/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2024 Rick Parrish <unitrunker@unitrunker.net>.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include <sys/queue.h>
#include <sys/stat.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <limits.h>
#include <mqueue.h>
#include <pwd.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

struct Creation {
        /* true if the queue exists. */
        bool exists;
        /* true if a mode value was specified. */
        bool set_mode;
        /* access mode with rwx permission bits. */
        mode_t mode;
        /* maximum queue depth. default to an invalid depth. */
        long depth;
        /* maximum message size. default to an invalid size. */
        long size;
        /* true for blocking I/O and false for non-blocking I/O. */
        bool block;
        /* true if a group ID was specified. */
        bool set_group;
        /* group ID. */
        gid_t group;
        /* true if a user ID was specified. */
        bool set_user;
        /* user ID. */
        uid_t user;
};

struct element {
        STAILQ_ENTRY(element) links;
        const char *text;
};

static struct element *
malloc_element(const char *context)
{
        struct element *item = malloc(sizeof(struct element));

        if (item == NULL)
                /* the only non-EX_* prefixed exit code. */
                err(1, "malloc(%s)", context);
        return (item);
}

static STAILQ_HEAD(tqh, element)
        queues = STAILQ_HEAD_INITIALIZER(queues),
        contents = STAILQ_HEAD_INITIALIZER(contents);
/* send defaults to medium priority. */
static long priority = MQ_PRIO_MAX / 2;
static struct Creation creation = {
        .exists = false,
        .set_mode = false,
        .mode = 0755,
        .depth = -1,
        .size = -1,
        .block = true,
        .set_group = false,
        .group = 0,
        .set_user = false,
        .user = 0
};
static const mqd_t fail = (mqd_t)-1;
static const mode_t accepted_mode_bits =
    S_IRWXU | S_IRWXG | S_IRWXO | S_ISUID | S_ISGID | S_ISTXT;

/* OPTIONS parsing utilitarian */

static void
parse_long(const char *text, long *capture, const char *knob, const char *name)
{
        char *cursor = NULL;
        long value = strtol(text, &cursor, 10);

        if (cursor > text && *cursor == 0) {
                *capture = value;
        } else {
                warnx("%s %s invalid format [%s].", knob, name, text);
        }
}

static void
parse_unsigned(const char *text, bool *set,
   unsigned *capture, const char *knob, const char *name)
{
        char *cursor = NULL;
        unsigned value = strtoul(text, &cursor, 8);

        if (cursor > text && *cursor == 0) {
                *set = true;
                *capture = value;
        } else {
                warnx("%s %s format [%s] ignored.", knob, name, text);
        }
}

static bool
sane_queue(const char *queue)
{
        int size = 0;

        if (queue[size] != '/') {
                warnx("queue name [%-.*s] must start with '/'.", NAME_MAX, queue);
                return (false);
        }

        for (size++; queue[size] != 0 && size < NAME_MAX; size++) {
                if (queue[size] == '/') {
                        warnx("queue name [%-.*s] - only one '/' permitted.",
                            NAME_MAX, queue);
                        return (false);
                }
        }

        if (size == NAME_MAX && queue[size] != 0) {
                warnx("queue name [%-.*s...] may not be longer than %d.",
                    NAME_MAX, queue, NAME_MAX);
                return (false);
        }
        return (true);
}

/* OPTIONS parsers */

static void
parse_block(const char *text)
{
        if (strcmp(text, "true") == 0 || strcmp(text, "yes") == 0) {
                creation.block = true;
        } else if (strcmp(text, "false") == 0 || strcmp(text, "no") == 0) {
                creation.block = false;
        } else {
                char *cursor = NULL;
                long value = strtol(text, &cursor, 10);
                if (cursor > text) {
                        creation.block = value != 0;
                } else {
                        warnx("bad -b block format [%s] ignored.", text);
                }
        }
}

static void
parse_content(const char *content)
{
        struct element *n1 = malloc_element("content");

