/** @file getopt_long.c
 ** @brief getopt_long - Definition
 ** @author Andrea Vedaldi
 **/

/*
Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
All rights reserved.

This file is part of the VLFeat library and is made available under
the terms of the BSD license (see the COPYING file).
*/

/**
@file   getopt_long.h
@brief  getopt_long
@author Andrea Vedaldi

This is a drop-in replacament of GNU getopt_long meant to be used
on platforms that do not support such functionality.
**/

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

#include "generic.h"
#include "getopt_long.h"

int    opterr = 1 ;
int    optind = 1 ;
int    optopt ;
char * optarg ;
int    optreset ;

#define BADCH	'?'
#define BADARG	':'
#define EEND    -1
#define EMSG	""

/** @brief Parse long options (BSD style)
 ** @param argc number of arguments.
 ** @param argv pointer to the vector of arguments.
 ** @param optstring list of abbreviated options
 ** @param longopts list of long options.
 ** @param longindex index of current option in @a longopts.
 ** @return the code of the next option.
 **
 ** This function extract long and short options from the argument
 ** list @a argv of @a argc entries.
 **
 ** A short options sequence is introduced by a single dash character
 ** @c -. Each short option is described by a single character in the
 ** string @a optstring, possibly followed by a @c : character to
 ** denote a (mandatory) argument of the short option. A short option
 ** with an argument cannot appear in the middle of a short option
 ** sequence, but only at the end.
 **
 ** A long option is introduced by a double dash @c --. Each long
 ** option is described by an instance of the ::option structure in
 ** the @a longopts table (the last entry must be filled with zeroes
 ** to denote the end).
 **
 ** Illegal options and missing arguments cause the function to skip
 ** the option and return '?'. If ::opterr is @c true (default), the
 ** function prints an error message to @a stderr. Finally, if @a
 ** optstring has a leading @c :, then error messages are suppressed
 ** and a missing argument causes @a : to be returned.
 **
 ** @remark The function is currently <em>not</em> thread safe.
 **/

VL_EXPORT int
getopt_long(int argc, char *const argv[],
            const char *optstring,
            const struct option * longopts,
            int *longindex)
{
  static char *place = EMSG;	/* option letter processing */
  static int   optbegin  = 0 ;
  static int   optend    = 0 ;
  char        *oli;		/* option letter list index */
  int          has_colon = 0 ;
  int          ret_val   = 0 ;

  /*
     A semicolon at the beginning of optstring has a special meaning.
     If we find one, we annote and remove it.
  */
  has_colon = optstring && optstring[0] == ':' ;
  if (has_colon) ++ optstring ;

  /*
   Here we are either processing a short option sequence or
   we start processing a new option. This is indicated by optreset.
  */

  if (optreset || *place == '\0') {

    /* ---------------------------------------------------------------
     *                                 Look for next short/long option
     * ------------------------------------------------------------ */
    optreset = 0 ;

    /* no more arguments ? */
    if (optind >= argc) {
      place = EMSG ;
      return -1 ;
    }

    /* next argument that may hold an option */
    optbegin = optind ;

    /* ---------------------------------------------------------------
     *                                     Look for an option to parse
     * ------------------------------------------------------------ */

  parse_option_at_optbegin :

    /* place points to the candidate option */
    place = argv [optbegin] ;

    /* an option is introduced by '-' */
    if (place [0] != '-') {
      /* this argument is not an option: try next argument */
      ++ optbegin ;
      if (optbegin >= argc) {
        /* no more arguments to look for options */
        place = EMSG ;
        return -1 ;
      }
      goto parse_option_at_optbegin ;
    }

    /* consume leading `-' */
    ++ place ;

    /* assume the option is composed of one argument only */
    optend = optbegin + 1 ;

    /* assume no argument */
    optarg = 0 ;

    /* ---------------------------------------------------------------
     *                                                     option `--'
     * ------------------------------------------------------------ */

    /* this special option (void long option) ends the option processing */
    if (place[0]        &&
        place[0] == '-' &&
        place[1] == '\0') {

      optind  = optend ;
      place   = EMSG ;
      ret_val = -1 ;
      goto done_option ;
    }

