Handle status edit histories with < 2 entries (#3747)

This can happen if the edit history has not been propogated to the user's server.

If the edit history is missing then show an error with a link to the specifc Mastodon issue.

Fixes #3743

app/src/main/java/com/keylesspalace/tusky/components/viewthread/edits/ViewEditsFragment.kt

@@ -111,13 +111,28 @@ class ViewEditsFragment :
                         binding.statusView.show()
                         binding.initialProgressBar.hide()
 
-                        if (uiState.throwable is IOException) {
+                        when (uiState.throwable) {
-                            binding.statusView.setup(R.drawable.elephant_offline, R.string.error_network) {
+                            is IOException -> {
-                                viewModel.loadEdits(statusId, force = true)
+                                binding.statusView.setup(
+                                    R.drawable.elephant_offline,
+                                    R.string.error_network
+                                ) {
+                                    viewModel.loadEdits(statusId, force = true)
+                                }
                             }
-                        } else {
+                            is ViewEditsViewModel.MissingEditsException -> {
-                            binding.statusView.setup(R.drawable.elephant_error, R.string.error_generic) {
+                                binding.statusView.setup(
-                                viewModel.loadEdits(statusId, force = true)
+                                    R.drawable.elephant_friend_empty,
+                                    R.string.error_missing_edits
+                                )
+                            }
+                            else -> {
+                                binding.statusView.setup(
+                                    R.drawable.elephant_error,
+                                    R.string.error_generic
+                                ) {
+                                    viewModel.loadEdits(statusId, force = true)
+                                }
                             }
                         }
                     }

app/src/main/java/com/keylesspalace/tusky/components/viewthread/edits/ViewEditsViewModel.kt

@@ -17,7 +17,7 @@ package com.keylesspalace.tusky.components.viewthread.edits
 
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
-import at.connyduck.calladapter.networkresult.fold
+import at.connyduck.calladapter.networkresult.getOrElse
 import com.keylesspalace.tusky.components.viewthread.edits.TuskyTagHandler.Companion.DELETED_TEXT_EL
 import com.keylesspalace.tusky.components.viewthread.edits.TuskyTagHandler.Companion.INSERTED_TEXT_EL
 import com.keylesspalace.tusky.entity.StatusEdit
@@ -48,6 +48,9 @@ class ViewEditsViewModel @Inject constructor(private val api: MastodonApi) : Vie
     private val _uiState: MutableStateFlow<EditsUiState> = MutableStateFlow(EditsUiState.Initial)
     val uiState: StateFlow<EditsUiState> = _uiState.asStateFlow()
 
+    /** The API call to fetch edit history returned less than two items */
+    object MissingEditsException : Exception()
+
     fun loadEdits(statusId: String, force: Boolean = false, refreshing: Boolean = false) {
         if (!force && _uiState.value !is EditsUiState.Initial) return
 
@@ -58,63 +61,68 @@ class ViewEditsViewModel @Inject constructor(private val api: MastodonApi) : Vie
         }
 
         viewModelScope.launch {
-            api.statusEdits(statusId).fold(
+            val edits = api.statusEdits(statusId).getOrElse {
-                { edits ->
+                _uiState.value = EditsUiState.Error(it)
-                    // Diff each status' content against the previous version, producing new
+                return@launch
-                    // content with additional `ins` or `del` elements marking inserted or
+            }
-                    // deleted content.
-                    //
-                    // This can be CPU intensive depending on the number of edits and the size
-                    // of each, so don't run this on Dispatchers.Main.
-                    viewModelScope.launch(Dispatchers.Default) {
-                        val sortedEdits = edits.sortedBy { it.createdAt }
-                            .reversed()
-                            .toMutableList()
 
-                        SAXLoader.setXMLReaderClass("org.xmlpull.v1.sax2.Driver")
+            // `edits` might have fewer than the minimum number of entries because of
-                        val loader = SAXLoader()
+            // https://github.com/mastodon/mastodon/issues/25398.
-                        loader.config = DiffConfig(
+            if (edits.size < 2) {
-                            false,
+                _uiState.value = EditsUiState.Error(MissingEditsException)
-                            WhiteSpaceProcessing.PRESERVE,
+                return@launch
-                            TextGranularity.SPACE_WORD
+            }
+
+            // Diff each status' content against the previous version, producing new
+            // content with additional `ins` or `del` elements marking inserted or
+            // deleted content.
+            //
+            // This can be CPU intensive depending on the number of edits and the size
+            // of each, so don't run this on Dispatchers.Main.
+            viewModelScope.launch(Dispatchers.Default) {
+                val sortedEdits = edits.sortedBy { it.createdAt }
+                    .reversed()
+                    .toMutableList()
+
+                SAXLoader.setXMLReaderClass("org.xmlpull.v1.sax2.Driver")
+                val loader = SAXLoader()
+                loader.config = DiffConfig(
+                    false,
+                    WhiteSpaceProcessing.PRESERVE,
+                    TextGranularity.SPACE_WORD
+                )
+                val processor = OptimisticXMLProcessor()
+                processor.setCoalesce(true)
+                val output = HtmlDiffOutput()
+
+                try {
+                    // The XML processor expects `br` to be closed
+                    var currentContent =
+                        loader.load(sortedEdits[0].content.replace("<br>", "<br/>"))
+                    var previousContent =
+                        loader.load(sortedEdits[1].content.replace("<br>", "<br/>"))
+
+                    for (i in 1 until sortedEdits.size) {
+                        processor.diff(previousContent, currentContent, output)
+                        sortedEdits[i - 1] = sortedEdits[i - 1].copy(
+                            content = output.xml.toString()
                         )
-                        val processor = OptimisticXMLProcessor()
-                        processor.setCoalesce(true)
-                        val output = HtmlDiffOutput()
 