        n1->text = content;
        STAILQ_INSERT_TAIL(&contents, n1, links);
}

static void
parse_depth(const char *text)
{
        parse_long(text, &creation.depth, "-d", "depth");
}

static void
parse_group(const char *text)
{
        struct group *entry = getgrnam(text);

        if (entry == NULL) {
                parse_unsigned(text, &creation.set_group,
                    &creation.group, "-g", "group");
        } else {
                creation.set_group = true;
                creation.group = entry->gr_gid;
        }
}

static void
parse_mode(const char *text)
{
        char *cursor = NULL;
        long value = strtol(text, &cursor, 8);

        // verify only accepted mode bits are set.
        if (cursor > text && *cursor == 0 && (value & accepted_mode_bits) == value) {
                creation.set_mode = true;
                creation.mode = (mode_t)value;
        } else {
                warnx("impossible -m mode value [%s] ignored.", text);
        }
}

static void
parse_priority(const char *text)
{
        char *cursor = NULL;
        long value = strtol(text, &cursor, 10);

        if (cursor > text && *cursor == 0) {
                if (value >= 0 && value < MQ_PRIO_MAX) {
                        priority = value;
                } else {
                        warnx("bad -p priority range [%s] ignored.", text);
                }
        } else {
                warnx("bad -p priority format [%s] ignored.", text);
        }
}

static void
parse_queue(const char *queue)
{
        if (sane_queue(queue)) {
                struct element *n1 = malloc_element("queue name");

                n1->text = queue;
                STAILQ_INSERT_TAIL(&queues, n1, links);
        }
}

static void
parse_single_queue(const char *queue)
{
        if (sane_queue(queue)) {
                if (STAILQ_EMPTY(&queues)) {
                        struct element *n1 = malloc_element("queue name");

                        n1->text = queue;
                        STAILQ_INSERT_TAIL(&queues, n1, links);
                } else
                        warnx("ignoring extra -q queue [%s].", queue);
        }
}

static void
parse_size(const char *text)
{
        parse_long(text, &creation.size, "-s", "size");
}

static void
parse_user(const char *text)
{
        struct passwd *entry = getpwnam(text);
        if (entry == NULL) {
                parse_unsigned(text, &creation.set_user,
                    &creation.user, "-u", "user");
        } else {
                creation.set_user = true;
                creation.user = entry->pw_uid;
        }
}

/* OPTIONS validators */

static bool
validate_always_true(void)
{
        return (true);
}

static bool
validate_content(void)
{
        bool valid = !STAILQ_EMPTY(&contents);

        if (!valid)
                warnx("no content to send.");
        return (valid);
}

static bool
validate_depth(void)
{
        bool valid = creation.exists || creation.depth > 0;

        if (!valid)
                warnx("-d maximum queue depth not provided.");
        return (valid);
}

static bool
validate_queue(void)
{
        bool valid = !STAILQ_EMPTY(&queues);

        if (!valid)
                warnx("missing -q, or no sane queue name given.");
        return (valid);
}

static bool
validate_single_queue(void)
{
        bool valid = !STAILQ_EMPTY(&queues) &&
            STAILQ_NEXT(STAILQ_FIRST(&queues), links) == NULL;

        if (!valid)
                warnx("expected one queue.");
        return (valid);
}

static bool
validate_size(void)
{
        bool valid = creation.exists || creation.size > 0;

        if (!valid)
                warnx("-s maximum message size not provided.");
        return (valid);
}

/* OPTIONS table handling. */

struct Option {
        /* points to array of string pointers terminated by a null pointer. */
        const char **pattern;
        /* parse argument. */
        void (*parse)(const char *);
        /*
         * displays an error and returns false if this parameter is not valid.
         * returns true otherwise.
         */
        bool (*validate)(void);
};

