RateLimitQueue.hpp

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/*
    MIT License
 
    DiscordCoreAPI, A bot library for Discord, written in C++, and featuring explicit multithreading through the usage of custom, asynchronous C++ CoRoutines.
 
    Copyright 2022, 2023 Chris M. (RealTimeChris)
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:
 
    The above copyright notice and this permission notice shall be included in all
    copies or substantial portions of the Software.
 
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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*/
/// RateLimitQueue.hpp - Header file for the "rate_limit_queue stuff".
/// May 12, 2021
/// https://discordcoreapi.com
/// \file RateLimitQueue.hpp
#pragma once
 
#include <discordcoreapi/Utilities/TCPConnection.hpp>
#include <discordcoreapi/Utilities/UniquePtr.hpp>
#include <discordcoreapi/JsonSpecializations.hpp>
#include <mutex>
 
namespace discord_core_api {
 
    namespace discord_core_internal {
 
        struct rate_limit_data {
            friend class https_connection_stack_holder;
            friend class https_connection_manager;
            friend class rate_limit_stack_holder;
            friend class https_rnr_builder;
            friend class rate_limit_queue;
            friend class https_client;
 
          protected:
            std::unique_lock<std::mutex> lock{ accessMutex, std::defer_lock };
            std::atomic<milliseconds> sampledTimeInMs{ milliseconds{} };
            std::atomic<seconds> sRemain{ seconds{} };
            std::atomic_int64_t getsRemaining{ 1 };
            std::atomic_bool areWeASpecialBucket{};
            std::atomic_bool didWeHitRateLimit{};
            std::atomic_bool doWeWait{};
            jsonifier::string bucket{};
            std::mutex accessMutex{};
        };
 
        class rate_limit_queue {
          public:
            friend class https_client;
 
            inline rate_limit_queue() = default;
 
            inline void initialize() {
                for (int64_t enumOne = static_cast<int64_t>(https_workload_type::Unset); enumOne != static_cast<int64_t>(https_workload_type::Last); enumOne++) {
                    auto tempBucket = jsonifier::toString(std::chrono::duration_cast<nanoseconds>(hrclock::now().time_since_epoch()).count());
                    buckets.emplace(static_cast<https_workload_type>(enumOne), tempBucket);
                    rateLimits.emplace(tempBucket, makeUnique<rate_limit_data>())
                        .getRawPtr()
                        ->second->sampledTimeInMs.store(std::chrono::duration_cast<milliseconds>(sys_clock::now().time_since_epoch()));
                    std::this_thread::sleep_for(1ms);
                }
            }
 
            inline rate_limit_data* getEndpointAccess(https_workload_type workloadType) {
                stop_watch<milliseconds> stopWatch{ milliseconds{ 25000 } };
                stopWatch.reset();
                auto targetTime =
                    std::chrono::duration_cast<std::chrono::duration<int64_t, std::milli>>(rateLimits[buckets[workloadType]]->sampledTimeInMs.load(std::memory_order_acquire)) +
                    std::chrono::duration_cast<std::chrono::duration<int64_t, std::milli>>(rateLimits[buckets[workloadType]]->sRemain.load(std::memory_order_acquire));
                if (rateLimits[buckets[workloadType]]->getsRemaining.load(std::memory_order_acquire) <= 0) {
                    auto newNow = std::chrono::duration_cast<std::chrono::duration<int64_t, std::milli>>(sys_clock::now().time_since_epoch());
                    while ((newNow - targetTime).count() <= 0) {
                        if (stopWatch.hasTimeElapsed()) {
                            return nullptr;
                        }
                        newNow = std::chrono::duration_cast<std::chrono::duration<int64_t, std::milli>>(sys_clock::now().time_since_epoch());
                        std::this_thread::sleep_for(1us);
                    }
                }
                stopWatch.reset();
                while (!rateLimits[buckets[workloadType]]->accessMutex.try_lock()) {
                    std::this_thread::sleep_for(1us);
                    if (stopWatch.hasTimeElapsed()) {
                        return nullptr;
                    }
                }
                return rateLimits[buckets[workloadType]].get();
            }
 
            inline void releaseEndPointAccess(https_workload_type type) {
                rateLimits[buckets[type]]->accessMutex.unlock();
            }
 
          protected:
            unordered_map<jsonifier::string, unique_ptr<rate_limit_data>> rateLimits{};
            unordered_map<https_workload_type, jsonifier::string> buckets{};
        };
 
    }// namespace discord_core_internal
}