Fix #118: Introduce TopicController (#174)

* Introduce TopicController & tests.

* Introduce 6 sample thumbnail graphics locally and a proto data structure
for thumbnails that can be used for lessons.

* Update topic data structures to include comments and better thumbnails.

* Address review comments.

* Introduce support for retrieving concept cards in TopicController (in a
stubbed way), without tests.

This also cleans up the voiceover/translation proto dependencies a bit,
and migrates Playability over to the ChapterPlayState enum.

* Add remaining tests. Fix post-merge build. Clean up proto files.

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

@@ -0,0 +1,277 @@
+package org.oppia.domain.topic
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import org.oppia.app.model.ChapterPlayState
+import java.lang.IllegalArgumentException
+import javax.inject.Inject
+import javax.inject.Singleton
+import org.oppia.app.model.ChapterSummary
+import org.oppia.app.model.ConceptCard
+import org.oppia.app.model.LessonThumbnail
+import org.oppia.app.model.LessonThumbnailGraphic
+import org.oppia.app.model.SkillSummary
+import org.oppia.app.model.StorySummary
+import org.oppia.app.model.SubtitledHtml
+import org.oppia.app.model.Topic
+import org.oppia.app.model.Translation
+import org.oppia.app.model.TranslationMapping
+import org.oppia.app.model.Voiceover
+import org.oppia.app.model.VoiceoverMapping
+import org.oppia.util.data.AsyncResult
+
+const val TEST_SKILL_ID_0 = "test_skill_id_0"
+const val TEST_SKILL_ID_1 = "test_skill_id_1"
+const val TEST_SKILL_ID_2 = "test_skill_id_2"
+const val TEST_SKILL_CONTENT_ID_0 = "test_skill_content_id_0"
+const val TEST_SKILL_CONTENT_ID_1 = "test_skill_content_id_1"
+
+/** Controller for retrieving all aspects of a topic. */
+@Singleton
+class TopicController @Inject constructor() {
+  /** Returns the [Topic] corresponding to the specified topic ID, or a failed result if no such topic exists. */
+  fun getTopic(topicId: String): LiveData<AsyncResult<Topic>> {
+    return MutableLiveData(
+      when (topicId) {
+        TEST_TOPIC_ID_0 -> AsyncResult.success(createTestTopic0())
+        TEST_TOPIC_ID_1 -> AsyncResult.success(createTestTopic1())
+        else -> AsyncResult.failed(IllegalArgumentException("Invalid topic ID: $topicId"))
+      }
+    )
+  }
+
+  // TODO(#173): Move this to its own controller once structural data & saved progress data are better distinguished.
+
+  /** Returns the [StorySummary] corresponding to the specified story ID, or a failed result if there is none. */
+  fun getStory(storyId: String): LiveData<AsyncResult<StorySummary>> {
+    return MutableLiveData(
+      when (storyId) {
+        TEST_STORY_ID_0 -> AsyncResult.success(createTestTopic0Story0())
+        TEST_STORY_ID_1 -> AsyncResult.success(createTestTopic0Story1())
+        TEST_STORY_ID_2 -> AsyncResult.success(createTestTopic1Story2())
+        else -> AsyncResult.failed(IllegalArgumentException("Invalid story ID: $storyId"))
+      }
+    )
+  }
+
+  /** Returns the [ConceptCard] corresponding to the specified skill ID, or a failed result if there is none. */
+  fun getConceptCard(skillId: String): LiveData<AsyncResult<ConceptCard>> {
+    return MutableLiveData(
+      when (skillId) {
+        TEST_SKILL_ID_0 -> AsyncResult.success(createTestConceptCardForSkill0())
+        TEST_SKILL_ID_1 -> AsyncResult.success(createTestConceptCardForSkill1())
+        TEST_SKILL_ID_2 -> AsyncResult.success(createTestConceptCardForSkill2())
+        else -> AsyncResult.failed(IllegalArgumentException("Invalid skill ID: $skillId"))
+      }
+    )
+  }
+
+  private fun createTestTopic0(): Topic {
+    return Topic.newBuilder()
+      .setTopicId(TEST_TOPIC_ID_0)
+      .setName("First Test Topic")
+      .setDescription("A topic investigating the interesting aspects of the Oppia Android app.")
+      .addStory(createTestTopic0Story0())
+      .addStory(createTestTopic0Story1())