-                        try {
+                        if (i < sortedEdits.size - 1) {
-                            // The XML processor expects `br` to be closed
+                            currentContent = previousContent
-                            var currentContent =
+                            previousContent = loader.load(
-                                loader.load(sortedEdits[0].content.replace("<br>", "<br/>"))
+                                sortedEdits[i + 1].content.replace("<br>", "<br/>")
-                            var previousContent =
+                            )
-                                loader.load(sortedEdits[1].content.replace("<br>", "<br/>"))
-
-                            for (i in 1 until sortedEdits.size) {
-                                processor.diff(previousContent, currentContent, output)
-                                sortedEdits[i - 1] = sortedEdits[i - 1].copy(
-                                    content = output.xml.toString()
-                                )
-
-                                if (i < sortedEdits.size - 1) {
-                                    currentContent = previousContent
-                                    previousContent = loader.load(
-                                        sortedEdits[i + 1].content.replace("<br>", "<br/>")
-                                    )
-                                }
-                            }
-                            _uiState.value = EditsUiState.Success(sortedEdits)
-                        } catch (_: LoadingException) {
-                            // Something failed parsing the XML from the server. Rather than
-                            // show an error just return the sorted edits so the user can at
-                            // least visually scan the differences.
-                            _uiState.value = EditsUiState.Success(sortedEdits)
                         }
                     }
-                },
+                    _uiState.value = EditsUiState.Success(sortedEdits)
-                { throwable ->
+                } catch (_: LoadingException) {
-                    _uiState.value = EditsUiState.Error(throwable)
+                    // Something failed parsing the XML from the server. Rather than
+                    // show an error just return the sorted edits so the user can at
+                    // least visually scan the differences.
+                    _uiState.value = EditsUiState.Success(sortedEdits)
                 }
-            )
+            }
         }
     }
 

app/src/main/java/com/keylesspalace/tusky/view/BackgroundMessageView.kt

@@ -1,6 +1,7 @@
 package com.keylesspalace.tusky.view
 
 import android.content.Context
+import android.text.method.LinkMovementMethod
 import android.util.AttributeSet
 import android.view.Gravity
 import android.view.LayoutInflater
@@ -44,6 +45,7 @@ class BackgroundMessageView @JvmOverloads constructor(
         clickListener: ((v: View) -> Unit)? = null
     ) {
         binding.messageTextView.setText(messageRes)
+        binding.messageTextView.movementMethod = LinkMovementMethod.getInstance()
         binding.imageView.setImageResource(imageRes)
         binding.button.setOnClickListener(clickListener)
         binding.button.visible(clickListener != null)

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

@@ -35,7 +35,7 @@
             android:scaleType="centerInside"
             android:src="@drawable/elephant_offline" />
 
-        <TextView
+        <com.keylesspalace.tusky.view.ClickableSpanTextView
             android:id="@+id/messageTextView"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"

app/src/main/res/values/strings.xml

@@ -764,10 +764,9 @@
     <string name="pref_reading_order_oldest_first">Oldest first</string>
     <string name="pref_reading_order_newest_first">Newest first</string>
 
-    <!--@Tusky edited 19th December 2022 13:37 -->
     <string name="status_edit_info">Edited: %1$s</string>
-    <!--@Tusky created 19th December 2022 13:12 -->
     <string name="status_created_info">Created: %1$s</string>
+    <string name="error_missing_edits">Your server knows that this post was edited, but does not have a copy of the edits, so they can\'t be shown to you.\n\nThis is <a href="https://github.com/mastodon/mastodon/issues/25398">Mastodon issue #25398</a>.</string>
     <string name="a11y_label_loading_thread">Loading thread</string>
 
     <!--@knossos@fosstodon.org created 2023-01-07 -->