wlan-cloud-owprov/src/framework/RESTAPI_RateLimiter.h

//
// Created by stephane bourque on 2022-10-25.
//

#pragma once

#include "framework/SubSystemServer.h"

#include "Poco/ExpireLRUCache.h"
#include "Poco/Net/HTTPServerRequest.h"
#include "Poco/URI.h"

#include "fmt/format.h"

namespace OpenWifi {

	class RESTAPI_RateLimiter : public SubSystemServer {
	  public:
		struct ClientCacheEntry {
			int64_t Start = 0;
			int Count = 0;
		};

		static auto instance() {
			static auto instance_ = new RESTAPI_RateLimiter;
			return instance_;
		}

		inline int Start() final { return 0; };
		inline void Stop() final{};

		inline bool IsRateLimited(const Poco::Net::HTTPServerRequest &R, int64_t Period,
								  int64_t MaxCalls) {
			Poco::URI uri(R.getURI());
			auto H = str_hash(uri.getPath() + R.clientAddress().host().toString());
			auto E = Cache_.get(H);
			auto Now = std::chrono::duration_cast<std::chrono::milliseconds>(
						   std::chrono::system_clock::now().time_since_epoch())
						   .count();
			if (E.isNull()) {
				Cache_.add(H, ClientCacheEntry{.Start = Now, .Count = 1});
				return false;
			}
			if ((Now - E->Start) < Period) {
				E->Count++;
				Cache_.update(H, E);
				if (E->Count > MaxCalls) {
					poco_warning(Logger(), fmt::format("RATE-LIMIT-EXCEEDED: from '{}'",
													   R.clientAddress().toString()));
					return true;
				}
				return false;
			}
			E->Start = Now;
			E->Count = 1;
			Cache_.update(H, E);
			return false;
		}

		inline void Clear() { Cache_.clear(); }

	  private:
		Poco::ExpireLRUCache<uint64_t, ClientCacheEntry> Cache_{2048};
		std::hash<std::string> str_hash;

		RESTAPI_RateLimiter() noexcept
			: SubSystemServer("RateLimiter", "RATE-LIMITER", "rate.limiter") {}
	};

	inline auto RESTAPI_RateLimiter() { return RESTAPI_RateLimiter::instance(); }

} // namespace OpenWifi