+      .addSkill(createTestTopic0Skill0())
+      .addSkill(createTestTopic0Skill1())
+      .setTopicThumbnail(createTestTopic0Thumbnail())
+      .build()
+  }
+
+  private fun createTestTopic0Thumbnail(): LessonThumbnail {
+    return LessonThumbnail.newBuilder()
+      .setThumbnailGraphic(LessonThumbnailGraphic.CHILD_WITH_BOOK)
+      .setBackgroundColorRgb(0xd5836f)
+      .build()
+  }
+
+  private fun createTestTopic1(): Topic {
+    return Topic.newBuilder()
+      .setTopicId(TEST_TOPIC_ID_1)
+      .setName("Second Test Topic")
+      .setDescription(
+        "A topic considering the various implications of having especially long topic descriptions. " +
+            "These descriptions almost certainly need to wrap, which should be interesting in the UI (especially on " +
+            "small screens). Consider also that there may even be multiple points pertaining to a topic, some of which " +
+            "may require expanding the description section in order to read the whole topic description."
+      )
+      .addStory(createTestTopic1Story2())
+      .addSkill(createTestTopic1Skill0())
+      .setTopicThumbnail(createTestTopic1Thumbnail())
+      .build()
+  }
+
+  private fun createTestTopic1Thumbnail(): LessonThumbnail {
+    return LessonThumbnail.newBuilder()
+      .setThumbnailGraphic(LessonThumbnailGraphic.CHILD_WITH_CUPCAKES)
+      .setBackgroundColorRgb(0xf7bf73)
+      .build()
+  }
+
+  private fun createTestTopic0Story0(): StorySummary {
+    return StorySummary.newBuilder()
+      .setStoryId(TEST_STORY_ID_0)
+      .setStoryName("First Story")
+      .addChapter(createTestTopic0Story0Chapter0())
+      .build()
+  }
+
+  private fun createTestTopic0Story0Chapter0(): ChapterSummary {
+    return ChapterSummary.newBuilder()
+      .setExplorationId(TEST_EXPLORATION_ID_0)
+      .setName("First Exploration")
+      .setChapterPlayState(ChapterPlayState.COMPLETED)
+      .setChapterThumbnail(createTestTopic0Story0Chapter0Thumbnail())
+      .build()
+  }
+
+  private fun createTestTopic0Story0Chapter0Thumbnail(): LessonThumbnail {
+    return LessonThumbnail.newBuilder()
+      .setThumbnailGraphic(LessonThumbnailGraphic.CHILD_WITH_FRACTIONS_HOMEWORK)
+      .setBackgroundColorRgb(0x494276)
+      .build()
+  }
+
+  private fun createTestTopic0Story1(): StorySummary {
+    return StorySummary.newBuilder()
+      .setStoryId(TEST_STORY_ID_1)
+      .setStoryName("Second Story")
+      .addChapter(createTestTopic0Story1Chapter0())
+      .addChapter(createTestTopic0Story1Chapter1())
+      .addChapter(createTestTopic0Story1Chapter2())
+      .build()
+  }
+
+  private fun createTestTopic0Story1Chapter0(): ChapterSummary {
+    return ChapterSummary.newBuilder()
+      .setExplorationId(TEST_EXPLORATION_ID_1)
+      .setName("Second Exploration")
+      .setChapterPlayState(ChapterPlayState.COMPLETED)
+      .setChapterThumbnail(createTestTopic0Story1ChapterThumbnail())
+      .build()
+  }
+
+  private fun createTestTopic0Story1Chapter1(): ChapterSummary {
+    return ChapterSummary.newBuilder()
+      .setExplorationId(TEST_EXPLORATION_ID_2)
+      .setName("Third Exploration")
+      .setChapterPlayState(ChapterPlayState.NOT_STARTED)
+      .setChapterThumbnail(createTestTopic0Story1ChapterThumbnail())
+      .build()
+  }
+
+  private fun createTestTopic0Story1Chapter2(): ChapterSummary {
+    return ChapterSummary.newBuilder()
+      .setExplorationId(TEST_EXPLORATION_ID_3)
+      .setName("Fourth Exploration")
+      .setChapterPlayState(ChapterPlayState.NOT_PLAYABLE_MISSING_PREREQUISITES)
+      .setChapterThumbnail(createTestTopic0Story1ChapterThumbnail())
+      .build()
+  }
+
+  /** Returns the [LessonThumbnail] associated for each chapter in story 1. */
+  private fun createTestTopic0Story1ChapterThumbnail(): LessonThumbnail {
+    return LessonThumbnail.newBuilder()
+      .setThumbnailGraphic(LessonThumbnailGraphic.DUCK_AND_CHICKEN)
+      .setBackgroundColorRgb(0xa5d3ec)
+      .build()
