// Copyright (c) 2012, 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.

part of dart.io;

/// Information about the environment in which the current program is running.
///
/// Platform provides information such as the operating system,
/// the hostname of the computer, the value of environment variables,
/// the path to the running program,
/// and other global properties of the program being run.
///
/// ## Get the URI of the current Dart script
///
/// Use the [script] getter to get the URI to the currently running
/// Dart script.
/// ```dart
/// import 'dart:io' show Platform;
///
/// void main() {
///   // Get the URI of the script being run.
///   var uri = Platform.script;
///   // Convert the URI to a path.
///   var path = uri.toFilePath();
/// }
/// ```
/// ## Get the value of an environment variable
///
/// The [environment] getter returns a the names and values of environment
/// variables in a [Map] that contains key-value pairs of strings. The Map is
/// unmodifiable. This sample shows how to get the value of the `PATH`
/// environment variable.
/// ```dart
/// import 'dart:io' show Platform;
///
/// void main() {
///   Map<String, String> envVars = Platform.environment;
///   print(envVars['PATH']);
/// }
/// ```
/// ## Determine the OS
///
/// You can get the name of the operating system as a string with the
/// [operatingSystem] getter. You can also use one of the static boolean
/// getters: [isMacOS], [isLinux], and [isWindows].
/// ```dart
/// import 'dart:io' show Platform;
///
/// void main() {
///   // Get the operating system as a string.
///   String os = Platform.operatingSystem;
///   // Or, use a predicate getter.
///   if (Platform.isMacOS) {
///     print('is a Mac');
///   } else {
///     print('is not a Mac');
///   }
/// }
/// ```
class Platform {
  static final _numberOfProcessors = _Platform.numberOfProcessors;
  static final _pathSeparator = _Platform.pathSeparator;
  static final _operatingSystem = _Platform.operatingSystem;
  static final _operatingSystemVersion = _Platform.operatingSystemVersion;
  static final _localHostname = _Platform.localHostname;
  static final _version = _Platform.version;

  /// The number of individual execution units of the machine.
  static int get numberOfProcessors => _numberOfProcessors;

  /// The path separator used by the operating system to separate
  /// components in file paths.
  static String get pathSeparator => _pathSeparator;

  /// Get the name of the current locale.
  static String get localeName => _Platform.localeName();

  /// A string representing the operating system or platform.
  static String get operatingSystem => _operatingSystem;

  /// A string representing the version of the operating system or platform.
  static String get operatingSystemVersion => _operatingSystemVersion;

  /// The local hostname for the system.
  static String get localHostname => _localHostname;

  /// Whether the operating system is a version of
  /// [Linux](https://en.wikipedia.org/wiki/Linux).
  ///
  /// This value is `false` if the operating system is a specialized
  /// version of Linux that identifies itself by a different name,
  /// for example Android (see [isAndroid]).
  static final bool isLinux = (_operatingSystem == "linux");

  /// Whether the operating system is a version of
  /// [macOS](https://en.wikipedia.org/wiki/MacOS).
  static final bool isMacOS = (_operatingSystem == "macos");

  /// Whether the operating system is a version of
  /// [Microsoft Windows](https://en.wikipedia.org/wiki/Microsoft_Windows).
  static final bool isWindows = (_operatingSystem == "windows");

  /// Whether the operating system is a version of
  /// [Android](https://en.wikipedia.org/wiki/Android_%28operating_system%29).
  static final bool isAndroid = (_operatingSystem == "android");

  /// Whether the operating system is a version of
  /// [iOS](https://en.wikipedia.org/wiki/IOS).
  static final bool isIOS = (_operatingSystem == "ios");

  /// Whether the operating system is a version of
  /// [Fuchsia](https://en.wikipedia.org/wiki/Google_Fuchsia).
  static final bool isFuchsia = (_operatingSystem == "fuchsia");

  /// The environment for this process as a map from string key to string value.
  ///
  /// The map is unmodifiable,
  /// and its content is retrieved from the operating system on its first use.
  ///
  /// Environment variables on Windows are case-insensitive,
  /// so on Windows the map is case-insensitive and will convert
  /// all keys to upper case.
  /// On other platforms, keys can be distinguished by case.
  static Map<String, String> get environment => _Platform.environment;

  /// The path of the executable used to run the script in this isolate.
  ///
  /// The literal path used to identify the script.
  /// This path might be relative or just be a name from which the executable
  /// was found by searching the system path.
  ///
  /// Use [resolvedExecutable] to get an absolute path to the executable.
  static String get executable => _Platform.executable;

  /// The path of the executable used to run the script in this
  /// isolate after it has been resolved by the OS.
  ///
  /// This is the absolute path, with all symlinks resolved, to the
  /// executable used to run the script.
  static String get resolvedExecutable => _Platform.resolvedExecutable;

  /// The absolute URI of the script being run in this isolate.
  ///
  /// If the script argument on the command line is relative,
  /// it is resolved to an absolute URI before fetching the script, and
  /// that absolute URI is returned.
  ///
  /// URI resolution only does string manipulation on the script path, and this
  /// may be different from the file system's path resolution behavior. For
  /// example, a symbolic link immediately followed by '..' will not be
  /// looked up.
  ///
  /// If the executable environment does not support [script],
  /// the URI is empty.
  static Uri get script => _Platform.script;

  /// The flags passed to the executable used to run the script in this isolate.
  ///
  /// These are the command-line flags to the executable that precedes
  /// the script name.
  /// Provides a new list every time the value is read.
  static List<String> get executableArguments => _Platform.executableArguments;

  /// This returns `null`, as `packages/` directories are no longer supported.
  ///
  @Deprecated('packages/ directory resolution is not supported in Dart 2')
  static String? get packageRoot => null; // TODO(mfairhurst): remove this

  /// The `--packages` flag passed to the executable used to run the script
  /// in this isolate.
  ///
  /// If present, it specifies a file describing how Dart packages are looked up.
  ///
  /// Is `null` if there is no `--packages` flag.
  static String? get packageConfig => _Platform.packageConfig;

  /// The version of the current Dart runtime.
  ///
  /// The value is a [semantic versioning](http://semver.org)
  /// string representing the version of the current Dart runtime,
  /// possibly followed by whitespace and other version and
  /// build details.
  static String get version => _version;
}