/*	$OpenBSD: fmt.c,v 1.15 1999/12/30 18:00:42 provos Exp $	*/

/* Sensible version of fmt
 *
 * Syntax: fmt [ options ] [ goal [ max ] ] [ filename ... ]
 *
 * Since the documentation for the original fmt is so poor, here
 * is an accurate description of what this one does. It's usually
 * the same. The *mechanism* used may differ from that suggested
 * here. Note that we are *not* entirely compatible with fmt,
 * because fmt gets so many things wrong.
 *
 * 1. Tabs are expanded, assuming 8-space tab stops.
 *    If the `-t <n>' option is given, we assume <n>-space
 *    tab stops instead.
 *    Trailing blanks are removed from all lines.
 *    x\b == nothing, for any x other than \b.
 *    Other control characters are simply stripped. This
 *    includes \r.
 * 2. Each line is split into leading whitespace and
 *    everything else. Maximal consecutive sequences of
 *    lines with the same leading whitespace are considered
 *    to form paragraphs, except that a blank line is always
 *    a paragraph to itself.
 *    If the `-p' option is given then the first line of a
 *    paragraph is permitted to have indentation different
 *    from that of the other lines.
 *    If the `-m' option is given then a line that looks
 *    like a mail message header, if it is not immediately
 *    preceded by a non-blank non-message-header line, is
 *    taken to start a new paragraph, which also contains
 *    any subsequent lines with non-empty leading whitespace.
 * 3. The "everything else" is split into words; a word
 *    includes its trailing whitespace, and a word at the
 *    end of a line is deemed to be followed by a single
 *    space, or two spaces if it ends with a sentence-end
 *    character. (See the `-d' option for how to change that.)
 *    If the `-s' option has been given, then a word's trailing
 *    whitespace is replaced by what it would have had if it
 *    had occurred at end of line.
 * 4. Each paragraph is sent to standard output as follows.
 *    We output the leading whitespace, and then enough words
 *    to make the line length as near as possible to the goal
 *    without exceeding the maximum. (If a single word would
 *    exceed the maximum, we output that anyway.) Of course
 *    the trailing whitespace of the last word is ignored.
 *    We then emit a newline and start again if there are any
 *    words left.
 *    Note that for a blank line this translates as "We emit
 *    a newline".
 *    If the `-l <n>' option is given, then leading whitespace
 *    is modified slightly: <n> spaces are replaced by a tab.
 *    Indented paragraphs (see above under `-p') make matters
 *    more complicated than this suggests. Actually every paragraph
 *    has two `leading whitespace' values; the value for the first
 *    line, and the value for the most recent line. (While processing
 *    the first line, the two are equal. When `-p' has not been
 *    given, they are always equal.) The leading whitespace
 *    actually output is that of the first line (for the first
 *    line of *output*) or that of the most recent line (for
 *    all other lines of output).
 *    When `-m' has been given, message header paragraphs are
 *    taken as having first-leading-whitespace empty and
 *    subsequent-leading-whitespace two spaces.
 *
 * Multiple input files are formatted one at a time, so that a file
 * never ends in the middle of a line.
 *
 * There's an alternative mode of operation, invoked by giving
 * the `-c' option. In that case we just center every line,
 * and most of the other options are ignored. This should
 * really be in a separate program, but we must stay compatible
 * with old `fmt'.
 *
 * QUERY: Should `-m' also try to do the right thing with quoted text?
 * QUERY: `-b' to treat backslashed whitespace as old `fmt' does?
 * QUERY: Option meaning `never join lines'?
 * QUERY: Option meaning `split in mid-word to avoid overlong lines'?
 * (Those last two might not be useful, since we have `fold'.)
 *
 * Differences from old `fmt':
 *
 *   - We have many more options. Options that aren't understood
 *     generate a lengthy usage message, rather than being
 *     treated as filenames.
 *   - Even with `-m', our handling of message headers is
 *     significantly different. (And much better.)
 *   - We don't treat `\ ' as non-word-breaking.
 *   - Downward changes of indentation start new paragraphs
 *     for us, as well as upward. (I think old `fmt' behaves
 *     in the way it does in order to allow indented paragraphs,
 *     but this is a broken way of making indented paragraphs
 *     behave right.)
 *   - Given the choice of going over or under |goal_length|
 *     by the same amount, we go over; old `fmt' goes under.
 *   - We treat `?' as ending a sentence, and not `:'. Old `fmt'
 *     does the reverse.
 *   - We return approved return codes. Old `fmt' returns
 *     1 for some errors, and *the number of unopenable files*
 *     when that was all that went wrong.
 *   - We have fewer crashes and more helpful error messages.
 *   - We don't turn spaces into tabs at starts of lines unless
 *     specifically requested.
 *   - New `fmt' is somewhat smaller and slightly faster than
 *     old `fmt'.
 *
 * Bugs:
 *
 *   None known. There probably are some, though.
 *
 * Portability:
 *
 *   I believe this code to be pretty portable. It does require
 *   that you have `getopt'. If you need to include "getopt.h"
 *   for this (e.g., if your system didn't come with `getopt'
 *   and you installed it yourself) then you should arrange for
 *   NEED_getopt_h to be #defined.
 *
 *   Everything here should work OK even on nasty 16-bit
 *   machines and nice 64-bit ones. However, it's only really
 *   been tested on my FreeBSD machine. Your mileage may vary.
 */

