#ifndef WIN32
    #define _GNU_SOURCE
#endif

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

#ifdef WIN32
    #include <winsock.h>
    #include <windows.h>
    typedef int socklen_t;
#else
    #include <unistd.h>
    #include <sys/socket.h>
    #include <sys/types.h>
    #include <arpa/inet.h>
    #include <netinet/in.h>
    #include <netdb.h>
    #include <dlfcn.h>  // -ldl
    #define mysendto sendto
    static ssize_t (*old_sendto)(int s, void *buf, size_t len, int flags, struct sockaddr *to, int tolen) = NULL;
#endif



#define VER         "0.1"
#define PLAYERS     6



u_char *mymemmem(u_char *ptr, int offset, u_char *value, int valsz, int num) {
    int     i;

    if(valsz < 0) valsz = strlen(value);
    for(i = offset; i <= (num - valsz); i++) {
        if(!memcmp(ptr + i, value, valsz)) return(ptr + i + valsz);
    }
    return(NULL);
}



int myrand(void) {
    static int  rnd = 0;
    if(!rnd) rnd = time(NULL);
    rnd = ((rnd * 0x343FD) + 0x269EC3) >> 1;
    return(rnd & 0x7fffffff);
}



ssize_t __cdecl mysendto(int s, u_char **retbuf, int len, int flags, const struct sockaddr *to, int tolen) {
    int     i,
            chr  = '\\',    // default delimiter
            num  = 0,       // 0 players in the reply
            lame = 0;
    u_char  *new,           // it's automatically freed by proxocket
            *p;
    u_char  *buf = *retbuf; // do NOT touch this

#ifndef WIN32
    if(!old_sendto) old_sendto = dlsym(RTLD_NEXT, "sendto");
    len = old_sendto(s, buf, len, flags, to, tolen);
#endif

    if(len < 30) return(len);

    // Quake 3 getstatus
    if(!memcmp(buf, "\xff\xff\xff\xff" "statusResponse", 18)) {
        p = mymemmem(buf, 18 + 1, "\n", 1, len);
        if(p) {
            for(i = p - buf; i < len; i++) {
                if(p[i] == '\n') num++;
            }
        }
        if(num >= PLAYERS) return(len);

        new = malloc(len + 1024);
        memcpy(new, buf, len);
        buf = new;

        p = buf + len;
        for(; num < PLAYERS; num++) {
            p += sprintf(p, "%d %d \"BOssMan\"\n", myrand() % 50, num);
        }
        len = p - buf;

    } else {
        // Quake 3 getinfo
        if(!memcmp(buf, "\xff\xff\xff\xff" "infoResponse", 16)) {
            p = mymemmem(buf, 16, "\\clients\\", -1, len);
            if(!p) p = mymemmem(buf, 16, "\\players\\", -1, len);
            if(!p) p = mymemmem(buf, 16, "\\privateClients\\", -1, len);

        // Gamespy 2 and 3
        } else if(!memcmp(buf + 5, "hostname\0", 9)) {
            p = mymemmem(buf, 5, "\0""numplayers""\0", 1+10+1, len);
            chr = 0;

        // Half-Life
        } else if(!memcmp(buf, "\xff\xff\xff\xff" "infostringresponse", 22)) {
            p = mymemmem(buf, 14, "\\players\\", -1, len);

        // Half-Life (m)
        } else if(!memcmp(buf, "\xff\xff\xff\xff" "m", 5)) {
            p = buf + 5;
            for(i = 0; i < 5; i++) {
                p += strlen(p) + 1;
                if(p >= (buf + len)) return(len);
            }
            // p[0] is the number of players, trick
            chr = p[1]; // trick

        // Source (I)
        } else if(!memcmp(buf, "\xff\xff\xff\xff" "I", 5)) {
            p = buf + 5 + 1;
            for(i = 0; i < 6; i++) {
                p += strlen(p) + 1;
                if(p >= (buf + len)) return(len);
            }
            // p[0] is the number of players, trick
            chr = p[1]; // trick

        /*
        // Source (E): no players info in "rules"
        } else if(!memcmp(buf, "\xff\xff\xff\xff" "E", 5)) {
            p = mymemmem(buf, 5, "\0""clients""\0", 1+7+1, len);
            if(!p) p = mymemmem(buf, 5, "\0""players""\0", 1+7+1, len);
            chr = 0;
        */

        /*
        // Doom 3: not supported
        } else if(!memcmp(buf, "\xff\xff" "infoResponse", 14)) {
        */

        // Gamespy 1
        } else if(buf[0] == '\\') {
            p = mymemmem(buf, 0, "\\numplayers\\", -1, len);

        // All seeying eye
        } else if(!memcmp(buf, "EYE1", 4)) {
            p = buf + 4;
            for(i = 0; i < 7; i++) {
                if(!((p < (buf + len)) && (*p > 1))) return(len);
                p += *p;
            }
            p++;
            // p[0] is the number of players, trick
            chr = p[*p];    // trick

        } else {
            return(len);
        }
        if(!p) return(len); // boring

        if(*p < '0') lame = 1;  // it's only a lame trick for non textual players (max 47)

        if(lame) {
            num = *p;
        } else {
            num = atoi(p);
        }
        if((num < 0) || (num >= PLAYERS)) return(len);

        i = p - buf;
        new = malloc(len + 16);
        memcpy(new, buf, i);                // copy till the players parameter (included)
        p = new + i;
        if(lame) {
            *p++ = PLAYERS;
        } else {
            p += sprintf(p, "%d", PLAYERS); // put the new one
        }
        while(buf[i] != chr) i++;           // skip the old value
        memcpy(p, buf + i, len - i);        // copy the rest
        p += (len - i);
        buf = new;
        len = p - buf;
    }

    *retbuf = buf;  // do NOT touch this
    return(len);
}



#ifdef WIN32
BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpReserved) {
    if(fdwReason == DLL_PROCESS_ATTACH) DisableThreadLibraryCalls(hinstDLL);
    return(TRUE);
}
#endif