content: // 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.
  
  library uri_extras;
  
  import 'dart:math';
  
  String relativize(Uri base, Uri uri, bool isWindows) {
    if (!base.path.startsWith('/')) {
      // Also throw an exception if [base] or base.path is null.
      throw new ArgumentError('Expected absolute path: ${base.path}');
    }
    if (!uri.path.startsWith('/')) {
      // Also throw an exception if [uri] or uri.path is null.
      throw new ArgumentError('Expected absolute path: ${uri.path}');
    }
    bool equalsNCS(String a, String b) {
      return a.toLowerCase() == b.toLowerCase();
    }
  
    String normalize(String path) {
      if (isWindows) {
        return path.toLowerCase();
      } else {
        return path;
      }
    }
  
    if (equalsNCS(base.scheme, 'file') &&
        equalsNCS(base.scheme, uri.scheme) &&
        base.userInfo == uri.userInfo &&
        equalsNCS(base.host, uri.host) &&
        base.port == uri.port &&
        uri.query == "" && uri.fragment == "") {
      if (normalize(uri.path).startsWith(normalize(base.path))) {
        return uri.path.substring(base.path.length);
      }
      List<String> uriParts = uri.path.split('/');
      List<String> baseParts = base.path.split('/');
      int common = 0;
      int length = min(uriParts.length, baseParts.length);
      while (common < length &&
             normalize(uriParts[common]) == normalize(baseParts[common])) {
        common++;
      }
      if (common == 1 || (isWindows && common == 2)) {
        // The first part will always be an empty string because the
        // paths are absolute. On Windows, we must also consider drive
        // letters or hostnames.
        return uri.path;
      }
      StringBuffer sb = new StringBuffer();
      for (int i = common + 1; i < baseParts.length; i++) {
        sb.write('../');
      }
      for (int i = common; i < uriParts.length - 1; i++) {
        sb.write('${uriParts[i]}/');
      }
      sb.write('${uriParts.last}');
      return sb.toString();
    }
    return uri.toString();
  }
  