/*
 * parse options by table.
 * index - current index into argv list.
 * argc, argv - command line parameters.
 * options - null terminated list of pointers to options.
 */
static void
parse_options(int index, int argc,
    const char *argv[], const struct Option **options)
{
        while ((index + 1) < argc) {
                const struct Option **cursor = options;
                bool match = false;
                while (*cursor != NULL && !match) {
                        const struct Option *option = cursor[0];
                        const char **pattern = option->pattern;

                        while (*pattern != NULL && !match) {
                                const char *knob = *pattern;

                                match = strcmp(knob, argv[index]) == 0;
                                if (!match)
                                        pattern++;
                        }

                        if (match) {
                                option->parse(argv[index + 1]);
                                index += 2;
                                break;
                        }
                        cursor++;
                }

                if (!match && index < argc) {
                        warnx("skipping [%s].", argv[index]);
                        index++;
                }
        }

        if (index < argc) {
                warnx("skipping [%s].", argv[index]);
        }
}

/* options - null terminated list of pointers to options. */
static bool
validate_options(const struct Option **options)
{
        bool valid = true;

        while (*options != NULL) {
                const struct Option *option = options[0];

                if (!option->validate())
                        valid = false;
                options++;
        }
        return (valid);
}

/* SUBCOMMANDS */

/*
 * queue: name of queue to be created.
 * q_creation: creation parameters (copied by value).
 */
static int
create(const char *queue, struct Creation q_creation)
{
        int flags = O_RDWR;
        struct mq_attr stuff = {
                .mq_curmsgs = 0,
                .mq_maxmsg = q_creation.depth,
                .mq_msgsize = q_creation.size,
                .mq_flags = 0
        };

        if (!q_creation.block) {
                flags |= O_NONBLOCK;
                stuff.mq_flags |= O_NONBLOCK;
        }

        mqd_t handle = mq_open(queue, flags);
        q_creation.exists = handle != fail;
        if (!q_creation.exists) {
                /*
                 * apply size and depth checks here.
                 * if queue exists, we can default to existing depth and size.
                 * but for a new queue, we require that input.
                 */
                if (validate_size() && validate_depth()) {
                        /* no need to re-apply mode. */
                        q_creation.set_mode = false;
                        flags |= O_CREAT;
                        handle = mq_open(queue, flags, q_creation.mode, &stuff);
                }
        }

        if (handle == fail) {
                errno_t what = errno;

                warnc(what, "mq_open(create)");
                return (what);
        }

#ifdef __FreeBSD__
        /*
         * undocumented.
         * See https://bugs.freebsd.org/bugzilla//show_bug.cgi?id=273230
         */
        int fd = mq_getfd_np(handle);

        if (fd < 0) {
                errno_t what = errno;

                warnc(what, "mq_getfd_np(create)");
                mq_close(handle);
                return (what);
        }
        struct stat status = {0};
        int result = fstat(fd, &status);
        if (result != 0) {
                errno_t what = errno;

                warnc(what, "fstat(create)");
                mq_close(handle);
                return (what);
        }

        /* do this only if group and / or user given. */
        if (q_creation.set_group || q_creation.set_user) {
                q_creation.user =
                    q_creation.set_user ? q_creation.user : status.st_uid;
                q_creation.group =
                    q_creation.set_group ? q_creation.group : status.st_gid;
                result = fchown(fd, q_creation.user, q_creation.group);
                if (result != 0) {
                        errno_t what = errno;

                        warnc(what, "fchown(create)");
                        mq_close(handle);
                        return (what);
                }
        }

        /* do this only if altering mode of an existing queue. */
        if (q_creation.exists && q_creation.set_mode &&
            q_creation.mode != (status.st_mode & accepted_mode_bits)) {
                result = fchmod(fd, q_creation.mode);
                if (result != 0) {
                        errno_t what = errno;

