/*
 *  ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
 *
 *  Copyright (c) 1997-2014 ircd-hybrid development team
 *
 *  This program 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 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *  USA
 */

/*! \file parse.c
 * \brief The message parser.
 * \version $Id$
 */

#include "stdinc.h"
#include "client.h"
#include "parse.h"
#include "channel.h"
#include "hash.h"
#include "irc_string.h"
#include "ircd.h"
#include "numeric.h"
#include "log.h"
#include "send.h"
#include "conf.h"
#include "memory.h"
#include "s_user.h"
#include "s_serv.h"


/*
 * (based on orabidoo's parser code)
 *
 * This has always just been a trie. Look at volume III of Knuth ACP
 *
 *
 * ok, you start out with an array of pointers, each one corresponds
 * to a letter at the current position in the command being examined.
 *
 * so roughly you have this for matching 'trie' or 'tie'
 *
 * 't' points -> [MessageTree *] 'r' -> [MessageTree *] -> 'i'
 *   -> [MessageTree *] -> [MessageTree *] -> 'e' and matches
 *
 *                               'i' -> [MessageTree *] -> 'e' and matches
 *
 * BUGS (Limitations!)
 *
 * I designed this trie to parse ircd commands. Hence it currently
 * casefolds. This is trivial to fix by increasing MAXPTRLEN.
 * This trie also "folds" '{' etc. down. This means, the input to this
 * trie must be alpha tokens only. This again, is a limitation that
 * can be overcome by increasing MAXPTRLEN to include upper/lower case
 * at the expense of more memory. At the extreme end, you could make
 * MAXPTRLEN 128.
 *
 * This is also not a patricia trie. On short ircd tokens, this is
 * not likely going to matter.
 *
 * Diane Bruce (Dianora), June 6 2003
 */

#define MAXPTRLEN 32
                                /* Must be a power of 2, and
				 * larger than 26 [a-z]|[A-Z]
				 * its used to allocate the set
				 * of pointers at each node of the tree
				 * There are MAXPTRLEN pointers at each node.
				 * Obviously, there have to be more pointers
				 * Than ASCII letters. 32 is a nice number
				 * since there is then no need to shift
				 * 'A'/'a' to base 0 index, at the expense
				 * of a few never used pointers. For a small
				 * parser like this, this is a good compromise
				 * and does make it somewhat faster.
				 *
				 * - Dianora
				 */

struct MessageTree
{
  int links; /* Count of all pointers (including msg) at this node
              * used as reference count for deletion of _this_ node.
              */
  struct Message *msg;
  struct MessageTree *pointers[MAXPTRLEN];
};

static struct MessageTree msg_tree;

static char *para[MAXPARA + 2]; /* <prefix> + <params> + NULL */

static int cancel_clients(struct Client *, struct Client *, char *);
static void remove_unknown(struct Client *, char *, char *);
static void handle_numeric(char[], struct Client *, struct Client *, int, char *[]);
static void handle_command(struct Message *, struct Client *, struct Client *, unsigned int, char *[]);


/*
 * parse a buffer.
 *
 * NOTE: parse() should not be called recusively by any other functions!
 */
void
parse(struct Client *client_p, char *pbuffer, char *bufend)
{
  struct Client *from = client_p;
  struct Message *msg_ptr = NULL;
  char *ch = NULL;
  char *s = NULL;
  char *numeric = NULL;
  unsigned int parc = 0;
  unsigned int paramcount;

  if (IsDefunct(client_p))
    return;

  assert(client_p->localClient->fd.flags.open);
  assert((bufend - pbuffer) < IRCD_BUFSIZE);

  for (ch = pbuffer; *ch == ' '; ++ch)  /* skip spaces */
    /* null statement */  ;

  if (*ch == ':')
  {
    /*
     * Copy the prefix to 'sender' assuming it terminates
     * with SPACE (or NULL, which is an error, though).
     */
    char *sender = ++ch;

    if ((s = strchr(ch, ' ')) != NULL)
    {
      *s = '\0';
      ch = ++s;
    }

    if (*sender && IsServer(client_p))
    {
      if ((from = find_person(client_p, sender)) == NULL)
        from = hash_find_server(sender);

