Fix #379: Collapse past wrong answers

app/src/main/java/org/oppia/app/player/state/StateFragment.kt

@@ -6,7 +6,7 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import org.oppia.app.fragment.InjectableFragment
-import org.oppia.app.model.InteractionObject
+import org.oppia.app.model.UserAnswer
 import org.oppia.app.player.audio.CellularDataInterface
 import org.oppia.app.player.state.answerhandling.InteractionAnswerReceiver
 import javax.inject.Inject
@@ -48,7 +48,7 @@ class StateFragment : InjectableFragment(), CellularDataInterface, InteractionAn
     stateFragmentPresenter.handleDisableAudio(saveUserChoice)
   }
 
-  override fun onAnswerReadyForSubmission(answer: InteractionObject) {
+  override fun onAnswerReadyForSubmission(answer: UserAnswer) {
     stateFragmentPresenter.handleAnswerReadyForSubmission(answer)
   }
 

app/src/main/java/org/oppia/app/player/state/StateFragmentPresenter.kt

@@ -7,6 +7,7 @@ import android.view.ViewGroup
 import android.view.inputmethod.InputMethodManager
 import androidx.appcompat.app.AppCompatActivity
 import androidx.databinding.DataBindingUtil
+import androidx.databinding.ObservableBoolean
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.Observer
@@ -18,18 +19,20 @@ import org.oppia.app.databinding.ContinueInteractionItemBinding
 import org.oppia.app.databinding.FeedbackItemBinding
 import org.oppia.app.databinding.FractionInteractionItemBinding
 import org.oppia.app.databinding.NumericInputInteractionItemBinding
+import org.oppia.app.databinding.PreviousResponsesHeaderItemBinding
 import org.oppia.app.databinding.SelectionInteractionItemBinding
 import org.oppia.app.databinding.StateButtonItemBinding
 import org.oppia.app.databinding.StateFragmentBinding
+import org.oppia.app.databinding.SubmittedAnswerItemBinding
 import org.oppia.app.databinding.TextInputInteractionItemBinding
 import org.oppia.app.fragment.FragmentScope
 import org.oppia.app.model.AnswerAndResponse
 import org.oppia.app.model.AnswerOutcome
 import org.oppia.app.model.CellularDataPreference
 import org.oppia.app.model.EphemeralState
 import org.oppia.app.model.Interaction
-import org.oppia.app.model.InteractionObject
 import org.oppia.app.model.SubtitledHtml
+import org.oppia.app.model.UserAnswer
 import org.oppia.app.player.audio.AudioFragment
 import org.oppia.app.player.audio.CellularDataDialogFragment
 import org.oppia.app.player.state.answerhandling.InteractionAnswerReceiver
@@ -39,11 +42,14 @@ import org.oppia.app.player.state.itemviewmodel.FeedbackViewModel
 import org.oppia.app.player.state.itemviewmodel.FractionInteractionViewModel
 import org.oppia.app.player.state.itemviewmodel.InteractionViewModelFactory
 import org.oppia.app.player.state.itemviewmodel.NumericInputViewModel
+import org.oppia.app.player.state.itemviewmodel.PreviousResponsesHeaderViewModel
 import org.oppia.app.player.state.itemviewmodel.SelectionInteractionViewModel
 import org.oppia.app.player.state.itemviewmodel.StateItemViewModel
 import org.oppia.app.player.state.itemviewmodel.StateNavigationButtonViewModel
 import org.oppia.app.player.state.itemviewmodel.StateNavigationButtonViewModel.ContinuationNavigationButtonType
+import org.oppia.app.player.state.itemviewmodel.SubmittedAnswerViewModel
 import org.oppia.app.player.state.itemviewmodel.TextInputViewModel
+import org.oppia.app.player.state.listener.PreviousResponsesHeaderClickListener
 import org.oppia.app.player.state.listener.StateNavigationButtonListener
 import org.oppia.app.recyclerview.BindableAdapter
 import org.oppia.app.viewmodel.ViewModelProvider
@@ -74,7 +80,7 @@ class StateFragmentPresenter @Inject constructor(
   private val htmlParserFactory: HtmlParser.Factory,
   private val context: Context,
   private val interactionViewModelFactoryMap: Map<String, @JvmSuppressWildcards InteractionViewModelFactory>
-) : StateNavigationButtonListener {
+) : StateNavigationButtonListener, PreviousResponsesHeaderClickListener {
 
