WIP: Implement undo/redo commands

Signed-off-by: William Brawner <me@wbrawner.com>

app/src/main/java/com/wbrawner/simplemarkdown/view/fragment/EditFragment.kt

@@ -24,6 +24,7 @@ import com.wbrawner.simplemarkdown.model.Readability
 import com.wbrawner.simplemarkdown.utility.hideKeyboard
 import com.wbrawner.simplemarkdown.utility.showKeyboard
 import com.wbrawner.simplemarkdown.view.ViewPagerPage
+import com.wbrawner.simplemarkdown.viewmodel.EditorCommand
 import com.wbrawner.simplemarkdown.viewmodel.MarkdownViewModel
 import kotlinx.coroutines.*
 import kotlin.coroutines.CoroutineContext
@@ -94,8 +95,11 @@ class EditFragment : Fragment(), ViewPagerPage, CoroutineScope {
             }
             false
         }
-        markdownEditor?.setText(viewModel.markdownUpdates.value)
+        markdownEditor?.setText(viewModel.markdown.value)
-        viewModel.originalMarkdown.observe(viewLifecycleOwner, Observer {
+        viewModel.editorCommands.observe(viewLifecycleOwner, Observer {
+            when (it) {
+                is EditorCommand.Undo -> markdownEditor?.text?.
+            }
             markdownEditor?.setText(it)
         })
         launch {

app/src/main/java/com/wbrawner/simplemarkdown/view/fragment/MainFragment.kt

@@ -75,7 +75,7 @@ class MainFragment : Fragment(), ActivityCompat.OnRequestPermissionsResultCallba
                     }
                     R.id.action_share -> {
                         val shareIntent = Intent(Intent.ACTION_SEND)
-                        shareIntent.putExtra(Intent.EXTRA_TEXT, viewModel.markdownUpdates.value)
+                        shareIntent.putExtra(Intent.EXTRA_TEXT, viewModel.markdown.value)
                         shareIntent.type = "text/plain"
                         startActivity(Intent.createChooser(
                                 shareIntent,
@@ -223,7 +223,7 @@ class MainFragment : Fragment(), ActivityCompat.OnRequestPermissionsResultCallba
     }
 
     private fun promptSaveOrDiscardChanges() {
-        if (viewModel.originalMarkdown.value == viewModel.markdownUpdates.value) {
+        if (viewModel.originalMarkdown.value == viewModel.markdown.value) {
             viewModel.reset("Untitled.md")
             return
         }

app/src/main/java/com/wbrawner/simplemarkdown/view/fragment/PreviewFragment.kt

@@ -63,8 +63,8 @@ class PreviewFragment : Fragment(), CoroutineScope {
 
     override fun onAttach(context: Context) {
         super.onAttach(context)
-        updateWebContent(viewModel.markdownUpdates.value ?: "")
+        updateWebContent(viewModel.markdown.value ?: "")
-        viewModel.markdownUpdates.observe(this, Observer {
+        viewModel.markdown.observe(this, Observer {
             updateWebContent(it)
         })
     }

app/src/main/java/com/wbrawner/simplemarkdown/viewmodel/MarkdownViewModel.kt

@@ -12,12 +12,12 @@ import java.io.Reader
 
 class MarkdownViewModel : ViewModel() {
     val fileName = MutableLiveData<String>("Untitled.md")
-    val markdownUpdates = MutableLiveData<String>()
+    val editorCommands = MutableLiveData<EditorCommand>()
-    val originalMarkdown = MutableLiveData<String>()
+    val markdown = MutableLiveData<String>()
     val uri = MutableLiveData<Uri>()
 
     fun updateMarkdown(markdown: String?) {
-        this.markdownUpdates.postValue(markdown ?: "")
+        this.markdown.postValue(markdown ?: "")
     }
 
