// Copyright (c) 2017, 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.

/// A file system operation used by the [MemoryFileSytem] to allow
/// tests to insert errors for certain operations.
///
/// This is not implemented as an enum to allow new values to be added in a
/// backwards compatible manner.
class FileSystemOp {
  const FileSystemOp._(this._value);

  // This field added to ensure const values can be different.
  // ignore: unused_field
  final int _value;

  /// A file system operation used for all read methods.
  ///
  /// * [FileSystemEntity.readAsString]
  /// * [FileSystemEntity.readAsStringSync]
  /// * [FileSystemEntity.readAsBytes]
  /// * [FileSystemEntity.readAsBytesSync]
  static const FileSystemOp read = FileSystemOp._(0);

  /// A file system operation used for all write methods.
  ///
  /// * [FileSystemEntity.writeAsString]
  /// * [FileSystemEntity.writeAsStringSync]
  /// * [FileSystemEntity.writeAsBytes]
  /// * [FileSystemEntity.writeAsBytesSync]
  static const FileSystemOp write = FileSystemOp._(1);

  /// A file system operation used for all delete methods.
  ///
  /// * [FileSystemEntity.delete]
  /// * [FileSystemEntity.deleteSync]
  static const FileSystemOp delete = FileSystemOp._(2);

  /// A file system operation used for all create methods.
  ///
  /// * [FileSystemEntity.create]
  /// * [FileSystemEntity.createSync]
  static const FileSystemOp create = FileSystemOp._(3);

  @override
  String toString() {
    switch (_value) {
      case 0:
        return 'FileSystemOp.read';
      case 1:
        return 'FileSystemOp.write';
      case 2:
        return 'FileSystemOp.delete';
      case 3:
        return 'FileSystemOp.create';
      default:
        throw StateError('Invalid FileSytemOp type: $this');
    }
  }
}