#include <stdio.h>
#include <stdlib.h>

#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
#include <sys/times.h>
#include <sys/unistd.h>
#include <float.h>

#define MAX_STR 64
char *DEFAULT_HOST = "localhost";
u_char *DEFAULT_COMMUNITY = (u_char *) "public";

oid OID[256] = {1, 3, 6, 1, 2, 1, 4, 21, 1, 1, 0, 0, 0, 0};
oid OID_LEN = 10;
int ip[4];
char tmp[MAX_STR];

/* funkce pro prevod IP adresy ulozene ve strukture variable_list
na retezec s ciselnym vyjadrenim */
void str2ip(struct variable_list *vars, char *str)
{
    char tmp[MAX_STR];
    int i;
    
    for (i = 0; i < vars->val_len - 1; i++)
    {
        sprintf(tmp, "%d.", *(vars->val.string + i));
        strcat(str, tmp);
//        ip[i] = atoi(tmp);
    }

    sprintf(tmp, "%d", *(vars->val.string + i));
    strcat(str, tmp);
//    ip[3] = atoi(tmp);
    
}

int main(int argc, char** argv)
{
    struct snmp_session session, *ss;
    struct snmp_pdu *pdu = NULL;
    struct snmp_pdu *response = NULL;
    struct variable_list *vars = NULL;
    struct timeval sendtv, rectv;
    struct tm *tm;
    FILE *logfile;

    int status;

    int interface = -1;
    char dest[MAX_STR];
    char next[MAX_STR];
    char mask[MAX_STR];

    dest[0] = '\0';
    next[0] = '\0';
    mask[0] = '\0';

    long last = -1;
    long current = -1;
    int loop = 1;

    clock_t starttime, stoptime;
    struct tms cas;
    int clk_tck;

    float diff;
    float min = FLT_MAX;
    float max = 0;
    float sum = 0;
    int count = 0;

    init_snmp("snmpclient");
    snmp_sess_init(&session);

    /* zpracovani vstupu a nastaveni serveru a community */
    switch (argc)
    {
    case 1:
        session.peername = DEFAULT_HOST;
        session.community = DEFAULT_COMMUNITY;
        break;

    case 2:
        session.peername = argv[1];
        session.community = DEFAULT_COMMUNITY;
        break;

    case 3:
        session.peername = argv[1];
        session.community = (u_char*) argv[2];
        break;
        
    default:
        printf("Usage: snmpclient [host [community]]\n");
        exit(1);
    }

    session.community_len = strlen((char*) session.community);
    session.version = SNMP_VERSION_1;

    /* vytvoreni spojeni */
    ss = snmp_open(&session);
    if (!ss)
    {
        printf("Could not connect to %s\n", session.peername);
        exit(1);
    }

    /* otevreni logovaciho souboru */
    if ((logfile = fopen("snmpclient.log", "w")) == NULL)
    {
        printf("Can not open logfile.\n");
        exit(1);
    }

    /* zjisteni poctu tiku casovace za sekundu */
    clk_tck = sysconf(_SC_CLK_TCK);

    /* vypis hlavicky vystupu */
    printf("hostname: %s\n", session.peername);
    printf("community: %s\n", session.community);
    printf("Tabulka: .iso.org.dod.internet.mgmt.mib-2.ip.ipRouteTable\n");
    printf("OID:     .1.3.6.1.2.1.4.21\n\n");

    printf("Sloupecek: ipRouteDest    (OID: .1.3.6.1.2.1.4.21.1.1)\n");
    printf("Sloupecek: ipRouteIfIndex (OID: .1.3.6.1.2.1.4.21.1.2)\n");
    printf("Sloupecek: ipRouteNextHop (OID: .1.3.6.1.2.1.4.21.1.7)\n");
    printf("Sloupecek: ipRouteMask    (OID: .1.3.6.1.2.1.4.21.1.11)\n\n");

    printf("ipRouteIfIndex ipRouteDest      ipRouteNextHop   ipRouteMask\n");
    printf("------------------------------------------------------------\n");

    fprintf(logfile, "request time     response time    OID\n");
    fprintf(logfile, "-------------------------------------------------------------\n");

    while (loop)
    {
        /* vytvoreni pozadavku */
        pdu = snmp_pdu_create(SNMP_MSG_GETNEXT);
        snmp_add_null_var(pdu, OID, OID_LEN);
        pdu->variables->type = 6;

