AppFlowy/frontend/app_flowy/packages/flowy_editor/lib/document/node.dart

import 'dart:collection';
import 'package:flowy_editor/document/path.dart';
import 'package:flutter/material.dart';

typedef Attributes = Map<String, dynamic>;

class Node extends ChangeNotifier with LinkedListEntry<Node> {
  Node? parent;
  final String type;
  final LinkedList<Node> children;
  final Attributes attributes;

  String? get subtype {
    // TODO: make 'subtype' as a const value.
    if (attributes.containsKey('subtype')) {
      assert(attributes['subtype'] is String?,
          'subtype must be a [String] or [null]');
      return attributes['subtype'] as String?;
    }
    return null;
  }

  Path get path => _path();

  Node({
    required this.type,
    required this.children,
    required this.attributes,
    this.parent,
  });

  factory Node.fromJson(Map<String, Object> json) {
    assert(json['type'] is String);

    // TODO: check the type that not exist on plugins.
    final jType = json['type'] as String;
    final jChildren = json['children'] as List?;
    final jAttributes = json['attributes'] != null
        ? Attributes.from(json['attributes'] as Map)
        : Attributes.from({});

    final LinkedList<Node> children = LinkedList();
    if (jChildren != null) {
      children.addAll(
        jChildren.map(
          (jChild) => Node.fromJson(
            Map<String, Object>.from(jChild),
          ),
        ),
      );
    }

    final node = Node(
      type: jType,
      children: children,
      attributes: jAttributes,
    );

    for (final child in children) {
      child.parent = node;
    }

    return node;
  }

  void updateAttributes(Attributes attributes) {
    bool shouldNotifyParent =
        this.attributes['subtype'] != attributes['subtype'];

    for (final attribute in attributes.entries) {
      this.attributes[attribute.key] = attribute.value;
    }
    // Notify the new attributes
    // if attributes contains 'subtype', should notify parent to rebuild node
    // else, just notify current node.
    shouldNotifyParent ? parent?.notifyListeners() : notifyListeners();
  }

  Node? childAtIndex(int index) {
    if (children.length <= index) {
      return null;
    }

    return children.elementAt(index);
  }

  Node? childAtPath(Path path) {
    if (path.isEmpty) {
      return this;
    }

    return childAtIndex(path.first)?.childAtPath(path.sublist(1));
  }

  @override
  void insertAfter(Node entry) {
    entry.parent = parent;
    super.insertAfter(entry);

    // Notify the new node.
    parent?.notifyListeners();
  }

  @override
  void insertBefore(Node entry) {
    entry.parent = parent;
    super.insertBefore(entry);

    // Notify the new node.
    parent?.notifyListeners();
  }

  @override
  void unlink() {
    super.unlink();

    parent?.notifyListeners();
    parent = null;
  }

  Map<String, Object> toJson() {
    var map = <String, Object>{
      'type': type,
    };
    if (children.isNotEmpty) {
      map['children'] = children.map((node) => node.toJson());
    }
    if (attributes.isNotEmpty) {
      map['attributes'] = attributes;
    }
    return map;
  }

  Path _path([Path previous = const []]) {
    if (parent == null) {
      return previous;
    }
    var index = 0;
    for (var child in parent!.children) {
      if (child == this) {
        break;
      }
      index += 1;
    }
    return parent!._path([index, ...previous]);
  }
}