      /*
       * Hmm! If the client corresponding to the prefix is not found--what is
       * the correct action??? Now, I will ignore the message (old IRC just
       * let it through as if the prefix just wasn't there...) --msa
       */
      if (from == NULL)
      {
        ++ServerStats.is_unpf;
        remove_unknown(client_p, sender, pbuffer);
        return;
      }

      if (from->from != client_p)
      {
        ++ServerStats.is_wrdi;
        cancel_clients(client_p, from, pbuffer);
        return;
      }
    }

    while (*ch == ' ')
      ++ch;
  }

  if (*ch == '\0')
  {
    ++ServerStats.is_empt;
    return;
  }

  /*
   * Extract the command code from the packet. Point s to the end
   * of the command code and calculate the length using pointer
   * arithmetic. Note: only need length for numerics and *all*
   * numerics must have parameters and thus a space after the command
   * code. -avalon
   */

  /* EOB is 3 chars long but is not a numeric */
  if (*(ch + 3) == ' ' && /* ok, lets see if its a possible numeric.. */
      IsDigit(*ch) && IsDigit(*(ch + 1)) && IsDigit(*(ch + 2)))
  {
    numeric = ch;
    paramcount = 2;  /* destination, and the rest of it */
    ++ServerStats.is_num;
    s = ch + 3;  /* I know this is ' ' from above if            */
    *s++ = '\0';  /* blow away the ' ', and point s to next part */
  }
  else
  {
    unsigned int ii = 0;

    if ((s = strchr(ch, ' ')) != NULL)
      *s++ = '\0';

    if ((msg_ptr = find_command(ch)) == NULL)
    {
      /*
       * Note: Give error message *only* to recognized
       * persons. It's a nightmare situation to have
       * two programs sending "Unknown command"'s or
       * equivalent to each other at full blast....
       * If it has got to person state, it at least
       * seems to be well behaving. Perhaps this message
       * should never be generated, though...  --msa
       * Hm, when is the buffer empty -- if a command
       * code has been found ?? -Armin
       */
      if (*pbuffer != '\0')
      {
        if (IsClient(from))
          sendto_one(from, form_str(ERR_UNKNOWNCOMMAND),
                     me.name, from->name, ch);
      }

      ++ServerStats.is_unco;
      return;
    }

    assert(msg_ptr->cmd != NULL);

    paramcount = msg_ptr->args_max;
    ii = bufend - ((s) ? s : ch);
    msg_ptr->bytes += ii;
  }

  /*
   * Must the following loop really be so devious? On surface it
   * splits the message to parameters from blank spaces. But, if
   * paramcount has been reached, the rest of the message goes into
   * this last parameter (about same effect as ":" has...) --msa
   */

  /* Note initially true: s==NULL || *(s-1) == '\0' !! */

  para[parc] = from->name;

  if (s)
  {
    if (paramcount > MAXPARA)
      paramcount = MAXPARA;

    while (1)
    {
       while (*s == ' ')
         *s++ = '\0';

       if (*s == '\0')
         break;

       if (*s == ':')
       {
         /* The rest is a single parameter */
         para[++parc] = s + (!numeric);  /* keep the colon if it's a numeric */
         break;
       }

       para[++parc] = s;

       if (parc >= paramcount)
         break;

       while (*s && *s != ' ')
         ++s;
    }
  }

  para[++parc] = NULL;

  if (msg_ptr != NULL)
    handle_command(msg_ptr, client_p, from, parc, para);
  else
    handle_numeric(numeric, client_p, from, parc, para);
}

