HttpRequestManager.hpp

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#pragma once
#ifndef KURLYK_HEADER_KURLYK_HTTP_HTTP_REQUEST_MANAGER_HPP_INCLUDED
#define KURLYK_HEADER_KURLYK_HTTP_HTTP_REQUEST_MANAGER_HPP_INCLUDED

 
#include <type_traits>
 
#include "HttpRequestManager/HttpRequestContext.hpp"
#include "HttpRequestManager/HttpRequestHandler.hpp"
#include "HttpRequestManager/HttpRateLimitDelay.hpp"
#include "HttpRequestManager/HttpRateLimitHandle.hpp"
#include "HttpRequestManager/HttpRateLimiter.hpp"
#include "HttpRequestManager/HttpBatchRequestHandler.hpp"
 
 
namespace kurlyk {

    class HttpRequestManager final : public core::INetworkTaskManager {
    public:

        static HttpRequestManager& get_instance() {
            static HttpRequestManager* instance = new HttpRequestManager();
            return *instance;
        }

        bool add_request(
                std::unique_ptr<HttpRequest> request_ptr,
                HttpResponseCallback callback) {
            return submit_request(std::move(request_ptr), std::move(callback)).accepted;
        }

        SubmitResult submit_request(
                std::unique_ptr<HttpRequest> request_ptr,
                HttpResponseCallback callback) {
            std::lock_guard<std::mutex> lock(m_mutex);
            if (m_shutdown) {
                return SubmitResult{false, utils::make_error_code(utils::ClientError::ShuttingDown)};
            }
 
            const std::size_t queue_limit = m_max_pending_requests.load();
            if (queue_limit && m_pending_requests.size() >= queue_limit) {
                return SubmitResult{false, utils::make_error_code(utils::ClientError::QueueLimitExceeded)};
            }
 
#           if __cplusplus >= 201402L
            auto context = std::make_unique<HttpRequestContext>(std::move(request_ptr), std::move(callback));
#           else
            auto context = std::unique_ptr<HttpRequestContext>(
                new HttpRequestContext(std::move(request_ptr), std::move(callback)));
#           endif
            context->in_flight_token = m_next_in_flight_token.fetch_add(1, std::memory_order_relaxed);
            m_pending_requests.push_back(std::move(context));
            return SubmitResult{true, std::error_code()};
        }

        HttpRateLimitHandlePtr create_rate_limit(long requests_per_period, long period_ms, bool sequential = false) {
            return m_rate_limiter.create_limit_handle(requests_per_period, period_ms, sequential);
        }

        HttpRateLimitHandlePtr get_rate_limit(long limit_id) {
            return m_rate_limiter.get_limit(limit_id);
        }

        bool remove_limit(long limit_id) {
            return m_rate_limiter.remove_limit(limit_id);
        }

        bool remove_limit(const HttpRateLimitHandlePtr& limit) {
            return m_rate_limiter.remove_limit(limit);
        }

        bool allow_request(
                const HttpRateLimitHandlePtr& general_limit,
                const HttpRateLimitHandlePtr& specific_limit,
                uint64_t in_flight_token,
                const std::string& general_key,
                const std::string& specific_key) {
            return m_rate_limiter.allow_request(
                general_limit, specific_limit, in_flight_token, general_key, specific_key);
        }

        void release_request(
                const HttpRateLimitHandlePtr& general_limit,
                const HttpRateLimitHandlePtr& specific_limit,
                uint64_t in_flight_token,
                const std::string& general_key,
                const std::string& specific_key) {
            m_rate_limiter.release_request(
                general_limit, specific_limit, in_flight_token, general_key, specific_key);
        }

        template<typename Duration = std::chrono::milliseconds>
        RateLimitDelay<Duration> time_until_next_allowed(
            const HttpRateLimitHandlePtr& general_limit,
            const HttpRateLimitHandlePtr& specific_limit,
            const std::string& general_key,
            const std::string& specific_key
            ) {
            return m_rate_limiter.time_until_next_allowed<Duration>(
                general_limit, specific_limit, general_key, specific_key);
        }

        uint64_t generate_request_id() {
            return m_request_id_counter++;
        }

        uint64_t generate_group_id() {
            return m_group_id_counter++;
        }

        void set_max_pending_requests(std::size_t max_pending_requests) {
            m_max_pending_requests.store(max_pending_requests);
        }

        std::size_t max_pending_requests() const {
            return m_max_pending_requests.load();
        }

        bool has_requests_by_group_id(uint64_t group_id) const {
            return group_request_count(group_id) != 0;
        }

        std::size_t group_request_count(uint64_t group_id) const {
            std::lock_guard<std::mutex> lock(m_mutex);
            return group_request_count_unlocked(group_id);
        }

