Node.length, Node.offset caching added

lib/src/models/documents/nodes/container.dart

@@ -47,11 +47,14 @@ abstract base class QuillContainer<T extends Node?> extends Node {
   /// Always returns fresh instance.
   T get defaultChild;
 
+  int? _length;
+
   /// Adds [node] to the end of this container children list.
   void add(T node) {
     assert(node?.parent == null);
     node?.parent = this;
     _children.add(node as Node);
+    clearLengthCache();
   }
 
   /// Adds [node] to the beginning of this container children list.
@@ -59,6 +62,7 @@ abstract base class QuillContainer<T extends Node?> extends Node {
     assert(node?.parent == null);
     node?.parent = this;
     _children.addFirst(node as Node);
+    clearLengthCache();
   }
 
   /// Removes [node] from this container.
@@ -66,6 +70,7 @@ abstract base class QuillContainer<T extends Node?> extends Node {
     assert(node?.parent == this);
     node?.parent = null;
     _children.remove(node as Node);
+    clearLengthCache();
   }
 
   /// Moves children of this node to [newParent].
@@ -118,11 +123,20 @@ abstract base class QuillContainer<T extends Node?> extends Node {
           .map((e) => e.toPlainText(embedBuilders, unknownEmbedBuilder))
           .join();
 
-  /// Content length of this node's children.
-  ///
-  /// To get number of children in this node use [childCount].
   @override
-  int get length => _children.fold(0, (cur, node) => cur + node.length);
+  int get length {
+    _length ??= _children.fold(0, (cur, node) => (cur ?? 0) + node.length);
+    return _length!;
+  }
+
+  @override
+  void clearLengthCache() {
+    _length = null;
+    clearOffsetCache();
+    if (parent != null) {
+      parent!.clearLengthCache();
+    }
+  }
 
   @override
   void insert(int index, Object data, Style? style) {

lib/src/models/documents/nodes/leaf.dart

@@ -24,18 +24,39 @@ abstract base class Leaf extends Node {
   /// Contents of this node, either a String if this is a [QuillText] or an
   /// [Embed] if this is an [BlockEmbed].
   Object get value => _value;
+
+  set value(Object v) {
+    _value = v;
+    _length = null;
+    clearOffsetCache();
+  }
+
   Object _value;
 
   @override
   Line? get parent => super.parent as Line?;
 
+  int? _length;
+
   @override
   int get length {
+    if (_length != null) {
+      return _length!;
+    }
     if (_value is String) {
-      return (_value as String).length;
+      _length = (_value as String).length;
+    } else {
+      // return 1 for embedded object
+      _length = 1;
+    }
+    return _length!;
+  }
+
+  @override
+  void clearLengthCache() {
+    if (parent != null) {
+      parent!.clearLengthCache();
     }
-    // return 1 for embedded object
-    return 1;
   }
 
   @override
@@ -47,6 +68,7 @@ abstract base class Leaf extends Node {
 
   @override
   void insert(int index, Object data, Style? style) {
+    final length = this.length;
     assert(index >= 0 && index <= length);
     final node = Leaf(data);
     if (index < length) {
@@ -75,6 +97,7 @@ abstract base class Leaf extends Node {
 
   @override
   void delete(int index, int? len) {
+    final length = this.length;
     assert(index < length);
 
     final local = math.min(length - index, len!);
@@ -117,7 +140,7 @@ abstract base class Leaf extends Node {
     // Merging it with previous node if style is the same.
     final prev = node.previous;
     if (!node.isFirst && prev is QuillText && prev.style == node.style) {
-      prev._value = prev.value + node.value;
+      prev.value = prev.value + node.value;
       node.unlink();
       node = prev;
     }
@@ -125,7 +148,7 @@ abstract base class Leaf extends Node {
     // Merging it with next node if style is the same.
     final next = node.next;
     if (!node.isLast && next is QuillText && next.style == node.style) {
-      node._value = node.value + next.value;
+      node.value = node.value + next.value;
       next.unlink();
     }
   }
@@ -152,7 +175,7 @@ abstract base class Leaf extends Node {
 
     assert(this is QuillText);
     final text = _value as String;
-    _value = text.substring(0, index);
+    value = text.substring(0, index);
     final split = Leaf(text.substring(index))..applyStyle(style);
     insertAfter(split);
     return split;

lib/src/models/documents/nodes/line.dart

@@ -127,11 +127,11 @@ base class Line extends QuillContainer<Leaf?> {
     if (style == null) {
       return;
     }
-    final thisLength = length;
+    final length = this.length;
 
-    final local = math.min(thisLength - index, len!);
+    final local = math.min(length - index, len!);
     // If index is at newline character then this is a line/block style update.
-    final isLineFormat = (index + local == thisLength) && local == 1;
+    final isLineFormat = (index + local == length) && local == 1;
 
     if (isLineFormat) {
       assert(
@@ -145,7 +145,7 @@ base class Line extends QuillContainer<Leaf?> {
       assert(style.values.every((attr) =>
           attr.scope == AttributeScope.inline ||
           attr.scope == AttributeScope.ignore));
-      assert(index + local != thisLength);
+      assert(index + local != length);
       super.retain(index, local, style);
     }
 
@@ -158,6 +158,7 @@ base class Line extends QuillContainer<Leaf?> {
 
   @override
   void delete(int index, int? len) {
+    final length = this.length;
     final local = math.min(length - index, len!);
     final isLFDeleted = index + local == length; // Line feed
     if (isLFDeleted) {

lib/src/models/documents/nodes/node.dart

@@ -47,24 +47,41 @@ abstract base class Node extends LinkedListEntry<Node> {
   /// Length of this node in characters.
   int get length;
 
+  void clearLengthCache();
+
   Node clone() => newInstance()..applyStyle(style);
 
+  int? _offset;
+
   /// Offset in characters of this node relative to [parent] node.
   ///
   /// To get offset of this node in the document see [documentOffset].
   int get offset {
-    var offset = 0;
+    if (_offset != null) {
+      return _offset!;
+    }
 
     if (list == null || isFirst) {
-      return offset;
+      return 0;
+    }
+    var offset = 0;
+    for (final node in list!) {
+      if (node == this) {
+        break;
+      }
+      offset += node.length;
     }
 
-    var cur = this;
-    do {
-      cur = cur.previous!;
-      offset += cur.length;
-    } while (!cur.isFirst);
-    return offset;
+    _offset = offset;
+    return _offset!;
+  }
+
+  void clearOffsetCache() {
+    _offset = null;
+    final next = this.next;
+    if (next != null) {
+      next.clearOffsetCache();
+    }
   }
 
   /// Offset in characters of this node in the document.
@@ -100,6 +117,7 @@ abstract base class Node extends LinkedListEntry<Node> {
     assert(entry.parent == null && parent != null);
     entry.parent = parent;
     super.insertBefore(entry);
+    clearLengthCache();
   }
 
   @override
@@ -107,11 +125,13 @@ abstract base class Node extends LinkedListEntry<Node> {
     assert(entry.parent == null && parent != null);
     entry.parent = parent;
     super.insertAfter(entry);
+    clearLengthCache();
   }
 
   @override
   void unlink() {
     assert(parent != null);
+    clearLengthCache();
     parent = null;
     super.unlink();
   }