Request now has the same body model as Response

lib/src/message.dart

 // Copyright (c) 2014, 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 shelf.message;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:http_parser/http_parser.dart';
 import 'package:stack_trace/stack_trace.dart';
 
 import 'shelf_unmodifiable_map.dart';
+import 'util.dart';
 
 /// Represents logic shared between [Request] and [Response].
 abstract class Message {
   /// The HTTP headers.
   ///
   /// The value is immutable.
   final Map<String, String> headers;
 
   /// Extra context that can be used by for middleware and handlers.
   ///
@@ skipping 14 matching lines @@
   final Stream<List<int>> _body;
 
   /// This boolean indicates whether [_body] has been read.
   ///
   /// After calling [read], or [readAsString] (which internally calls [read]),
   /// this will be `true`.
   bool _bodyWasRead = false;
 
   /// Creates a new [Message].
   ///
+  /// [body] is the response body. It may be either a [String], a
+  /// [Stream<List<int>>], or `null` to indicate no body. If it's a [String],
+  /// [encoding] is used to encode it to a [Stream<List<int>>]. It defaults to
+  /// UTF-8.
+  ///
   /// If [headers] is `null`, it is treated as empty.
-  Message(this._body,
-      {Map<String, String> headers, Map<String, Object> context})
-      : this.headers = new ShelfUnmodifiableMap<String>(headers,
-          ignoreKeyCase: true),
+  ///
+  /// If [encoding] is passed, the "encoding" field of the Content-Type header
+  /// in [headers] will be set appropriately. If there is no existing
+  /// Content-Type header, it will be set to "application/octet-stream".
+  Message(body, {Encoding encoding, Map<String, String> headers,
+      Map<String, Object> context})
+      : this._body = _bodyToStream(body, encoding),
+        this.headers = new ShelfUnmodifiableMap<String>(
+            _adjustHeaders(headers, encoding), ignoreKeyCase: true),
         this.context = new ShelfUnmodifiableMap<Object>(context,
             ignoreKeyCase: false);
 
   /// The contents of the content-length field in [headers].
   ///
   /// If not set, `null`.
   int get contentLength {
     if (_contentLengthCache != null) return _contentLengthCache;
     if (!headers.containsKey('content-length')) return null;
     _contentLengthCache = int.parse(headers['content-length']);
@@ skipping 60 matching lines @@
   Future<String> readAsString([Encoding encoding]) {
     if (encoding == null) encoding = this.encoding;
     if (encoding == null) encoding = UTF8;
     return Chain.track(encoding.decodeStream(read()));
   }
 
   /// Creates a new [Message] by copying existing values and applying specified
   /// changes.
   Message change({Map<String, String> headers, Map<String, Object> context});
 }
+
+/// Converts [body] to a byte stream.
+///
+/// [body] may be either a [String], a [Stream<List<int>>], or `null`. If it's a
+/// [String], [encoding] will be used to convert it to a [Stream<List<int>>].
+Stream<List<int>> _bodyToStream(body, Encoding encoding) {
+  if (encoding == null) encoding = UTF8;
+  if (body == null) return new Stream.fromIterable([]);
+  if (body is String) return new Stream.fromIterable([encoding.encode(body)]);
+  if (body is Stream) return body;
+
+  throw new ArgumentError('Response body "$body" must be a String or a '
+      'Stream.');
+}
+
+/// Adds information about [encoding] to [headers].
+///
+/// Returns a new map without modifying [headers].
+Map<String, String> _adjustHeaders(
+    Map<String, String> headers, Encoding encoding) {
+  if (headers == null) headers = const {};
+  if (encoding == null) return headers;
+  if (headers['content-type'] == null) {
+    return addHeader(headers, 'content-type',
+        'application/octet-stream; charset=${encoding.name}');
+  }
+
+  var contentType = new MediaType.parse(headers['content-type']).change(
+      parameters: {'charset': encoding.name});
+  return addHeader(headers, 'content-type', contentType.toString());
+}