/* $OpenBSD$ */

/*

 * Copyright (c) 2019 Nicholas Marriott <nicholas.marriott@gmail.com>

 *

 * 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);

}