/* Copyright 1988,1990,1993,1994 by Paul Vixie
 * All rights reserved
 *
 * Distribute freely, except: don't remove my name from the source or
 * documentation (don't take credit for my work), mark your changes (don't
 * get me blamed for your possible bugs), don't alter or remove this
 * notice.  May be sold if buildable source is provided to buyer.  No
 * warrantee of any kind, express or implied, is included with this
 * software; use at your own risk, responsibility for damages (if any) to
 * anyone resulting from the use of this software rests entirely with the
 * user.
 *
 * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
 * I'll try to keep a version up to date.  I can be reached as follows:
 * Paul Vixie          <paul@vix.com>          uunet!decwrl!vixie!paul
 *
 * $FreeBSD: src/usr.sbin/cron/cron/database.c,v 1.8 1999/08/28 01:15:50 peter Exp $
 */

/* vix 26jan87 [RCS has the log]
 */


#include "cron.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/file.h>


#define TMAX(a,b) ((a)>(b)?(a):(b))


static  void    process_crontab(const char *, const char *, const char *,
                                struct stat *, cron_db *, cron_db *);


void
load_database(cron_db *old_db)
{
        DIR             *dir;
        struct stat     statbuf;
        struct stat     syscron_stat;
        DIR_T           *dp;
        cron_db         new_db;
        user            *u, *nu;

        Debug(DLOAD, ("[%d] load_database()\n", getpid()))

        /* before we start loading any data, do a stat on SPOOL_DIR
         * so that if anything changes as of this moment (i.e., before we've
         * cached any of the database), we'll see the changes next time.
         */
        if (stat(SPOOL_DIR, &statbuf) < OK) {
                log_it("CRON", getpid(), "STAT FAILED", SPOOL_DIR);
                exit(ERROR_EXIT);
        }

        /* track system crontab file
         */
        if (stat(SYSCRONTAB, &syscron_stat) < OK)
                syscron_stat.st_mtime = 0;

        /* if spooldir's mtime has not changed, we don't need to fiddle with
         * the database.
         *
         * Note that old_db->mtime is initialized to 0 in main(), and
         * so is guaranteed to be different than the stat() mtime the first
         * time this function is called.
         */
        if (old_db->mtime == TMAX(statbuf.st_mtime, syscron_stat.st_mtime)) {
                Debug(DLOAD, ("[%d] spool dir mtime unch, no load needed.\n",
                              getpid()))
                return;
        }

        /* something's different.  make a new database, moving unchanged
         * elements from the old database, reloading elements that have
         * actually changed.  Whatever is left in the old database when
         * we're done is chaff -- crontabs that disappeared.
         */
        new_db.mtime = TMAX(statbuf.st_mtime, syscron_stat.st_mtime);
        new_db.head = new_db.tail = NULL;

        if (syscron_stat.st_mtime) {
                process_crontab("root", SYS_NAME,
                                SYSCRONTAB, &syscron_stat,
                                &new_db, old_db);
        }

        /* we used to keep this dir open all the time, for the sake of
         * efficiency.  however, we need to close it in every fork, and
         * we fork a lot more often than the mtime of the dir changes.
         */
        if (!(dir = opendir(SPOOL_DIR))) {
                log_it("CRON", getpid(), "OPENDIR FAILED", SPOOL_DIR);
                exit(ERROR_EXIT);
        }

        while (NULL != (dp = readdir(dir))) {
                char    fname[NAME_MAX + 1 - 5], tabname[NAME_MAX + 1];

                /* avoid file names beginning with ".".  this is good
                 * because we would otherwise waste two guaranteed calls
                 * to getpwnam() for . and .., and also because user names
                 * starting with a period are just too nasty to consider.
                 */
                if (dp->d_name[0] == '.')
                        continue;

                strlcpy(fname, dp->d_name, sizeof(fname));
                snprintf(tabname, sizeof tabname, CRON_TAB(fname));

                process_crontab(fname, fname, tabname,
                                &statbuf, &new_db, old_db);
        }
        closedir(dir);

        /* if we don't do this, then when our children eventually call
         * getpwnam() in do_command.c's child_process to verify MAILTO=,
         * they will screw us up (and v-v).
         */
        endpwent();

        /* whatever's left in the old database is now junk.
         */
        Debug(DLOAD, ("unlinking old database:\n"))
        for (u = old_db->head;  u != NULL;  u = nu) {
                Debug(DLOAD, ("\t%s\n", u->name))
                nu = u->next;
                unlink_user(old_db, u);
                free_user(u);
        }

        /* overwrite the database control block with the new one.
         */
        *old_db = new_db;
        Debug(DLOAD, ("load_database is done\n"))
}


void
link_user(cron_db *db, user *u)
{
        if (db->head == NULL)
                db->head = u;
        if (db->tail)
                db->tail->next = u;
        u->prev = db->tail;
        u->next = NULL;
        db->tail = u;
}


void
unlink_user(cron_db *db, user *u)
{
        if (u->prev == NULL)
                db->head = u->next;
        else
                u->prev->next = u->next;

        if (u->next == NULL)
                db->tail = u->prev;
        else
                u->next->prev = u->prev;
}


user *
find_user(cron_db *db, const char *name)
{
        user    *u;

        for (u = db->head;  u != NULL;  u = u->next)
                if (!strcmp(u->name, name))
                        break;
        return u;
}


static void
process_crontab(const char *uname, const char *fname, const char *tabname,
                struct stat *statbuf, cron_db *new_db, cron_db *old_db)
{
        struct passwd   *pw = NULL;
        int             crontab_fd = OK - 1;
        user            *u;

        if (strcmp(fname, SYS_NAME) && !(pw = getpwnam(uname))) {
                /* file doesn't have a user in passwd file.
                 */
                log_it(fname, getpid(), "ORPHAN", "no passwd entry");
                goto next_crontab;
        }

        if ((crontab_fd = open(tabname, O_RDONLY, 0)) < OK) {
                /* crontab not accessible?
                 */
                log_it(fname, getpid(), "CAN'T OPEN", tabname);
                goto next_crontab;
        }

        if (fstat(crontab_fd, statbuf) < OK) {
                log_it(fname, getpid(), "FSTAT FAILED", tabname);
                goto next_crontab;
        }

        Debug(DLOAD, ("\t%s:", fname))
        u = find_user(old_db, fname);
        if (u != NULL) {
                /* if crontab has not changed since we last read it
                 * in, then we can just use our existing entry.
                 */
                if (u->mtime == statbuf->st_mtime) {
                        Debug(DLOAD, (" [no change, using old data]"))
                        unlink_user(old_db, u);
                        link_user(new_db, u);
                        goto next_crontab;
                }

                /* before we fall through to the code that will reload
                 * the user, let's deallocate and unlink the user in
                 * the old database.  This is more a point of memory
                 * efficiency than anything else, since all leftover
                 * users will be deleted from the old database when
                 * we finish with the crontab...
                 */
                Debug(DLOAD, (" [delete old data]"))
                unlink_user(old_db, u);
                free_user(u);
                log_it(fname, getpid(), "RELOAD", tabname);
        }
        u = load_user(crontab_fd, pw, fname);
        if (u != NULL) {
                u->mtime = statbuf->st_mtime;
                link_user(new_db, u);
        }

next_crontab:
        if (crontab_fd >= OK) {
                Debug(DLOAD, (" [done]\n"))
                close(crontab_fd);
        }
}