/* grep.c - print lines what match given regular expression
 *
 * Copyright 2013 CE Strake <strake888 at gmail.com>
 *
 * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/
 * See http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/cmdbehav.html

USE_GREP(NEWTOY(grep, "EFHabhinosvwclqe*f*m#", TOYFLAG_BIN))

config GREP
  bool "grep"
  default n
  help
    usage: grep [-EFivw] [-cloqs] [-Hbhn] [-e REGEX]... [-f FILENAME] [FILE]...

    Show lines matching regular expressions. If no -e, first argument is
    regular expression to match. With no files (or "-" filename) read stdin.
    Returns 0 if matched, 1 if no match found.

    -e  Regex to match. (May be repeated.)
    -f  File containing regular expressions to match.

    match type:
    -E  extended regex syntax    -F  fixed (match literal string)
    -i  case insensitive         -v  invert match
    -w  whole words (implies -E)

    display modes: (default: matched line)
    -c  count of matching lines  -l  show matching filenames
    -o  only matching part       -q  quiet (errors only)
    -s  silent (no error msg)    

    prefix modes (default: filename if checking more than 1 file)
    -H  force filename           -b  byte offset of match
    -h  hide filename            -n  line number of match
*/

#define FOR_grep
#include "toys.h"
#include <regex.h>

static regex_t re; /* fails in GLOBALS */

GLOBALS(
  long mArgu;
  struct arg_list *fArgu, *eArgu;
  char mode, *re_xs;
)

static void do_grep(int fd, char *name)
{
  int n = 0, nMatch = 0, which = toys.optflags & FLAG_w ? 2 : 0;

  for (;;) {
    char *x, *y;
    regmatch_t matches[3];
    int atBOL = 1;

    x = get_rawline(fd, 0, '\n');
    if (!x) break;
    y = x;
    n++; /* start at 1 */

    while (regexec (&re, y, 3, matches, atBOL ? 0 : REG_NOTBOL) == 0)
    {
      if (atBOL) nMatch++;
      toys.exitval = 0;
      atBOL = 0;
      switch (TT.mode) {
      case 'q':
        xexit();
      case 'l':
        if (!(toys.optflags & FLAG_h)) printf("%s\n", name);
        free(x);
        return;
      case 'c':
        break;
      default:
        if (!(toys.optflags & FLAG_h)) printf("%s:", name);
        if ((toys.optflags & FLAG_n)) printf("%d:", n);
        if ((toys.optflags & FLAG_b))
          printf("%ld:", lseek (0, 0, SEEK_CUR) - strlen (y) +
                 (toys.optflags & FLAG_o ? matches[which].rm_so : 0));
        if (!(toys.optflags & FLAG_o)) fputs(x, stdout);
        else {
          y += matches[which].rm_so;
          printf("%.*s\n", matches[which].rm_eo - matches[which].rm_so, y++);
        }
      }
      if (!(toys.optflags & FLAG_o)) break;
    }

    free(x);

    if ((toys.optflags & FLAG_m) && nMatch >= TT.mArgu) break;
  }

  if (TT.mode == 'c') printf("%s:%d\n", name, nMatch);
}

char *regfix(char *re_xs)
{
  char *re_ys;
  int ii, jj = 0;

  re_ys = xmalloc(2*strlen (re_xs) + 1);
  for (ii = 0; re_xs[ii]; ii++) {
    if (strchr("^.[]$()|*+?{}\\", re_xs[ii])) re_ys[jj++] = '\\';
    re_ys[jj++] = re_xs[ii];
  }
  re_ys[jj] = 0;

  return re_ys;
}

void addRE(char *x)
{
  if (toys.optflags & FLAG_F) x = regfix(x);
  if (TT.re_xs) TT.re_xs = xastrcat(TT.re_xs, "|");
  TT.re_xs = xastrcat(TT.re_xs, x);
  if (toys.optflags & FLAG_F) free(x);
}

void buildRE(void)
{
  for (; TT.eArgu; TT.eArgu = TT.eArgu -> next) addRE(TT.eArgu -> arg);
  for (; TT.fArgu; TT.fArgu = TT.fArgu -> next) {
    FILE *f;
    char *x, *y;
    size_t l;

    f = xfopen(TT.fArgu -> arg, "r");
    x = 0;
    for (;;) {
      if (getline (&x, &l, f) < 0) {
        if (feof(f)) break;
        toys.exitval = 2;
        perror_exit("failed to read");
      }
      y = x + strlen(x) - 1;
      if (y[0] == '\n') y[0] = 0;

      addRE(x);
    }
    free(x);
    fclose(f);
  }

  if (!TT.re_xs) {
    if (toys.optc < 1) {
      toys.exitval = 2;
      error_exit("no RE");
    }
    TT.re_xs = (toys.optflags & FLAG_F) ? regfix(toys.optargs[0])
        : toys.optargs[0];
    toys.optc--; toys.optargs++;
  }

  TT.re_xs = xmsprintf((toys.optflags & FLAG_w)
      ? "(^|[^_[:alnum:]])(%s)($|[^_[:alnum:]])" : "%s", TT.re_xs);

  if (regcomp(&re, TT.re_xs,
               ((toys.optflags & (FLAG_E | FLAG_F)) ? REG_EXTENDED : 0) |
               ((toys.optflags &  FLAG_i)           ? REG_ICASE    : 0)) != 0) {
    toys.exitval = 2;
    error_exit("bad RE");
  }
}

void grep_main(void)
{
  if ((toys.optflags & FLAG_w)
    && !(toys.optflags & FLAG_E || toys.optflags & FLAG_F))
      error_exit ("must not use -w sans -E");

  buildRE();

  if (toys.optflags & FLAG_c) TT.mode = 'c';
  if (toys.optflags & FLAG_l) TT.mode = 'l';
  if (toys.optflags & FLAG_q) TT.mode = 'q';

  if (!(toys.optflags & FLAG_H) && (toys.optc < 2)) toys.optflags |= FLAG_h;

  toys.exitval = 1;
  loopfiles_rw(toys.optargs, O_RDONLY, 0, toys.optflags & FLAG_s, do_grep);
  xexit();
}