#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define MAX_EVENTS 1024
#define PORT 8888

// 设置文件描述符为非阻塞
int set_nonblocking(int fd) {
    int flags = fcntl(fd, F_GETFL, 0);
    if (flags == -1) flags = 0;
    return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}

int main() {
    int listen_sock, conn_sock, epoll_fd;
    struct sockaddr_in serv_addr, cli_addr;
    socklen_t cli_len = sizeof(cli_addr);
    struct epoll_event ev, events[MAX_EVENTS];

    // 创建监听 socket
    listen_sock = socket(AF_INET, SOCK_STREAM, 0);
    set_nonblocking(listen_sock);

    // 绑定地址和端口
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(PORT);

    bind(listen_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
    listen(listen_sock, 10);

    // 创建 epoll 实例
    epoll_fd = epoll_create1(0);
    if (epoll_fd == -1) {
        perror("epoll_create1");
        return -1;
    }

    // 将监听 socket 加入 epoll，监听新连接
    ev.events = EPOLLIN;
    ev.data.fd = listen_sock;
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, listen_sock, &ev) == -1) {
        perror("epoll_ctl: listen_sock");
        return -1;
    }

    printf("Server running on port %d\n", PORT);

    while (1) {
        int nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
        if (nfds == -1) {
            perror("epoll_wait");
            break;
        }

        for (int i = 0; i < nfds; i++) {
            if (events[i].data.fd == listen_sock) {
                // 新连接到来
                conn_sock = accept(listen_sock, (struct sockaddr*)&cli_addr, &cli_len);
                if (conn_sock == -1) {
                    if (errno != EAGAIN && errno != EWOULDBLOCK)
                        perror("accept");
                    continue;
                }
                set_nonblocking(conn_sock);
                ev.events = EPOLLIN | EPOLLET;  // 边缘触发模式
                ev.data.fd = conn_sock;
                if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, conn_sock, &ev) == -1) {
                    perror("epoll_ctl: conn_sock");
                    close(conn_sock);
                }
            } else {
                // 已连接 socket 有数据可读
                conn_sock = events[i].data.fd;
                char buf[1024];
                ssize_t count;

                while ((count = read(conn_sock, buf, sizeof(buf))) > 0) {
                    write(conn_sock, buf, count); // 回显数据
                }

                if (count == 0) {
                    // 客户端关闭连接
                    close(conn_sock);
                    epoll_ctl(epoll_fd, EPOLL_CTL_DEL, conn_sock, NULL);
                } else if (count == -1) {
                    if (errno != EAGAIN)
                        close(conn_sock);
                }
            }
        }
    }

    close(listen_sock);
    close(epoll_fd);
    return 0;
}