    /* ---------------------------------------------------------------
     *                                                     long option
     * ------------------------------------------------------------ */

    if (place[0]        &&
        place[0] == '-' &&
        place[1] ) {

      size_t namelen ;
      int i ;

      /* consume second `-' */
      ++ place ;

      /* count characters before `=' */
      namelen = strcspn(place, "=") ;

      /* scan longopts for this option */
      for (i = 0 ; longopts[i].name != NULL ; ++ i) {

        if (strlen  (       longopts[i].name) == namelen &&
            strncmp (place, longopts[i].name, namelen) == 0 ) {

          /* save back long option index */
          if (longindex) *longindex = i ;

          /* process long option argument */
          if (longopts[i].has_arg == required_argument ||
              longopts[i].has_arg == optional_argument) {

            /* --option=value style */
            if (place[namelen] == '=') {
              optarg = place + namelen + 1 ;
            }

            /* --option value style (only required_argument) */
            else if (longopts[i].has_arg == required_argument) {
              /* missing argument ? */
              if (optbegin >= argc - 1) {
                if (! has_colon && opterr)
                  fprintf(stderr,
                          "%s: option requires an argument -- %s\n",
                          argv[0], place);
                place   = EMSG ;
                ret_val = has_colon ? BADARG : BADCH ;
                goto done_option ;
              }
              optarg = argv [optend] ;
              ++ optend ;
            }
          }

          /* determine return value */
          if (longopts[i].flag == NULL) {
            ret_val = longopts[i].val ;
          }
          else {
            *longopts[i].flag = longopts[i].val;
            ret_val = 0 ;
          }

          /* mark sequence closed */
          place = EMSG ;
          goto done_option ;
        } /* if match */

      } /* scan longoptions */

      /* no matching option found */
      if (! has_colon && opterr)
        fprintf(stderr,
                "%s: illegal option -- %s\n", argv[0], place) ;
      place   = EMSG ;
      ret_val = BADCH ;
      goto done_option ;
    }
  } /* end new option */

  /* -----------------------------------------------------------------
   *                                      Finish short option sequence
   * -------------------------------------------------------------- */
  optopt = (int) *place++ ;

  /* search charcater in option list */
  oli = strchr(optstring, optopt);

  /* short option not found */
  if (!oli) {

    if (! has_colon && opterr)
      fprintf(stderr,
              "%s: illegal option -- %c\n",
              argv[0], optopt);

    if (*place) {
      /* more short options in the list */
      return BADCH ;
    }

    else {
      /* error occured as last option in the list */
      place   = EMSG ;
      ret_val = BADCH ;
      goto done_option ;
    }
  } /* end short option not found */

  if (oli[1] != ':') {
    /* short option with no argument */

    if (*place) {
      /* more short options in the list */
      return optopt ;
    }
    else {
      /* last option in the list */
      place   = EMSG ;
      ret_val = optopt ;
      goto done_option ;
    }

  } else {
    /* short option with argument */

    /* -ovalue style */
    if (*place) {
      optarg  = place ;
      place   = EMSG ;
      ret_val = optopt ;
      goto done_option ;
    }
    /* -o value style: missing argument */
    else if (optbegin >= argc - 1) {
      if (! has_colon && opterr)
        fprintf(stderr,
                "%s: option requires an argument -- %c\n",
                argv[0], optopt);
      place   = EMSG ;
      ret_val = has_colon ? BADARG : BADCH ;
      goto done_option ;
    }

    /* -o value style: process argument */
    optarg = argv [optend] ;
    ++ optend ;
    place   = EMSG ;
    ret_val = optopt ;
    goto done_option ;
  } /* short with argument */

 done_option :
  {
    int pos = optend - optbegin ;  /* n of circular shifts */
    int c   = pos ;

    while (c --) {
      int i ;
      char *tmp = argv [optend - 1] ;
      for (i = optend - 1 ; i > optind ; -- i) {
        ((char**)argv) [i] = argv [i-1] ;
      }
      ((char**)argv) [optind] = tmp ;
    }
    optind += pos ;
  }

  return ret_val ;
}