/*
 * Mini grep implementation for busybox using libc regex.
 *
 * Copyright (C) 1999,2000,2001 by Lineo, inc. and Mark Whitley
 * Copyright (C) 1999,2000,2001 by Mark Whitley <markw@codepoet.org> 
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <regex.h>
#include <string.h> /* for strerror() */
#include <errno.h>
#include "busybox.h"


extern int optind; /* in unistd.h */
extern void xregcomp(regex_t *preg, const char *regex, int cflags); /* in busybox.h */

/* options */
static int reflags            = REG_NOSUB; 
static int print_filename     = 0;
static int print_line_num     = 0;
static int print_match_counts = 0;
static int be_quiet           = 0;
static int invert_search      = 0;
static int suppress_err_msgs  = 0;
static int print_files_with_matches  = 0;

#ifdef CONFIG_FEATURE_GREP_CONTEXT
extern char *optarg; /* in getopt.h */
static int lines_before      = 0;
static int lines_after       = 0;
static char **before_buf     = NULL;
static int last_line_printed = 0;
#endif /* CONFIG_FEATURE_GREP_CONTEXT */

/* globals used internally */
static regex_t *regexes = NULL; /* growable array of compiled regular expressions */
static int nregexes = 0; /* number of elements in above arrary */
static int matched; /* keeps track of whether we ever matched */
static char *cur_file = NULL; /* the current file we are reading */


static void print_line(const char *line, int linenum, char decoration)
{
#ifdef CONFIG_FEATURE_GREP_CONTEXT
	/* possibly print the little '--' seperator */
	if ((lines_before || lines_after) && last_line_printed &&
			last_line_printed < linenum - 1) {
		puts("--");
	}
	last_line_printed = linenum;
#endif
	if (print_filename)
		printf("%s%c", cur_file, decoration);
	if (print_line_num)
		printf("%i%c", linenum, decoration);
	puts(line);
}


static void grep_file(FILE *file)
{
	char *line = NULL;
	int ret;
	int linenum = 0;
	int nmatches = 0;
	int i;
#ifdef CONFIG_FEATURE_GREP_CONTEXT
	int print_n_lines_after = 0;
	int curpos = 0; /* track where we are in the circular 'before' buffer */
	int idx = 0; /* used for iteration through the circular buffer */
#endif /* CONFIG_FEATURE_GREP_CONTEXT */ 

	while ((line = get_line_from_file(file)) != NULL) {
		chomp(line);
		linenum++;

		for (i = 0; i < nregexes; i++) {
			/*
			 * test for a postitive-assertion match (regexec returns success (0)
			 * and the user did not specify invert search), or a negative-assertion
			 * match (regexec returns failure (REG_NOMATCH) and the user specified
			 * invert search)
			 */
			ret = regexec(&regexes[i], line, 0, NULL, 0);
			if ((ret == 0 && !invert_search) || (ret == REG_NOMATCH && invert_search)) {

				/* if we found a match but were told to be quiet, stop here and
				 * return success */
				if (be_quiet)
					exit(0);

				/* keep track of matches */
				nmatches++;

				/* if we're just printing filenames, we stop after the first match */
				if (print_files_with_matches)
					break;

				/* print the matched line */
				if (print_match_counts == 0) {
#ifdef CONFIG_FEATURE_GREP_CONTEXT
					int prevpos = (curpos == 0) ? lines_before - 1 : curpos - 1;

					/* if we were told to print 'before' lines and there is at least
					 * one line in the circular buffer, print them */
					if (lines_before && before_buf[prevpos] != NULL) {
						int first_buf_entry_line_num = linenum - lines_before;

						/* advance to the first entry in the circular buffer, and
						 * figure out the line number is of the first line in the
						 * buffer */
						idx = curpos;
						while (before_buf[idx] == NULL) {
							idx = (idx + 1) % lines_before;
							first_buf_entry_line_num++;
						}

						/* now print each line in the buffer, clearing them as we go */
						while (before_buf[idx] != NULL) {
							print_line(before_buf[idx], first_buf_entry_line_num, '-');
							free(before_buf[idx]);
							before_buf[idx] = NULL;
							idx = (idx + 1) % lines_before;
							first_buf_entry_line_num++;
						}
					}

					/* make a note that we need to print 'after' lines */
					print_n_lines_after = lines_after;
#endif /* CONFIG_FEATURE_GREP_CONTEXT */ 
					print_line(line, linenum, ':');
				}
			}
#ifdef CONFIG_FEATURE_GREP_CONTEXT
			else { /* no match */
				/* Add the line to the circular 'before' buffer */
				if(lines_before) {
					if(before_buf[curpos])
						free(before_buf[curpos]);
					before_buf[curpos] = xstrdup(line);
					curpos = (curpos + 1) % lines_before;
				}
			}

			/* if we need to print some context lines after the last match, do so */
			if (print_n_lines_after && (last_line_printed != linenum)) {
				print_line(line, linenum, '-');
				print_n_lines_after--;
			}
#endif /* CONFIG_FEATURE_GREP_CONTEXT */ 
		} /* for */
		free(line);
	}


	/* special-case file post-processing for options where we don't print line
	 * matches, just filenames and possibly match counts */

