/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun IoT System Studio
 *                  All rights reserved.
 *
 *       Filename:  socketd.c
 *    Description:  This file is TCP socket server example program.
 *
 *        Version:  1.0.0(10/20/2025)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "10/20/2025 09:48:51 PM"
 *
 ********************************************************************************/
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <getopt.h>
#include <ctype.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <pthread.h>

#define BACKLOG              13

int         g_stop = 0; /* program stop or not */

void *workbody(void *ctx);

void sig_handler(int signum)
{
    switch(signum)
    {
        case SIGTERM:
            printf("SIGTERM signal detected(kill/killall)\n");
            break;

        case SIGSEGV:
            printf("SIGSEGV signal detected(segmentation fault)\n");
            break;

        case SIGPIPE:
            printf("SIGPIPE signal detected(socket error)\n");
            break;

        case SIGINT:
            printf("SIGINT signal detected(Ctrl+C)\n");
            break;

        default:
            break;
    }

    g_stop = 1;
}

void print_usage(char *progname)
{
    printf("%s usage: \n", progname);
    printf("  -p(--port): sepcify listen port.\n");
    printf("  -h(--Help): print this help information.\n");

    return ;
}

int main(int argc, char **argv)
{
    int                     rv = -1;
    int                     listen_fd,  client_fd = -1;
    int                     port = 10086;
    struct sockaddr_in      serv_addr;
    struct sockaddr_in      cli_addr;
    socklen_t               addr_len = sizeof(cli_addr);
    int                     reuse = 1;
    pthread_t               tid;

    int                     debug = 0;
    struct rlimit           limit;
    pid_t                   pid;

    int                     ch;
    struct option           opts[] = {
        {"debug", no_argument, NULL, 'd'},
        {"port", required_argument, NULL, 'p'},
        {"help", no_argument, NULL, 'h'},
        {NULL, 0, NULL, 0}
    };

    /* parser command line input arguments */
    while( (ch=getopt_long(argc, argv, "dp:h", opts, NULL)) != -1 )
    {
        switch(ch)
        {
            case 'd':
                debug = 1;
                break;

            case 'p':
                port=atoi(optarg);
                break;

            case 'h':
                print_usage(argv[0]);
                return 0;
        }
    }

    /* set Max. fd limit */
    getrlimit(RLIMIT_NOFILE, &limit);
    limit.rlim_cur = limit.rlim_max;
    setrlimit(RLIMIT_NOFILE, &limit);

    if( !debug )
    {
        daemon(0, 0);
    }

    /* install signal */
    //signal(SIGTERM, sig_handler);  /* capture kill/killall signal */
    //signal(SIGINT,  sig_handler);  /* capture Ctrl+C signal */
    signal(SIGSEGV, sig_handler);  /* capture segmentation fault signal */
    signal(SIGPIPE, sig_handler);  /* capture socket error signal */

    /* create TCP socket */
    listen_fd = socket(AF_INET, SOCK_STREAM, 0);
    if(listen_fd < 0 )
    {
        printf("create socket failure: %s\n", strerror(errno));
        return -1;
    }

    /* resolve the "Address already in use" error when using bind() */
    setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));

    /* bind socket server information */
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(port);
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    if( bind(listen_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0 )
    {
        printf("create socket failure: %s\n", strerror(errno));
        return -2;
    }
    printf("socket[%d] bind on port[%d] for all IP address ok\n", listen_fd, port);

    /* start listen socket */
    listen(listen_fd, BACKLOG);

    while( !g_stop )
    {
        /* accept new incoming socket client  */
        printf("\nStart waiting and accept new client connect...\n");
        client_fd = accept(listen_fd, (struct sockaddr*)&cli_addr, &addr_len);
        if(client_fd < 0)
        {
            printf("accept new socket failure: %s\n", strerror(errno));
            return -2;
        }
        printf("Accept new client[%s:%d] with fd [%d]\n", inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port), client_fd);

        /* create new thread to handle the client */
        pthread_create(&tid, NULL, workbody, (void *)(intptr_t)client_fd);
    }

    close(listen_fd);
    return 0;
}

void *workbody(void *ctx)
{
    int                  clifd;
    int                  rv;
    char                 buf[1024];
    int                  i;

    if( !ctx )
    {
        printf("Invalid input arguments in %s()\n", __FUNCTION__);
        pthread_exit(NULL);
    }

    clifd = (int)(intptr_t)ctx;

    pthread_detach(pthread_self());

    printf("New thread start to commuicate with socket client...\n");

    while(1)
    {
        /* receive data from socket client */
        memset(buf, 0, sizeof(buf));
        rv=read(clifd, buf, sizeof(buf));
        if( rv < 0)
        {
            printf("Read data from client sockfd[%d] failure: %s and thread will exit\n", clifd, strerror(errno));
            close(clifd);
            pthread_exit(NULL);
        }
        else if( rv == 0)
        {
            printf("Socket[%d] get disconnected and thread will exit.\n", clifd);
            close(clifd);
            pthread_exit(NULL);
        }
        else if( rv > 0 )
        {
            printf("Read %d bytes data from Server: %s\n", rv, buf);
        }

        /* convert letter from lowercase to uppercase */
        for(i=0; i<rv; i++)
        {
            buf[i]=toupper(buf[i]);
        }

        /* write back data to socket client */
        rv=write(clifd, buf, rv);
        if(rv < 0)
        {
            printf("Write to client by sockfd[%d] failure: %s and thread will exit\n", clifd, strerror(errno));
            close(clifd);
            pthread_exit(NULL);
        }
    }
}