/* handle_command()
 *
 * inputs	- pointer to message block
 *		- pointer to client
 *		- pointer to client message is from
 *		- count of number of args
 *		- pointer to argv[] array
 * output	- -1 if error from server
 * side effects	-
 */
static void
handle_command(struct Message *mptr, struct Client *client_p,
               struct Client *from, unsigned int i, char *hpara[])
{
  MessageHandler handler = 0;

  if (IsServer(client_p))
    mptr->rcount++;

  mptr->count++;

  handler = mptr->handlers[client_p->handler];

  /* check right amount of params is passed... --is */
  if (i < mptr->args_min)
  {
    if (!IsServer(client_p))
    {
      sendto_one(client_p, form_str(ERR_NEEDMOREPARAMS), me.name,
                 EmptyString(hpara[0]) ? "*" : hpara[0], mptr->cmd);
    }
    else
    {
      sendto_realops_flags(UMODE_ALL, L_ALL, SEND_NOTICE,
                           "Dropping server %s due to (invalid) command '%s' "
                           "with only %d arguments (expecting %d).",
                           client_p->name, mptr->cmd, i, mptr->args_min);
      ilog(LOG_TYPE_IRCD, "Insufficient parameters (%d) for command '%s' from %s.",
           i, mptr->cmd, client_p->name);
      exit_client(client_p, client_p,
                  "Not enough arguments to server command.");
    }
  }
  else
    (*handler)(client_p, from, i, hpara);
}

/* add_msg_element()
 *
 * inputs	- pointer to MessageTree
 *		- pointer to Message to add for given command
 *		- pointer to current portion of command being added
 * output	- NONE
 * side effects	- recursively build the Message Tree ;-)
 */
/*
 * How this works.
 *
 * The code first checks to see if its reached the end of the command
 * If so, that struct MessageTree has a msg pointer updated and the links
 * count incremented, since a msg pointer is a reference.
 * Then the code descends recursively, building the trie.
 * If a pointer index inside the struct MessageTree is NULL a new
 * child struct MessageTree has to be allocated.
 * The links (reference count) is incremented as they are created
 * in the parent.
 */
static void
add_msg_element(struct MessageTree *mtree_p, struct Message *msg_p,
                const char *cmd)
{
  struct MessageTree *ntree_p;

  if (*cmd == '\0')
  {
    mtree_p->msg = msg_p;
    mtree_p->links++;  /* Have msg pointer, so up ref count */
  }
  else
  {
    /*
     * *cmd & (MAXPTRLEN-1)
     * convert the char pointed to at *cmd from ASCII to an integer
     * between 0 and MAXPTRLEN.
     * Thus 'A' -> 0x1 'B' -> 0x2 'c' -> 0x3 etc.
     */
    if ((ntree_p = mtree_p->pointers[*cmd & (MAXPTRLEN - 1)]) == NULL)
    {
      ntree_p = MyMalloc(sizeof(struct MessageTree));
      mtree_p->pointers[*cmd & (MAXPTRLEN - 1)] = ntree_p;

      mtree_p->links++;  /* Have new pointer, so up ref count */
    }

    add_msg_element(ntree_p, msg_p, cmd + 1);
  }
}

/* del_msg_element()
 *
 * inputs	- Pointer to MessageTree to delete from
 *		- pointer to command name to delete
 * output	- NONE
 * side effects	- recursively deletes a token from the Message Tree ;-)
 */
/*
 * How this works.
 *
 * Well, first off, the code recursively descends into the trie
 * until it finds the terminating letter of the command being removed.
 * Once it has done that, it marks the msg pointer as NULL then
 * reduces the reference count on that allocated struct MessageTree
 * since a command counts as a reference.
 *
 * Then it pops up the recurse stack. As it comes back up the recurse
 * The code checks to see if the child now has no pointers or msg
 * i.e. the links count has gone to zero. If its no longer used, the
 * child struct MessageTree can be deleted. The parent reference
 * to this child is then removed and the parents link count goes down.
 * Thus, we continue to go back up removing all unused MessageTree(s)
 */
static void
del_msg_element(struct MessageTree *mtree_p, const char *cmd)
{
  struct MessageTree *ntree_p;