        void wait_requests_by_group_id(uint64_t group_id, std::function<void()> callback) {
            if (m_shutdown || group_id == 0) {
                if (callback) callback();
                return;
            }
 
            bool invoke_now = false;
            {
                std::lock_guard<std::mutex> lock(m_mutex);
                if (group_request_count_unlocked(group_id) == 0) {
                    invoke_now = true;
                } else {
                    m_group_waiters[group_id].push_back(std::move(callback));
                }
            }
 
            if (invoke_now && callback) {
                callback();
            }
        }

        void cancel_request_by_id(uint64_t request_id, std::function<void()> callback) {
            if (m_shutdown || request_id == 0) {
                if (callback) callback();
                return;
            }
            std::lock_guard<std::mutex> lock(m_mutex);
            m_requests_to_cancel_by_id[request_id].push_back(std::move(callback));
        }

        void cancel_requests_by_group_id(uint64_t group_id, std::function<void()> callback) {
            if (m_shutdown || group_id == 0) {
                if (callback) callback();
                return;
            }
            bool invoke_now = false;
            {
                std::lock_guard<std::mutex> lock(m_mutex);
                if (group_request_count_unlocked(group_id) == 0) {
                    invoke_now = true;
                } else {
                    m_groups_to_cancel[group_id].push_back(std::move(callback));
                }
            }
            if (invoke_now && callback) {
                callback();
            }
        }

        void process() override {
            if (m_shutdown) {
                notify_all_group_waiters();
                return;
            }
            process_pending_requests();
            process_active_requests();
            process_retry_failed_requests();
            process_cancel_requests();
            notify_group_waiters_if_idle();
        }

        void shutdown() override {
            if (m_shutdown.exchange(true)) {
                notify_all_group_waiters();
                return;
            }
            cleanup_pending_requests();
            process_cancel_requests();
            m_active_request_batches.clear();
            notify_all_group_waiters();
        }

        bool is_loaded() const override {
            std::lock_guard<std::mutex> lock(m_mutex);
            return
                !m_pending_requests.empty() ||
                !m_failed_requests.empty() ||
                !m_active_request_batches.empty() ||
                !m_requests_to_cancel_by_id.empty() ||
                !m_groups_to_cancel.empty();
        }
 
    private:
        mutable std::mutex                                  m_mutex;                  
        std::list<std::unique_ptr<HttpRequestContext>>      m_pending_requests;       
        std::list<std::unique_ptr<HttpRequestContext>>      m_failed_requests;        
        std::list<std::unique_ptr<HttpBatchRequestHandler>> m_active_request_batches; 
        using callback_list_t = std::list<std::function<void()>>;
        using cancel_map_t = std::unordered_map<uint64_t, callback_list_t>;
        cancel_map_t                                       m_requests_to_cancel_by_id; 
        cancel_map_t                                       m_groups_to_cancel;         
        cancel_map_t                                       m_group_waiters;            
        HttpRateLimiter                                     m_rate_limiter;           
        std::atomic<uint64_t>                               m_next_in_flight_token{1}; 
        std::atomic<uint64_t>                               m_request_id_counter = ATOMIC_VAR_INIT(1); 
        std::atomic<uint64_t>                               m_group_id_counter = ATOMIC_VAR_INIT(1); 
        std::atomic<bool>                                   m_shutdown = ATOMIC_VAR_INIT(false); 
        std::atomic<std::size_t>                            m_max_pending_requests = ATOMIC_VAR_INIT(0); 
 
        std::size_t group_request_count_unlocked(uint64_t group_id) const {
            if (group_id == 0) return 0;
 
            std::size_t count = 0;
            for (const auto& context : m_pending_requests) {
                if (context && context->request && context->request->group_id == group_id) {
                    ++count;
                }
            }
            for (const auto& context : m_failed_requests) {
                if (context && context->request && context->request->group_id == group_id) {
                    ++count;
                }
            }
            for (const auto& batch : m_active_request_batches) {
                if (batch) {
                    count += batch->group_request_count(group_id);
                }
            }
            return count;
        }
 
        void notify_group_waiters_if_idle() {
            cancel_map_t ready_waiters;
            {
                std::lock_guard<std::mutex> lock(m_mutex);
                auto it = m_group_waiters.begin();
                while (it != m_group_waiters.end()) {
                    if (group_request_count_unlocked(it->first) != 0) {
                        ++it;
                        continue;
                    }
                    ready_waiters.emplace(it->first, std::move(it->second));
                    it = m_group_waiters.erase(it);
                }
            }
 
            for (const auto& item : ready_waiters) {
                for (const auto& callback : item.second) {
                    if (callback) callback();
                }
            }
        }
 
        void notify_all_group_waiters() {
            cancel_map_t waiters;
            {
                std::lock_guard<std::mutex> lock(m_mutex);
                waiters = std::move(m_group_waiters);
                m_group_waiters.clear();
            }
 
