaPrimaryText"
         android:textSize="18sp"
         android:textStyle="italic"

app/src/main/res/layout/topic_summary_view.xml

@@ -100,7 +100,7 @@
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
           android:fontFamily="sans-serif-light"
-          android:text="@{@plurals/lesson_count(viewModel.canonicalStoryCount, viewModel.canonicalStoryCount)}"
+          android:text="@{@plurals/lesson_count(viewModel.totalChapterCount, viewModel.totalChapterCount)}"
           android:textColor="@color/white_80"
           android:textSize="14sp"
           android:textStyle="italic"

domain/src/main/assets/about_oppia.json

@@ -1,4 +1,5 @@
 {
+  "exploration_id": "1",
   "author_notes": "",
   "blurb": "",
   "category": "Welcome",

domain/src/main/assets/oppia_exploration.json

@@ -1,4 +1,5 @@
 {
+  "exploration_id": "3",
   "author_notes": "",
   "blurb": "",
   "category": "Welcome",

domain/src/main/assets/prototype_exploration.json

@@ -1,4 +1,5 @@
 {
+  "exploration_id": "2",
   "language_code": "en",
   "param_specs": {},
   "param_changes": [],

domain/src/main/assets/welcome.json

@@ -1,4 +1,5 @@
 {
+  "exploration_id": "0",
   "author_notes": "",
   "blurb": "",
   "category": "Welcome",

domain/src/main/java/org/oppia/domain/audio/AudioPlayerController.kt

@@ -1,6 +1,8 @@
 package org.oppia.domain.audio
 
+import android.media.MediaDataSource
 import android.media.MediaPlayer
+import android.os.Build
 import androidx.annotation.VisibleForTesting
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
@@ -9,6 +11,8 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
+import org.oppia.util.caching.AssetRepository
+import org.oppia.util.caching.CacheAssetsLocally
 import org.oppia.util.data.AsyncResult
 import org.oppia.util.logging.Logger
 import org.oppia.util.threading.BackgroundDispatcher
@@ -28,7 +32,9 @@ import kotlin.concurrent.withLock
 @Singleton
 class AudioPlayerController @Inject constructor(
   private val logger: Logger,
-  @BackgroundDispatcher private val backgroundDispatcher: CoroutineDispatcher
+  private val assetRepository: AssetRepository,
+  @BackgroundDispatcher private val backgroundDispatcher: CoroutineDispatcher,
+  @CacheAssetsLocally private val cacheAssetsLocally: Boolean
 ) {
 
   inner class AudioMutableLiveData : MutableLiveData<AsyncResult<PlayProgress>>() {
@@ -125,7 +131,37 @@ class AudioPlayerController @Inject constructor(
 
   private fun prepareDataSource(url: String) {
     try {
-      mediaPlayer.setDataSource(url)
+      if (cacheAssetsLocally && Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+        val mediaDataSource: MediaDataSource = object : MediaDataSource() {
+          private val audioFileBuffer: ByteArray by lazy {
+            // Ensure that the download occurs off the main thread to avoid strict mode violations for
+            // cases when we need to stream audio.
+            assetRepository.loadRemoteBinaryAsset(url)()
+          }
+
+          // https://medium.com/@jacks205/implementing-your-own-android-mediadatasource-e67adb070731.
+          override fun readAt(position: Long, buffer: ByteArray?, offset: Int, size: Int): Int {
+            checkNotNull(buffer)
+            val intPosition = position.toInt()
+            if (intPosition >= audioFileBuffer.size) {
+              return -1
+            }
+            val availableData = audioFileBuffer.size - intPosition
+            val adjustedSize = size.coerceIn(0 until availableData)
+            audioFileBuffer.copyInto(buffer, offset, intPosition, intPosition + adjustedSize)
+            return adjustedSize
+          }
+
+          override fun getSize(): Long {
+            return audioFileBuffer.size.toLong()
+          }
+
+          override fun close() {}
+        }
+        mediaPlayer.setDataSource(mediaDataSource)
+      } else {
+        mediaPlayer.setDataSource(url)
+      }
       mediaPlayer.prepareAsync()
     } catch (e: IOException) {
       logger.e("AudioPlayerController", "Failed to set data source for media player", e)

domain/src/main/java/org/oppia/domain/exploration/ExplorationRetriever.kt

@@ -14,10 +14,10 @@ import org.oppia.domain.util.StateRetriever
 import java.io.IOException
 import javax.inject.Inject
 