  /*
   * In case this is called for a nonexistent command
   * check that there is a msg pointer here, else links-- goes -ve
   * -db
   */
  if ((*cmd == '\0') && (mtree_p->msg != NULL))
  {
    mtree_p->msg = NULL;
    mtree_p->links--;
  }
  else
  {
    if ((ntree_p = mtree_p->pointers[*cmd & (MAXPTRLEN - 1)]) != NULL)
    {
      del_msg_element(ntree_p, cmd + 1);

      if (ntree_p->links == 0)
      {
        mtree_p->pointers[*cmd & (MAXPTRLEN - 1)] = NULL;
        mtree_p->links--;
        MyFree(ntree_p);
      }
    }
  }
}

/* msg_tree_parse()
 *
 * inputs	- Pointer to command to find
 *		- Pointer to MessageTree root
 * output	- Find given command returning Message * if found NULL if not
 * side effects	- none
 */
static struct Message *
msg_tree_parse(const char *cmd)
{
  struct MessageTree *mtree = &msg_tree;
  assert(cmd && *cmd);

  while (IsAlpha(*cmd) && (mtree = mtree->pointers[*cmd & (MAXPTRLEN - 1)]))
    if (*++cmd == '\0')
      return mtree->msg;

  return NULL;
}

/* mod_add_cmd()
 *
 * inputs	- pointer to struct Message
 * output	- none
 * side effects - load this one command name
 *		  msg->count msg->bytes is modified in place, in
 *		  modules address space. Might not want to do that...
 */
void
mod_add_cmd(struct Message *msg)
{
  assert(msg && msg->cmd);

  /* command already added? */
  if (msg_tree_parse(msg->cmd))
    return;

  add_msg_element(&msg_tree, msg, msg->cmd);
  msg->count = msg->rcount = msg->bytes = 0;
}

/* mod_del_cmd()
 *
 * inputs	- pointer to struct Message
 * output	- none
 * side effects - unload this one command name
 */
void
mod_del_cmd(struct Message *msg)
{
  assert(msg && msg->cmd);

  if (!msg_tree_parse(msg->cmd))
    return;

  del_msg_element(&msg_tree, msg->cmd);
}

/* find_command()
 *
 * inputs	- command name
 * output	- pointer to struct Message
 * side effects - none
 */
struct Message *
find_command(const char *cmd)
{
  return msg_tree_parse(cmd);
}

static void
recurse_report_messages(struct Client *source_p, const struct MessageTree *mtree)
{
  unsigned int i;

  if (mtree->msg != NULL)
    sendto_one(source_p, form_str(RPL_STATSCOMMANDS),
               me.name, source_p->name, mtree->msg->cmd,
               mtree->msg->count, mtree->msg->bytes,
               mtree->msg->rcount);

  for (i = 0; i < MAXPTRLEN; ++i)
    if (mtree->pointers[i] != NULL)
      recurse_report_messages(source_p, mtree->pointers[i]);
}

/* report_messages()
 *
 * inputs	- pointer to client to report to
 * output	- NONE
 * side effects	- client is shown list of commands
 */
void
report_messages(struct Client *source_p)
{
  const struct MessageTree *mtree = &msg_tree;
  unsigned int i;

  for (i = 0; i < MAXPTRLEN; ++i)
    if (mtree->pointers[i] != NULL)
      recurse_report_messages(source_p, mtree->pointers[i]);
}

/* cancel_clients()
 *
 * inputs	-
 * output	-
 * side effects	-
 */
static int
cancel_clients(struct Client *client_p, struct Client *source_p, char *cmd)
{
  /*
   * Kill all possible points that are causing confusion here,
   * I'm not sure I've got this all right...
   * - avalon
   *
   * Knowing avalon, probably not.
   */