            for (const auto& item : waiters) {
                for (const auto& callback : item.second) {
                    if (callback) callback();
                }
            }
        }

        void process_pending_requests() {
            std::unique_lock<std::mutex> lock(m_mutex);
            if (m_pending_requests.empty()) return;
 
            std::vector<std::unique_ptr<HttpRequestContext>> pending_request;
            std::vector<std::unique_ptr<HttpRequestContext>> failed_requests;
 
            auto it = m_pending_requests.begin();
            while (it != m_pending_requests.end()) {
                auto& context = *it;
                auto& request = context->request;
                // Check if the request is valid.
                if (!request) {
                    failed_requests.push_back(std::move(context));
                    it = m_pending_requests.erase(it);
                    continue;
                }
 
                // Set up completion callback before allow_request so it is armed
                // even if an exception occurs after the token is committed.
                auto general_limit = request->general_rate_limit;
                auto specific_limit = request->specific_rate_limit;
                uint64_t token = context->in_flight_token;
                auto general_key = request->general_rate_limit_key;
                auto specific_key = request->specific_rate_limit_key;
 
                // Preserve any previous on_complete so a retry that already owns
                // a sequential token does not lose its cleanup callback.
                auto old_on_complete = std::move(context->on_complete);
                context->on_complete = [this, general_limit, specific_limit, token, general_key, specific_key]() {
                    m_rate_limiter.release_request(general_limit, specific_limit, token, general_key, specific_key);
                };
 
                // Check if the request is allowed by the rate limiter.
                const bool allowed = m_rate_limiter.allow_request(
                    general_limit,
                    specific_limit,
                    token,
                    request->general_rate_limit_key,
                    request->specific_rate_limit_key);
                if (!allowed) {
                    context->on_complete = std::move(old_on_complete);
                    ++it;
                    continue;
                }
 
                pending_request.push_back(std::move(context));
                it = m_pending_requests.erase(it);
            }
            lock.unlock();
 
            // Handle failed requests by calling their callback with a 400 status.
            if (!failed_requests.empty()) {
                for (const auto &context : failed_requests) {
#                   if __cplusplus >= 201402L
                    auto response = std::make_unique<HttpResponse>();
#                   else
                    auto response = std::unique_ptr<HttpResponse>(new HttpResponse());
#                   endif
                    const long BAD_REQUEST = 400;
                    response->error_code = utils::make_error_code(CURLE_OK);
                    response->status_code = BAD_REQUEST;
                    response->ready = true;
                    context->callback(std::move(response));
                    context->complete();
                }
                failed_requests.clear();
            }
 
            // If there are ready requests, create a new HttpBatchRequestHandler to manage them.
            if (pending_request.empty()) return;
            try {
#               if __cplusplus >= 201402L
                m_active_request_batches.push_back(std::make_unique<HttpBatchRequestHandler>(pending_request));
#               else
                m_active_request_batches.push_back(std::unique_ptr<HttpBatchRequestHandler>(new HttpBatchRequestHandler(pending_request)));
#               endif
            } catch (...) {
                for (auto& context : pending_request) {
                    if (!context || !context->callback) continue;
#                   if __cplusplus >= 201402L
                    auto response = std::make_unique<HttpResponse>();
#                   else
                    auto response = std::unique_ptr<HttpResponse>(new HttpResponse());
#                   endif
                    response->error_code = utils::make_error_code(utils::ClientError::AbortedDuringDestruction);
                    response->status_code = 499; // Client closed request
                    response->ready = true;
                    context->callback(std::move(response));
                    context->complete();
                }
                return;
            }
        }

        void process_active_requests() {
            auto it = m_active_request_batches.begin();
            while (it != m_active_request_batches.end()) {
                auto& request = *it;
                if (!request->process()) {
                    ++it;
                    continue;
                }
                auto failed_requests = request->extract_failed_requests();
                it = m_active_request_batches.erase(it);
                for (auto& request : failed_requests) {
                    m_failed_requests.push_back(std::move(request));
                }
            }
        }

        void process_retry_failed_requests() {
            auto it = m_failed_requests.begin();
            while (it != m_failed_requests.end()) {
                auto& request_context = *it;
                if (!request_context || !request_context->request) {
                    it = m_failed_requests.erase(it);
                    continue;
                }
 
                const auto now = std::chrono::steady_clock::now();
                const auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(now - request_context->start_time);
                const auto& retry_delay_ms = request_context->request->retry_delay_ms;
                if (duration.count() >= retry_delay_ms) {
                    std::unique_lock<std::mutex> lock(m_mutex);
                    m_pending_requests.push_back(std::move(request_context));
                    lock.unlock();
                    it = m_failed_requests.erase(it);
                    continue;
                }
                ++it;
            }
        }