   private var showCellularDataDialog = true
   private var useCellularData = false
@@ -86,6 +92,18 @@ class StateFragmentPresenter @Inject constructor(
   private val ephemeralStateLiveData: LiveData<AsyncResult<EphemeralState>> by lazy {
     explorationProgressController.getCurrentState()
   }
+  /**
+   * A list of view models corresponding to past view models that are hidden by default. These are intentionally not
+   * retained upon configuration changes since the user can just re-expand the list. Note that the first element of this
+   * list (when initialized), will always be the previous answers header to help locate the items in the recycler view
+   * (when present).
+   */
+  private val previousAnswerViewModels: MutableList<StateItemViewModel> = mutableListOf()
+  /**
+   * Whether the previously submitted wrong answers should be expanded. This value is intentionally not retained upon
+   * configuration changes since the user can just re-expand the list.
+   */
+  private var hasPreviousResponsesExpanded: Boolean = false
 
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?): View? {
     cellularDialogController.getCellularDataPreference()
@@ -178,6 +196,30 @@ class StateFragmentPresenter @Inject constructor(
         setViewModel = TextInputInteractionItemBinding::setViewModel,
         transformViewModel = { it as TextInputViewModel }
       )
+      .registerViewBinder(
+        viewType = StateItemViewModel.ViewType.SUBMITTED_ANSWER,
+        inflateView = { parent ->
+          SubmittedAnswerItemBinding.inflate(
+            LayoutInflater.from(parent.context), parent, /* attachToParent= */ false
+          ).root
+        },
+        bindView = { view, viewModel ->
+          val binding = DataBindingUtil.findBinding<SubmittedAnswerItemBinding>(view)!!
+          val userAnswer = (viewModel as SubmittedAnswerViewModel).submittedUserAnswer
+          when (userAnswer.textualAnswerCase) {
+            UserAnswer.TextualAnswerCase.HTML_ANSWER -> binding.submittedAnswer = htmlParserFactory.create(
+              entityType, explorationId).parseOppiaHtml(userAnswer.htmlAnswer, binding.submittedAnswerTextView
+            )
+            else -> binding.submittedAnswer = userAnswer.plainAnswer
+          }
+        }
+      )
+      .registerViewDataBinder(
+        viewType = StateItemViewModel.ViewType.PREVIOUS_RESPONSES_HEADER,
+        inflateDataBinding = PreviousResponsesHeaderItemBinding::inflate,
+        setViewModel = PreviousResponsesHeaderItemBinding::setViewModel,
+        transformViewModel = { it as PreviousResponsesHeaderViewModel }
+      )
       .build()
   }
 
@@ -207,7 +249,7 @@ class StateFragmentPresenter @Inject constructor(
     }
   }
 
-  fun handleAnswerReadyForSubmission(answer: InteractionObject) {
+  fun handleAnswerReadyForSubmission(answer: UserAnswer) {
     // An interaction has indicated that an answer is ready for submission.
     handleSubmitAnswer(answer)
   }
@@ -271,14 +313,15 @@ class StateFragmentPresenter @Inject constructor(
     val scrollToTop = ::currentStateName.isInitialized && currentStateName != ephemeralState.state.name
 
     currentStateName = ephemeralState.state.name
+    previousAnswerViewModels.clear() // But retain whether the list is currently open.
     val pendingItemList = mutableListOf<StateItemViewModel>()
     addContentItem(pendingItemList, ephemeralState)
     val interaction = ephemeralState.state.interaction
     if (ephemeralState.stateTypeCase == EphemeralState.StateTypeCase.PENDING_STATE) {
-      addPreviousAnswers(pendingItemList, interaction, ephemeralState.pendingState.wrongAnswerList)
+      addPreviousAnswers(pendingItemList, ephemeralState.pendingState.wrongAnswerList)
       addInteractionForPendingState(pendingItemList, interaction)
     } else if (ephemeralState.stateTypeCase == EphemeralState.StateTypeCase.COMPLETED_STATE) {
-      addPreviousAnswers(pendingItemList, interaction, ephemeralState.completedState.answerList)
+      addPreviousAnswers(pendingItemList, ephemeralState.completedState.answerList)
     }
 
     val hasPreviousState = ephemeralState.hasPreviousState
@@ -355,7 +398,7 @@ class StateFragmentPresenter @Inject constructor(
     moveToNextState()
   }
 