  /*
   * With TS, fake prefixes are a common thing, during the
   * connect burst when there's a nick collision, and they
   * must be ignored rather than killed because one of the
   * two is surviving.. so we don't bother sending them to
   * all ops everytime, as this could send 'private' stuff
   * from lagged clients. we do send the ones that cause
   * servers to be dropped though, as well as the ones from
   * non-TS servers -orabidoo
   */
  /*
   * Incorrect prefix for a server from some connection. If it is a
   * client trying to be annoying, just QUIT them, if it is a server
   * then the same deal.
   */
  if (IsServer(source_p) || IsMe(source_p))
  {
    sendto_realops_flags(UMODE_DEBUG, L_ADMIN, SEND_NOTICE,
                         "Message for %s[%s] from %s",
                         source_p->name, source_p->from->name,
                         get_client_name(client_p, SHOW_IP));
    sendto_realops_flags(UMODE_DEBUG, L_OPER, SEND_NOTICE,
                         "Message for %s[%s] from %s",
                         source_p->name, source_p->from->name,
                         get_client_name(client_p, MASK_IP));
    sendto_realops_flags(UMODE_DEBUG, L_ALL, SEND_NOTICE,
                         "Not dropping server %s (%s) for Fake Direction",
                         client_p->name, source_p->name);
    return -1;
    /* return exit_client(client_p, client_p, &me, "Fake Direction");*/
  }

  /*
   * Ok, someone is trying to impose as a client and things are
   * confused. If we got the wrong prefix from a server, send out a
   * kill, else just exit the lame client.
   */
  /*
   * If the fake prefix is coming from a TS server, discard it
   * silently -orabidoo
   *
   * all servers must be TS these days --is
   */
  sendto_realops_flags(UMODE_DEBUG, L_ADMIN, SEND_NOTICE,
                       "Message for %s[%s@%s!%s] from %s (TS, ignored)",
                       source_p->name, source_p->username, source_p->host,
                       source_p->from->name, get_client_name(client_p, SHOW_IP));
  sendto_realops_flags(UMODE_DEBUG, L_OPER, SEND_NOTICE,
                       "Message for %s[%s@%s!%s] from %s (TS, ignored)",
                       source_p->name, source_p->username, source_p->host,
                       source_p->from->name, get_client_name(client_p, MASK_IP));

  return 0;
}

/* remove_unknown()
 *
 * inputs	-
 * output	-
 * side effects	-
 */
static void
remove_unknown(struct Client *client_p, char *lsender, char *lbuffer)
{
  /*
   * Do kill if it came from a server because it means there is a ghost
   * user on the other server which needs to be removed. -avalon
   * Tell opers about this. -Taner
   */
  /*
   * '[0-9]something'  is an ID      (KILL/SQUIT depending on its length)
   * 'nodots'          is a nickname (KILL)
   * 'no.dot.at.start' is a server   (SQUIT)
   */
  if ((IsDigit(*lsender) && strlen(lsender) <= IRC_MAXSID) ||
      strchr(lsender, '.') != NULL)
  {
    sendto_realops_flags(UMODE_DEBUG, L_ADMIN, SEND_NOTICE,
                         "Unknown prefix (%s) from %s, Squitting %s",
                         lbuffer, get_client_name(client_p, SHOW_IP), lsender);
    sendto_realops_flags(UMODE_DEBUG, L_OPER, SEND_NOTICE,
                         "Unknown prefix (%s) from %s, Squitting %s",
                         lbuffer, client_p->name, lsender);
    sendto_one(client_p, ":%s SQUIT %s :(Unknown prefix (%s) from %s)",
               me.name, lsender, lbuffer, client_p->name);
  }
  else
    sendto_one(client_p, ":%s KILL %s :%s (Unknown Client)",
               me.name, lsender, me.name);
}

