blob: 1aa3a150e5827485580d45c34d23a5d1db969e0f [file] [log] [blame]
// 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.
import 'package:http/http.dart' as http;
import 'package:path/path.dart' as p;
import 'package:shelf/shelf.dart';
import 'src/utils.dart';
/// A handler that proxies requests to [url].
/// To generate the proxy request, this concatenates [url] and [Request.url].
/// This means that if the handler mounted under `/documentation` and [url] is
/// ``, a request to `/documentation/tutorials`
/// will be proxied to ``.
/// [url] must be a [String] or [Uri].
/// [client] is used internally to make HTTP requests. It defaults to a
/// `dart:io`-based client.
/// [proxyName] is used in headers to identify this proxy. It should be a valid
/// HTTP token or a hostname. It defaults to `shelf_proxy`.
Handler proxyHandler(url, {http.Client client, String proxyName}) {
Uri uri;
if (url is String) {
uri = Uri.parse(url);
} else if (url is Uri) {
uri = url;
} else {
throw new ArgumentError.value(url, 'url', 'url must be a String or Uri.');
client ??= new http.Client();
proxyName ??= 'shelf_proxy';
return (serverRequest) async {
// TODO(nweiz): Support WebSocket requests.
// TODO(nweiz): Handle TRACE requests correctly. See
var requestUrl = uri.resolve(serverRequest.url.toString());
var clientRequest =
new http.StreamedRequest(serverRequest.method, requestUrl);
clientRequest.followRedirects = false;
clientRequest.headers['Host'] = uri.authority;
// Add a Via header. See
_addHeader(clientRequest.headers, 'via',
'${serverRequest.protocolVersion} $proxyName');
store(, clientRequest.sink);
var clientResponse = await client.send(clientRequest);
// Add a Via header. See
_addHeader(clientResponse.headers, 'via', '1.1 $proxyName');
// Remove the transfer-encoding since the body has already been decoded by
// [client].
// If the original response was gzipped, it will be decoded by [client]
// and we'll have no way of knowing its actual content-length.
if (clientResponse.headers['content-encoding'] == 'gzip') {
// Add a Warning header. See
clientResponse.headers, 'warning', '214 $proxyName "GZIP decoded"');
// Make sure the Location header is pointing to the proxy server rather
// than the destination server, if possible.
if (clientResponse.isRedirect &&
clientResponse.headers.containsKey('location')) {
var location =
if (p.url.isWithin(uri.toString(), location)) {
clientResponse.headers['location'] =
'/' + p.url.relative(location, from: uri.toString());
} else {
clientResponse.headers['location'] = location;
return new Response(clientResponse.statusCode,
body:, headers: clientResponse.headers);
/// Use [proxyHandler] instead.
Handler createProxyHandler(Uri rootUri) => proxyHandler(rootUri);
// TODO(nweiz): use built-in methods for this when http and shelf support them.
/// Add a header with [name] and [value] to [headers], handling existing headers
/// gracefully.
void _addHeader(Map<String, String> headers, String name, String value) {
if (headers.containsKey(name)) {
headers[name] += ', $value';
} else {
headers[name] = value;