/*
     This file is part of GNUnet.
     (C) 2012 Christian Grothoff (and other contributing authors)

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

#include "platform.h"
#include <gnunet_util_lib.h>
#include "gns_proxy_proto.h"
#include "gns.h"

#define GNUNET_GNS_PROXY_PORT 7777

//TODO maybe make this an api call
/**
 * Checks if name is in tld
 *
 * @param name the name to check
 * @param tld the TLD to check for
 * @return GNUNET_YES or GNUNET_NO
 */
int
is_tld(const char* name, const char* tld)
{
  int offset = 0;

  if (strlen(name) <= strlen(tld))
  {
    return GNUNET_NO;
  }

  offset = strlen(name)-strlen(tld);
  if (strcmp (name+offset, tld) != 0)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
               "%s is not in .%s TLD\n", name, tld);
    return GNUNET_NO;
  }

  return GNUNET_YES;
}

struct Socks5Request
{
  struct Socks5Request *prev;
  struct Socks5Request *next;

  struct GNUNET_NETWORK_Handle *sock;
  struct GNUNET_NETWORK_Handle *remote_sock;

  int state;

  GNUNET_SCHEDULER_TaskIdentifier rtask;
  GNUNET_SCHEDULER_TaskIdentifier wtask;

  char rbuf[512];
  char wbuf[512];
  unsigned int rbuf_len;
  unsigned int wbuf_len;
};

struct Socks5Connections
{
  struct Socks5Request *head;
  struct Socks5Request *tail;
};


unsigned long port = GNUNET_GNS_PROXY_PORT;
static struct GNUNET_NETWORK_Handle *lsock;
GNUNET_SCHEDULER_TaskIdentifier ltask;
static struct Socks5Connections s5conns;

/**
 * Write data to socket
 *
 * @param cls the closure
 * @param tc scheduler context
 */
static void
do_write (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct Socks5Request *s5r = cls;
  unsigned int len = s5r->wbuf_len;

  s5r->wtask = GNUNET_SCHEDULER_NO_TASK;

  if ((NULL != tc->read_ready) &&
      (GNUNET_NETWORK_fdset_isset (tc->write_ready, s5r->sock)) &&
      (len = GNUNET_NETWORK_socket_send (s5r->sock, &s5r->wbuf,
                                         len)))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Successfully sent %d bytes to socket\n",
                len);
  }
  else
  {
    GNUNET_NETWORK_socket_close (s5r->sock);
    GNUNET_free(s5r);
    return;
  }
}

/**
 * Read data from incoming connection
 *
 * @param cls the closure
 * @param tc the scheduler context
 */
static void
do_read (void* cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct Socks5Request *s5r = cls;
  unsigned int len;
  struct socks5_client_hello *c_hello;
  struct socks5_server_hello *s_hello;
  struct socks5_client_request *c_req;
  struct socks5_server_response *s_resp;

  char domain[256];
  uint8_t dom_len;
  uint16_t req_port;
  struct hostent *phost;
  uint32_t remote_ip;
  struct sockaddr_in remote_addr;
  struct in_addr *r_sin_addr;

  s5r->rtask = GNUNET_SCHEDULER_NO_TASK;

  if ((NULL != tc->write_ready) &&
      (GNUNET_NETWORK_fdset_isset (tc->read_ready, s5r->sock)) &&
      (len = GNUNET_NETWORK_socket_recv (s5r->sock, &s5r->rbuf,
                                         sizeof (s5r->rbuf))))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Successfully read %d bytes from socket\n",
                len);
  }
  else
  {
    //ERROR!
    GNUNET_NETWORK_socket_close (s5r->sock);
    GNUNET_free(s5r);
    return;
  }

  if (s5r->state == SOCKS5_INIT)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "SOCKS5 init\n");
    c_hello = (struct socks5_client_hello*)&s5r->rbuf;

    GNUNET_assert (c_hello->version == SOCKS_VERSION_5);

    s_hello = (struct socks5_server_hello*)&s5r->wbuf;
    s5r->wbuf_len = sizeof( struct socks5_server_hello );

    s_hello->version = c_hello->version;
    s_hello->auth_method = SOCKS_AUTH_NONE;

    /* Write response to client */
    s5r->wtask = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                                s5r->sock,
                                                &do_write, s5r);

    s5r->rtask = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                                s5r->sock,
                                                &do_read, s5r);

    s5r->state = SOCKS5_REQUEST;
    return;
  }

  if (s5r->state == SOCKS5_REQUEST)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Processing SOCKS5 request\n");
    c_req = (struct socks5_client_request*)&s5r->rbuf;
    s_resp = (struct socks5_server_response*)&s5r->wbuf;
    s5r->wbuf_len = sizeof (struct socks5_server_response);

    GNUNET_assert (c_req->addr_type == 3);

    dom_len = *((uint8_t*)(&(c_req->addr_type) + 1));
    memset(domain, 0, sizeof(domain));
    strncpy(domain, (char*)(&(c_req->addr_type) + 2), dom_len);
    req_port = *((uint16_t*)(&(c_req->addr_type) + 2 + dom_len));

