/* This file is part of addts
 * Copyright (C) 2018, 2019 Sergey Poznyakoff
 * 
 * Addts 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 3, or (at your option)
 * any later version.
 * 
 * Addts 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 addts.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <sys/time.h>

static char default_fmt[] = "%Y-%m-%d %H:%M:%S: ";

enum mode {
	PREFIX,
	SUFFIX,
	NMODE
};

enum state {
	SINI, /* initial */
	SEOL, /* end of line */
	SLIN, /* Midle of line */
	STIM, /* Time to insert timestamp */
	NSTATE
};

enum alpha {
	ACHR,
	AEOL,
	NALPHA
};

int prefix_trans[NSTATE][NALPHA] = {
	/* ACHR     AEOL */
	{  STIM,    SEOL }, /* SINI */
	{  STIM,    SEOL }, /* SEOL */
	{  SLIN,    SEOL }, /* SLIN */
	{  SLIN,    SEOL }  /* STIM */
};

int suffix_trans[NSTATE][NALPHA] = {
	/* ACHR     AEOL */
	{  SLIN,    SEOL }, /* SINI */
	{  SLIN,    SEOL }, /* SEOL */
	{  SLIN,    STIM }, /* SLIN */
	{  SLIN,    SEOL }  /* STIM */
};

static inline int
alpha(int c)
{
	return c == '\n' ? AEOL : ACHR;
}

static void
help(char *progname)
{
	printf("Usage: %s [OPTION]... [FILE]\n", progname);
	puts("add timestamps at the beginning of each line\n");
	puts("  -a                 append to FILE, instead of overwriting it");
        puts("  -f FORMAT          strftime(3) format for timestamps");
	puts("  -s                 add timestamp to the end of each line");
	puts("  -u                 report times in UTC");
	puts("  -w CHR             replace CHR with a horizontal space in FORMAT");
	putchar('\n');
	printf("Default FORMAT is \"%s\"\n", default_fmt);
	putchar('\n');
	puts("Report bugs to <gray@gnu.org>");
}

int
main(int argc, char **argv)
{
	int c;
	char buf[512];
	int utc_opt = 0;
	int append_opt = 0;
	int ws_opt = 0;
	int end_opt = 0;
	char *p;
	char *fmt = NULL;
	FILE *fp;

	enum state state = SINI;
	int (*trans)[NALPHA] = prefix_trans;
	
	while ((c = getopt(argc, argv, "?af:suw:")) != EOF) {
		switch (c) {
		case 'a':
			append_opt = 1;
			break;
		case 'f':
			fmt = optarg;
			break;
		case 's':
			trans = suffix_trans;
			break;
		case 'u':
			utc_opt = 1;
			break;
		case 'w':
			ws_opt = optarg[0];
			break;
		default:
			if (optopt == 0) {
				help(argv[0]);
				return 0;
			}
			return 1;
		}
	}

	if (fmt) {
		if (ws_opt) {
			for (p = fmt; *p; p++)
				if (*p == ws_opt)
					*p = ' ';
		}
	} else
		fmt = default_fmt;
	
	argc -= optind;
	argv += optind;
	
	switch (argc) {
	case 0:
		fp = stdout;
		break;
	case 1:
		fp = fopen(argv[0], append_opt ? "a" : "w");
		if (!fp) {
			perror(argv[0]);
			return 1;
		}
		break;
	default:
		fprintf(stderr, "%s: too many arguments\n", argv[0]);
		return 1;
	}
	setvbuf(fp, NULL, _IOLBF, 0);

	while ((c = getchar()) != EOF) {
		state = trans[state][alpha(c)];
		if (state == STIM) {
			struct timeval tv;
			struct tm *tm;
			size_t sz;
			char *start, *p;
			
			gettimeofday(&tv, NULL);
			tm = (utc_opt ? gmtime : localtime)(&tv.tv_sec);
			sz = strftime(buf, sizeof(buf), fmt, tm);
			if (sz == 0 || sz == sizeof(buf)) {
				strcpy(buf, "[OVERFLOW]: ");
				sz = strlen(buf);
			}
			start = buf;
			while ((p = strstr(start, "%@")) != NULL) {
				fwrite(start, 1, p - start, fp);
				fprintf(fp, "%06d", tv.tv_usec);
				sz -= p - start + 2;
				start = p + 2;
			}
			fwrite(start, 1, sz, fp);
		}
		fputc(c, fp);
	}
	fclose(fp);
	return 0;
}