-const val TEST_EXPLORATION_ID_5 = "DIWZiVgs0km-"
-const val TEST_EXPLORATION_ID_6 = "test_exp_id_6"
-const val TEST_EXPLORATION_ID_30 = "30"
-const val TEST_EXPLORATION_ID_7 = "test_exp_id_7"
+const val TEST_EXPLORATION_ID_5 = "0"
+const val TEST_EXPLORATION_ID_6 = "1"
+const val TEST_EXPLORATION_ID_30 = "2"
+const val TEST_EXPLORATION_ID_7 = "3"
 
 // TODO(#59): Make this class inaccessible outside of the domain package except for tests. UI code should not be allowed
 //  to depend on this utility.
@@ -27,9 +27,9 @@ class ExplorationRetriever @Inject constructor(
   private val jsonAssetRetriever: JsonAssetRetriever,
   private val stateRetriever: StateRetriever
 ) {
+  // TODO(#169): Force callers of this method on a background thread.
   /** Loads and returns an exploration for the specified exploration ID, or fails. */
-  @Suppress("RedundantSuspendModifier") // Force callers to call this on a background thread.
-  internal suspend fun loadExploration(explorationId: String): Exploration {
+  internal fun loadExploration(explorationId: String): Exploration {
     return when (explorationId) {
       TEST_EXPLORATION_ID_5 -> loadExplorationFromAsset("welcome.json")
       TEST_EXPLORATION_ID_6 -> loadExplorationFromAsset("about_oppia.json")
@@ -50,6 +50,7 @@ class ExplorationRetriever @Inject constructor(
     try {
       val explorationObject = jsonAssetRetriever.loadJsonFromAsset(assetName) ?: return Exploration.getDefaultInstance()
       return Exploration.newBuilder()
+        .setId(explorationObject.getString("exploration_id"))
         .setTitle(explorationObject.getString("title"))
         .setLanguageCode(explorationObject.getString("language_code"))
         .setInitStateName(explorationObject.getString("init_state_name"))

domain/src/main/java/org/oppia/domain/topic/StoryProgressController.kt

@@ -28,6 +28,9 @@ const val RATIOS_EXPLORATION_ID_0 = "2mzzFVDLuAj8"
 const val RATIOS_EXPLORATION_ID_1 = "5NWuolNcwH6e"
 const val RATIOS_EXPLORATION_ID_2 = "k2bQ7z5XHNbK"
 const val RATIOS_EXPLORATION_ID_3 = "tIoSb3HZFN6e"
+private val FRACTIONS_COMPLETED_CHAPTERS = listOf(FRACTIONS_EXPLORATION_ID_0)
+private val RATIOS_COMPLETED_CHAPTERS = listOf<String>()
+val COMPLETED_EXPLORATIONS = FRACTIONS_COMPLETED_CHAPTERS + RATIOS_COMPLETED_CHAPTERS
 
 /** Controller that records and provides completion statuses of chapters within the context of a story. */
 @Singleton
@@ -68,6 +71,11 @@ class StoryProgressController @Inject constructor(
     }
   }
 
+  // TODO(#21): Hide this functionality behind a data provider rather than punching a hole in this controller.
+  internal fun retrieveStoryProgress(storyId: String): StoryProgress {
+    return createStoryProgressSnapshot(storyId)
+  }
+
   private fun trackCompletedChapter(storyId: String, explorationId: String) {
     check(storyId in trackedStoriesProgress) { "No story found with ID: $storyId" }
     trackedStoriesProgress.getValue(storyId).markChapterCompleted(explorationId)
@@ -91,19 +99,13 @@ class StoryProgressController @Inject constructor(
 
   private fun createStoryProgressForJsonStory(fileName: String, index: Int): TrackedStoryProgress {
     val storyData = jsonAssetRetriever.loadJsonFromAsset(fileName)?.getJSONArray("story_list")!!
-    if (storyData.length() < index) {
-      return TrackedStoryProgress(
-        chapterList = listOf(),
-        completedChapters = setOf()
-      )
-    }
     val explorationIdList = getExplorationIdsFromStory(
       storyData.getJSONObject(index).getJSONObject("story")
         .getJSONObject("story_contents").getJSONArray("nodes")
     )
     return TrackedStoryProgress(
       chapterList = explorationIdList,
-      completedChapters = setOf()
+      completedChapters = COMPLETED_EXPLORATIONS.filter(explorationIdList::contains).toSet()
     )
   }