flutter-quill/lib/src/models/rules/rule.dart

import '../documents/attribute.dart';
import '../documents/document.dart';
import '../quill_delta.dart';
import 'delete.dart';
import 'format.dart';
import 'insert.dart';

enum RuleType { INSERT, DELETE, FORMAT }

abstract class Rule {
  const Rule();

  Delta? apply(Delta document, int index,
      {int? len, Object? data, Attribute? attribute}) {
    validateArgs(len, data, attribute);
    return applyRule(document, index,
        len: len, data: data, attribute: attribute);
  }

  void validateArgs(int? len, Object? data, Attribute? attribute);

  /// Applies heuristic rule to an operation on a [document] and returns
  /// resulting [Delta].
  Delta? applyRule(Delta document, int index,
      {int? len, Object? data, Attribute? attribute});

  RuleType get type;
}

class Rules {
  Rules(this._rules);

  List<Rule> _customRules = [];

  final List<Rule> _rules;
  static final Rules _instance = Rules([
    const FormatLinkAtCaretPositionRule(),
    const ResolveLineFormatRule(),
    const ResolveInlineFormatRule(),
    const InsertEmbedsRule(),
    const AutoExitBlockRule(),
    const PreserveBlockStyleOnInsertRule(),
    const PreserveLineStyleOnSplitRule(),
    const ResetLineFormatOnNewLineRule(),
    const AutoFormatLinksRule(),
    const AutoFormatMultipleLinksRule(),
    const PreserveInlineStylesRule(),
    const CatchAllInsertRule(),
    const EnsureEmbedLineRule(),
    const PreserveLineStyleOnMergeRule(),
    const CatchAllDeleteRule(),
    const EnsureLastLineBreakDeleteRule()
  ]);

  static Rules getInstance() => _instance;

  void setCustomRules(List<Rule> customRules) {
    _customRules = customRules;
  }

  Delta apply(RuleType ruleType, Document document, int index,
      {int? len, Object? data, Attribute? attribute}) {
    final delta = document.toDelta();
    for (final rule in _customRules + _rules) {
      if (rule.type != ruleType) {
        continue;
      }
      try {
        final result = rule.apply(delta, index,
            len: len, data: data, attribute: attribute);
        if (result != null) {
          return result..trim();
        }
      } catch (e) {
        rethrow;
      }
    }
    throw 'Apply rules failed';
  }
}