/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * David Hitz of Auspex Systems, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * look -- find lines in a sorted list.
 *
 * The man page said that TABs and SPACEs participate in -d comparisons.
 * In fact, they were ignored.  This implements historic practice, not
 * the manual page.
 */

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <limits.h>
#include <locale.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>
#include <wctype.h>

#include "pathnames.h"

static char _path_words[] = _PATH_WORDS;

#define EQUAL           0
#define GREATER         1
#define LESS            (-1)

static int dflag, fflag;

static char     *binary_search(wchar_t *, unsigned char *, unsigned char *);
static int       compare(wchar_t *, unsigned char *, unsigned char *);
static char     *linear_search(wchar_t *, unsigned char *, unsigned char *);
static int       look(wchar_t *, unsigned char *, unsigned char *);
static wchar_t  *prepkey(const char *, wchar_t);
static void      print_from(wchar_t *, unsigned char *, unsigned char *);

static void usage(void) __dead2;

static struct option longopts[] = {
        { "alternative",no_argument,    NULL, 'a' },
        { "alphanum",   no_argument,    NULL, 'd' },
        { "ignore-case",no_argument,    NULL, 'i' },
        { "terminate",  required_argument, NULL, 't'},
        { NULL,         0,              NULL, 0 },
};

int
main(int argc, char *argv[])
{
        struct stat sb;
        int ch, fd, match;
        wchar_t termchar;
        unsigned char *back, *front;
        unsigned const char *file;
        wchar_t *key;

        (void) setlocale(LC_CTYPE, "");

        file = _path_words;
        termchar = L'\0';
        while ((ch = getopt_long(argc, argv, "+adft:", longopts, NULL)) != -1)
                switch(ch) {
                case 'a':
                        /* COMPATIBILITY */
                        break;
                case 'd':
                        dflag = 1;
                        break;
                case 'f':
                        fflag = 1;
                        break;
                case 't':
                        if (mbrtowc(&termchar, optarg, MB_LEN_MAX, NULL) !=
                            strlen(optarg))
                                errx(2, "invalid termination character");
                        break;
                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc == 0)
                usage();
        if (argc == 1)                  /* But set -df by default. */
                dflag = fflag = 1;
        key = prepkey(*argv++, termchar);
        if (argc >= 2)
                file = *argv++;

        match = 1;

        do {
                if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb))
                        err(2, "%s", file);
                if ((uintmax_t)sb.st_size > (uintmax_t)SIZE_T_MAX)
                        errx(2, "%s: %s", file, strerror(EFBIG));
                if (sb.st_size == 0) {
                        close(fd);
                        continue;
                }
                if ((front = mmap(NULL, (size_t)sb.st_size, PROT_READ, MAP_SHARED, fd, (off_t)0)) == MAP_FAILED)
                        err(2, "%s", file);
                back = front + sb.st_size;
                match *= (look(key, front, back));
                close(fd);
        } while (argc-- > 2 && (file = *argv++));

        exit(match);
}

static wchar_t *
prepkey(const char *string, wchar_t termchar)
{
        const char *readp;
        wchar_t *key, *writep;
        wchar_t ch;
        size_t clen;

        /*
         * Reformat search string and convert to wide character representation
         * to avoid doing it multiple times later.
         */
        if ((key = malloc(sizeof(wchar_t) * (strlen(string) + 1))) == NULL)
                err(2, NULL);
        readp = string;
        writep = key;
        while ((clen = mbrtowc(&ch, readp, MB_LEN_MAX, NULL)) != 0) {
                if (clen == (size_t)-1 || clen == (size_t)-2)
                        errc(2, EILSEQ, NULL);
                if (fflag)
                        ch = towlower(ch);
                if (!dflag || iswalnum(ch))
                        *writep++ = ch;
                readp += clen;
        }
        *writep = L'\0';
        if (termchar != L'\0' && (writep = wcschr(key, termchar)) != NULL)
                *++writep = L'\0';
        return (key);
}

static int
look(wchar_t *string, unsigned char *front, unsigned char *back)
{

        front = binary_search(string, front, back);
        front = linear_search(string, front, back);

        if (front)
                print_from(string, front, back);
        return (front ? 0 : 1);
}