-  private fun handleSubmitAnswer(answer: InteractionObject) {
+  private fun handleSubmitAnswer(answer: UserAnswer) {
     subscribeToAnswerOutcome(explorationProgressController.submitAnswer(answer))
   }
 
@@ -365,25 +408,22 @@ class StateFragmentPresenter @Inject constructor(
 
   override fun onNextButtonClicked() = moveToNextState()
 
+  override fun onResponsesHeaderClicked() {
+    togglePreviousAnswers()
+  }
+
   private fun moveToNextState() {
-    explorationProgressController.moveToNextState()
+    explorationProgressController.moveToNextState().observe(fragment, Observer<AsyncResult<Any?>> {
+      hasPreviousResponsesExpanded = false
+    })
   }
 
   private fun addInteractionForPendingState(
     pendingItemList: MutableList<StateItemViewModel>, interaction: Interaction
-  ) = addInteraction(pendingItemList, interaction)
-
-  private fun addInteractionForCompletedState(
-    pendingItemList: MutableList<StateItemViewModel>, interaction: Interaction, existingAnswer: InteractionObject
-  ) = addInteraction(pendingItemList, interaction, existingAnswer = existingAnswer, isReadOnly = true)
-
-  private fun addInteraction(
-    pendingItemList: MutableList<StateItemViewModel>, interaction: Interaction, existingAnswer:
-    InteractionObject? = null, isReadOnly: Boolean = false
   ) {
     val interactionViewModelFactory = interactionViewModelFactoryMap.getValue(interaction.id)
     pendingItemList += interactionViewModelFactory(
-      explorationId, interaction, fragment as InteractionAnswerReceiver, existingAnswer, isReadOnly
+      explorationId, interaction, fragment as InteractionAnswerReceiver
     )
   }
 
@@ -393,21 +433,69 @@ class StateFragmentPresenter @Inject constructor(
   }
 
   private fun addPreviousAnswers(
-    pendingItemList: MutableList<StateItemViewModel>, interaction: Interaction,
-    answersAndResponses: List<AnswerAndResponse>
+    pendingItemList: MutableList<StateItemViewModel>, answersAndResponses: List<AnswerAndResponse>
   ) {
-    // TODO: add support for displaying the previous answer, too.
-    for (answerAndResponse in answersAndResponses) {
-      addInteractionForCompletedState(pendingItemList, interaction, answerAndResponse.userAnswer)
-      addFeedbackItem(pendingItemList, answerAndResponse.feedback)
+    if (answersAndResponses.size > 1) {
+      PreviousResponsesHeaderViewModel(
+        answersAndResponses.size - 1, ObservableBoolean(hasPreviousResponsesExpanded), this
+      ).let { viewModel ->
+        pendingItemList += viewModel
+        previousAnswerViewModels += viewModel
+      }
+      // Only add previous answers if current responses are expanded.
+      for (answerAndResponse in answersAndResponses.take(answersAndResponses.size - 1)) {
+        createSubmittedAnswer(answerAndResponse.userAnswer).let { viewModel ->
+          if (hasPreviousResponsesExpanded) {
+            pendingItemList += viewModel
+          }
+          previousAnswerViewModels += viewModel
+        }
+        createFeedbackItem(answerAndResponse.feedback)?.let { viewModel ->
+          if (hasPreviousResponsesExpanded) {
+            pendingItemList += viewModel
+          }
+          previousAnswerViewModels += viewModel
+        }
+      }
     }
+    answersAndResponses.lastOrNull()?.let { answerAndResponse ->
+      pendingItemList += createSubmittedAnswer(answerAndResponse.userAnswer)
+      createFeedbackItem(answerAndResponse.feedback)?.let(pendingItemList::add)
+    }
+  }
+
+  /**
+   * Toggles whether the previous answers should be shown based on the current state stored in
+   * [PreviousResponsesHeaderViewModel].
+   */
+  private fun togglePreviousAnswers() {
+    val headerModel = previousAnswerViewModels.first() as PreviousResponsesHeaderViewModel
+    val expandPreviousAnswers = !headerModel.isExpanded.get()
+    val headerIndex = viewModel.itemList.indexOf(headerModel)
+    val previousAnswersAndFeedbacks = previousAnswerViewModels.takeLast(previousAnswerViewModels.size - 1)
+    if (expandPreviousAnswers) {
+      // Add the pending view models to the recycler view to expand them.
+      viewModel.itemList.addAll(headerIndex + 1, previousAnswersAndFeedbacks)
+    } else {
+      // Remove the pending view models to collapse the list.
+      viewModel.itemList.removeAll(previousAnswersAndFeedbacks)
+    }
+    // Ensure the header matches the updated state.
+    headerModel.isExpanded.set(expandPreviousAnswers)
+    hasPreviousResponsesExpanded = expandPreviousAnswers
+    recyclerViewAdapter.notifyDataSetChanged()
+  }
+
+  private fun createSubmittedAnswer(userAnswer: UserAnswer): SubmittedAnswerViewModel {
+    return SubmittedAnswerViewModel(userAnswer)
   }
 