/* Copyright (c) 1997 Gareth McCaughan. All rights reserved.
 *
 * Redistribution and use of this code, in source or binary forms,
 * with or without modification, are permitted subject to the following
 * conditions:
 *
 *  - Redistribution of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 *  - If you distribute modified source code it must also include
 *    a notice saying that it has been modified, and giving a brief
 *    description of what changes have been made.
 *
 * Disclaimer: I am not responsible for the results of using this code.
 *             If it formats your hard disc, sends obscene messages to
 *             your boss and kills your children then that's your problem
 *             not mine. I give absolutely no warranty of any sort as to
 *             what the program will do, and absolutely refuse to be held
 *             liable for any consequences of your using it.
 *             Thank you. Have a nice day.
 */

/* RCS change log:
 * Revision 1.5  1998/03/02 18:02:21  gjm11
 * Minor changes for portability.
 *
 * Revision 1.4  1997/10/01 11:51:28  gjm11
 * Repair broken indented-paragraph handling.
 * Add mail message header stuff.
 * Improve comments and layout.
 * Make usable with non-BSD systems.
 * Add revision display to usage message.
 *
 * Revision 1.3  1997/09/30 16:24:47  gjm11
 * Add copyright notice, rcsid string and log message.
 *
 * Revision 1.2  1997/09/30 16:13:39  gjm11
 * Add options: -d <chars>, -l <width>, -p, -s, -t <width>, -h .
 * Parse options with `getopt'. Clean up code generally.
 * Make comments more accurate.
 *
 * Revision 1.1  1997/09/30 11:29:57  gjm11
 * Initial revision
 */

#ifndef lint
static const char rcsid[] =
  "$OpenBSD: fmt.c,v 1.15 1999/12/30 18:00:42 provos Exp $";
static const char copyright[] =
  "Copyright (c) 1997 Gareth McCaughan. All rights reserved.\n";
#endif /* not lint */

/* Cater for BSD and non-BSD systems.
 * I hate the C preprocessor.
 */

#undef HAVE_errx
#undef HAVE_sysexits

#ifdef unix
# include <sys/param.h>
# ifdef BSD
#  define HAVE_errx
#  if BSD >= 199306
#   define HAVE_sysexits
#  endif
# endif
#endif

#ifdef HAVE_errx
# include <err.h>
#else
# define errx(rc,str) { fprintf(stderr,"fmt: %s\n",str); exit(rc); }
#endif

#ifdef HAVE_sysexits
# include <sysexits.h>
#else
# define EX_USAGE 1
# define EX_NOINPUT 1
# define EX_SOFTWARE 1
# define EX_OSERR 1
#endif

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

#ifdef NEED_getopt_h
# include "getopt.h"
#endif

/* Something that, we hope, will never be a genuine line length,
 * indentation etc.
 */
#define SILLY ((size_t)-1)

/* I used to use |strtoul| for this, but (1) not all systems have it
 * and (2) it's probably better to use |strtol| to detect negative
 * numbers better.
 * If |fussyp==0| then we don't complain about non-numbers
 * (returning 0 instead), but we do complain about bad numbers.
 */
size_t get_positive(const char *s, const char *err_mess, int fussyP) {
  char *t;
  long result = strtol(s,&t,0);
  if (*t) { if (fussyP) goto Lose; else return 0; }
  if (result<=0) { Lose: errx(EX_USAGE, err_mess); }
  return (size_t) result;
}

