/*-
 * Copyright (c) 2026 Dag-Erling Smørgrav <des@FreeBSD.org>
 * Copyright (c) 2015-2021 Baptiste Daroussin <bapt@FreeBSD.org>
 * Copyright (c) 2015 Xin LI <delphij@FreeBSD.org>
 *
 * 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
 *    in this position and unchanged.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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 AUTHOR(S) 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.
 */

#include <sys/types.h>
#include <sys/capsicum.h>
#include <sys/sbuf.h>

#include <capsicum_helpers.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <getopt.h>
#include <locale.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <libcasper.h>
#include <casper/cap_fileargs.h>

typedef enum {
        /* state        condition to transit to next state */
        INIT,           /* '$' */
        DELIM_SEEN,     /* letter */
        KEYWORD,        /* punctuation mark */
        PUNC_SEEN,      /* ':' -> _SVN; space -> TEXT */
        PUNC_SEEN_SVN,  /* space */
        TEXT
} analyzer_states;

static int
scan(FILE *fp, const char *name, bool quiet)
{
        int c;
        bool hasid = false;
        bool subversion = false;
        analyzer_states state = INIT;
        FILE *buffp;
        char *buf;
        size_t sz;

        sz = 0;
        buf = NULL;
        if ((buffp = open_memstream(&buf, &sz)) == NULL)
                goto bufferr;

        if (name != NULL) {
                printf("%s:\n", name);
                if (fflush(stdout) == EOF)
                        err(EXIT_FAILURE, "stdout");
        }

        while ((c = fgetc(fp)) != EOF) {
                switch (state) {
                case INIT:
                        if (c == '$') {
                                /* Transit to DELIM_SEEN if we see $ */
                                state = DELIM_SEEN;
                        } else {
                                /* Otherwise, stay in INIT state */
                                continue;
                        }
                        break;
                case DELIM_SEEN:
                        if (isalpha(c)) {
                                /* Transit to KEYWORD if we see letter */
                                if (buf != NULL)
                                        memset(buf, 0, sz);
                                if (fseek(buffp, 0, SEEK_SET) != 0 ||
                                    fputc('$', buffp) == EOF ||
                                    fputc(c, buffp) == EOF)
                                        goto bufferr;
                                state = KEYWORD;

                                continue;
                        } else if (c == '$') {
                                /* Or, stay in DELIM_SEEN if more $ */
                                continue;
                        } else {
                                /* Otherwise, transit back to INIT */
                                state = INIT;
                        }
                        break;
                case KEYWORD:
                        if (fputc(c, buffp) == EOF)
                                goto bufferr;

                        if (isalpha(c)) {
                                /*
                                 * Stay in KEYWORD if additional letter is seen
                                 */
                                continue;
                        } else if (c == ':') {
                                /*
                                 * See ':' for the first time, transit to
                                 * PUNC_SEEN.
                                 */
                                state = PUNC_SEEN;
                                subversion = false;
                        } else if (c == '$') {
                                /*
                                 * Incomplete ident.  Go back to DELIM_SEEN
                                 * state because we see a '$' which could be
                                 * the beginning of a keyword.
                                 */
                                state = DELIM_SEEN;
                        } else {
                                /*
                                 * Go back to INIT state otherwise.
                                 */
                                state = INIT;
                        }
                        break;
                case PUNC_SEEN:
                case PUNC_SEEN_SVN:
                        if (fputc(c, buffp) == EOF)
                                goto bufferr;

