/*
 * Copyright (c) 1998 Michael Smith.
 * All rights reserved.
 *
 * 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/cdefs.h>

/*
 * Manage an environment-like space in which string variables may be stored.
 * Provide support for some method-like operations for setting/retrieving
 * variables in order to allow some type strength.
 */

#include "stand.h"

#include <string.h>

struct env_var *environ = NULL;

/*
 * Look up (name) and return it's env_var structure.
 */
struct env_var  *
env_getenv(const char *name)
{
        struct env_var  *ev;

        for (ev = environ; ev != NULL; ev = ev->ev_next)
                if (strcmp(ev->ev_name, name) == 0)
                        break;
        return (ev);
}

/*
 * Some notes:
 *
 * If the EV_VOLATILE flag is set, a copy of the variable is made.
 * If EV_DYNAMIC is set, the variable has been allocated with
 * malloc and ownership transferred to the environment.
 * If (value) is NULL, the variable is set but has no value.
 */
int
env_setenv(const char *name, int flags, const void *value,
    ev_sethook_t sethook, ev_unsethook_t unsethook)
{
        struct env_var  *ev, *curr, *last;

        if ((ev = env_getenv(name)) != NULL) {
                /*
                 * If there's a set hook, let it do the work
                 * (unless we are working for one already).
                 */
                if ((ev->ev_sethook != NULL) && !(flags & EV_NOHOOK))
                        return (ev->ev_sethook(ev, flags, value));

                /* If there is data in the variable, discard it. */
                if (ev->ev_value != NULL && (ev->ev_flags & EV_DYNAMIC) != 0)
                        free(ev->ev_value);
                ev->ev_value = NULL;
                ev->ev_flags &= ~EV_DYNAMIC;

        } else {
                /*
                 * New variable; create and sort into list
                 */
                ev = malloc(sizeof (struct env_var));
                ev->ev_name = strdup(name);
                ev->ev_value = NULL;
                ev->ev_flags = 0;
                /* hooks can only be set when the variable is instantiated */
                ev->ev_sethook = sethook;
                ev->ev_unsethook = unsethook;

                /* Sort into list */
                ev->ev_prev = NULL;
                ev->ev_next = NULL;
                /* Search for the record to insert before */
                for (last = NULL, curr = environ; curr != NULL;
                    last = curr, curr = curr->ev_next) {

                        if (strcmp(ev->ev_name, curr->ev_name) < 0) {
                                if (curr->ev_prev) {
                                        curr->ev_prev->ev_next = ev;
                                } else {
                                        environ = ev;
                                }
                                ev->ev_next = curr;
                                ev->ev_prev = curr->ev_prev;
                                curr->ev_prev = ev;
                                break;
                        }
                }
                if (curr == NULL) {
                        if (last == NULL) {
                                environ = ev;
                        } else {
                                last->ev_next = ev;
                                ev->ev_prev = last;
                        }
                }
        }

        /* If we have a new value, use it */
        if (flags & EV_VOLATILE) {
                ev->ev_value = strdup(value);
                ev->ev_flags |= EV_DYNAMIC;
        } else {
                ev->ev_value = (char *)value;
                ev->ev_flags |= flags & EV_DYNAMIC;
        }

        return (0);
}

char *
getenv(const char *name)
{
        struct env_var  *ev;

        /* Set but no value gives empty string */
        if ((ev = env_getenv(name)) != NULL) {
                if (ev->ev_value != NULL)
                        return (ev->ev_value);
                return ("");
        }
        return (NULL);
}

int
setenv(const char *name, const char *value, int overwrite)
{
        /* No guarantees about state, always assume volatile */
        if (overwrite || (env_getenv(name) == NULL))
                return (env_setenv(name, EV_VOLATILE, value, NULL, NULL));
        return (0);
}

int
putenv(const char *string)
{
        char    *value, *copy;
        int     result;

        copy = strdup(string);
        if ((value = strchr(copy, '=')) != NULL)
                *(value++) = 0;
        result = setenv(copy, value, 1);
        free(copy);
        return (result);
}

int
unsetenv(const char *name)
{
        struct env_var  *ev;
        int             err;

        err = 0;
        if ((ev = env_getenv(name)) == NULL) {
                err = ENOENT;
        } else {
                if (ev->ev_unsethook != NULL)
                        err = ev->ev_unsethook(ev);
                if (err == 0) {
                        env_discard(ev);
                }
        }
        return (err);
}

void
env_discard(struct env_var *ev)
{
        if (ev->ev_prev)
                ev->ev_prev->ev_next = ev->ev_next;
        if (ev->ev_next)
                ev->ev_next->ev_prev = ev->ev_prev;
        if (environ == ev)
                environ = ev->ev_next;
        free(ev->ev_name);
        if (ev->ev_value != NULL && (ev->ev_flags & EV_DYNAMIC) != 0)
                free(ev->ev_value);
        free(ev);
}

int
env_noset(struct env_var *ev __unused, int flags __unused,
    const void *value __unused)
{
        return (EPERM);
}

int
env_nounset(struct env_var *ev __unused)
{
        return (EPERM);
}