#include <grass/config.h>

#ifndef USE_G_SOCKS
#ifndef __MINGW32__

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#include <fcntl.h>
#include <pwd.h>
/* for locking based on inode number of a fifo */
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#include <sys/stat.h>

#include <grass/gis.h>
#include <grass/glocale.h>
#include <grass/raster.h>
#include <grass/monitors.h>

#include "open.h"

extern int _rfd, _wfd;
extern int _quiet;

extern int sync_driver(char *);

#define BUFFERSIZ   2048

#define LOCK_OK 1
#define ALREADY_LOCKED 0
#define CANT_CREATE -1
#define CANT_READ -2
#define CANT_WRITE -3

static int _fifo_ino;

static volatile int no_mon;

static int find_process(int);
static int get_ids(char *,int *,int);
static char *who_locked_driver(void);
static int lockfile(char *);
static int fifoto(char *,char *,int);
static RETSIGTYPE dead(int);

static int lock_driver(int);

int unlock_driver(int);

/******************************************************************
* lock_driver(pid)
*
*   this routine "locks" the driver for process pid as follows:
*
*   1. if lockfile exists, 2 old pids are read out of the file.
*
*      the first pid is the global lock, the second is the
*      process id lock. If both match the pid and the current
*      pid, nothing needs to be done.
*
*   2. If the 2nd pid is not the same as the current process
*      and that process is still running, then can't lock
*
*   3. If the first pid is not the same and that process is still
*      running, then can't lock
*
*   4. the driver is locked by writing pid and curretn pid into the file.
*
*   5. The user's name is also written to the file
*
* note: since file is created by this routine, it shouldn't be
*       a file that is used for any other purpose.
*
*       also, this lock mechanism is advisory. programs must call this
*       routine and check the return status.
*
* returns:
*       1 ok lock is in place.
*       0 could not lock because another process has the file locked already
*      -1 error. could not create the lock file
*      -2 error. could not read the lock file.
*      -3 error. could not write the lock file.
******************************************************************/

static RETSIGTYPE dead(int sig)
{
    no_mon = 1 ;
}

static int lockfile(char *file)
{
    char *name;
    char *hostname ;
    int mask;
    char lock_dir[1024] ;

/* create the lock_dir */
    mask = umask(0);
    sprintf(lock_dir, "%s/locks", G_gisbase());
    mkdir(lock_dir,01777);

/* get machine name, if it has one */
    hostname = G__machine_name();
    if (hostname)
    {
        for(name=hostname; *name!='\0'; name++) /* use only first part */
        {
            if (*name == '.')
            {
                *name = 0 ;
                break ;
            }
        }
        strcat(lock_dir, "/");
        strcat(lock_dir, hostname);
        mkdir(lock_dir,0777);
    }
    umask(mask);

    sprintf(file, "%s/mon.%d", lock_dir, _fifo_ino);

        return 0;
}

static int lock_driver(int lock_pid)
{
    char file[512];
    int fd;
    int mask;
    int n;
    int id[3];
    int me;

    lockfile(file);
    me = getpid();
    if (access(file, 0) == 0)      /* file exists */
    {
        for (n = 0; n < 2; n++)
        {
            if (get_ids(file, id, 2))
                break;
            if (n == 0)
                G_sleep(1); /* allow time for file creator to write its pid */
        }
        if (n == 2)
            return CANT_READ;
        if (lock_pid == id[1] && me == id[0])
            return LOCK_OK;
        if (me != id[0] && id[0] >= 0 && find_process(id[0]))
            return ALREADY_LOCKED;
        if (lock_pid != id[1] && find_process(id[1]))
            return ALREADY_LOCKED;
    }
    mask = umask(0);
    fd = creat(file, 0666) ;
    umask(mask);
    if (fd < 0)
        return CANT_CREATE;
    id[0] = me;
    id[1] = lock_pid;
    id[2] = getuid();
    if (write(fd, id, sizeof id) != sizeof id)
    {
        close(fd);
        return CANT_WRITE;
    }
    close(fd);
    return LOCK_OK;
}

static char *who_locked_driver(void)
{
    char file[512];
    int id[3];
    struct passwd *pw;

    lockfile(file);
    if (!get_ids(file, id, 3))
        return ((char *)NULL);
    if ((pw = getpwuid(id[2])) == NULL)
        return ((char *)NULL);
    return (pw->pw_name);
}

static int get_ids(char *file, int *id, int x)
{
    int fd;
    int n;

    if ((fd = open(file, 0)) < 0)
        return 0;
    n = read(fd, id, x*sizeof(*id));
    close(fd);
    return (n == x*sizeof(*id));
}

static int find_process(int pid)
{
    /* attempt to kill pid with NULL signal. if success, then
       process pid is still running. otherwise, must check if
       kill failed because no such process, or because user is
       not owner of process
    */
    if (pid <= 0)
        return 0;/* no such process */

    if (kill(pid, 0) == 0)
        return 1;
    return errno != ESRCH;
}

int unlock_driver(int wipeout)
{
    char file[512];
    int fd;
    int pid;

    lockfile(file);
    if (*file == 0) return 0;
/*
 * two flavors of unlock.
 *   wipeout==0 for current process only
 *   wipeout==1 for global locking key as well
 */
    if (access(file,0) != 0)
        return 0;
    if (!wipeout)
    {
        fd = open(file, 1);
        if (fd < 0) wipeout = 1;
    }
    if (!wipeout)
    {
        pid = -1;
        if(write(fd, &pid, sizeof(pid)) != sizeof(pid))
            wipeout = 1;
        close(fd);
    }
    if (wipeout)
    {
        remove(file);
        if (access(file,0) != 0)
            return 1;
    }
    return -1;
}

