//
// File: <vs_cgi.c>
//
// simple cgi program so can use a web server as a front end
// to vserver, some people behind firewalls can only talk to
// a web server.
//
// Written by: David M. Stanhope
//

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#include "timestamp.h"

static char server_name[] = "127.0.0.1";
static int  server_port   =  8009      ;

FILE *fp_debug = NULL;
#define LOG(x...) if(fp_debug) { fprintf(fp_debug, ## x); fflush(fp_debug); }

#define MSG2(x) // nothing
#define ERR(x)  LOG x

#define SOCKET int
#define Socket_Error() Show_Error()

static char *
Show_Error(void)
{
    static char buf[256];
    sprintf(buf, "%d:%s", errno, strerror(errno));
    return buf;
}

#include "util.c"

void
respond(char *msg)
{
    write(fileno(stdout), msg, strlen(msg) + 1);
}

// TODO: COULD MOVE THIS TO VSERVER SINCE MIGHT BE BETTER PLACE
char *
decode_escapes(char *src, char *dst)
{
    int c, t, esc_flag = 0;

    while(c = *src++)
    {
        if(esc_flag == 0)
        {
            if(c == '\\')
            {
                esc_flag = 1;
            }
            else
            {
                *dst++ = c;
            }
        }
        else if(esc_flag == 1)
        {
            if((c >= '0') && (c <= '9'))
            {
                t =  (c - '0');
            }
            else if((c >= 'A') && (c <= 'F'))
            {
                t = ((c - 'A') + 10);
            }
            else if((c >= 'a') && (c <= 'f'))
            {
                t = ((c - 'a') + 10);
            }
            else
            {
                return NULL; // return error
            }
            esc_flag = 2;
        }
        else if(esc_flag == 2)
        {
            if((c >= '0') && (c <= '9'))
            {
                *dst++ = ((t << 4) |  (c - '0'));
            }
            else if((c >= 'A') && (c <= 'F'))
            {
                *dst++ = ((t << 4) | ((c - 'A') + 10));
            }
            else if((c >= 'a') && (c <= 'f'))
            {
                *dst++ = ((t << 4) | ((c - 'a') + 10));
            }
            else
            {
                return NULL; // return error
            }
            esc_flag = 0;
        }
        else // bogus state, should never happen
        {
            return NULL; // return error
        }
    }

    if(esc_flag) // unfinished escape sequence
    {
        return NULL; // return error
    }

    *dst = '\0'; // insure valid termination

    return dst;
}

main(int argc, char *argv[])
{
    int fd, n, r, err = 0;
    char *p, *query_string, *peer_ip, *peer_port;
    char buf[4096];

    struct sockaddr_in server;

    if((query_string = getenv("QUERY_STRING")) == NULL) { err++; }
    if((peer_ip      = getenv("REMOTE_ADDR" )) == NULL) { err++; }
    if((peer_port    = getenv("REMOTE_PORT" )) == NULL) { err++; }

    fp_debug = fopen("/tmp/vs_cgi.log", "a");

    LOG("-----------------------------------------------------------\n")
    LOG("Connection at (%s)\n", timestamp())

    if(query_string) { LOG("QUERY_STRING(%s)\n"  , query_string) }
    if(peer_ip     ) { LOG("REMOTE_ADDRESS(%s)\n", peer_ip     ) }
    if(peer_port   ) { LOG("REMOTE_PORT(%s)\n"   , peer_port   ) }

    if(err)
    {
        LOG("Missing required info\n")
        exit(-1);
    }

    // client will have escaped the spaces in 'query' so un-escape them

    if((p = decode_escapes(query_string, buf)) == NULL)
    {
        LOG("BOGUS QUERY_STRING\n")
        exit(-1);
    }
    else
    {
        // add REMOTE_ADDRESS and REMOTE_PORT to message since 'vserver'
        // can't see client via getpeername()
        sprintf(p, "|peer_ip=%s|peer_port=%s", peer_ip, peer_port);
        // LOG("QUERY(%s)\n", buf)
    }

    // connect to 'vserver'
    if((fd = Connect_TCP(server_name, server_port)) < 0)
    {
        // error message already output
        exit(-1);
    }

    n = strlen(buf) + 1; // lenght + '\0'

    if((r = write(fd, buf, n)) != n) // send message to 'vserver'
    {
        LOG("Write To Server Failed, sent(%d), returned(%d)\n", n, r)
        close(fd);
        exit(-1);
    }

    // TODO: READ UNTIL TIMEOUT OR GET TRAILING '\0'

    n = read(fd, buf, sizeof(buf)); // get response from 'vserver'

    // TODO: ADD SOME VALIDATION

    close(fd);

    if(n < 0)
    {
        LOG("Response Error(%s)\n", Show_Error())
        exit(-1);
    }
    else if(n == 0)
    {
        LOG("Response Empty\n")
        exit(-1);
    }
    else if(buf[n - 1] != '\0')
    {
        LOG("Response Bogus, No EOS\n")
        exit(-1);
    }
    else
    {
        LOG("Response(%s)\n", buf);
    }

    // --------------------------------------------------
    // spit out minimum header to keep web-server happy
    // --------------------------------------------------

    fprintf(stdout, "Content-Type: text/html\n");
    fprintf(stdout, "\n");
    fflush(stdout);

    respond(buf);

    exit(0);
}

//
// The End!
//