#define _GNU_SOURCE

#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/timerfd.h>
#include <unistd.h>

#include "diskuring/diskuring.h"
#include "server.h"

#define CONNECTION_SIZE 65536
#define MAX_PORTS 20
#define RECV_BATCH_BYTES 4096
#define CHAIN_BUFFER_CHUNK 4096
#define MAX_CONN_READ_BYTES (32u * 1024u * 1024u)
#define MAX_CONN_WRITE_BYTES (32u * 1024u * 1024u)

#if ENABLE_KVSTORE
typedef int (*msg_handler)(struct conn *conn);
static msg_handler kvs_handler;

extern iouring_ctx_t global_uring_ctx;

int kvs_request(struct conn *c) {
    return kvs_handler ? kvs_handler(c) : -1;
}

int kvs_response(struct conn *c) {
    (void)c;
    return 0;
}
#endif

int accept_cb(int fd);
int recv_cb(int fd);
int send_cb(int fd);

static int epfd = -1;
static int wakeup_fd = -1;
static int timer_fd = -1;
static struct timeval begin;
static struct conn conn_list[CONNECTION_SIZE];

static int conn_fd_valid(int fd) {
    return fd >= 0 && fd < CONNECTION_SIZE;
}

static int set_nonblocking(int fd) {
    int flags = fcntl(fd, F_GETFL, 0);
    if (flags < 0) {
        return -1;
    }
    if ((flags & O_NONBLOCK) != 0) {
        return 0;
    }
    return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}

static void conn_clear_slot(int fd) {
    struct conn *c;

    if (!conn_fd_valid(fd)) {
        return;
    }

    c = &conn_list[fd];
    chain_buffer_reset(&c->rbuf);
    chain_buffer_reset(&c->wbuf);
    memset(c, 0, sizeof(*c));
    c->fd = -1;
}

static void close_conn(int fd) {
    if (!conn_fd_valid(fd)) {
        return;
    }
    epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);
    close(fd);
    conn_clear_slot(fd);
}

static int set_event(int fd, int event, int is_add) {
    struct epoll_event ev;
    int op = is_add ? EPOLL_CTL_ADD : EPOLL_CTL_MOD;

    memset(&ev, 0, sizeof(ev));
    ev.events = (uint32_t)event;
    ev.data.fd = fd;

    if (epoll_ctl(epfd, op, fd, &ev) < 0) {
        return -1;
    }
    return 0;
}

static int update_conn_events(int fd) {
    struct conn *c;
    int events = EPOLLIN;

    if (!conn_fd_valid(fd)) {
        return -1;
    }

    c = &conn_list[fd];
    if (chain_buffer_len(&c->wbuf) > 0) {
        events |= EPOLLOUT;
    }

    return set_event(fd, events, 0);
}

int event_register(int fd, int event) {
    struct conn *c;

    if (!conn_fd_valid(fd)) {
        if (fd >= 0) {
            close(fd);
        }
        return -1;
    }

    if (set_nonblocking(fd) < 0) {
        close(fd);
        return -1;
    }

    conn_clear_slot(fd);

    c = &conn_list[fd];
    c->fd = fd;
    c->r_action.recv_callback = recv_cb;
    c->send_callback = send_cb;
    c->is_stop = 0;
    chain_buffer_init(&c->rbuf, CHAIN_BUFFER_CHUNK);
    chain_buffer_init(&c->wbuf, CHAIN_BUFFER_CHUNK);

    if (set_event(fd, event, 1) < 0) {
        close_conn(fd);
        return -1;
    }
    return 0;
}

int accept_cb(int fd) {
    while (1) {
        struct sockaddr_in clientaddr;
        socklen_t len = sizeof(clientaddr);
        int clientfd = accept4(fd, (struct sockaddr *)&clientaddr, &len, SOCK_NONBLOCK | SOCK_CLOEXEC);

        if (clientfd < 0) {
            if (errno == EAGAIN || errno == EWOULDBLOCK) {
                return 0;
            }
            if (errno == EINTR) {
                continue;
            }
            printf("accept errno: %d --> %s\n", errno, strerror(errno));
            return -1;
        }

        if (!conn_fd_valid(clientfd)) {
            printf("drop client fd=%d, out of conn_list range\n", clientfd);
            close(clientfd);
            continue;
        }

        if (event_register(clientfd, EPOLLIN) < 0) {
            continue;
        }

        if ((clientfd % 1000) == 0) {
            struct timeval current;
            int time_used;

            gettimeofday(&current, NULL);
            time_used = (int)((current.tv_sec - begin.tv_sec) * 1000 +
                              (current.tv_usec - begin.tv_usec) / 1000);
            begin = current;
            (void)time_used;
        }
    }
}

int recv_cb(int fd) {
    struct conn *c;
    int total = 0;

