/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */
/*
 * Copyright (c) 2014, Joyent, Inc.  All rights reserved.
 * Copyright 2020 Oxide Computer Company
 */


#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <locale.h>
#include <string.h>
#include <ctype.h>
#include <err.h>

#define DEF_LINE_COUNT  10

static  void    copyout(off_t, int);
static  void    Usage();
static  FILE    *input;


/*
 * head - give the first few lines of a stream or of each of a set of files.
 * Optionally shows a specific number of bytes instead.
 */
int
main(int argc, char **argv)
{
        int     fileCount;
        int     around = 0;
        int     i;
        int     opt;
        off_t   linecnt = DEF_LINE_COUNT;
        int     isline = 1;
        int     error = 0;
        int     quiet = 0;
        int     verbose = 0;

        (void) setlocale(LC_ALL, "");
#if !defined(TEXT_DOMAIN)       /* Should be defined by cc -D */
#define TEXT_DOMAIN "SYS_TEST"  /* Use this only if it weren't */
#endif
        (void) textdomain(TEXT_DOMAIN);

        /* check for non-standard "-line-count" option */
        for (i = 1; i < argc; i++) {
                if (strcmp(argv[i], "--") == 0)
                        break;

                if ((argv[i][0] == '-') && isdigit(argv[i][1])) {
                        if (strlen(&argv[i][1]) !=
                            strspn(&argv[i][1], "0123456789")) {
                                (void) fprintf(stderr, gettext(
                                    "%s: Badly formed number\n"), argv[0]);
                                Usage();
                        }

                        linecnt = (off_t)strtoll(&argv[i][1], (char **)NULL,
                            10);
                        while (i < argc) {
                                argv[i] = argv[i + 1];
                                i++;
                        }
                        argc--;
                }
        }

        /* get options */
        while ((opt = getopt(argc, argv, "qvn:c:")) != EOF) {
                switch (opt) {
                case 'n':
                case 'c':
                        if ((strcmp(optarg, "--") == 0) || (optind > argc)) {
                                (void) fprintf(stderr, gettext(
                                    "%s: Missing -%c argument\n"), argv[0],
                                    optopt);
                                Usage();
                        }
                        linecnt = (off_t)strtoll(optarg, (char **)NULL, 10);
                        if (linecnt <= 0) {
                                (void) fprintf(stderr, gettext(
                                    "%s: Invalid \"-%c %s\" option\n"),
                                    argv[0], optopt, optarg);
                                Usage();
                        }
                        isline = optopt != 'c';
                        break;
                case 'q':
                        quiet = 1;
                        verbose = 0;
                        break;
                case 'v':
                        quiet = 0;
                        verbose = 1;
                        break;
                default:
                        Usage();
                }
        }

        fileCount = argc - optind;

        do {
                if ((argv[optind] == NULL) && around)
                        break;

                if (argv[optind] != NULL) {
                        if (input != NULL)
                                (void) fclose(input);
                        if ((input = fopen(argv[optind], "r")) == NULL) {
                                perror(argv[optind]);
                                error = 1;
                                optind++;
                                continue;
                        }
                } else {
                        input = stdin;
                }

                if (quiet == 0) {
                        if (around)
                                (void) putchar('\n');

                        if (fileCount > 1 || verbose != 0) {
                                const char *file = argv[optind];
                                if (file == NULL) {
                                        file = "standard input";
                                }
                                (void) printf("==> %s <==\n", file);
                        }
                }

                if (argv[optind] != NULL)
                        optind++;

                copyout(linecnt, isline);
                (void) fflush(stdout);
                around++;

        } while (argv[optind] != NULL);

        return (error);
}

static void
copyout(off_t cnt, int isline)
{
        char lbuf[BUFSIZ];
        size_t len;

        while (cnt > 0) {
                len = fread(lbuf, sizeof (char), sizeof (lbuf) / sizeof (char),
                    input);
                if (len == 0) {
                        return;
                }

                if (isline) {
                        size_t i;
                        for (i = 0; i < len; i++) {
                                if (lbuf[i] == '\n') {
                                        cnt--;
                                        if (cnt == 0) {
                                                i++;
                                                break;
                                        }
                                }
                        }
                        len = i;
                } else {
                        if (len > cnt) {
                                len = cnt;
                        }
                        cnt -= len;
                }

                if (fwrite(lbuf, sizeof (char), len, stdout) != len) {
                        err(EXIT_FAILURE, "failed to write to stdout");
                }
        }
}

static void
Usage()
{
        (void) printf(gettext("usage: head [-q] [-v] [-n #] [-c #] [-#] "
            "[filename...]\n"));
        exit(1);
}