feat: implement delete command

lib/src/editor/editor_component/service/shortcuts/command_shortcut_events/delete_command.dart

@@ -34,69 +34,44 @@ CommandShortcutEventHandler _deleteInCollapsedSelection = (editorState) {
 
   final position = selection.start;
   final node = editorState.getNodeAtPath(position.path);
-  if (node == null || node.delta == null) {
+  final delta = node?.delta;
+  if (node == null || delta == null) {
     return KeyEventResult.ignored;
   }
 
-  // Why do we use nextRunePosition instead of the position end offset?
-  // Because some character's length > 1, for example, emoji.
-  final index = node.delta!.nextRunePosition(position.offset);
   final transaction = editorState.transaction;
-  if (index == node.delta!.length) {
-    // merge the next node in the current node.
-    final nextNode = node.next;
-    if (nextNode == null) {
-      return KeyEventResult.ignored;
-    }
-    //TODO(Lucas): add logic for merging a bulletList or numberedList item.
-    if (nextNode.next == null && nextNode.children.isEmpty) {
-      final path = node.path;
+
+  // merge the next node with delta
+  if (position.offset == delta.length) {
+    final next = node.findDownward((element) => element.delta != null);
+    if (next != null) {
+      if (next.children.isNotEmpty) {
+        final path = node.path + [node.children.length];
+        transaction.insertNodes(path, next.children);
+      }
       transaction
-        ..mergeText(node, nextNode)
-        ..deleteNode(nextNode)
-        ..afterSelection = Selection.collapsed(
-          Position(
-            path: path,
-            offset: index,
-          ),
+        ..deleteNode(next)
+        ..mergeText(
+          node,
+          next,
         );
-    } else {
-      // merge with the previous node contains delta.
-      final nextNodeWithDelta =
-          node.lastNodeWhere((element) => element.delta != null);
-      if (nextNodeWithDelta != null) {
-        assert(nextNodeWithDelta.delta != null);
-        transaction
-          ..mergeText(nextNodeWithDelta, node)
-          ..insertNodes(
-            // insert children to previous node
-            nextNodeWithDelta.path.next,
-            node.children.toList(),
-          )
-          ..deleteNode(node)
-          ..afterSelection = Selection.collapsed(
-            Position(
-              path: nextNodeWithDelta.path,
-              offset: nextNodeWithDelta.delta!.length,
-            ),
-          );
-      } else {
-        // do nothing if there is no previous node contains delta.
-        return KeyEventResult.ignored;
-      }
+      editorState.apply(transaction);
+      return KeyEventResult.handled;
     }
   } else {
-    // Although the selection may be collapsed,
-    //  its length may not always be equal to 1 because some characters have a length greater than 1.
-    transaction.deleteText(
-      node,
-      position.offset,
-      index - position.offset,
-    );
+    final nextIndex = delta.nextRunePosition(position.offset);
+    if (nextIndex <= delta.length) {
+      transaction.deleteText(
+        node,
+        position.offset,
+        nextIndex - position.offset,
+      );
+      editorState.apply(transaction);
+      return KeyEventResult.handled;
+    }
   }
 
-  editorState.apply(transaction);
-  return KeyEventResult.handled;
+  return KeyEventResult.ignored;
 };
 
 /// Handle delete key event when selection is not collapsed.

lib/src/editor/editor_component/service/shortcuts/command_shortcut_events/select_all_command.dart

@@ -29,7 +29,7 @@ CommandShortcutEventHandler _selectAllCommandHandler = (editorState) {
       )
       ?.selectable;
   final lastSelectable = editorState.document.root
-      .lastNodeWhere(
+      .lastChildWhere(
         (element) => element.selectable != null,
       )
       ?.selectable;

lib/src/extensions/node_extensions.dart

@@ -29,7 +29,7 @@ extension NodeExtensions on Node {
   Node? previousNodeWhere(bool Function(Node element) test) {
     var previous = this.previous;
     while (previous != null) {
-      final last = previous.lastNodeWhere(test);
+      final last = previous.lastChildWhere(test);
       if (last != null) {
         return last;
       }
@@ -49,11 +49,11 @@ extension NodeExtensions on Node {
   }
 
   /// Returns the last node in the subtree that satisfies the given predicate
-  Node? lastNodeWhere(bool Function(Node element) test) {
+  Node? lastChildWhere(bool Function(Node element) test) {
     final children = this.children.toList().reversed;
     for (final child in children) {
       if (child.children.isNotEmpty) {
-        final last = child.lastNodeWhere(test);
+        final last = child.lastChildWhere(test);
         if (last != null) {
           return last;
         }
@@ -65,6 +65,30 @@ extension NodeExtensions on Node {
     return null;
   }
 
+  // find the node from it's children or it's next sibling to find the node that matches the given predicate
+  Node? findDownward(bool Function(Node element) test) {
+    final children = this.children.toList();
+    for (final child in children) {
+      if (test(child)) {
+        return child;
+      }
+      if (child.children.isNotEmpty) {
+        final node = child.findDownward(test);
+        if (node != null) {
+          return node;
+        }
+      }
+    }
+    final next = this.next;
+    if (next != null) {
+      if (test(next)) {
+        return next;
+      }
+      return next.findDownward(test);
+    }
+    return null;
+  }
+
   bool allSatisfyInSelection(
     Selection selection,
     bool Function(Delta delta) test,

test/new/service/shortcuts/command_shortcut_events/delete_command_test.dart

@@ -326,10 +326,12 @@ void main() async {
       final delta = Delta()..insert(text);
       final editor = tester.editor
         ..addNode(headingNode(level: 1, delta: delta))
-        ..addNode(bulletedListNode(
-          delta: delta,
-          children: [bulletedListNode(delta: delta)],
-        ));
+        ..addNode(
+          bulletedListNode(
+            delta: delta,
+            children: [bulletedListNode(delta: delta)],
+          ),
+        );
 
       await editor.startTesting();
 
@@ -374,10 +376,12 @@ void main() async {
       final delta = Delta()..insert(text);
       final editor = tester.editor
         ..addNode(bulletedListNode(delta: delta))
-        ..addNode(bulletedListNode(
-          delta: delta,
-          children: [bulletedListNode(delta: delta)],
-        ));
+        ..addNode(
+          bulletedListNode(
+            delta: delta,
+            children: [bulletedListNode(delta: delta)],
+          ),
+        );
 
       await editor.startTesting();