/* Just for the sake of linguistic purity: */

#ifdef BRITISH
# define CENTER "centre"
#else
# define CENTER "center"
#endif

/* Global variables */

static int centerP=0;		/* Try to center lines? */
static size_t goal_length=0;	/* Target length for output lines */
static size_t max_length=0;	/* Maximum length for output lines */
static int coalesce_spaces_P=0;	/* Coalesce multiple whitespace -> ' ' ? */
static int allow_indented_paragraphs=0;	/* Can first line have diff. ind.? */
static int tab_width=8;		/* Number of spaces per tab stop */
static int output_tab_width=0;	/* Ditto, when squashing leading spaces */
static char *sentence_enders=".?!";	/* Double-space after these */
static int grok_mail_headers=0;	/* treat embedded mail headers magically? */

static int n_errors=0;		/* Number of failed files. Return on exit. */
static char *output_buffer=0;	/* Output line will be built here */
static size_t x;		/* Horizontal position in output line */
static size_t x0;		/* Ditto, ignoring leading whitespace */
static size_t pending_spaces;	/* Spaces to add before next word */
static int output_in_paragraph=0;	/* Any of current para written out yet? */

/* Prototypes */

static void process_named_file (const char *);
static void     process_stream (FILE *, const char *);
static size_t    indent_length (const char *, size_t);
static int     might_be_header (const char *);
static void      new_paragraph (size_t, size_t);
static void        output_word (size_t, size_t, const char *, size_t, size_t);
static void      output_indent (size_t);
static void      center_stream (FILE *, const char *);
static char *         get_line (FILE *, size_t *);
static void *         xrealloc (void *, size_t);

#define XMALLOC(x) xrealloc(0,x)

/* Here is perhaps the right place to mention that this code is
 * all in top-down order. Hence, |main| comes first.
 */
int
main(int argc, char *argv[]) {
  int ch;			/* used for |getopt| processing */

  /* 1. Grok parameters. */

  while ((ch = getopt(argc, argv, "cd:hl:mpst:")) != -1) switch(ch) {
    case 'c':
      centerP = 1;
      continue;
    case 'd':
      sentence_enders = XMALLOC(strlen(optarg)+1);
      strcpy(sentence_enders, optarg);	/* ok */
      continue;
    case 'l':
      output_tab_width
        = get_positive(optarg, "output tab width must be positive", 1);
      continue;
    case 'm':
      grok_mail_headers = 1;
      continue;
    case 'p':
      allow_indented_paragraphs = 1;
      continue;
    case 's':
      coalesce_spaces_P = 1;
      continue;
    case 't':
      tab_width = get_positive(optarg, "tab width must be positive", 1);
      continue;
    case 'h': default:
      fprintf(stderr,
"Usage:   fmt [-cmps] [-d chars] [-l num] [-t num] [goal [maximum]] [file...]\n"
"Options: -c     " CENTER " each line instead of formatting\n"
"         -d <chars> double-space after <chars> at line end\n"
"         -l <n> turn each <n> spaces at start of line into a tab\n"
"         -m     try to make sure mail header lines stay separate\n"
"         -p     allow indented paragraphs\n"
"         -s     coalesce whitespace inside lines\n"
"         -t <n> have tabs every <n> columns\n");
      exit(ch=='h' ? 0 : EX_USAGE);
  }
  argc -= optind; argv += optind;

  /* [ goal [ maximum ] ] */

  if (argc>0
      && (goal_length=get_positive(*argv,"goal length must be positive", 0))
         != 0) {
    --argc; ++argv;
    if (argc>0
        && (max_length=get_positive(*argv,"max length must be positive", 0))
           != 0) {
      --argc; ++argv;
      if (max_length<goal_length)
        errx(EX_USAGE, "max length must be >= goal length");
    }
  }
  if (goal_length==0) goal_length = 65;
  if (max_length==0) max_length = goal_length+10;
  output_buffer = XMALLOC(max_length+1);	/* really needn't be longer */

  /* 2. Process files. */

  if (argc>0) {
    while (argc-->0) process_named_file(*argv++);
  }
  else {
    process_stream(stdin, "standard input");
  }

  /* We're done. */

  return n_errors ? EX_NOINPUT : 0;

}

/* Process a single file, given its name.
 */
static void
process_named_file(const char *name) {
  FILE *f=fopen(name, "r");
  if (!f) { perror(name); ++n_errors; }
  else {
    process_stream(f, name);
    fclose(f);
  }
}