     suspend fun load(context: Context, uri: Uri?): Boolean {
@@ -28,8 +28,8 @@ class MarkdownViewModel : ViewModel() {
                     val fileInput = FileInputStream(it.fileDescriptor)
                     val fileName = uri.getName(context)
                     val content = fileInput.reader().use(Reader::readText)
-                    originalMarkdown.postValue(content)
+                    markdown.postValue(content)
-                    markdownUpdates.postValue(content)
+                    editorCommands.postValue(EditorCommand.Load(content))
                     this@MarkdownViewModel.fileName.postValue(fileName)
                     this@MarkdownViewModel.uri.postValue(uri)
                     true
@@ -48,7 +48,7 @@ class MarkdownViewModel : ViewModel() {
                 context.contentResolver.openOutputStream(uri, "rwt")
                         ?.writer()
                         ?.use {
-                            it.write(markdownUpdates.value ?: "")
+                            it.write(markdown.value ?: "")
                         }
                         ?: return@withContext false
                 this@MarkdownViewModel.fileName.postValue(fileName)
@@ -62,7 +62,23 @@ class MarkdownViewModel : ViewModel() {
 
     fun reset(untitledFileName: String) {
         fileName.postValue(untitledFileName)
-        originalMarkdown.postValue("")
+        editorCommands.postValue(EditorCommand.Load(""))
-        markdownUpdates.postValue("")
+        markdown.postValue("")
+    }
+
+    fun undo() {
+        editorCommands.postValue(EditorCommand.Undo())
+    }
+
+    fun redo() {
+        editorCommands.postValue(EditorCommand.Redo())
     }
 }
+
+sealed class EditorCommand {
+    val consumed = false
+
+    class Undo: EditorCommand()
+    class Redo: EditorCommand()
+    class Load(val text: String): EditorCommand()
+}

app/src/main/res/drawable/ic_redo.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M18.4,10.6C16.55,8.99 14.15,8 11.5,8c-4.65,0 -8.58,3.03 -9.96,7.22L3.9,16c1.05,-3.19 4.05,-5.5 7.6,-5.5 1.95,0 3.73,0.72 5.12,1.88L13,16h9V7l-3.6,3.6z"/>
+</vector>

app/src/main/res/drawable/ic_undo.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M12.5,8c-2.65,0 -5.05,0.99 -6.9,2.6L2,7v9h9l-3.62,-3.62c1.39,-1.16 3.16,-1.88 5.12,-1.88 3.54,0 6.55,2.31 7.6,5.5l2.37,-0.78C21.08,11.03 17.15,8 12.5,8z"/>
+</vector>

app/src/main/res/menu/menu_edit.xml

@@ -6,6 +6,17 @@
         android:icon="@drawable/ic_share"
         android:title="@string/action_share"
         app:showAsAction="ifRoom" />
+    <item
+        android:id="@+id/action_undo"
+        android:icon="@drawable/ic_undo"
+        android:title="@string/action_undo"
+        app:showAsAction="ifRoom" />
+    <item
+        android:id="@+id/action_redo"
+        android:icon="@drawable/ic_redo"
+        android:title="@string/action_redo"
+        app:showAsAction="ifRoom" />
+    <group android:id="@+id/editGroup">
         <item
             android:id="@+id/action_new"
             android:title="@string/action_new"
@@ -20,6 +31,7 @@
         <item
             android:id="@+id/action_save_as"
             android:title="@string/action_save_as" />
+    </group>
     <item
         android:id="@+id/action_lock_swipe"
         android:checkable="true"

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

@@ -77,6 +77,8 @@
     <string name="action_rate">Rate SimpleMarkdown</string>
     <string name="support_thank_you">Thank you so much for your support!</string>
     <string name="description_heart">Heart</string>
+    <string name="action_undo">Undo</string>
+    <string name="action_redo">Redo</string>
     <string-array name="pref_entries_dark_mode">
         <item>@string/pref_value_light</item>
         <item>@string/pref_value_dark</item>