                        switch (c) {
                        case ':':
                                /*
                                 * If we see '::' (seen : in PUNC_SEEN),
                                 * activate subversion treatment and transit
                                 * to PUNC_SEEN_SVN state.
                                 *
                                 * If more than two :'s were seen, the ident
                                 * is invalid and we would therefore go back
                                 * to INIT state.
                                 */
                                if (state == PUNC_SEEN) {
                                        state = PUNC_SEEN_SVN;
                                        subversion = true;
                                } else {
                                        state = INIT;
                                }
                                break;
                        case ' ':
                                /*
                                 * A space after ':' or '::' indicates we are at the
                                 * last component of potential ident.
                                 */
                                state = TEXT;
                                break;
                        default:
                                /* All other characters are invalid */
                                state = INIT;
                                break;
                        }
                        break;
                case TEXT:
                        if (fputc(c, buffp) == EOF)
                                goto bufferr;

                        if (iscntrl(c)) {
                                /* Control characters are not allowed in this state */
                                state = INIT;
                        } else if (c == '$') {
                                if (fflush(buffp) == EOF)
                                        goto bufferr;
                                /*
                                 * valid ident should end with a space.
                                 *
                                 * subversion extension uses '#' to indicate that
                                 * the keyword expansion have exceeded the fixed
                                 * width, so it is also permitted if we are in
                                 * subversion mode.  No length check is enforced
                                 * because GNU RCS ident(1) does not do it either.
                                 */
                                c = buf[strlen(buf) - 2];
                                if (c == ' ' || (subversion && c == '#')) {
                                        printf("     %s\n", buf);
                                        if (fflush(stdout) == EOF)
                                                err(EXIT_FAILURE, "stdout");
                                        hasid = true;
                                }
                                state = INIT;
                        }
                        /* Other characters: stay in the state */
                        break;
                }
        }
        if (fclose(buffp) == EOF)
                goto bufferr;
        free(buf);

        if (!hasid) {
                if (!quiet) {
                        fprintf(stderr, "%s warning: no id keywords in %s\n",
                            getprogname(), name ? name : "standard input");
                }
                return (EXIT_FAILURE);
        }

        return (EXIT_SUCCESS);
bufferr:
        err(EXIT_FAILURE, "buffer");
}

static void
usage(void)
{
        fprintf(stderr, "usage: %s [-q] [-V] [file...]", getprogname());
        exit(EXIT_FAILURE);
}

static struct option longopts[] = {
        { "quiet",      no_argument,    NULL,   'q' },
        { "version",    no_argument,    NULL,   'V' },
        { NULL,         0,              NULL,   0 }
};

int
main(int argc, char **argv)
{
        fileargs_t *fa;
        cap_rights_t rights;
        bool quiet = false;
        int i, opt, ret;
        FILE *fp;

        setlocale(LC_CTYPE, "C");

        while ((opt = getopt_long(argc, argv, "+qV", longopts, NULL)) != -1) {
                switch (opt) {
                case 'q':
                        quiet = true;
                        break;
                case 'V':
                        /* Do nothing, compat with GNU rcs's ident */
                        return (EXIT_SUCCESS);
                default:
                        usage();
                }
        }

        argc -= optind;
        argv += optind;

        cap_rights_init(&rights, CAP_READ, CAP_FSTAT, CAP_FCNTL);
        fa = fileargs_init(argc, argv, O_RDONLY, 0, &rights, FA_OPEN);
        if (fa == NULL)
                err(EXIT_FAILURE, "Unable to initialize casper");
        caph_cache_catpages();
        if (caph_limit_stdio() != 0)
                err(EXIT_FAILURE, "Unable to limit stdio");
        if (caph_enter_casper() != 0)
                err(EXIT_FAILURE, "Unable to enter capability mode");

        if (argc == 0) {
                ret = scan(stdin, NULL, quiet);
        } else {
                ret = EXIT_SUCCESS;
                for (i = 0; i < argc; i++) {
                        if ((fp = fileargs_fopen(fa, argv[i], "r")) == NULL)
                                err(EXIT_FAILURE, "%s", argv[i]);
                        if (scan(fp, argv[i], quiet) != EXIT_SUCCESS)
                                ret = EXIT_FAILURE;
                        (void)fclose(fp);
                }
        }

        fileargs_free(fa);
        return (ret);
}