Add service rate limiter

example/pubspec.yaml

@@ -1,6 +1,8 @@
 name: example
 publish_to: none
 dependencies:
+  angel_production: ^1.0.0
+  angel_redis: ^1.0.0
   angel_security:
     path: ../
   pretty_logging: ^1.0.0

example/rate_limit_redis.dart

@@ -0,0 +1,36 @@
+import 'package:angel_framework/angel_framework.dart';
+import 'package:angel_framework/http.dart';
+import 'package:angel_security/angel_security.dart';
+import 'package:logging/logging.dart';
+import 'package:pretty_logging/pretty_logging.dart';
+
+main() async {
+  // Logging boilerplate.
+  Logger.root.onRecord.listen(prettyLog);
+
+  // Create an app, and HTTP driver.
+  var app = Angel(logger: Logger('rate_limit_redis')), http = AngelHttp(app);
+
+  // Create a simple rate limiter that limits users to 5
+  // queries per 30 seconds.
+  //
+  // In this case, we rate limit users by IP address.
+  //
+  // Our Redis store will be used to manage windows.
+  var rateLimiter =
+      InMemoryRateLimiter(5, Duration(seconds: 30), (req, res) => req.ip);
+
+  // `RateLimiter.handleRequest` is a middleware, and can be used anywhere
+  // a middleware can be used. In this case, we apply the rate limiter to
+  // *all* incoming requests.
+  app.fallback(rateLimiter.handleRequest);
+
+  // Basic routes.
+  app
+    ..get('/', (req, res) => 'Hello!')
+    ..fallback((req, res) => throw AngelHttpException.notFound());
+
+  // Start the server.
+  await http.startServer('127.0.0.1', 3000);
+  print('Rate limiting (redis) example listening at ${http.uri}');
+}

lib/angel_security.dart

@@ -2,3 +2,4 @@ export 'src/cookie_signer.dart';
 export 'src/in_memory_rate_limiter.dart';
 export 'src/rate_limiter.dart';
 export 'src/rate_limiting_window.dart';
+export 'src/service_rate_limiter.dart';

lib/src/rate_limiting_window.dart

@@ -32,4 +32,19 @@ class RateLimitingWindow<User> {
 
   RateLimitingWindow(this.user, this.startTime, this.pointsConsumed,
       {this.pointLimit, this.remainingPoints, this.resetTime});
+
+  factory RateLimitingWindow.fromJson(Map<String, dynamic> map) {
+    return RateLimitingWindow(
+        map['user'] as User,
+        DateTime.parse(map['start_time'] as String),
+        int.parse(map['points_consumed'] as String));
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'user': user,
+      'start_time': startTime.toIso8601String(),
+      'points_consumed': pointsConsumed.toString(),
+    };
+  }
 }

lib/src/service_rate_limiter.dart

@@ -0,0 +1,39 @@
+import 'dart:async';
+import 'package:angel_framework/angel_framework.dart';
+import 'rate_limiter.dart';
+import 'rate_limiting_window.dart';
+
+/// A RateLimiter] implementation that uses a [Service]
+/// to store rate limiting information.
+class ServiceRateLimiter<Id> extends RateLimiter<Id> {
+  /// The underlying [Service] used to store data.
+  final Service<Id, Map<String, dynamic>> service;
+
+  /// A callback used to compute the current user ID.
+  final FutureOr<Id> Function(RequestContext, ResponseContext) getId;
+
+  ServiceRateLimiter(
+      int maxPointsPerWindow, Duration windowDuration, this.service, this.getId,
+      {String errorMessage})
+      : super(maxPointsPerWindow, windowDuration, errorMessage: errorMessage);
+
+  @override
+  FutureOr<RateLimitingWindow<Id>> getCurrentWindow(
+      RequestContext req, ResponseContext res, DateTime currentTime) async {
+    var id = await getId(req, res);
+    var existing = await service.read(id);
+    if (existing != null) {
+      return RateLimitingWindow.fromJson(existing);
+    }
+
+    var window = RateLimitingWindow(id, currentTime, 0);
+    await updateCurrentWindow(req, res, window, currentTime);
+    return window;
+  }
+
+  @override
+  FutureOr<void> updateCurrentWindow(RequestContext req, ResponseContext res,
+      RateLimitingWindow<Id> window, DateTime currentTime) async {
+    await service.update(window.user, window.toJson());
+  }
+}

pubspec.yaml

@@ -9,6 +9,8 @@ dependencies:
   angel_framework: ^2.0.0
 dev_dependencies: 
   angel_auth: ^2.0.0
+  angel_production: ^1.0.0
+  angel_redis: ^1.0.0
   angel_test: ^2.0.0
   angel_validate: ^2.0.0
   crypto: ^2.0.0