/* -*- Mode: C; fill-column: 79 -*- *******************************************
*******************************************************************************
 unprefix.c
 Time-stamp: <1998-08-10 19:47:13 awk@oxygene.vnet.net>
 by Alexander Kourakos <Alexander@Kourakos.com>

 This UDF for mySQL strips one article off the front of a string, for
 example, ``The Grapes of Wrath'' -> ``Grapes of Wrath''.

 It was originally designed for a music database. Sometimes musical artists
 put ``The'' in front of their names, sometimes not. With this function, you
 could do something like:
     SELECT DISTINCT unprefix(ArtistName) FROM db ORDER BY 1
 or
     SELECT Title,ArtistName,unprefix(ArtistName) FROM db ORDER BY 3,1
 and just use the first two columns in your application.

 After a while, using the mySQL built-ins was too messy so I wrote this
 function. I hope someone finds it useful!
*******************************************************************************
******************************************************************************/

#include <global.h>
#include <my_sys.h>
#include <mysql.h>
#include <m_string.h>
#include <m_ctype.h>

typedef struct ignorestruct {
  size_t l;
  char *s;
} ignorestruct;

/*
 * The table currently contains English and French articles.
 */

static const ignorestruct ignore[] = {
  { 2, "a "   },
  { 3, "an "  },
  { 4, "the " },
  { 3, "la "  },
  { 3, "le "  },
  { 2, "l'"   },
  { 0, NULL   }
};

my_bool unprefix_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void unprefix_deinit(UDF_INIT *);
char *unprefix(UDF_INIT *initid, UDF_ARGS *args, char *result,
               unsigned long *length, char *is_null, char *error);

my_bool unprefix_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count != 1 || args->arg_type[0] != STRING_RESULT) {
    strmov(message, "Wrong argument(s) to unprefix(STRING).");
    return 1;
  }
  return 0;
}

void unprefix_deinit(UDF_INIT *initid)
{
}

char *unprefix(UDF_INIT *initid, UDF_ARGS *args, char *result,
               unsigned long *length, char *is_null, char *error)
{
  char *the_str = args->args[0];
  unsigned long the_len = args->lengths[0];
  const ignorestruct *p;

  if (!the_str) {
    *is_null = 1;
    return NULL;
  }

  for (p = ignore; p->l > 0; ++p)
    if (!strncasecmp(p->s, the_str, p->l)) {
      the_str += p->l;
      the_len -= p->l;
      break;
    }

  *length = the_len;
  strncpy(result, the_str, the_len);
  return result;
}

/******************************************************************************
                                  END OF FILE
******************************************************************************/