RateLimiter.h

#pragma once
#include <drogon/exports.h>
#include <memory>
#include <chrono>
#include <mutex>
#include <string>
 
namespace drogon
{
enum class DROGON_EXPORT RateLimiterType
{
    kFixedWindow,
    kSlidingWindow,
    kTokenBucket
};
 
inline RateLimiterType stringToRateLimiterType(const std::string &type)
{
    if (type == "fixedWindow" || type == "fixed_window")
        return RateLimiterType::kFixedWindow;
    else if (type == "slidingWindow" || type == "sliding_window")
        return RateLimiterType::kSlidingWindow;
    return RateLimiterType::kTokenBucket;
}
class DROGON_EXPORT RateLimiter;
using RateLimiterPtr = std::shared_ptr<RateLimiter>;

class DROGON_EXPORT RateLimiter
{
  public:
    static RateLimiterPtr newRateLimiter(
        RateLimiterType type,
        size_t capacity,
        std::chrono::duration<double> timeUnit = std::chrono::seconds(60));
    virtual bool isAllowed() = 0;
    virtual ~RateLimiter() noexcept = default;
};
 
class DROGON_EXPORT SafeRateLimiter : public RateLimiter
{
  public:
    SafeRateLimiter(RateLimiterPtr limiter) : limiter_(limiter)
    {
    }
 
    bool isAllowed() override
    {
        std::lock_guard<std::mutex> lock(mutex_);
        return limiter_->isAllowed();
    }
 
    ~SafeRateLimiter() noexcept override = default;
 
  private:
    RateLimiterPtr limiter_;
    std::mutex mutex_;
};
}  // namespace drogon