#pragma once
#include "Utils/ThreadPool.hpp"
#include "Socket/WSAManager.hpp"
#include "Socket/TCPSocket.hpp"
#include "Socket/Log.hpp"
#include "Packet/Packet.hpp"
#include <functional>
#include <vector>
#include <queue>

#include "precomp.hpp"

#ifdef __linux__

typedef struct _OVERLAPPED {
    char dummy;
} OVERLAPPED;

typedef struct __WSABUF {
    std::uint32_t len;
    char *buf;
} WSABUF;

#endif

namespace Chattr {

class IOCP;

enum class IOCPEVENT {
    ERROR_,
    READ,
    WRITE
};

struct IOCPPASSINDATA {
    OVERLAPPED overlapped;
    IOCPEVENT event;
    std::shared_ptr<TCPSocket> socket;
    char buf[1501];
    std::uint32_t recvbytes;
    std::uint32_t sendbytes;
    std::uint32_t transferredbytes;
    WSABUF wsabuf;
    IOCP* IOCPInstance;
#ifdef __linux__
    std::shared_ptr<std::queue<IOCPPASSINDATA*>> sendQueue;
#endif
};

class IOCP {
public:
#ifdef _WIN32
    static void iocpWather(ThreadPool* threadPool, HANDLE completionPort_, std::function<void(ThreadPool*, IOCPPASSINDATA*)> callback) {
        DWORD tid = GetCurrentThreadId();
        spdlog::trace("Waiting IO to complete on TID: {}.", tid);
        IOCPPASSINDATA* data;
        SOCKET sock;
        DWORD cbTransfrred;
        int retVal = GetQueuedCompletionStatus(completionPort_, &cbTransfrred, (PULONG_PTR)&sock, (LPOVERLAPPED*)&data, INFINITE);
        if (retVal == 0 || cbTransfrred == 0) {
            spdlog::debug("Client disconnected. [{}]", (std::string)(data->socket->remoteAddr));
            delete data;
            threadPool->enqueueJob(iocpWather, completionPort_, callback);
            return;
        }
        data->transferredbytes = cbTransfrred;
        threadPool->enqueueJob(callback, data);
        threadPool->enqueueJob(iocpWather, completionPort_, callback);
    };
#elif __linux__
    static void socketReader(ThreadPool* threadPool, epoll_event event, int epollfd, std::function<void(ThreadPool*, IOCPPASSINDATA*)> callback) {
        pthread_t tid = pthread_self();

        if (event.data.ptr == nullptr) {
            spdlog::error("invalid call on {}", tid);
            return;
        }
        
        IOCPPASSINDATA* rootIocpData = (IOCPPASSINDATA*)event.data.ptr;

        std::lock_guard<std::mutex> lock(rootIocpData->socket->readMutex);
        char peekBuffer[1];
        while (rootIocpData->socket->recv(peekBuffer, 1, MSG_PEEK)) {
            Chattr::IOCPPASSINDATA* ptr = new Chattr::IOCPPASSINDATA;
            ::memcpy(ptr, rootIocpData, sizeof(IOCPPASSINDATA));
            ::memset(&ptr->overlapped, 0, sizeof(OVERLAPPED));
            ptr->recvbytes = ptr->sendbytes = 0;
            ptr->wsabuf.buf = ptr->buf;
            ptr->wsabuf.len = 1500;

            int redSize = 0;
            int headerSize = 8;
            int totalRedSize = 0;

            while (totalRedSize < headerSize) {
                redSize = ptr->socket->recv(ptr->buf + totalRedSize, headerSize - totalRedSize, 0);
                
                if (redSize == SOCKET_ERROR) {
                    spdlog::error("recv() [{}]", strerror(errno));
                    ::epoll_ctl(epollfd, EPOLL_CTL_DEL, ptr->socket->sock, NULL);
                    delete ptr;
                    return;
                }
                else if (redSize == 0) {
                    spdlog::debug("Client disconnected. [{}]", (std::string)ptr->socket->remoteAddr);
                    ::epoll_ctl(epollfd, EPOLL_CTL_DEL, ptr->socket->sock, NULL);
                    delete ptr;
                    return;
                }
                totalRedSize += redSize;
            }

            Packet packet;
            ::memcpy(packet.serialized, ptr->buf, headerSize);

            redSize = 0;
            int dataLength = ntohs(packet.__data.packetLength);

            while (totalRedSize < dataLength + headerSize) {
                redSize = ptr->socket->recv(ptr->buf + totalRedSize, dataLength + headerSize - totalRedSize, 0);
                
                if (redSize == SOCKET_ERROR) {
                    spdlog::error("recv() [{}]", strerror(errno));
                    ::epoll_ctl(epollfd, EPOLL_CTL_DEL, ptr->socket->sock, NULL);
                    delete ptr;
                    return;
                }
                else if (redSize == 0) {
                    spdlog::debug("Client disconnected. [{}]", (std::string)ptr->socket->remoteAddr);
                    ::epoll_ctl(epollfd, EPOLL_CTL_DEL, ptr->socket->sock, NULL);
                    delete ptr;
                    return;
                }
                totalRedSize += redSize;
            }
            ptr->transferredbytes = totalRedSize;
            threadPool->enqueueJob(callback, ptr);
        }
    };
    static void socketWriter(ThreadPool* threadPool, epoll_event event, int epollfd, std::function<void(ThreadPool*, IOCPPASSINDATA*)> callback) {
        pthread_t tid = pthread_self();

        if (event.data.ptr == nullptr) {
            spdlog::error("invalid call on {}", tid);
            return;
        }
        
