sdk/pkg/analyzer/test/util/tree_string_sink.dart

// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// Wrapper around a [StringSink] for writing tree structures.
class TreeStringSink {
  final StringSink _sink;
  String _indent = '';

  TreeStringSink({
    required StringSink sink,
    required String indent,
  })  : _sink = sink,
        _indent = indent;

  void withIndent(void Function() f) {
    final indent = _indent;
    _indent = '$indent  ';
    f();
    _indent = indent;
  }

  void write(Object object) {
    _sink.write(object);
  }

  void writeElements<T extends Object>(
    String name,
    List<T> elements,
    void Function(T) f,
  ) {
    if (elements.isNotEmpty) {
      writelnWithIndent(name);
      withIndent(() {
        for (var element in elements) {
          f(element);
        }
      });
    }
  }

  Future<void> writeFlags(Map<String, bool> flags) async {
    if (flags.values.any((flag) => flag)) {
      writeIndentedLine(() {
        write('flags:');
        for (final entry in flags.entries) {
          if (entry.value) {
            write(' ${entry.key}');
          }
        }
      });
    }
  }

  void writeIf(bool flag, Object object) {
    if (flag) {
      write(object);
    }
  }

  void writeIndent() {
    _sink.write(_indent);
  }

  void writeIndentedLine(void Function() f) {
    writeIndent();
    f();
    writeln();
  }

  void writeln([Object? object = '']) {
    _sink.writeln(object);
  }

  void writelnWithIndent(Object object) {
    _sink.write(_indent);
    _sink.writeln(object);
  }

  void writeWithIndent(Object object) {
    _sink.write(_indent);
    _sink.write(object);
  }
}