    if (!conn_fd_valid(fd)) {
        return -1;
    }

    c = &conn_list[fd];
    while (1) {
        uint8_t tmp[RECV_BATCH_BYTES];
        ssize_t n = recv(fd, tmp, sizeof(tmp), 0);

        if (n > 0) {
            size_t cur_len = chain_buffer_len(&c->rbuf);
            if (cur_len > MAX_CONN_READ_BYTES - (size_t)n) {
                printf("fd=%d read buffer overflow, close connection\n", fd);
                close_conn(fd);
                return 0;
            }
            if (chain_buffer_append(&c->rbuf, tmp, (size_t)n) < 0) {
                printf("fd=%d append read buffer failed: %s\n", fd, strerror(errno));
                close_conn(fd);
                return 0;
            }
            total += (int)n;
            continue;
        }

        if (n == 0) {
            close_conn(fd);
            return 0;
        }

        if (errno == EINTR) {
            continue;
        }
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            break;
        }

        printf("recv fd=%d errno=%d, %s\n", fd, errno, strerror(errno));
        close_conn(fd);
        return 0;
    }

    if (total <= 0) {
        return 0;
    }

#if ENABLE_HTTP
    http_request(c);
#elif ENABLE_WEBSOCKET
    ws_request(c);
#elif ENABLE_KVSTORE
    {
        int consumed = kvs_request(c);
        size_t readable = chain_buffer_len(&c->rbuf);

        if (consumed < 0) {
            close_conn(fd);
            return 0;
        }

        if ((size_t)consumed > readable) {
            printf("fd=%d invalid consumed=%d readable=%zu\n", fd, consumed, readable);
            close_conn(fd);
            return 0;
        }

        if (consumed > 0) {
            chain_buffer_drain(&c->rbuf, (size_t)consumed);
        }

        if (chain_buffer_len(&c->wbuf) > MAX_CONN_WRITE_BYTES) {
            printf("fd=%d write buffer overflow, close connection\n", fd);
            close_conn(fd);
            return 0;
        }
    }
#endif

    if (update_conn_events(fd) < 0) {
        close_conn(fd);
        return 0;
    }

    return total;
}

int send_cb(int fd) {
    struct conn *c;
    int sent_total = 0;

    if (!conn_fd_valid(fd)) {
        return -1;
    }
    c = &conn_list[fd];

#if ENABLE_HTTP
    http_response(c);
#elif ENABLE_WEBSOCKET
    ws_response(c);
#elif ENABLE_KVSTORE
    kvs_response(c);
#endif

    while (chain_buffer_len(&c->wbuf) > 0) {
        ssize_t n = chain_buffer_send_fd(&c->wbuf, fd, MSG_NOSIGNAL);
        if (n > 0) {
            sent_total += (int)n;
            continue;
        }

        if (n == 0) {
            break;
        }

        if (errno == EINTR) {
            continue;
        }
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            break;
        }

        printf("send fd=%d errno=%d %s\n", fd, errno, strerror(errno));
        close_conn(fd);
        return 0;
    }

    if (update_conn_events(fd) < 0) {
        close_conn(fd);
        return 0;
    }

    return sent_total;
}

int handle_wakeup_fd_cb(int fd) {
    uint64_t v;

    while (1) {
        ssize_t n = read(fd, &v, sizeof(v));
        if (n == (ssize_t)sizeof(v)) {
            continue;
        }
        if (n < 0 && errno == EINTR) {
            continue;
        }
        if (n < 0 && errno == EAGAIN) {
            break;
        }
        break;
    }

    cleanup_finished_iouring_tasks(&global_uring_ctx);
    return 0;
}

int init_wakeup_fd(void) {
    int wfd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
    struct conn *c;

    if (wfd < 0) {
        printf("eventfd failed: errno=%d %s\n", errno, strerror(errno));
        return -1;
    }
    if (!conn_fd_valid(wfd)) {
        close(wfd);
        return -1;
    }

    conn_clear_slot(wfd);
    c = &conn_list[wfd];
    c->fd = wfd;
    c->r_action.recv_callback = handle_wakeup_fd_cb;

    if (set_event(wfd, EPOLLIN, 1) < 0) {
        close_conn(wfd);
        return -1;
    }
    return wfd;
}

void sync_wakeup() {
    uint64_t one = 1;
    ssize_t n;

    if (wakeup_fd < 0) {
        return;
    }

    while (1) {
        n = write(wakeup_fd, &one, sizeof(one));
        if (n == (ssize_t)sizeof(one)) {
            return;
        }
        if (n < 0 && errno == EINTR) {
            continue;
        }
        if (n < 0 && errno == EAGAIN) {
            return;
        }
        return;
    }
}

int handle_timer_fd_cb(int fd) {
    uint64_t v;