                        warnc(what, "fchmod(create)");
                        mq_close(handle);
                        return (what);
                }
        }
#endif /* __FreeBSD__ */

        return (mq_close(handle));
}

/* queue: name of queue to be removed. */
static int
rm(const char *queue)
{
        int result = mq_unlink(queue);

        if (result != 0) {
                errno_t what = errno;

                warnc(what, "mq_unlink");
                return (what);
        }

        return (result);
}

/* Return the display character for non-zero mode. */
static char
dual(mode_t mode, char display)
{
        return (mode != 0 ? display : '-');
}

/* Select one of four display characters based on mode and modifier. */
static char
quad(mode_t mode, mode_t modifier)
{
        static const char display[] = "-xSs";
        unsigned index = 0;
        if (mode != 0)
                index += 1;
        if (modifier)
                index += 2;
        return (display[index]);
}

/* queue: name of queue to be inspected. */
static int
info(const char *queue)
{
        mqd_t handle = mq_open(queue, O_RDONLY);

        if (handle == fail) {
                errno_t what = errno;

                warnc(what, "mq_open(info)");
                return (what);
        }

        struct mq_attr actual;

        int result = mq_getattr(handle, &actual);
        if (result != 0) {
                errno_t what = errno;

                warnc(what, "mq_getattr(info)");
                return (what);
        }

        fprintf(stdout,
            "queue: '%s'\nQSIZE: %lu\nMSGSIZE: %ld\nMAXMSG: %ld\n"
            "CURMSG: %ld\nflags: %03ld\n",
            queue, actual.mq_msgsize * actual.mq_curmsgs, actual.mq_msgsize,
            actual.mq_maxmsg, actual.mq_curmsgs, actual.mq_flags);
#ifdef __FreeBSD__

        int fd = mq_getfd_np(handle);
        struct stat status;

        result = fstat(fd, &status);
        if (result != 0) {
                warn("fstat(info)");
        } else {
                mode_t mode = status.st_mode;

                fprintf(stdout, "UID: %u\nGID: %u\n", status.st_uid, status.st_gid);
                fprintf(stdout, "MODE: %c%c%c%c%c%c%c%c%c%c\n",
                    dual(mode & S_ISVTX, 's'),
                    dual(mode & S_IRUSR, 'r'),
                    dual(mode & S_IWUSR, 'w'),
                    quad(mode & S_IXUSR, mode & S_ISUID),
                    dual(mode & S_IRGRP, 'r'),
                    dual(mode & S_IWGRP, 'w'),
                    quad(mode & S_IXGRP, mode & S_ISGID),
                    dual(mode & S_IROTH, 'r'),
                    dual(mode & S_IWOTH, 'w'),
                    dual(mode & S_IXOTH, 'x'));
        }
#endif /* __FreeBSD__ */

        return (mq_close(handle));
}

/* queue: name of queue to drain one message. */
static int
recv(const char *queue)
{
        mqd_t handle = mq_open(queue, O_RDONLY);

        if (handle == fail) {
                errno_t what = errno;

                warnc(what, "mq_open(recv)");
                return (what);
        }

        struct mq_attr actual;

        int result = mq_getattr(handle, &actual);

        if (result != 0) {
                errno_t what = errno;

                warnc(what, "mq_attr(recv)");
                mq_close(handle);
                return (what);
        }

        char *text = malloc(actual.mq_msgsize + 1);
        unsigned q_priority = 0;

        memset(text, 0, actual.mq_msgsize + 1);
        result = mq_receive(handle, text, actual.mq_msgsize, &q_priority);
        if (result < 0) {
                errno_t what = errno;

                warnc(what, "mq_receive");
                mq_close(handle);
                return (what);
        }

        fprintf(stdout, "[%u]: %-*.*s\n", q_priority, result, result, text);
        return (mq_close(handle));
}

