erl.h

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#ifndef FASTLY_ERL_H
#define FASTLY_ERL_H
 
#include <chrono>
#include <fastly/expected.h>
 
namespace fastly::erl {
class ERLError {
public:
  enum Code {
    Unexpected,
    Unknown,
    InvalidArgument,
  };
  explicit ERLError(Code code) : code_(code) {}
  Code code() const { return code_; }
 
private:
  Code code_;
};

class PenaltyBox {
public:
  explicit PenaltyBox(std::string name) : name_(std::move(name)) {};
  tl::expected<void, ERLError> add(std::string_view entry,
                                   std::chrono::minutes ttl);
  tl::expected<bool, ERLError> has(std::string_view entry) const;
  std::string_view name() const { return name_; }
 
private:
  std::string name_;
};

enum class CounterDuration {
  TenSec = 10,
  TwentySecs = 20,
  ThirtySecs = 30,
  FortySecs = 40,
  FiftySecs = 50,
  SixtySecs = 60
};

enum class RateWindow {
  OneSec = 1,
  TenSecs = 10,
  SixtySecs = 60,
};

class RateCounter {
public:
  explicit RateCounter(std::string name) : name_(std::move(name)) {}
  tl::expected<void, ERLError> increment(std::string_view entry,
                                         std::uint32_t delta);
  tl::expected<std::uint32_t, ERLError> lookup_rate(std::string_view entry,
                                                    RateWindow window) const;
  tl::expected<std::uint32_t, ERLError>
  lookup_count(std::string_view entry, CounterDuration duration) const;
  std::string_view name() const { return name_; }
 
private:
  std::string name_;
};
 
class ERL {
public:
  ERL(RateCounter rate_counter, PenaltyBox penalty_box)
      : rate_counter_(std::move(rate_counter)),
        penalty_box_(std::move(penalty_box)) {}

  tl::expected<bool, ERLError>
  check_rate(std::string_view entry, std::uint32_t delta, RateWindow window,
             std::uint32_t limit, std::chrono::minutes ttl) const;
 
  const RateCounter &rate_counter() const { return rate_counter_; }
  const PenaltyBox &penalty_box() const { return penalty_box_; }
 
private:
  RateCounter rate_counter_;
  PenaltyBox penalty_box_;
};
} // namespace fastly::erl
#endif