    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Requested connection is %s:%d\n",
                domain,
                ntohs(req_port));

    if (is_tld (domain, GNUNET_GNS_TLD) ||
        is_tld (domain, GNUNET_GNS_TLD_ZKEY))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Requested connection is gnunet tld\n",
                  domain);
    }
    else
    {
      phost = (struct hostent*)gethostbyname (domain);
      if (phost == NULL)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                    "Resolve %s error!\n", domain );
        s_resp->version = 0x05;
        s_resp->reply = 0x01;
        s5r->wtask = 
          GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                          s5r->sock,
                                          &do_write, s5r);
        //ERROR!
        //TODO! close socket after the write! schedule task
        //GNUNET_NETWORK_socket_close (s5r->sock);
        //GNUNET_free(s5r);
        return;
      }

      s5r->remote_sock = GNUNET_NETWORK_socket_create (AF_INET,
                                                       SOCK_STREAM,
                                                       0);
      r_sin_addr = (struct in_addr*)(phost->h_addr);
      remote_ip = r_sin_addr->s_addr;
      memset(&remote_addr, 0, sizeof(remote_addr));
      remote_addr.sin_family = AF_INET;
      remote_addr.sin_addr.s_addr = remote_ip;
      remote_addr.sin_port = req_port;
      
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "target server: %s:%u\n", inet_ntoa(remote_addr.sin_addr),
                  ntohs(req_port));

      GNUNET_assert ( s5r->remote_sock != NULL );

      if (GNUNET_OK != 
          GNUNET_NETWORK_socket_connect ( s5r->remote_sock,
                                          (struct sockaddr*)&remote_addr,
                                          sizeof (struct sockaddr)))
      {
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                    "socket request error...\n");
        s_resp->version = 0x05;
        s_resp->reply = 0x01;
        s5r->wtask =
          GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                          s5r->sock,
                                          &do_write, s5r);
        //TODO see above
        return;
      }

      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "new remote connection\n");

      s_resp->version = 0x05;
      s_resp->reply = 0x00;
      s_resp->reserved = 0x00;
      s_resp->addr_type = 0x01;

      s5r->state = SOCKS5_DATA_TRANSFER;

      s5r->wtask =
        GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                        s5r->sock,
                                        &do_write, s5r);

    }
  }

  //GNUNET_CONTAINER_DLL_remove (s5conns.head, s5conns.tail, s5r);

}

/**
 * Accept new incoming connections
 *
 * @param cls the closure
 * @param tc the scheduler context
 */
static void
do_accept (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_NETWORK_Handle *s;
  struct Socks5Request *s5r;

  ltask = GNUNET_SCHEDULER_NO_TASK;
  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
    return;

  ltask = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                         lsock,
                                         &do_accept, NULL);

  s = GNUNET_NETWORK_socket_accept (lsock, NULL, NULL);

  if (NULL == s)
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_INFO, "accept");
    return;
  }

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Got an inbound connection, waiting for data\n");

  s5r = GNUNET_malloc (sizeof (struct Socks5Request));
  s5r->sock = s;
  s5r->state = SOCKS5_INIT;
  s5r->rtask = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                              s5r->sock,
                                              &do_read, s5r);
  GNUNET_CONTAINER_DLL_insert (s5conns.head, s5conns.tail, s5r);
}

/**
 * Main function that will be run
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg configuration
 */
static void
run (void *cls, char *const *args, const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  struct sockaddr_in sa;

  memset (&sa, 0, sizeof (sa));
  sa.sin_family = AF_INET;
  sa.sin_port = htons (port);
#if HAVE_SOCKADDR_IN_SIN_LEN
  sa.sin_len = sizeof (sa);
#endif

  lsock = GNUNET_NETWORK_socket_create (AF_INET,
                                        SOCK_STREAM,
                                        0);

  if ((NULL == lsock) ||
      (GNUNET_OK !=
       GNUNET_NETWORK_socket_bind (lsock, (const struct sockaddr *) &sa,
                                   sizeof (sa))))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to create listen socket bound to `%s'",
                GNUNET_a2s ((const struct sockaddr *) &sa, sizeof (sa)));
    if (NULL != lsock)
      GNUNET_NETWORK_socket_close (lsock);
    return;
  }

  if (GNUNET_OK != GNUNET_NETWORK_socket_listen (lsock, 5))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to listen on socket bound to `%s'",
                GNUNET_a2s ((const struct sockaddr *) &sa, sizeof (sa)));
    return;
  }

  ltask = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
                                         lsock, &do_accept, NULL);

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Proxy listens on port %u\n",
              port);

}

/**
 * The main function for gnunet-gns-proxy.
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main (int argc, char *const *argv)
{
  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
    {'p', "port", NULL,
     gettext_noop ("listen on specified port"), 1,
     &GNUNET_GETOPT_set_string, &port},
    GNUNET_GETOPT_OPTION_END
  };

  int ret;

  GNUNET_log_setup ("gnunet-gns-proxy", "WARNING", NULL);
  ret =
      (GNUNET_OK ==
       GNUNET_PROGRAM_run (argc, argv, "gnunet-gns-proxy",
                           _("GNUnet GNS proxy"),
                           options,
                           &run, NULL)) ? 0 : 1;
  return ret;
}