#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "osd_ops.h"
#include "ringloop.h"

struct osd_client_t
{
    sockaddr_in peer_addr;
    socklen_t peer_addr_size;
    int peer_fd;
    bool ready;
};

class osd_t
{
    int wait_state = 0;
    int epoll_fd = 0;
    int listen_fd = 0;
    ring_consumer_t consumer;

    std::string bind_address;
    int bind_port, listen_backlog;
    ring_loop_t *ringloop;

    std::unordered_map<int,osd_client_t> clients;
    std::deque<int> ready_clients;

    void handle_epoll_events();
public:
    osd_t(ring_loop_t *ringloop);
    ~osd_t();
    void loop();
};

osd_t::osd_t(ring_loop_t *ringloop)
{
    this->ringloop = ringloop;

    listen_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_fd < 0)
    {
        throw std::runtime_error(std::string("socket: ") + strerror(errno));
    }

    sockaddr_in addr;
    if ((int r = inet_pton(AF_INET, bind_address.c_str(), &addr.sin_addr)) != 1)
    {
        close(listen_fd);
        throw std::runtime_error("bind address "+bind_address+(r == 0 ? " is not valid" : ": no ipv4 support"));
    }
    addr.sin_family = AF_INET;
    addr.sin_port = bind_port;

    if (bind(listen_fd, &addr, sizeof(addr)) < 0)
    {
        close(listen_fd);
        throw std::runtime_error(std::string("bind: ") + strerror(errno));
    }

    if (listen(listen_fd, listen_backlog) < 0)
    {
        close(listen_fd);
        throw std::runtime_error(std::string("listen: ") + strerror(errno));
    }

    fcntl(listen_fd, F_SETFL, fcntl(listen_fd, F_GETFL, 0) | O_NONBLOCK);

    epoll_fd = epoll_create(1);
    if (epoll_fd < 0)
    {
        close(listen_fd);
        throw std::runtime_error(std::string("epoll_create: ") + strerror(errno));
    }

    struct epoll_event ev;
    ev.data.fd = listen_fd;
    ev.events = EPOLLIN;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, listen_fd, &ev) < 0)
    {
        throw std::runtime_error(std::string("epoll_ctl: ") + strerror(errno));
    }

    consumer.loop = [this]() { loop(); };
    ringloop->register_consumer(consumer);
}

osd_t::~osd_t()
{
    ringloop->unregister_consumer(consumer);
    close(epoll_fd);
    close(listen_fd);
}

void osd_t::loop()
{
    if (wait_state == 1)
    {
        return;
    }
    struct io_uring_sqe *sqe = ringloop->get_sqe();
    if (!sqe)
    {
        wait_state = 0;
        return;
    }
    struct ring_data_t *data = ((ring_data_t*)sqe->user_data);
    my_uring_prep_poll_add(sqe, epoll_fd, POLLIN);
    data->callback = [&](ring_data_t *data)
    {
        if (data->res < 0)
        {
            throw std::runtime_error(std::string("epoll failed: ") + strerror(-data->res));
        }
        handle_epoll_events();
        wait_state = 0;
    };
    wait_state = 1;
    ringloop->submit();
}

#define MAX_EPOLL_EVENTS 16

int osd_t::handle_epoll_events()
{
    epoll_event events[MAX_EPOLL_EVENTS];
    int count = 0;
    int nfds;
    // FIXME: We shouldn't probably handle ALL available events, we should sometimes
    // yield control to Blockstore and possibly other consumers
    while ((nfds = epoll_wait(epoll_fd, events, MAX_EPOLL_EVENTS, 0)) > 0)
    {
        for (int i = 0; i < nfds; i++)
        {
            if (events[i].data.fd == listen_fd)
            {
                // Accept new connections
                struct sockaddr_in addr;
                socklen_t peer_addr_size = sizeof(addr);
                int peer_fd;
                while ((peer_fd = accept(listen_fd, &addr, &peer_addr_size)) >= 0)
                {
                    clients[peer_fd] = {
                        .peer_addr = addr,
                        .peer_addr_size = peer_addr_size,
                        .peer_fd = peer_fd,
                        .ready = false,
                    };
                    // Add FD to epoll
                    struct epoll_event ev;
                    ev.data.fd = peer_fd;
                    ev.events = EPOLLIN | EPOLLHUP;
                    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, peer_fd, &ev) < 0)
                    {
                        throw std::runtime_error(std::string("epoll_ctl: ") + strerror(errno));
                    }
                    // Try to accept next connection
                    peer_addr_size = sizeof(addr);
                }
                if (peer_fd == -1 && errno != EAGAIN)
                {
                    throw std::runtime_error(std::string("accept: ") + strerror(errno));
                }
            }
            else
            {
                auto & cl = clients[events[i].data.fd];
                if (events[i].events & EPOLLHUP)
                {
                    // Stop client
                    struct epoll_event ev;
                    ev.data.fd = cl.peer_fd;
                    ev.events = EPOLLIN | EPOLLHUP;
                    if (epoll_ctl(epoll_fd, EPOLL_CTL_DEL, cl.peer_fd, &ev) < 0)
                    {
                        throw std::runtime_error(std::string("epoll_ctl: ") + strerror(errno));
                    }
                    auto it = clients.find(cl.peer_fd);
                    clients.erase(it);
                    if (cl.ready)
                    {
                        for (auto it = ready_clients.begin(); it != ready_clients.end(); it++)
                        {
                            if (*it == cl.peer_fd)
                            {
                                ready_clients.erase(it);
                                break;
                            }
                        }
                    }
                }
                else if (!cl.ready)
                {
                    // Mark client as ready (i.e. some commands are available)
                    cl.ready = true;
                    ready_clients.push_back(cl.peer_fd);
                }
            }
            count++;
        }
    }
    return count;
}