/* Types of mail header continuation lines:
 */
typedef enum {
  hdr_ParagraphStart = -1,
  hdr_NonHeader      = 0,
  hdr_Header         = 1,
  hdr_Continuation   = 2
} HdrType;

/* Process a stream. This is where the real work happens,
 * except that centering is handled separately.
 */
static void
process_stream(FILE *stream, const char *name) {
  size_t last_indent=SILLY;	/* how many spaces in last indent? */
  size_t para_line_number=0;	/* how many lines already read in this para? */
  size_t first_indent=SILLY;	/* indentation of line 0 of paragraph */
  HdrType prev_header_type=hdr_ParagraphStart;
	/* ^-- header_type of previous line; -1 at para start */
  char *line;
  size_t length;

  if (centerP) { center_stream(stream, name); return; }
  while ((line=get_line(stream,&length)) != NULL) {
    size_t np=indent_length(line, length);
    { HdrType header_type=hdr_NonHeader;
      if (grok_mail_headers && prev_header_type!=hdr_NonHeader) {
        if (np==0 && might_be_header(line))
          header_type = hdr_Header;
        else if (np>0 && prev_header_type>hdr_NonHeader)
          header_type = hdr_Continuation;
      }
      /* We need a new paragraph if and only if:
       *   this line is blank,
       *   OR it's a mail header,
       *   OR it's not a mail header AND the last line was one,
       *   OR the indentation has changed
       *      AND the line isn't a mail header continuation line
       *      AND this isn't the second line of an indented paragraph.
       */
      if ( length==0
           || header_type==hdr_Header
           || (header_type==hdr_NonHeader && prev_header_type>hdr_NonHeader)
           || (np!=last_indent
               && header_type != hdr_Continuation
               && (!allow_indented_paragraphs || para_line_number != 1)) ) {
        new_paragraph(output_in_paragraph ? last_indent : first_indent, np);
        para_line_number = 0;
        first_indent = np;
        last_indent = np;
        if (header_type==hdr_Header) last_indent=2;	/* for cont. lines */
        if (length==0) {
          putchar('\n');
          prev_header_type=hdr_ParagraphStart;
          continue;
        }
      }
      else {
        /* If this is an indented paragraph other than a mail header
         * continuation, set |last_indent|.
         */
        if (np != last_indent && header_type != hdr_Continuation)
          last_indent=np;
      }
      prev_header_type = header_type;
    }

    { size_t n=np;
      while (n<length) {
        /* Find word end and count spaces after it */
        size_t word_length=0, space_length=0;
        while (n+word_length < length && line[n+word_length] != ' ')
          ++word_length;
        space_length = word_length;
        while (n+space_length < length && line[n+space_length] == ' ')
          ++space_length;
        /* Send the word to the output machinery. */
        output_word(first_indent, last_indent,
                    line+n, word_length, space_length-word_length);
        n += space_length;
      }
    }
    ++para_line_number;
  }
  new_paragraph(output_in_paragraph ? last_indent : first_indent, 0);
  if (ferror(stream)) { perror(name); ++n_errors; }
}

/* How long is the indent on this line?
 */
static size_t
indent_length(const char *line, size_t length) {
  size_t n=0;
  while (n<length && *line++ == ' ') ++n;
  return n;
}

/* Might this line be a mail header?
 * We deem a line to be a possible header if it matches the
 * Perl regexp /^[A-Z][-A-Za-z0-9]*:\s/. This is *not* the same
 * as in RFC whatever-number-it-is; we want to be gratuitously
 * conservative to avoid mangling ordinary civilised text.
 */
static int
might_be_header(const char *line) {
  if (!isupper(*line++)) return 0;
  while (*line && (isalnum(*line) || *line=='-')) ++line;
  return (*line==':' && isspace(line[1]));
}

/* Begin a new paragraph with an indent of |indent| spaces.
 */
static void
new_paragraph(size_t old_indent, size_t indent) {
  if (x0) {
    if (old_indent>0) output_indent(old_indent);
    fwrite(output_buffer, 1, x0, stdout);
    putchar('\n');
  }
  x=indent; x0=0; pending_spaces=0;
  output_in_paragraph = 0;
}

/* Output spaces or tabs for leading indentation.
 */
static void
output_indent(size_t n_spaces) {
  if (output_tab_width) {
    while (n_spaces >= output_tab_width) {
      putchar('\t');
      n_spaces -= output_tab_width;
    }
  }
  while (n_spaces-- > 0) putchar(' ');
}

