/* $Id$ */

/*
 * This file is part of ivcall.
 *
 * ivcall is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * ivcall is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ivcall; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 */

#include <unistd.h>
#include <sys/stat.h>
#include <stdio.h>
#include <limits.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <pwd.h>

#include "lock.h"
#include "util.h"

// Where do lockfiles reside?
#ifndef LOCK_DIR
#define LOCK_DIR "/var/lock"
#endif

static char* lockfile = NULL;

// Tries to lock a TTY-device, returns 0 on success
int device_lock(char *dev, char *appname) {
    char buf[256], u[16];
    char path[PATH_MAX];
    int fd;
    struct passwd *pwd;
    char *username;

    assert(dev && !lockfile);
    
    if (access(LOCK_DIR, W_OK) < 0)
        return -1;
        
    snprintf(path, sizeof(path), "%s/LCK..%s", LOCK_DIR, basename(dev));
      
    if ((fd = open(path, O_RDONLY)) >= 0) {
        int n = loop_read(fd, buf, sizeof(buf) - 1);
        close(fd);

        if (n > 0) {
            int pid;
            
            if (n == 4)
                pid = *(int*) buf;
            else {
                buf[n] = 0;
                sscanf(buf, "%d", &pid);
            }
	      
            if (pid > 0) {
                if (kill((pid_t) pid, 0) < 0 && errno == ESRCH) {
                    fprintf(stderr, "Lockfile is stale. Overriding it.\n");
                    unlink(path);
                } else
                    return -1;
            }
        }
    }

    if ((fd = open(path, O_WRONLY | O_CREAT | O_EXCL, 0666)) < 0)
        return -1;
      
    if ((pwd = getpwuid(getuid())))
        username = pwd->pw_name;
    else
        snprintf(username = u, sizeof(u), "%u", getuid());

    snprintf(buf, sizeof(buf), "%10ld %s %.20s\n", (long)getpid(), appname, username);
    
    if (loop_write(fd, buf, strlen(buf)) < 0) {
        close(fd);
        return -1;
    }
    
    close(fd);

    lockfile = strdup(path);
    
    return 0;
}

// Tries to lock the first free device, returns 0 on success
int device_lock_first(char *appname, char *dev, size_t l) {
    int i, found = 0;

    for (i = 2; i <= 20; i++) {
        snprintf(dev, l, "/dev/ttyI%i", i);
        
        if (!device_lock(dev, appname)) {
            found = 1;
            break;
        }
    }
    
    if (found)
        return 0;
    else {
        fprintf(stderr, "Could not find free device.\n");
        return -1;
    }
}

// Deletes the lockfile
void device_unlock(void) {
    if (lockfile) {
        unlink(lockfile);
        free (lockfile);
        lockfile = NULL;
    }
}