-  private fun addFeedbackItem(pendingItemList: MutableList<StateItemViewModel>, feedback: SubtitledHtml) {
+  private fun createFeedbackItem(feedback: SubtitledHtml): FeedbackViewModel? {
     // Only show feedback if there's some to show.
     if (feedback.html.isNotEmpty()) {
-      pendingItemList += FeedbackViewModel(feedback.html)
+      return FeedbackViewModel(feedback.html)
     }
+    return null
   }
 
   private fun updateNavigationButtonVisibility(

app/src/main/java/org/oppia/app/player/state/StateViewModel.kt

@@ -1,20 +1,20 @@
 package org.oppia.app.player.state
 
-import androidx.databinding.ObservableArrayList
 import androidx.databinding.ObservableField
 import androidx.databinding.ObservableList
 import androidx.lifecycle.ViewModel
 import org.oppia.app.fragment.FragmentScope
-import org.oppia.app.model.InteractionObject
+import org.oppia.app.model.UserAnswer
 import org.oppia.app.player.state.answerhandling.InteractionAnswerHandler
 import org.oppia.app.player.state.itemviewmodel.StateItemViewModel
+import org.oppia.app.viewmodel.ObservableArrayList
 import org.oppia.app.viewmodel.ObservableViewModel
 import javax.inject.Inject
 
 /** [ViewModel] for state-fragment. */
 @FragmentScope
 class StateViewModel @Inject constructor() : ObservableViewModel() {
-  val itemList: ObservableList<StateItemViewModel> = ObservableArrayList<StateItemViewModel>()
+  val itemList: ObservableList<StateItemViewModel> = ObservableArrayList()
 
   val isAudioBarVisible = ObservableField<Boolean>(false)
 
@@ -31,8 +31,8 @@ class StateViewModel @Inject constructor() : ObservableViewModel() {
   }
 
   // TODO(#164): Add a hasPendingAnswer() that binds to the enabled state of the Submit button.
-  fun getPendingAnswer(): InteractionObject {
-    return getPendingAnswerHandler(itemList)?.getPendingAnswer() ?: InteractionObject.getDefaultInstance()
+  fun getPendingAnswer(): UserAnswer {
+    return getPendingAnswerHandler(itemList)?.getPendingAnswer() ?: UserAnswer.getDefaultInstance()
   }
 
   private fun getPendingAnswerHandler(itemList: List<StateItemViewModel>): InteractionAnswerHandler? {

app/src/main/java/org/oppia/app/player/state/answerhandling/InteractionAnswerHandler.kt

@@ -1,6 +1,6 @@
 package org.oppia.app.player.state.answerhandling
 
-import org.oppia.app.model.InteractionObject
+import org.oppia.app.model.UserAnswer
 
 /**
  * A handler for interaction answers. Handlers can either require an additional user action before the answer can be
@@ -15,13 +15,13 @@ interface InteractionAnswerHandler {
   fun isExplicitAnswerSubmissionRequired(): Boolean = true
 
   /** Return the current answer that is ready for handling. */
-  fun getPendingAnswer(): InteractionObject
+  fun getPendingAnswer(): UserAnswer
 }
 