    while (1) {
        ssize_t n = read(fd, &v, sizeof(v));
        if (n == (ssize_t)sizeof(v)) {
            continue;
        }
        if (n < 0 && errno == EINTR) {
            continue;
        }
        if (n < 0 && errno == EAGAIN) {
            break;
        }
        break;
    }
    return 0;
}

int init_timer_fd(void) {
    int tfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
    struct itimerspec its;
    struct conn *c;

    if (tfd < 0) {
        printf("timerfd_create failed: errno=%d %s\n", errno, strerror(errno));
        return -1;
    }
    if (!conn_fd_valid(tfd)) {
        close(tfd);
        return -1;
    }

    memset(&its, 0, sizeof(its));
    its.it_interval.tv_nsec = 100 * 1000 * 1000;
    its.it_value.tv_nsec = 100 * 1000 * 1000;

    if (timerfd_settime(tfd, 0, &its, NULL) < 0) {
        close(tfd);
        return -1;
    }

    conn_clear_slot(tfd);
    c = &conn_list[tfd];
    c->fd = tfd;
    c->r_action.recv_callback = handle_timer_fd_cb;

    if (set_event(tfd, EPOLLIN, 1) < 0) {
        close_conn(tfd);
        return -1;
    }
    return tfd;
}

int r_init_server(unsigned short port) {
    int sockfd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
    int opt = 1;
    struct sockaddr_in servaddr;

    if (sockfd < 0) {
        return -1;
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
        close(sockfd);
        return -1;
    }

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(port);

    if (bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
        printf("bind failed on port %u: %s\n", port, strerror(errno));
        close(sockfd);
        return -1;
    }

    if (listen(sockfd, 128) < 0) {
        close(sockfd);
        return -1;
    }

    return sockfd;
}

int reactor_start(unsigned short port, msg_handler handler) {
    int listen_fds[MAX_PORTS];
    int listen_count = 0;
    int i;

    if (!handler) {
        return -1;
    }

    for (i = 0; i < CONNECTION_SIZE; i++) {
        conn_list[i].fd = -1;
    }

    kvs_handler = handler;
    epfd = epoll_create1(EPOLL_CLOEXEC);
    if (epfd < 0) {
        return -1;
    }

    wakeup_fd = init_wakeup_fd();
    if (wakeup_fd < 0) {
        close(epfd);
        epfd = -1;
        return -1;
    }

    timer_fd = init_timer_fd();
    if (timer_fd < 0) {
        close_conn(wakeup_fd);
        close(epfd);
        wakeup_fd = -1;
        epfd = -1;
        return -1;
    }

    for (i = 0; i < MAX_PORTS; i++) {
        int sockfd = r_init_server((unsigned short)(port + i));
        struct conn *c;
        if (sockfd < 0) {
            continue;
        }
        if (!conn_fd_valid(sockfd)) {
            close(sockfd);
            continue;
        }

        conn_clear_slot(sockfd);
        c = &conn_list[sockfd];
        c->fd = sockfd;
        c->r_action.recv_callback = accept_cb;
        c->is_stop = 0;

        if (set_event(sockfd, EPOLLIN, 1) < 0) {
            close_conn(sockfd);
            continue;
        }

        listen_fds[listen_count++] = sockfd;
    }

    if (listen_count == 0) {
        close_conn(timer_fd);
        close_conn(wakeup_fd);
        close(epfd);
        timer_fd = -1;
        wakeup_fd = -1;
        epfd = -1;
        return -1;
    }

    gettimeofday(&begin, NULL);

    while (1) {
        struct epoll_event events[1024];
        int nready = epoll_wait(epfd, events, 1024, -1);

        if (nready < 0) {
            if (errno == EINTR) {
                continue;
            }
            break;
        }

        for (i = 0; i < nready; i++) {
            int connfd = events[i].data.fd;
            uint32_t ev = events[i].events;

            if (!conn_fd_valid(connfd)) {
                continue;
            }

            if ((ev & (EPOLLERR | EPOLLHUP | EPOLLRDHUP)) &&
                conn_list[connfd].r_action.recv_callback == recv_cb) {
                close_conn(connfd);
                continue;
            }

            if ((ev & EPOLLIN) && conn_list[connfd].r_action.recv_callback) {
                conn_list[connfd].r_action.recv_callback(connfd);
            }

            if (!conn_fd_valid(connfd) || conn_list[connfd].fd < 0) {
                continue;
            }

            if ((ev & EPOLLOUT) && conn_list[connfd].send_callback) {
                conn_list[connfd].send_callback(connfd);
            }
        }
    }

    for (i = 0; i < listen_count; i++) {
        close_conn(listen_fds[i]);
    }
    if (timer_fd >= 0) {
        close_conn(timer_fd);
    }
    if (wakeup_fd >= 0) {
        close_conn(wakeup_fd);
    }
    if (epfd >= 0) {
        close(epfd);
    }

    timer_fd = -1;
    wakeup_fd = -1;
    epfd = -1;
    return 0;
}