Display embedded images for each message in a conversation

after they were loaded through the "Display embedded images" button for
any message.

There were some issues preventing the functionality from working which
were addressed in this PR:
- The same instance of MessageRenderer was not ready to work with
different messages (messageBody was not changeable and the is a check
that would stop execution when an image was "already rendered" which
didn't take account that different messages can contain the same image)
- When MessageRenderer returns the html, we need to display that
  through a new livedata which targets only the message currently opened,
  as resetting the whole ConversationUiModel causes UI glitches when the
  message is not the last one.

MAILAND-1931

app/src/main/java/ch/protonmail/android/activities/messageDetails/MessageDetailsAdapter.kt

@@ -68,7 +68,7 @@ internal class MessageDetailsAdapter(
     private val onLoadEmbeddedImagesClicked: ((Message) -> Unit)?,
     private val onDisplayRemoteContentClicked: ((Message) -> Unit)?,
     private val userManager: UserManager,
-    private val onLoadMessage: (Message) -> Unit,
+    private val onLoadMessageBody: (Message) -> Unit,
     private val onAttachmentDownloadCallback: (Attachment) -> Unit
 ) : ExpandableRecyclerAdapter<MessageDetailsAdapter.MessageDetailsListItem>(context) {
 
@@ -179,7 +179,7 @@ internal class MessageDetailsAdapter(
 
             Timber.v("Load data for message: ${message.messageId} at position $position")
             if (listItem.messageFormattedHtml == null) {
-                onLoadMessage(message)
+                onLoadMessageBody(message)
             }
 
             val webView = itemView.messageWebViewContainer.getChildAt(0) as? WebView ?: return

app/src/main/java/ch/protonmail/android/activities/messageDetails/MessageRenderer.kt

@@ -68,16 +68,12 @@ internal class MessageRenderer(
     /** The [String] html of the message body */
     var messageBody: String? = null
         set(value) {
-            // Return if body is already set
-            if (field != null) return
-
-            // Update if value is not null
-            if (value != null) field = value
+            field = value
+            // Clear inlined images to ensure when messageBody changes the loading of images doesn't get blocked
+            // (messageBody changing means we're loading images for another message in the same conversation)
+            inlinedImageIds.clear()
         }
 
-    /** reference to the [Document] */
-    private val document by lazy { documentParser(messageBody!!) }
-
     /** A [Channel] for receive new [EmbeddedImage] images to inline in [document] */
     val images = actor<List<EmbeddedImage>> {
         for (embeddedImages in channel) {
@@ -175,6 +171,10 @@ internal class MessageRenderer(
     private val imageInliner = actor<List<ImageString>> {
         for (imageStrings in channel) {
 
+            // Document is parsed for each emission because `messageBody`
+            // field can change when switching messages in a conversation
+            val document = documentParser(messageBody!!)
+
             for (imageString in imageStrings) {
 
                 val (embeddedImage, image64) = imageString
@@ -194,14 +194,8 @@ internal class MessageRenderer(
             // Extract the message ID for which embedded images are being loaded
             // to pass it back to the caller along with the rendered body
             val messageId = imageStrings.firstOrNull()?.first?.messageId ?: continue
-            documentStringifier.send(messageId)
-        }
-    }
-
-    /** Actor that will stringify the [document] */
-    private val documentStringifier = actor<String> {
-        for (messageId in channel)
             renderedMessage.send(RenderedMessage(messageId, document.toString()))
+        }
     }
 
     /** `CoroutineContext` for [idsListUpdater] for update [inlinedImageIds] of a single thread */
@@ -229,7 +223,7 @@ internal class MessageRenderer(
         private val imageDecoder: ImageDecoder = DefaultImageDecoder()
     ) {
 
-        /** @return new instance of [MessageRenderer] with the given [messageBody] */
+        /** @return new instance of [MessageRenderer] */
         fun create(scope: CoroutineScope) =
             MessageRenderer(dispatchers, documentParser, imageDecoder, attachmentsDirectory, scope)
     }

app/src/main/java/ch/protonmail/android/activities/messageDetails/viewmodel/MessageDetailsViewModel.kt

