Refactor pkg/path.

pkg/path/lib/src/style.dart

+// Copyright (c) 2013, 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.
+
+library path.style;
+
+import 'context.dart';
+import 'style/posix.dart';
+import 'style/url.dart';
+import 'style/windows.dart';
+
+/// An enum type describing a "flavor" of path.
+abstract class Style {
+  /// POSIX-style paths use "/" (forward slash) as separators. Absolute paths
+  /// start with "/". Used by UNIX, Linux, Mac OS X, and others.
+  static final posix = new PosixStyle();
+
+  /// Windows paths use "\" (backslash) as separators. Absolute paths start with
+  /// a drive letter followed by a colon (example, "C:") or two backslashes
+  /// ("\\") for UNC paths.
+  // TODO(rnystrom): The UNC root prefix should include the drive name too, not
+  // just the "\\".
+  static final windows = new WindowsStyle();
+
+  /// URLs aren't filesystem paths, but they're supported to make it easier to
+  /// manipulate URL paths in the browser.
+  ///
+  /// URLs use "/" (forward slash) as separators. Absolute paths either start
+  /// with a protocol and optional hostname (e.g. `http://dartlang.org`,
+  /// `file://`) or with "/".
+  static final url = new UrlStyle();
+
+  /// The style of the host platform.
+  ///
+  /// When running on the command line, this will be [windows] or [posix] based
+  /// on the host operating system. On a browser, this will be [url].
+  static final platform = _getPlatformStyle();
+
+  /// Gets the type of the host platform.
+  static Style _getPlatformStyle() {
+    // If we're running a Dart file in the browser from a `file:` URI,
+    // [Uri.base] will point to a file. If we're running on the standalone,
+    // it will point to a directory. We can use that fact to determine which
+    // style to use.
+    if (Uri.base.scheme != 'file') return Style.url;
+    if (!Uri.base.path.endsWith('/')) return Style.url;
+    if (new Uri(path: 'a/b').toFilePath() == 'a\\b') return Style.windows;
+    return Style.posix;
+  }
+
+  /// The name of this path style. Will be "posix" or "windows".
+  String get name;
+
+  /// The path separator for this style. On POSIX, this is `/`. On Windows,
+  /// it's `\`.
+  String get separator;
+
+  /// The [Pattern] that can be used to match a separator for a path in this
+  /// style. Windows allows both "/" and "\" as path separators even though "\"
+  /// is the canonical one.
+  Pattern get separatorPattern;
+
+  /// The [Pattern] that matches path components that need a separator after
+  /// them.
+  ///
+  /// Windows and POSIX styles just need separators when the previous component
+  /// doesn't already end in a separator, but the URL always needs to place a
+  /// separator between the root and the first component, even if the root
+  /// already ends in a separator character. For example, to join "file://" and
+  /// "usr", an additional "/" is needed (making "file:///usr").
+  Pattern get needsSeparatorPattern;
+
+  /// The [Pattern] that can be used to match the root prefix of an absolute
+  /// path in this style.
+  Pattern get rootPattern;
+
+  /// The [Pattern] that can be used to match the root prefix of a root-relative
+  /// path in this style.
+  ///
+  /// This can be null to indicate that this style doesn't support root-relative
+  /// paths.
+  final Pattern relativeRootPattern = null;
+
+  /// A [Context] that uses this style.
+  Context get context => new Context(style: this);
+
+  /// Gets the root prefix of [path] if path is absolute. If [path] is relative,
+  /// returns `null`.
+  String getRoot(String path) {
+    // TODO(rnystrom): Use firstMatch() when #7080 is fixed.
+    var matches = rootPattern.allMatches(path);
+    if (matches.isNotEmpty) return matches.first[0];
+    return getRelativeRoot(path);
+  }
+
+  /// Gets the root prefix of [path] if it's root-relative.
+  ///
+  /// If [path] is relative or absolute and not root-relative, returns `null`.
+  String getRelativeRoot(String path) {
+    if (relativeRootPattern == null) return null;
+    // TODO(rnystrom): Use firstMatch() when #7080 is fixed.
+    var matches = relativeRootPattern.allMatches(path);
+    if (matches.isEmpty) return null;
+    return matches.first[0];
+  }
+
+  /// Returns the path represented by [uri] in this style.
+  String pathFromUri(Uri uri);
+
+  /// Returns the URI that represents the relative path made of [parts].
+  Uri relativePathToUri(String path) =>
+      new Uri(pathSegments: context.split(path));
+
+  /// Returns the URI that represents [path], which is assumed to be absolute.
+  Uri absolutePathToUri(String path);
+
+  String toString() => name;
+}