+  }
+
+  private fun createTestTopic1Story2(): StorySummary {
+    return StorySummary.newBuilder()
+      .setStoryId(TEST_STORY_ID_2)
+      .setStoryName("Other Interesting Story")
+      .addChapter(createTestTopic1Story2Chapter0())
+      .build()
+  }
+
+  private fun createTestTopic1Story2Chapter0(): ChapterSummary {
+    return ChapterSummary.newBuilder()
+      .setExplorationId(TEST_EXPLORATION_ID_4)
+      .setName("Fifth Exploration")
+      .setChapterPlayState(ChapterPlayState.NOT_STARTED)
+      .setChapterThumbnail(createTestTopic1Story2Chapter0Thumbnail())
+      .build()
+  }
+
+  private fun createTestTopic1Story2Chapter0Thumbnail(): LessonThumbnail {
+    return LessonThumbnail.newBuilder()
+      .setThumbnailGraphic(LessonThumbnailGraphic.PERSON_WITH_PIE_CHART)
+      .setBackgroundColorRgb(0x7eb3ad)
+      .build()
+  }
+
+  private fun createTestTopic0Skill0(): SkillSummary {
+    return SkillSummary.newBuilder()
+      .setSkillId(TEST_SKILL_ID_0)
+      .setDescription("An important skill")
+      .build()
+  }
+
+  private fun createTestTopic0Skill1(): SkillSummary {
+    return SkillSummary.newBuilder()
+      .setSkillId(TEST_SKILL_ID_1)
+      .setDescription("Another important skill")
+      .build()
+  }
+
+  private fun createTestTopic1Skill0(): SkillSummary {
+    return SkillSummary.newBuilder()
+      .setSkillId(TEST_SKILL_ID_2)
+      .setDescription("A different skill in a different topic")
+      .build()
+  }
+
+  private fun createTestConceptCardForSkill0(): ConceptCard {
+    return ConceptCard.newBuilder()
+      .setSkillId(TEST_SKILL_ID_0)
+      .setSkillDescription(createTestTopic0Skill0().description)
+      .setExplanation(
+        SubtitledHtml.newBuilder().setHtml("Hello. Welcome to Oppia.").setContentId(TEST_SKILL_CONTENT_ID_0).build()
+      )
+      .addWorkedExample(
+        SubtitledHtml.newBuilder().setHtml("This is the first example.").setContentId(TEST_SKILL_CONTENT_ID_1).build()
+      )
+      .putRecordedVoiceover(
+        TEST_SKILL_CONTENT_ID_0, VoiceoverMapping.newBuilder().putVoiceoverMapping(
+          "es", Voiceover.newBuilder().setFileName("fake_spanish_xlated_explanation.mp3").setFileSizeBytes(456).build()
+        ).build()
+      )
+      .putRecordedVoiceover(
+        TEST_SKILL_CONTENT_ID_1, VoiceoverMapping.newBuilder().putVoiceoverMapping(
+          "es", Voiceover.newBuilder().setFileName("fake_spanish_xlated_example.mp3").setFileSizeBytes(123).build()
+        ).build()
+      )
+      .putWrittenTranslation(
+        TEST_SKILL_CONTENT_ID_0, TranslationMapping.newBuilder().putTranslationMapping(
+          "es", Translation.newBuilder().setHtml("Hola. Bienvenidos a Oppia.").build()
+        ).build()
+      )
+      .putWrittenTranslation(
+        TEST_SKILL_CONTENT_ID_1, TranslationMapping.newBuilder().putTranslationMapping(
+          "es", Translation.newBuilder().setHtml("Este es el primer ejemplo trabajado.").build()
+        ).build()
+      )
+      .build()
+  }
+
+  private fun createTestConceptCardForSkill1(): ConceptCard {
+    return ConceptCard.newBuilder()
+      .setSkillId(TEST_SKILL_ID_1)
+      .setSkillDescription(createTestTopic0Skill1().description)
+      .setExplanation(SubtitledHtml.newBuilder().setHtml("Explanation with <b>rich text</b>.").build())
+      .addWorkedExample(SubtitledHtml.newBuilder().setHtml("Worked example with <i>rich text</i>.").build())
+      .build()
+  }
+
+  private fun createTestConceptCardForSkill2(): ConceptCard {
+    return ConceptCard.newBuilder()
+      .setSkillId(TEST_SKILL_ID_2)
+      .setSkillDescription(createTestTopic1Skill0().description)
+      .setExplanation(SubtitledHtml.newBuilder().setHtml("Explanation without rich text.").build())
+      .addWorkedExample(SubtitledHtml.newBuilder().setHtml("Worked example without rich text.").build())
+      .addWorkedExample(SubtitledHtml.newBuilder().setHtml("Second worked example.").build())
+      .build()
+  }
+}