        IOCPPASSINDATA* rootIocpData = (IOCPPASSINDATA*)event.data.ptr;

        std::lock_guard<std::mutex> lock(rootIocpData->socket->writeMutex);
        auto queue = rootIocpData->sendQueue;
        while (!queue->empty()) {
            IOCPPASSINDATA* data = queue->front();
            queue->pop();

            int packetSize = data->wsabuf.len;
            int totalSentSize = 0;
            int sentSize = 0;

            spdlog::trace("Sending to: [{}]", (std::string)data->socket->remoteAddr);

            while (totalSentSize < packetSize) {
                sentSize = data->socket->send(data->buf + totalSentSize, packetSize - totalSentSize, 0);

                if (sentSize == SOCKET_ERROR) {
                    spdlog::error("send() [{}]", strerror(errno));
                    ::epoll_ctl(epollfd, EPOLL_CTL_DEL, data->socket->sock, NULL);
                    delete data;
                    return;
                }
                totalSentSize += sentSize;
            }
            data->transferredbytes = totalSentSize;
            threadPool->enqueueJob(callback, data);
        }
    };
    static void iocpWatcher(ThreadPool* threadPool, int epollfd, std::function<void(ThreadPool*, IOCPPASSINDATA*)> callback) {
        struct epoll_event events[FD_SETSIZE];
        pthread_t tid = pthread_self();

        spdlog::trace("epoll waiting on {}", tid);
        int nready = ::epoll_wait(epollfd, events, FD_SETSIZE, -1);

        for (int i=0; i<nready; i++) {
            struct epoll_event current_event = events[i];

            if (current_event.events & EPOLLIN) {
                std::function<void(ThreadPool*, IOCPPASSINDATA*)> task(callback);
                threadPool->enqueueJob(socketReader, current_event, epollfd, task);
            }
            else if (current_event.events & EPOLLOUT) {
                std::function<void(ThreadPool*, IOCPPASSINDATA*)> task(callback);
                threadPool->enqueueJob(socketWriter, current_event, epollfd, task);
            }
            if (--nready <= 0)
                break;
        }
        threadPool->enqueueJob(iocpWatcher, epollfd, callback);
    };
#endif

    IOCP();
    ~IOCP();

    template<typename _Callable>
    void init(ThreadPool* __IOCPThread, _Callable&& callback) {
        IOCPThread_ = __IOCPThread;
#ifdef _WIN32
        completionPort_ = ::CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
        if (completionPort_ == NULL)
            log::critical("CreateIoCompletionPort()");
#elif __linux__
        epollfd_ = ::epoll_create(1);
#endif
        auto boundFunc = [callback = std::move(callback)](ThreadPool* __IOCPThread, IOCPPASSINDATA* data) mutable {
            callback(__IOCPThread, data);
        };

#ifdef _WIN32
        int tCount = __IOCPThread->threadCount;

        spdlog::info("Resizing threadpool size to: {}", tCount * 2);

        __IOCPThread->respawnWorker(tCount * 2);

        for (int i = 0; i < tCount; i++) {
            std::function<void(ThreadPool*, IOCPPASSINDATA*)> task(boundFunc);
            __IOCPThread->enqueueJob(iocpWather, completionPort_, task);
        }
#elif __linux__
        __IOCPThread->respawnWorker(__IOCPThread->threadCount + 1);
        spdlog::info("Spawning 1 Epoll Waiter...");
        __IOCPThread->enqueueJob(iocpWatcher, epollfd_, boundFunc);
#endif
    }

    void destruct();

    void registerSocket(IOCPPASSINDATA* data);

    int recv(IOCPPASSINDATA* data, int bufferCount);
    int send(IOCPPASSINDATA* data, int bufferCount, int __flags, bool client = false);

private:
    struct WSAManager wsaManager;
    ThreadPool* IOCPThread_;

#ifdef _WIN32
    HANDLE completionPort_ = INVALID_HANDLE_VALUE;
#elif __linux__
    int epollfd_ = -1;
    std::unordered_map<std::shared_ptr<TCPSocket>, std::mutex> writeMutex;
    std::unordered_map<std::shared_ptr<TCPSocket>, std::queue<IOCPPASSINDATA*>> writeBuffer;
#endif
};

}