	/* grep -c: print [filename:]count, even if count is zero */
	if (print_match_counts) {
		if (print_filename)
			printf("%s:", cur_file);
		if (print_files_with_matches && nmatches > 0)
			printf("1\n");
		else
		    printf("%d\n", nmatches);
	}

	/* grep -l: print just the filename, but only if we grepped the line in the file  */
	if (print_files_with_matches && nmatches > 0) {
		puts(cur_file);
	}


	/* remember if we matched */
	if (nmatches != 0)
		matched = 1;
}


static void add_regex(const char *restr)
{
	regexes = xrealloc(regexes, sizeof(regex_t) * (++nregexes));
	xregcomp(&regexes[nregexes-1], restr, reflags);
}


static void	load_regexes_from_file(const char *filename)
{
	char *line;
	FILE *f = xfopen(filename, "r");
	while ((line = get_line_from_file(f)) != NULL) {
		chomp(line);
		add_regex(line);
		free(line);
	}
}


#ifdef CONFIG_FEATURE_CLEAN_UP
static void destroy_regexes(void)
{
	if (regexes == NULL)
		return;

	/* destroy all the elments in the array */
	while (--nregexes >= 0) {
		regfree(&(regexes[nregexes]));
	}
	if (regexes)
	    free(regexes);
}
#endif


extern int grep_main(int argc, char **argv)
{
	int opt;
#if defined (CONFIG_FEATURE_GREP_CONTEXT)
	char *junk;
#endif

#ifdef CONFIG_FEATURE_CLEAN_UP
	/* destroy command strings on exit */
	atexit(destroy_regexes);
#endif

#ifdef CONFIG_FEATURE_GREP_EGREP_ALIAS
	if (strcmp(get_last_path_component(argv[0]), "egrep") == 0)
		reflags |= REG_EXTENDED;
#endif

	/* do normal option parsing */
	while ((opt = getopt(argc, argv, "iHhlnqvsce:f:"
#ifdef CONFIG_FEATURE_GREP_CONTEXT
"A:B:C:"
#endif
#ifdef CONFIG_FEATURE_GREP_EGREP_ALIAS
"E"
#endif
)) > 0) {
		switch (opt) {
			case 'i':
				reflags |= REG_ICASE;
				break;
			case 'l':
				print_files_with_matches++;
				break;
			case 'H':
				print_filename++;
				break;
			case 'h':
				print_filename--;
				break;
			case 'n':
				print_line_num++;
				break;
			case 'q':
				be_quiet++;
				break;
			case 'v':
				invert_search++;
				break;
			case 's':
				suppress_err_msgs++;
				break;
			case 'c':
				print_match_counts++;
				break;
			case 'e':
				add_regex(optarg);
				break;
#ifdef CONFIG_FEATURE_GREP_EGREP_ALIAS
			case 'E':
				reflags |= REG_EXTENDED;
				break;
#endif
			case 'f':
				load_regexes_from_file(optarg);
				break;
#ifdef CONFIG_FEATURE_GREP_CONTEXT
			case 'A':
				lines_after = strtoul(optarg, &junk, 10);
				if(*junk != '\0')
					error_msg_and_die("invalid context length argument");
				break;
			case 'B':
				lines_before = strtoul(optarg, &junk, 10);
				if(*junk != '\0')
					error_msg_and_die("invalid context length argument");
				before_buf = (char **)xcalloc(lines_before, sizeof(char *));
				break;
			case 'C':
				lines_after = lines_before = strtoul(optarg, &junk, 10);
				if(*junk != '\0')
					error_msg_and_die("invalid context length argument");
				before_buf = (char **)xcalloc(lines_before, sizeof(char *));
				break;
#endif /* CONFIG_FEATURE_GREP_CONTEXT */
			default:
				show_usage();
		}
	}

	/* if we didn't get a pattern from a -e and no command file was specified,
	 * argv[optind] should be the pattern. no pattern, no worky */
	if (nregexes == 0) {
		if (argv[optind] == NULL)
			show_usage();
		else {
			add_regex(argv[optind]);
			optind++;
		}
	}

	/* sanity checks */
	if (print_match_counts || be_quiet || print_files_with_matches) {
		print_line_num = 0;
#ifdef CONFIG_FEATURE_GREP_CONTEXT
		lines_before = 0;
		lines_after = 0;
#endif
	}

	/* argv[(optind)..(argc-1)] should be names of file to grep through. If
	 * there is more than one file to grep, we will print the filenames */
	if ((argc-1) - (optind) > 0)
		print_filename++;

	/* If no files were specified, or '-' was specified, take input from
	 * stdin. Otherwise, we grep through all the files specified. */
	if (argv[optind] == NULL || (strcmp(argv[optind], "-") == 0)) {
		grep_file(stdin);
	}
	else {
		int i;
		FILE *file;
		for (i = optind; i < argc; i++) {
			cur_file = argv[i];
			file = fopen(cur_file, "r");
			if (file == NULL) {
				if (!suppress_err_msgs)
					perror_msg("%s", cur_file);
			}
			else {
				grep_file(file);
				fclose(file);
			}
		}
	}

	return !matched; /* invert return value 0 = success, 1 = failed */
}