        void process_cancel_requests() {
            std::unique_lock<std::mutex> lock(m_mutex);
            if (m_requests_to_cancel_by_id.empty() && m_groups_to_cancel.empty()) return;
 
            auto requests_to_cancel = std::move(m_requests_to_cancel_by_id);
            auto groups_to_cancel = std::move(m_groups_to_cancel);
            m_requests_to_cancel_by_id.clear();
            m_groups_to_cancel.clear();
 
            std::list<std::unique_ptr<HttpRequestContext>> canceled_pending_requests;
            auto pending_it = m_pending_requests.begin();
            while (pending_it != m_pending_requests.end()) {
                const auto& ctx = *pending_it;
                if (!matches_cancel(ctx, requests_to_cancel, groups_to_cancel)) {
                    ++pending_it;
                    continue;
                }
                canceled_pending_requests.push_back(std::move(*pending_it));
                pending_it = m_pending_requests.erase(pending_it);
            }
            lock.unlock();
 
            for (const auto& request_context : canceled_pending_requests) {
                request_context->callback(make_cancelled_response());
                request_context->complete();
            }
 
            auto failed_it = m_failed_requests.begin();
            while (failed_it != m_failed_requests.end()) {
                const auto& request_context = *failed_it;
                if (!matches_cancel(request_context, requests_to_cancel, groups_to_cancel)) {
                    ++failed_it;
                    continue;
                }
                request_context->callback(make_cancelled_response());
                request_context->complete();
                failed_it = m_failed_requests.erase(failed_it);
            }
 
            for (const auto &handler : m_active_request_batches) {
                handler->cancel_requests(requests_to_cancel, groups_to_cancel);
            }
 
            invoke_cancel_callbacks(requests_to_cancel);
            invoke_cancel_callbacks(groups_to_cancel);
        }
 
        static bool matches_cancel(
                const std::unique_ptr<HttpRequestContext>& ctx,
                const cancel_map_t& requests_to_cancel,
                const cancel_map_t& groups_to_cancel) {
            if (!ctx || !ctx->request) return false;
            const auto request_id = ctx->request->request_id;
            const auto group_id = ctx->request->group_id;
            return
                (request_id != 0 && requests_to_cancel.count(request_id) > 0) ||
                (group_id != 0 && groups_to_cancel.count(group_id) > 0);
        }
 
        static HttpResponsePtr make_cancelled_response() {
#           if __cplusplus >= 201402L
            auto response = std::make_unique<HttpResponse>();
#           else
            auto response = std::unique_ptr<HttpResponse>(new HttpResponse());
#           endif
            response->error_code = utils::make_error_code(utils::ClientError::CancelledByUser);
            response->status_code = 499;
            response->ready = true;
            return response;
        }
 
        static void invoke_cancel_callbacks(const cancel_map_t& requests_to_cancel) {
            for (const auto& request : requests_to_cancel) {
                for (const auto& callback : request.second) {
                    if (callback) callback();
                }
            }
        }

        void cleanup_pending_requests() {
            std::unique_lock<std::mutex> lock(m_mutex);
            auto pending_requests = std::move(m_pending_requests);
            auto failed_requests  = std::move(m_failed_requests);
            m_pending_requests.clear();
            m_failed_requests.clear();
            lock.unlock();
 
            for (const auto &request_context : pending_requests) {
#               if __cplusplus >= 201402L
                auto response = std::make_unique<HttpResponse>();
#               else
                auto response = std::unique_ptr<HttpResponse>(new HttpResponse());
#               endif
                const long CANCELED_REQUEST_CODE = 499;
                response->error_code = utils::make_error_code(CURLE_OK);
                response->status_code = CANCELED_REQUEST_CODE;
                response->ready = true;
                request_context->callback(std::move(response));
                request_context->complete();
            }
            for (const auto &request_context : failed_requests) {
#               if __cplusplus >= 201402L
                auto response = std::make_unique<HttpResponse>();
#               else
                auto response = std::unique_ptr<HttpResponse>(new HttpResponse());
#               endif
                const long CANCELED_REQUEST_CODE = 499;
                response->error_code = utils::make_error_code(CURLE_OK);
                response->status_code = CANCELED_REQUEST_CODE;
                response->ready = true;
                request_context->callback(std::move(response));
                request_context->complete();
            }
        }

        HttpRequestManager() {
            curl_global_init(CURL_GLOBAL_ALL);
        }

        virtual ~HttpRequestManager() {
            curl_global_cleanup();
        }

        HttpRequestManager(const HttpRequestManager&) = delete;

        HttpRequestManager& operator=(const HttpRequestManager&) = delete;
 
    }; // HttpRequestManager
 
}; // namespace kurlyk
 
#endif // KURLYK_HEADER_KURLYK_HTTP_HTTP_REQUEST_MANAGER_HPP_INCLUDED