/*
 * queue: name of queue to send one message.
 * text: message text.
 * q_priority: message priority in range of 0 to 63.
 */
static int
send(const char *queue, const char *text, unsigned q_priority)
{
        mqd_t handle = mq_open(queue, O_WRONLY);

        if (handle == fail) {
                errno_t what = errno;

                warnc(what, "mq_open(send)");
                return (what);
        }

        struct mq_attr actual;

        int result = mq_getattr(handle, &actual);

        if (result != 0) {
                errno_t what = errno;

                warnc(what, "mq_attr(send)");
                mq_close(handle);
                return (what);
        }

        int size = strlen(text);

        if (size > actual.mq_msgsize) {
                warnx("truncating message to %ld characters.\n", actual.mq_msgsize);
                size = actual.mq_msgsize;
        }

        result = mq_send(handle, text, size, q_priority);

        if (result != 0) {
                errno_t what = errno;

                warnc(what, "mq_send");
                mq_close(handle);
                return (what);
        }

        return (mq_close(handle));
}

static void
usage(FILE *file)
{
        fprintf(file,
            "usage:\n\tposixmqcontrol [rm|info|recv] -q <queue>\n"
            "\tposixmqcontrol create -q <queue> -s <maxsize> -d <maxdepth> "
            "[ -m <mode> ] [ -b <block> ] [-u <uid> ] [ -g <gid> ]\n"
            "\tposixmqcontrol send -q <queue> -c <content> "
            "[-p <priority> ]\n");
}

/* end of SUBCOMMANDS */

#define _countof(arg) ((sizeof(arg)) / (sizeof((arg)[0])))

/* convert an errno style error code to a sysexits code. */
static int
grace(int err_number)
{
        static const int xlat[][2] = {
                /* generally means the mqueuefs driver is not loaded. */
                {ENOSYS, EX_UNAVAILABLE},
                /* no such queue name. */
                {ENOENT, EX_OSFILE},
                {EIO, EX_IOERR},
                {ENODEV, EX_IOERR},
                {ENOTSUP, EX_TEMPFAIL},
                {EAGAIN, EX_IOERR},
                {EPERM, EX_NOPERM},
                {EACCES, EX_NOPERM},
                {0, EX_OK}
        };

        for (unsigned i = 0; i < _countof(xlat); i++) {
                if (xlat[i][0] == err_number)
                        return (xlat[i][1]);
        }

        return (EX_OSERR);
}

/* OPTIONS tables */

/* careful: these 'names' arrays must be terminated by a null pointer. */
static const char *names_queue[] = {"-q", "--queue", "-t", "--topic", NULL};
static const struct Option option_queue = {
        .pattern = names_queue,
        .parse = parse_queue,
        .validate = validate_queue};
static const struct Option option_single_queue = {
        .pattern = names_queue,
        .parse = parse_single_queue,
        .validate = validate_single_queue};
static const char *names_depth[] = {"-d", "--depth", "--maxmsg", NULL};
static const struct Option option_depth = {
        .pattern = names_depth,
        .parse = parse_depth,
        .validate = validate_always_true};
static const char *names_size[] = {"-s", "--size", "--msgsize", NULL};
static const struct Option option_size = {
        .pattern = names_size,
        .parse = parse_size,
        .validate = validate_always_true};
static const char *names_block[] = {"-b", "--block", NULL};
static const struct Option option_block = {
        .pattern = names_block,
        .parse = parse_block,
        .validate = validate_always_true};
static const char *names_content[] = {
        "-c", "--content", "--data", "--message", NULL};
static const struct Option option_content = {
        .pattern = names_content,
        .parse = parse_content,
        .validate = validate_content};
static const char *names_priority[] = {"-p", "--priority", NULL};
static const struct Option option_priority = {
        .pattern = names_priority,
        .parse = parse_priority,
        .validate = validate_always_true};
static const char *names_mode[] = {"-m", "--mode", NULL};
static const struct Option option_mode = {
        .pattern = names_mode,
        .parse = parse_mode,
        .validate = validate_always_true};
static const char *names_group[] = {"-g", "--gid", NULL};
static const struct Option option_group = {
        .pattern = names_group,
        .parse = parse_group,
        .validate = validate_always_true};
static const char *names_user[] = {"-u", "--uid", NULL};
static const struct Option option_user = {
        .pattern = names_user,
        .parse = parse_user,
        .validate = validate_always_true};

