Ratecatcher middleware

Sources/App/Core/RateCatcherMiddleware.swift

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+// Copyright Dave Verwer, Sven A. Schmidt, and other contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Vapor
+import Redis
+
+final class RateCatcherMiddleware: AsyncMiddleware {
+
+    let windowSize: Int // in seconds
+
+    public func respond(to request: Request, chainingTo next: AsyncResponder) async throws -> Response {
+        guard let cfray = request.headers.first(name: "cf-ray") else {
+            return try await next.respond(to: request)
+        }
+        let seconds: Int = Int(Date().timeIntervalSince1970)
+        let combinedKey: RedisKey = "\(cfray):\(seconds)"
+
+        var countOverWindow: Int = try await request.redis.increment(combinedKey).get()
+        for i in seconds - windowSize ..< seconds {
+            let key: RedisKey = "\(cfray):\(i)"
+            if let value = try await request.redis.get(key, as: Int.self).get() {
+                countOverWindow += value
+            }
+        }
+
+        if countOverWindow > 999 {
+            request.logger.log(level: .warning, "RateCatcherMiddleware blocking request with cf-ray \(cfray) due to \(countOverWindow) requests in the last \(windowSize) seconds.")
+            throw Abort(.tooManyRequests)
+        } else {
+            return try await next.respond(to: request)
+        }
+    }
+
+    init(windowSize: Int) {
+        self.windowSize = windowSize
+    }
+}