/*
 * Binary search for "string" in memory between "front" and "back".
 *
 * This routine is expected to return a pointer to the start of a line at
 * *or before* the first word matching "string".  Relaxing the constraint
 * this way simplifies the algorithm.
 *
 * Invariants:
 *      front points to the beginning of a line at or before the first
 *      matching string.
 *
 *      back points to the beginning of a line at or after the first
 *      matching line.
 *
 * Base of the Invariants.
 *      front = NULL;
 *      back = EOF;
 *
 * Advancing the Invariants:
 *
 *      p = first newline after halfway point from front to back.
 *
 *      If the string at "p" is not greater than the string to match,
 *      p is the new front.  Otherwise it is the new back.
 *
 * Termination:
 *
 *      The definition of the routine allows it return at any point,
 *      since front is always at or before the line to print.
 *
 *      In fact, it returns when the chosen "p" equals "back".  This
 *      implies that there exists a string is least half as long as
 *      (back - front), which in turn implies that a linear search will
 *      be no more expensive than the cost of simply printing a string or two.
 *
 *      Trying to continue with binary search at this point would be
 *      more trouble than it's worth.
 */
#define SKIP_PAST_NEWLINE(p, back) \
        while (p < back && *p++ != '\n');

static char *
binary_search(wchar_t *string, unsigned char *front, unsigned char *back)
{
        unsigned char *p;

        p = front + (back - front) / 2;
        SKIP_PAST_NEWLINE(p, back);

        /*
         * If the file changes underneath us, make sure we don't
         * infinitely loop.
         */
        while (p < back && back > front) {
                if (compare(string, p, back) == GREATER)
                        front = p;
                else
                        back = p;
                p = front + (back - front) / 2;
                SKIP_PAST_NEWLINE(p, back);
        }
        return (front);
}

/*
 * Find the first line that starts with string, linearly searching from front
 * to back.
 *
 * Return NULL for no such line.
 *
 * This routine assumes:
 *
 *      o front points at the first character in a line.
 *      o front is before or at the first line to be printed.
 */
static char *
linear_search(wchar_t *string, unsigned char *front, unsigned char *back)
{
        while (front < back) {
                switch (compare(string, front, back)) {
                case EQUAL:             /* Found it. */
                        return (front);
                case LESS:              /* No such string. */
                        return (NULL);
                case GREATER:           /* Keep going. */
                        break;
                }
                SKIP_PAST_NEWLINE(front, back);
        }
        return (NULL);
}

/*
 * Print as many lines as match string, starting at front.
 */
static void
print_from(wchar_t *string, unsigned char *front, unsigned char *back)
{
        for (; front < back && compare(string, front, back) == EQUAL; ++front) {
                for (; front < back && *front != '\n'; ++front)
                        if (putchar(*front) == EOF)
                                err(2, "stdout");
                if (putchar('\n') == EOF)
                        err(2, "stdout");
        }
}

/*
 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with
 * string2 (s1 ??? s2).
 *
 *      o Matches up to len(s1) are EQUAL.
 *      o Matches up to len(s2) are GREATER.
 *
 * Compare understands about the -f and -d flags, and treats comparisons
 * appropriately.
 *
 * The string "s1" is null terminated.  The string s2 is '\n' terminated (or
 * "back" terminated).
 */
static int
compare(wchar_t *s1, unsigned char *s2, unsigned char *back)
{
        wchar_t ch1, ch2;
        size_t len2;

        for (; *s1 && s2 < back && *s2 != '\n'; ++s1, s2 += len2) {
                ch1 = *s1;
                len2 = mbrtowc(&ch2, s2, back - s2, NULL);
                if (len2 == (size_t)-1 || len2 == (size_t)-2) {
                        ch2 = *s2;
                        len2 = 1;
                }
                if (fflag)
                        ch2 = towlower(ch2);
                if (dflag && !iswalnum(ch2)) {
                        /* Ignore character in comparison. */
                        --s1;
                        continue;
                }
                if (ch1 != ch2)
                        return (ch1 < ch2 ? LESS : GREATER);
        }
        return (*s1 ? GREATER : EQUAL);
}

static void
usage(void)
{
        (void)fprintf(stderr, "usage: look [-df] [-t char] string [file ...]\n");
        exit(2);
}