Add a CaseInsensitiveMap class.

lib/src/authentication_challenge.dart

 // Copyright (c) 2015, 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 http_paser.authentication_challenge;
 
 import 'dart:collection';
 
 import 'package:string_scanner/string_scanner.dart';
 
+import 'case_insensitive_map.dart';
 import 'scan.dart';
 import 'utils.dart';
 
 /// A single challenge in a WWW-Authenticate header, parsed as per [RFC 2617][].
 ///
 /// [RFC 2617]: http://tools.ietf.org/html/rfc2617
 ///
 /// Each WWW-Authenticate header contains one or more challenges, representing
 /// valid ways to authenticate with the server.
 class AuthenticationChallenge {
   /// The scheme describing the type of authentication that's required, for
   /// example "basic" or "digest".
   ///
   /// This is normalized to always be lower-case.
   final String scheme;
 
   /// The parameters describing how to authenticate.
   ///
-  /// The semantics of these parameters are scheme-specific.
+  /// The semantics of these parameters are scheme-specific. The keys of this
+  /// map are case-insensitive.
   final Map<String, String> parameters;
 
   /// Parses a WWW-Authenticate header, which should contain one or more
   /// challenges.
   ///
   /// Throws a [FormatException] if the header is invalid.
   static List<AuthenticationChallenge> parseHeader(String header) {
     return wrapFormatException("authentication header", header, () {
       var scanner = new StringScanner(header);
       scanner.scan(whitespace);
@@ skipping 12 matching lines @@
         _scanAuthParam(scanner, params);
 
         var beforeComma = scanner.position;
         while (scanner.scan(",")) {
           scanner.scan(whitespace);
 
           // Empty elements are allowed, but excluded from the results.
           if (scanner.matches(",") || scanner.isDone) continue;
 
           scanner.expect(token, name: "a token");
-          var name = scanner.lastMatch[0].toLowerCase();
+          var name = scanner.lastMatch[0];
           scanner.scan(whitespace);
 
           // If there's no "=", then this is another challenge rather than a
           // parameter for the current challenge.
           if (!scanner.scan('=')) {
             scanner.position = beforeComma;
             break;
           }
 
           scanner.scan(whitespace);
@@ skipping 49 matching lines @@
     if (scanner.lastMatch == null || !scanner.lastMatch[0].contains(" ")) {
       scanner.expect(" ", name: whitespaceName);
     }
 
     return scheme;
   }
 
   /// Scans a single authentication parameter and stores its result in [params].
   static void _scanAuthParam(StringScanner scanner, Map params) {
     scanner.expect(token, name: "a token");
-    var name = scanner.lastMatch[0].toLowerCase();
+    var name = scanner.lastMatch[0];
     scanner.scan(whitespace);
     scanner.expect('=');
     scanner.scan(whitespace);
 
     if (scanner.scan(token)) {
       params[name] = scanner.lastMatch[0];
     } else {            
       params[name] = expectQuotedString(
           scanner, name: "a token or a quoted string");
     }
 
     scanner.scan(whitespace);
   }
 
   /// Creates a new challenge value with [scheme] and [parameters].
   AuthenticationChallenge(this.scheme, Map<String, String> parameters)
-      : parameters = new UnmodifiableMapView(parameters);
+      : parameters = new UnmodifiableMapView(
+            new CaseInsensitiveMap.from(parameters));
 }