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

#include <capsicum_helpers.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <xlocale.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;
        locale_t l;

        l = newlocale(LC_ALL_MASK, "C", NULL);
        sz = 0;
        buf = NULL;
        buffp = open_memstream(&buf, &sz);
        if (buffp == NULL)
                err(EXIT_FAILURE, "open_memstream()");

        if (name != NULL)
                printf("%s:\n", name);

        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_l(c, l)) {
                                /* Transit to KEYWORD if we see letter */
                                if (buf != NULL)
                                        memset(buf, 0, sz);
                                rewind(buffp);
                                fputc('$', buffp);
                                fputc(c, buffp);
                                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:
                        fputc(c, buffp);

                        if (isalpha_l(c, l)) {
                                /*
                                 * 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:
                        fputc(c, buffp);

                        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:
                        fputc(c, buffp);

                        if (iscntrl_l(c, l)) {
                                /* Control characters are not allowed in this state */
                                state = INIT;
                        } else if (c == '$') {
                                fflush(buffp);
                                /*
                                 * 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);
                                        hasid = true;
                                }
                                state = INIT;
                        }
                        /* Other characters: stay in the state */
                        break;
                }
        }
        fclose(buffp);
        free(buf);
        freelocale(l);

        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);
}

int
main(int argc, char **argv)
{
        bool quiet = false;
        int ch, i, *fds, fd;
        int ret = EXIT_SUCCESS;
        size_t nfds;
        FILE *fp;

        while ((ch = getopt(argc, argv, "qV")) != -1) {
                switch (ch) {
                case 'q':
                        quiet = true;
                        break;
                case 'V':
                        /* Do nothing, compat with GNU rcs's ident */
                        return (EXIT_SUCCESS);
                default:
                        errx(EXIT_FAILURE, "usage: %s [-q] [-V] [file...]",
                            getprogname());
                }
        }

        argc -= optind;
        argv += optind;

        if (caph_limit_stdio() < 0)
                err(EXIT_FAILURE, "unable to limit stdio");

        if (argc == 0) {
                nfds = 1;
                fds = malloc(sizeof(*fds));
                if (fds == NULL)
                        err(EXIT_FAILURE, "unable to allocate fds array");
                fds[0] = STDIN_FILENO;
        } else {
                nfds = argc;
                fds = malloc(sizeof(*fds) * nfds);
                if (fds == NULL)
                        err(EXIT_FAILURE, "unable to allocate fds array");

                for (i = 0; i < argc; i++) {
                        fds[i] = fd = open(argv[i], O_RDONLY);
                        if (fd < 0) {
                                warn("%s", argv[i]);
                                ret = EXIT_FAILURE;
                                continue;
                        }
                        if (caph_limit_stream(fd, CAPH_READ) < 0)
                                err(EXIT_FAILURE,
                                    "unable to limit fcntls/rights for %s",
                                    argv[i]);
                }
        }

        /* Enter Capsicum sandbox. */
        if (caph_enter() < 0)
                err(EXIT_FAILURE, "unable to enter capability mode");

        for (i = 0; i < (int)nfds; i++) {
                if (fds[i] < 0)
                        continue;

                fp = fdopen(fds[i], "r");
                if (fp == NULL) {
                        warn("%s", argv[i]);
                        ret = EXIT_FAILURE;
                        continue;
                }
                if (scan(fp, argc == 0 ? NULL : argv[i], quiet) != EXIT_SUCCESS)
                        ret = EXIT_FAILURE;
                fclose(fp);
        }

        return (ret);
}