/* careful: these arrays must be terminated by a null pointer. */
#ifdef __FreeBSD__
static const struct Option *create_options[] = {
        &option_queue, &option_depth, &option_size, &option_block,
        &option_mode, &option_group, &option_user, NULL};
#else  /* !__FreeBSD__ */
static const struct Option *create_options[] = {
        &option_queue, &option_depth, &option_size, &option_block,
        &option_mode, NULL};
#endif /* __FreeBSD__ */
static const struct Option *info_options[] = {&option_queue, NULL};
static const struct Option *unlink_options[] = {&option_queue, NULL};
static const struct Option *recv_options[] = {&option_single_queue, NULL};
static const struct Option *send_options[] = {
        &option_queue, &option_content, &option_priority, NULL};

int
main(int argc, const char *argv[])
{
        STAILQ_INIT(&queues);
        STAILQ_INIT(&contents);

        if (argc > 1) {
                const char *verb = argv[1];
                int index = 2;

                if (strcmp("create", verb) == 0 || strcmp("attr", verb) == 0) {
                        parse_options(index, argc, argv, create_options);
                        if (validate_options(create_options)) {
                                int worst = 0;
                                struct element *itq;

                                STAILQ_FOREACH(itq, &queues, links) {
                                        const char *queue = itq->text;

                                        int result = create(queue, creation);
                                        if (result != 0)
                                                worst = result;
                                }

                                return (grace(worst));
                        }

                        return (EX_USAGE);
                } else if (strcmp("info", verb) == 0 || strcmp("cat", verb) == 0) {
                        parse_options(index, argc, argv, info_options);
                        if (validate_options(info_options)) {
                                int worst = 0;
                                struct element *itq;

                                STAILQ_FOREACH(itq, &queues, links) {
                                        const char *queue = itq->text;
                                        int result = info(queue);

                                        if (result != 0)
                                                worst = result;
                                }

                                return (grace(worst));
                        }

                        return (EX_USAGE);
                } else if (strcmp("send", verb) == 0) {
                        parse_options(index, argc, argv, send_options);
                        if (validate_options(send_options)) {
                                int worst = 0;
                                struct element *itq;

                                STAILQ_FOREACH(itq, &queues, links) {
                                        const char *queue = itq->text;
                                        struct element *itc;

                                        STAILQ_FOREACH(itc, &contents, links) {
                                                const char *content = itc->text;
                                                int result = send(queue, content, priority);

                                                if (result != 0)
                                                        worst = result;
                                        }
                                }

                                return (grace(worst));
                        }
                        return (EX_USAGE);
                } else if (strcmp("recv", verb) == 0 ||
                    strcmp("receive", verb) == 0) {
                        parse_options(index, argc, argv, recv_options);
                        if (validate_options(recv_options)) {
                                const char *queue = STAILQ_FIRST(&queues)->text;
                                int worst = recv(queue);

                                return (grace(worst));
                        }

                        return (EX_USAGE);
                } else if (strcmp("unlink", verb) == 0 ||
                    strcmp("rm", verb) == 0) {
                        parse_options(index, argc, argv, unlink_options);
                        if (validate_options(unlink_options)) {
                                int worst = 0;
                                struct element *itq;

                                STAILQ_FOREACH(itq, &queues, links) {
                                        const char *queue = itq->text;
                                        int result = rm(queue);

                                        if (result != 0)
                                                worst = result;
                                }

                                return (grace(worst));
                        }

                        return (EX_USAGE);
                } else if (strcmp("help", verb) == 0) {
                        usage(stdout);
                        return (EX_OK);
                } else {
                        warnx("Unknown verb [%s]", verb);
                        return (EX_USAGE);
                }
        }

        usage(stdout);
        return (EX_OK);
}