/* Output a single word, or add it to the buffer.
 * indent0 and indent1 are the indents to use on the first and subsequent
 * lines of a paragraph. They'll often be the same, of course.
 */
static void
output_word(size_t indent0, size_t indent1, const char *word, size_t length, size_t spaces) {
  size_t new_x = x+pending_spaces+length;
  size_t indent = output_in_paragraph ? indent1 : indent0;

  /* If either |spaces==0| (at end of line) or |coalesce_spaces_P|
   * (squashing internal whitespace), then add just one space;
   * except that if the last character was a sentence-ender we
   * actually add two spaces.
   */
  if (coalesce_spaces_P || spaces==0)
    spaces = strchr(sentence_enders, word[length-1]) ? 2 : 1;

  if (new_x<=goal_length) {
    /* After adding the word we still aren't at the goal length,
     * so clearly we add it to the buffer rather than outputing it.
     */
    memset(output_buffer+x0, ' ', pending_spaces);
    x0 += pending_spaces; x += pending_spaces;
    memcpy(output_buffer+x0, word, length);
    x0 += length; x += length;
    pending_spaces = spaces;
  }
  else {
    /* Adding the word takes us past the goal. Print the line-so-far,
     * and the word too iff either (1) the lsf is empty or (2) that
     * makes us nearer the goal but doesn't take us over the limit,
     * or (3) the word on its own takes us over the limit.
     * In case (3) we put a newline in between.
     */
    if (indent>0) output_indent(indent);
    fwrite(output_buffer, 1, x0, stdout);
    if (x0==0 || (new_x <= max_length && new_x-goal_length <= goal_length-x)) {
      printf("%*s", pending_spaces, "");
      goto write_out_word;
    }
    else {
      /* If the word takes us over the limit on its own, just
       * spit it out and don't bother buffering it.
       */
      if (indent+length > max_length) {
        putchar('\n');
        if (indent>0) output_indent(indent);
write_out_word:
        fwrite(word, 1, length, stdout);
        x0 = 0; x = indent1; pending_spaces = 0;
      }
      else {
        memcpy(output_buffer, word, length);
        x0 = length; x = length+indent1; pending_spaces = spaces;
      }
    }
    putchar('\n');
    output_in_paragraph = 1;
  }
}

/* Process a stream, but just center its lines rather than trying to
 * format them neatly.
 */
static void
center_stream(FILE *stream, const char *name) {
  char *line;
  size_t length;
  while ((line=get_line(stream, &length)) != 0) {
    size_t l=length;
    while (l>0 && isspace(*line)) { ++line; --l; }
    length=l;
    while (l<goal_length) { putchar(' '); l+=2; }
    fwrite(line, 1, length, stdout);
    putchar('\n');
  }
  if (ferror(stream)) { perror(name); ++n_errors; }
}

/* Get a single line from a stream. Expand tabs, strip control
 * characters and trailing whitespace, and handle backspaces.
 * Return the address of the buffer containing the line, and
 * put the length of the line in |lengthp|.
 * This can cope with arbitrarily long lines, and with lines
 * without terminating \n.
 * If there are no characters left or an error happens, we
 * return 0.
 * Don't confuse |spaces_pending| here with the global
 * |pending_spaces|.
 */
static char *
get_line(FILE *stream, size_t *lengthp) {
  static char *buf=NULL;
  static size_t length=0;
  size_t len=0;
  int ch;
  size_t spaces_pending=0;

  if (buf==NULL) { length=100; buf=XMALLOC(length); }
  while ((ch=getc(stream)) != '\n' && ch != EOF) {
    if (ch==' ') ++spaces_pending;
    else if (!iscntrl(ch)) {
      while (len+spaces_pending >= length) {
        length*=2; buf=xrealloc(buf, length);
      }
      while (spaces_pending > 0) { --spaces_pending; buf[len++]=' '; }
      buf[len++] = ch;
    }
    else if (ch=='\t')
      spaces_pending += tab_width - (len+spaces_pending)%tab_width;
    else if (ch=='\b') { if (len) --len; }
  }
  *lengthp=len;
  return (len>0 || ch!=EOF) ? buf : 0;
}

/* (Re)allocate some memory, exiting with an error if we can't.
 */
static void *
xrealloc(void *ptr, size_t nbytes) {
  void *p = realloc(ptr, nbytes);
  if (p == NULL) errx(EX_OSERR, "out of memory");
  return p;
}