/*
 *
 *      parc    number of arguments ('sender' counted as one!)
 *      parv[0] pointer to 'sender' (may point to empty string) (not used)
 *      parv[1]..parv[parc-1]
 *              pointers to additional parameters, this is a NULL
 *              terminated list (parv[parc] == NULL).
 *
 * *WARNING*
 *      Numerics are mostly error reports. If there is something
 *      wrong with the message, just *DROP* it! Don't even think of
 *      sending back a neat error message -- big danger of creating
 *      a ping pong error message...
 *
 * Rewritten by Nemesi, Jan 1999, to support numeric nicks in parv[1]
 *
 * Called when we get a numeric message from a remote _server_ and we are
 * supposed to forward it somewhere. Note that we always ignore numerics sent
 * to 'me' and simply drop the message if we can't handle with this properly:
 * the savvy approach is NEVER generate an error in response to an... error :)
 */
static void
handle_numeric(char numeric[], struct Client *client_p, struct Client *source_p,
               int parc, char *parv[])
{
  struct Client *target_p = NULL;
  struct Channel *chptr = NULL;

  /*
   * Avoid trash, we need it to come from a server and have a target
   */
  if (parc < 2 || !IsServer(source_p))
    return;

  /*
   * Who should receive this message ? Will we do something with it ?
   * Note that we use findUser functions, so the target can't be neither
   * a server, nor a channel (?) nor a list of targets (?) .. u2.10
   * should never generate numeric replies to non-users anyway
   * Ahem... it can be a channel actually, csc bots use it :\ --Nem
   */
  if (IsChanPrefix(*parv[1]))
    chptr = hash_find_channel(parv[1]);
  else
    target_p = find_person(client_p, parv[1]);

  if (((!target_p) || (target_p->from == client_p)) && !chptr)
    return;

  /*
   * Remap low number numerics, not that I understand WHY.. --Nemesi
   */
  /*
   * Numerics below 100 talk about the current 'connection', you're not
   * connected to a remote server so it doesn't make sense to send them
   * remotely - but the information they contain may be useful, so we
   * remap them up. Weird, but true.  -- Isomer
   */
  if (numeric[0] == '0')
    numeric[0] = '1';

  if (target_p)
  {
    /* Fake it for server hiding, if its our client */
    if (ConfigServerHide.hide_servers && MyClient(target_p) &&
        !HasUMode(target_p, UMODE_OPER))
      sendto_one(target_p, ":%s %s %s %s", me.name, numeric, target_p->name, parv[2]);
    else
      sendto_one(target_p, ":%s %s %s %s", ID_or_name(source_p, target_p),
                 numeric, ID_or_name(target_p, target_p), parv[2]);
  }
  else
    sendto_channel_butone(client_p, source_p, chptr, 0, "%s %s %s",
                          numeric, chptr->chname, parv[2]);
}

/* m_not_oper()
 * inputs	-
 * output	-
 * side effects	- just returns a nastyogram to given user
 */
int
m_not_oper(struct Client *client_p, struct Client *source_p,
           int parc, char *parv[])
{
  sendto_one(source_p, form_str(ERR_NOPRIVILEGES),
             me.name, source_p->name);
  return 0;
}

int
m_unregistered(struct Client *client_p, struct Client *source_p,
               int parc, char *parv[])
{
  sendto_one(source_p, form_str(ERR_NOTREGISTERED), me.name,
             source_p->name[0] ? source_p->name : "*");
  return 0;
}

int
m_registered(struct Client *client_p, struct Client *source_p,
             int parc, char *parv[])
{
  sendto_one(source_p, form_str(ERR_ALREADYREGISTRED),
             me.name, source_p->name);
  return 0;
}

int
m_ignore(struct Client *client_p, struct Client *source_p,
         int parc, char *parv[])
{
  return 0;
}