@@ -183,6 +183,7 @@ internal class MessageDetailsViewModel @Inject constructor(
 
     private val _prepareEditMessageIntentResult: MutableLiveData<Event<IntentExtrasData>> = MutableLiveData()
     private val _decryptedConversationUiModel: MutableLiveData<ConversationUiModel> = MutableLiveData()
+    private val _messageRenderedWithImages: MutableLiveData<Message> = MutableLiveData()
     private val _checkStoragePermission: MutableLiveData<Event<Boolean>> = MutableLiveData()
     private val _messageDetailsError: MutableLiveData<Event<String>> = MutableLiveData()
 
@@ -222,6 +223,9 @@ internal class MessageDetailsViewModel @Inject constructor(
     val decryptedConversationUiModel: LiveData<ConversationUiModel>
         get() = _decryptedConversationUiModel
 
+    val messageRenderedWithImages: LiveData<Message>
+        get() = _messageRenderedWithImages
+
     private var areImagesDisplayed: Boolean = false
 
     init {
@@ -230,7 +234,7 @@ internal class MessageDetailsViewModel @Inject constructor(
                 val currentUiModel = _decryptedConversationUiModel.value
                 val message = currentUiModel?.messages?.find { it.messageId == renderedMessage.messageId }
                 message?.decryptedHTML = renderedMessage.renderedHtmlBody
-                _decryptedConversationUiModel.value = currentUiModel
+                _messageRenderedWithImages.value = message
                 areImagesDisplayed = true
             }
         }

app/src/main/java/ch/protonmail/android/details/presentation/MessageDetailsActivity.kt

@@ -190,6 +190,15 @@ internal class MessageDetailsActivity : BaseStoragePermissionActivity() {
     private fun continueSetup() {
         viewModel.conversationUiModel.observe(this) { viewModel.loadMailboxItemDetails() }
         viewModel.decryptedConversationUiModel.observe(this, ConversationUiModelObserver())
+        viewModel.messageRenderedWithImages.observe(this) { message ->
+            val messageId = message.messageId ?: return@observe
+            messageExpandableAdapter.showMessageDetails(
+                message.decryptedHTML,
+                messageId,
+                false,
+                message.attachments
+            )
+        }
 
         viewModel.labels
             .onEach(messageExpandableAdapter::setAllLabels)
@@ -463,15 +472,15 @@ internal class MessageDetailsActivity : BaseStoragePermissionActivity() {
     private inner class ConversationUiModelObserver : Observer<ConversationUiModel> {
 
         override fun onChanged(conversation: ConversationUiModel) {
-            val message = lastMessage(conversation)
+            val lastMessage = conversation.messages.last()
 
             displayToolbarData(conversation)
-            setupLastMessageActionsListener(message)
+            setupLastMessageActionsListener(lastMessage)
 
-            Timber.v("New decrypted message ${message.messageId}")
+            Timber.v("New decrypted message ${lastMessage.messageId}")
             viewModel.renderedFromCache = AtomicBoolean(true)
-            val decryptedBody = getDecryptedBody(message.decryptedHTML)
-            if (decryptedBody.isEmpty() || message.messageBody.isNullOrEmpty()) {
+            val decryptedBody = getDecryptedBody(lastMessage.decryptedHTML)
+            if (decryptedBody.isEmpty() || lastMessage.messageBody.isNullOrEmpty()) {
                 UiUtil.showInfoSnack(mSnackLayout, this@MessageDetailsActivity, R.string.decryption_error_desc).show()
                 return
             }
@@ -548,8 +557,6 @@ internal class MessageDetailsActivity : BaseStoragePermissionActivity() {
         expandedToolbarTitleTextView.text = subject
     }
 
-    private fun lastMessage(conversation: ConversationUiModel): Message = conversation.messages.last()
-
     fun executeMessageAction(
         messageAction: Constants.MessageActionType,
         message: Message = requireNotNull(viewModel.decryptedConversationUiModel.value?.messages?.last())