/*	$NetBSD: expand.c,v 1.14 2016/09/05 00:40:28 sevan Exp $	*/

/*
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define _DEFAULT_SOURCE

#include <ctype.h>
#include <err.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

/*
 * expand - expand tabs to equivalent spaces
 */
size_t nstops;
size_t tabstops[100];
static const char * __progname;

static void getstops(const char *);
static void usage(void);

int main(int argc, char *argv[]) {
  int c;
  size_t n, column;

  __progname = basename(argv[0]);

  /* handle obsolete syntax */
  while (argc > 1 && argv[1][0] == '-' && isdigit((unsigned char)argv[1][1])) {
    getstops(&argv[1][1]);
    argc--;
    argv++;
  }

  while ((c = getopt(argc, argv, "t:")) != -1) {
    switch (c) {
    case 't':
      getstops(optarg);
      break;
    case '?':
    default:
      usage();
      /* NOTREACHED */
    }
  }
  argc -= optind;
  argv += optind;

  do {
    if (argc > 0) {
      if (freopen(argv[0], "r", stdin) == NULL)
        err(EXIT_FAILURE, "Cannot open `%s'", argv[0]);
      argc--, argv++;
    }
    column = 0;
    while ((c = getchar()) != EOF) {
      switch (c) {
      case '\t':
        if (nstops == 0) {
          do {
            putchar(' ');
            column++;
          } while (column & 07);
          continue;
        }
        if (nstops == 1) {
          do {
            putchar(' ');
            column++;
          } while (((column - 1) % tabstops[0]) != (tabstops[0] - 1));
          continue;
        }
        for (n = 0; n < nstops; n++)
          if (tabstops[n] > column)
            break;
        if (n == nstops) {
          putchar(' ');
          column++;
          continue;
        }
        while (column < tabstops[n]) {
          putchar(' ');
          column++;
        }
        continue;

      case '\b':
        if (column)
          column--;
        putchar('\b');
        continue;

      default:
        putchar(c);
        column++;
        continue;

      case '\n':
        putchar(c);
        column = 0;
        continue;
      }
    }
  } while (argc > 0);
  return EXIT_SUCCESS;
}

static void getstops(const char *spec) {
  int i;
  const char *cp = spec;

  nstops = 0;
  for (;;) {
    i = 0;
    while (*cp >= '0' && *cp <= '9')
      i = i * 10 + *cp++ - '0';
    if (i <= 0 || i > 256)
      errx(EXIT_FAILURE, "Too large tab stop spec `%d'", i);
    if (nstops > 0 && (size_t)i <= tabstops[nstops - 1])
      errx(EXIT_FAILURE, "Out of order tabstop spec `%d'", i);
    if (nstops == sizeof(tabstops) / sizeof(tabstops[0]) - 1)
      errx(EXIT_FAILURE, "Too many tabstops");
    tabstops[nstops++] = i;
    if (*cp == '\0')
      break;
    if (*cp != ',' && *cp != ' ')
      errx(EXIT_FAILURE, "Illegal tab stop spec `%s'", spec);
    cp++;
  }
}

static void usage(void) {
  fprintf(stderr, "Usage: %s [-t tablist] [file ...]\n", __progname);
  exit(EXIT_FAILURE);
}
