/* $OpenBSD$ */

/*
* Copyright (c) 2019 Nicholas Marriott <[email protected]>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
* IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include <sys/types.h>

#include <regex.h>
#include <string.h>

#include "tmux.h"

static void
regsub_copy(char **buf, ssize_t *len, const char *text, size_t start, size_t end)
{
       size_t  add = end - start;

       *buf = xrealloc(*buf, (*len) + add + 1);
       memcpy((*buf) + *len, text + start, add);
       (*len) += add;
}

static void
regsub_expand(char **buf, ssize_t *len, const char *with, const char *text,
   regmatch_t *m, u_int n)
{
       const char      *cp;
       u_int            i;

       for (cp = with; *cp != '\0'; cp++) {
               if (*cp == '\\') {
                       cp++;
                       if (*cp >= '0' && *cp <= '9') {
                               i = *cp - '0';
                               if (i < n && m[i].rm_so != m[i].rm_eo) {
                                       regsub_copy(buf, len, text, m[i].rm_so,
                                           m[i].rm_eo);
                                       continue;
                               }
                       }
               }
               *buf = xrealloc(*buf, (*len) + 2);
               (*buf)[(*len)++] = *cp;
       }
}

char *
regsub(const char *pattern, const char *with, const char *text, int flags)
{
       regex_t          r;
       regmatch_t       m[10];
       ssize_t          start, end, last, len = 0;
       int              empty = 0;
       char            *buf = NULL;

       if (*text == '\0')
               return (xstrdup(""));
       if (regcomp(&r, pattern, flags) != 0)
               return (NULL);

       start = 0;
       last = 0;
       end = strlen(text);

       while (start <= end) {
               if (regexec(&r, text + start, nitems(m), m, 0) != 0) {
                       regsub_copy(&buf, &len, text, start, end);
                       break;
               }

               /*
                * Append any text not part of this match (from the end of the
                * last match).
                */
               regsub_copy(&buf, &len, text, last, m[0].rm_so + start);

               /*
                * If the last match was empty and this one isn't (it is either
                * later or has matched text), expand this match. If it is
                * empty, move on one character and try again from there.
                */
               if (empty ||
                   start + m[0].rm_so != last ||
                   m[0].rm_so != m[0].rm_eo) {
                       regsub_expand(&buf, &len, with, text + start, m,
                           nitems(m));

                       last = start + m[0].rm_eo;
                       start += m[0].rm_eo;
                       empty = 0;
               } else {
                       last = start + m[0].rm_eo;
                       start += m[0].rm_eo + 1;
                       empty = 1;
               }

               /* Stop now if anchored to start. */
               if (*pattern == '^') {
                       regsub_copy(&buf, &len, text, start, end);
                       break;
               }
       }
       buf[len] = '\0';

       regfree(&r);
       return (buf);
}