        /* odeslani pozadavku */
        starttime = times(&cas);
        gettimeofday(&sendtv, NULL);
        status = snmp_synch_response(ss, pdu, &response);
        stoptime = times(&cas);
        gettimeofday(&rectv, NULL);

        /* zapis hodnot do logu */
        tm = localtime(&sendtv.tv_sec);
        fprintf(logfile, "%.2d:%.2d:%.2d.%.3d  ", tm->tm_hour, tm->tm_min, tm->tm_sec, (int) sendtv.tv_usec);
        tm = localtime(&rectv.tv_sec);
        fprintf(logfile, "%.2d:%.2d:%.2d.%.3d  ", tm->tm_hour, tm->tm_min, tm->tm_sec, (int) rectv.tv_usec);
        fprint_objid(logfile, OID, OID_LEN);

        /* vypocet casovych statistik */
        diff = (stoptime - starttime) / (double) clk_tck;
        sum += diff;

        if (diff < min)
        {
            min = diff;
        }

        if (diff > max)
        {
            max = diff;
        }

        count++;

        /* zpracovani odpovedi */
        if (status == STAT_SUCCESS && response->errstat == SNMP_ERR_NOERROR)
        {

            vars = response->variables;

            if (vars->type == ASN_APPLICATION)
            {
                vars->val.string[vars->val_len] = '\0';

                switch (OID[9])
                {
                case 1:
                    dest[0] = '\0';
                    str2ip(vars, dest);
                    current = *vars->val.integer;
                    int i;
                    for (i = 0; i < vars->val_len; i++)
                    {
                      sprintf(tmp, "%d.", *(vars->val.string + i));
                      ip[i] = atoi(tmp);
                    }
                    break;

                case 7:
                    next[0] = '\0';
                    str2ip(vars, next);
                    break;

                case 11:
                    mask[0] = '\0';
                    str2ip(vars, mask);
                    break;

                }
                
            }
            else if (OID[9] == 2)
            {
                interface = (int) * vars->val.integer;
            }
            else if (OID[9] == 1)
            {
                loop = 0;

            }

        }
        else if (status == STAT_SUCCESS)
        {
            fprintf(stderr, "Error: %s\n", snmp_errstring(response->errstat));
        }
        else
        {
            snmp_sess_perror("snmpget", ss);
        }

        if (response)
        {
            snmp_free_pdu(response);
        }

        if (OID[9] == 11)
        {
            if (current != last || 1)
            {
                printf("%-14d %-16s %-16s %-16s\n", interface, dest, next, mask);
            }
            last = current;
        }

        switch (OID[9])
        {
        case 1:
            OID[9] = 2;
            break;
            
        case 2:
            OID[9] = 7;
            break;
            
        case 7:
            OID[9] = 11;
            break;
            
        case 11:
            OID[9] = 1;
            OID_LEN = 14;
            int i;
            for (i = 0; i < 4; i++) {
              OID[10 + i] = ip[i];
            }
            break;

        }

    }

    snmp_close(ss);

    /* zapis statistik do logu */
    fprintf(logfile, "\nMinimum response time: %d ms\n", (int) (min * 1000));
    fprintf(logfile, "Maximum response time: %d ms\n", (int) (max * 1000));
    fprintf(logfile, "Average response time: %d ms\n", (int) (sum * 1000 / count));

    fclose(logfile);

    printf("\n");

    return 0;
}