/*************************************************
* fifoto(alarm_time)
*      this is the plumbing, the idea is to
*      open fifo pipes for read/write.
*************************************************/

static int fifoto(char *input, char *output, int alarm_time)
{
    struct sigaction mysig, savesig;
    sigset_t mask;
    
    /* Set up signal handling */
    sigemptyset(&mask);
    mysig.sa_handler = dead;
    mysig.sa_mask = mask;
    mysig.sa_flags = 0;
    
    no_mon = 0;
    sigaction(SIGALRM, &mysig, &savesig);
    alarm(alarm_time);
    _wfd = open(output, O_WRONLY);
    alarm(0);
    sigaction(SIGALRM, &savesig, NULL);
    if (no_mon)
        return 0 ;

    no_mon = 0;
    sigaction(SIGALRM, &mysig, &savesig);
    alarm(alarm_time);
    _rfd = open(input, O_RDONLY);
    alarm(0);
    sigaction(SIGALRM, &savesig, NULL);
    if (no_mon)
        return 0 ;

    if( (_wfd == -1) || (_rfd == -1) )
        return -1;

    return 1 ;
}

/* R_open_driver for communication over fifos -- 7 Oct 87 */
/* In verbose mode, errors print a message and exit.  In quiet mode, errors */
/* return a code and no messages are printed.  The flag quiet is set */
/* by calling R__open_quiet just before calling R_open_driver. */
/* Returns in quiet mode opens are defined in open.h */


/*!
 * \brief initialize graphics
 *
 * Initializes connection to
 * current graphics driver. Refer to GRASS User's Manual entries on the
 * <i>d.mon</i> command. If connection cannot be made, the application module
 * sends a message to the user stating that a driver has not been selected or
 * could not be opened. Note that only one application module can be connected to
 * a graphics driver at once.
 * After all graphics have been completed, the driver should be closed.
 *
 *  \param void
 *  \return int
 */

int REM_open_driver(void)
{
    int verbose;
    int try;
    struct MON_CAP *mon;
    char *name;
    char *user;
    char our_input_file[512], our_output_file[512];
    int key, lock;
    char *key_string;
    struct stat stat_buf;

    verbose = !_quiet;
    _quiet = 0;

    name = getenv("MONITOR_OVERRIDE");
    if (!name)
	name = G__getenv("MONITOR");

    if (!name)
    {
        if (verbose)           /* #31 Aug 87 - want error stuff */
        {
            fprintf(stderr,_("No graphics monitor has been selected for output.\n"));
            fprintf(stderr,_("Please run \"d.mon\" to select a graphics monitor.\n"));
            exit(-1);
        }
        return(NO_MON);
    }

    if ((mon = R_parse_monitorcap(MON_NAME,name)) == NULL)
    {
        if (verbose)
        {
            fprintf(stderr,_("No such graphics monitor as <%s>.\n"),name);
            fprintf(stderr,_("Please run \"d.mon\" to select a valid graphics monitor.\n"));
            exit(-1);
        }
        return(NO_MON);
    }

    /* get the fifos and get the inode number of one of them */
    sscanf(mon->link,"%s %s",our_output_file,our_input_file);
    if (stat(our_output_file, &stat_buf) != 0)
    {
        if (verbose)
        {
            fprintf(stderr, _("Can't stat %s\n"), our_output_file);
            exit(-1);
        }
        return (LOCK_FAILED);
    }
    _fifo_ino = stat_buf.st_ino; /* global: used by lockfile() */

    key_string = getenv("GIS_LOCK");
    if (key_string == NULL || sscanf(key_string,"%d",&key) != 1 || key <= 0)
        key = 0;
    lock = lock_driver(key);
    if (lock == 0)
    {
        if (verbose)
        {
            if ((user = who_locked_driver()) == NULL)
                fprintf(stderr,_("Error - Monitor <%s> is in use.\n"),name);
            else
                fprintf(stderr,_("Error - Monitor <%s> is in use by %s.\n"),name,user);
            exit(-1);
        }
        return(LOCKED);
    }
    if (lock < 0)
    {
        if (verbose)
        {
            char file[512];
            fprintf(stderr,_("Error - Could not complete locking process for monitor <%s>.\n"),name);
            lockfile(file);
            fprintf(stderr, "Lock file is %s\n", file);
            exit(-1);
        }
        return(LOCK_FAILED);
    }
    if (verbose)
    {
        for (try = 0; try < 2; try++)
        {
            switch (fifoto(our_input_file,our_output_file,try?15:3))
            {
            case -1:
                fprintf(stderr, _("Error - Can't set up pipe to graphics device.\n"));
                unlock_driver(1);
                exit(-1);
            case 0:
                if (try)
                {
                    fprintf(stderr, _("Error - Graphics monitor <%s> not running!\n"),name);
                    unlock_driver(1);
                    exit(1);
                }
                fprintf(stderr, _("Please start graphics monitor <%s>.\n"),name);
                break;
            default:
                sync_driver(name); /* syncronize driver */
                return(0);
            }             /* switch */
        }               /* for */
    }
    else /* non-verbose mode */
    {
    /*  switch (fifoto(our_input_file,our_output_file,3)) */
        switch (fifoto(our_input_file,our_output_file,1))
        {
        case -1:
            unlock_driver(1);
            return(NO_OPEN);
        case 0:
            unlock_driver(1);
            return(NO_RUN);
        default:
            return(OK);
        }
    }

    return 0;
}

#endif /* __MINGW32__ */
#endif /* USE_G_SOCKS */