 /**
  * A callback that will be called by [InteractionAnswerHandler]s when a user submits an answer. To be implemented by
  * the parent fragment of the handler.
  */
 interface InteractionAnswerReceiver {
-  fun onAnswerReadyForSubmission(answer: InteractionObject)
+  fun onAnswerReadyForSubmission(answer: UserAnswer)
 }

app/src/main/java/org/oppia/app/player/state/itemviewmodel/ContinueInteractionViewModel.kt

@@ -1,25 +1,26 @@
 package org.oppia.app.player.state.itemviewmodel
 
 import org.oppia.app.model.InteractionObject
+import org.oppia.app.model.UserAnswer
 import org.oppia.app.player.state.answerhandling.InteractionAnswerHandler
 import org.oppia.app.player.state.answerhandling.InteractionAnswerReceiver
-import org.oppia.domain.util.toAnswerString
 
 // For context:
 // https://github.com/oppia/oppia/blob/37285a/extensions/interactions/Continue/directives/oppia-interactive-continue.directive.ts
 private const val DEFAULT_CONTINUE_INTERACTION_TEXT_ANSWER = "Please continue."
 
 /** [ViewModel] for the 'Continue' button. */
 class ContinueInteractionViewModel(
-  private val interactionAnswerReceiver: InteractionAnswerReceiver, existingAnswer: InteractionObject?,
-  val isReadOnly: Boolean
+  private val interactionAnswerReceiver: InteractionAnswerReceiver
 ): StateItemViewModel(ViewType.CONTINUE_INTERACTION), InteractionAnswerHandler {
-  val answerText: CharSequence = existingAnswer?.toAnswerString() ?: ""
 
   override fun isExplicitAnswerSubmissionRequired(): Boolean = false
 
-  override fun getPendingAnswer(): InteractionObject {
-    return InteractionObject.newBuilder().setNormalizedString(DEFAULT_CONTINUE_INTERACTION_TEXT_ANSWER).build()
+  override fun getPendingAnswer(): UserAnswer {
+    return UserAnswer.newBuilder()
+      .setAnswer(InteractionObject.newBuilder().setNormalizedString(DEFAULT_CONTINUE_INTERACTION_TEXT_ANSWER))
+      .setPlainAnswer(DEFAULT_CONTINUE_INTERACTION_TEXT_ANSWER)
+      .build()
   }
 
   fun handleButtonClicked() {

app/src/main/java/org/oppia/app/player/state/itemviewmodel/FractionInteractionViewModel.kt

@@ -1,20 +1,23 @@
 package org.oppia.app.player.state.itemviewmodel
 
 import org.oppia.app.model.InteractionObject
+import org.oppia.app.model.UserAnswer
 import org.oppia.app.parser.StringToFractionParser
 import org.oppia.app.player.state.answerhandling.InteractionAnswerHandler
-import org.oppia.domain.util.toAnswerString
 
-class FractionInteractionViewModel(
-  existingAnswer: InteractionObject?, val isReadOnly: Boolean
-): StateItemViewModel(ViewType.FRACTION_INPUT_INTERACTION), InteractionAnswerHandler {
-  var answerText: CharSequence = existingAnswer?.toAnswerString() ?: ""
+/** [ViewModel] for the fraction input interaction. */
+class FractionInteractionViewModel: StateItemViewModel(ViewType.FRACTION_INPUT_INTERACTION), InteractionAnswerHandler {
+  var answerText: CharSequence = ""
 
-  override fun getPendingAnswer(): InteractionObject {
-    val interactionObjectBuilder = InteractionObject.newBuilder()
+  override fun getPendingAnswer(): UserAnswer {
+    val userAnswerBuilder = UserAnswer.newBuilder()
     if (answerText.isNotEmpty()) {
-      interactionObjectBuilder.fraction = StringToFractionParser().getFractionFromString(answerText.toString())
+      val answerTextString = answerText.toString()
+      userAnswerBuilder.answer = InteractionObject.newBuilder()
+        .setFraction(StringToFractionParser().getFractionFromString(answerTextString))
+        .build()
+      userAnswerBuilder.plainAnswer = answerTextString
     }
-    return interactionObjectBuilder.build()
+    return userAnswerBuilder.build()
   }
 }