/**
 * \file user_config.c
 *
 * \brief GIS Library - Routines related to user's GRASS configuration, tmp, and 
 * miscellaneous files.
 *
 * Functions related to the user's GRASS configuration, tmp, and 
 * miscellaneous files. Provides a set of routines for creating and 
 * accessing elements within the user's "rc" directory. The 
 * directory is in $HOME/.grass.<br>
 *
 * <b>NOTE:</b> As of 2001-03-25 this file is not hooked up.  It is 
 * provided as a candidate for handling $HOME/.grass files and 
 * subdirectories. There may be more functionality desired (such as 
 * deletion routines, directory globs).<br>
 *
 * (C) 2001-2008 by the GRASS Development Team
 *
 * This program is free software under the GNU General Public License
 * (>=v2). Read the file COPYING that comes with GRASS for details.
 *
 * \author Eric G Miller - egm2 at jps net
 *
 * \date 2007-04-14
 */

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#ifndef __MINGW32__
#include <pwd.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <grass/gis.h>


/**************************************************************************
 * _make_toplevel(): make user's toplevel config directory if it doesn't
 * already exist.  Adjust perms to 1700. Returns the toplevel directory
 * path [caller must G_free ()] on success, or NULL on failure
 *************************************************************************/

#ifndef __MINGW32__  /* TODO */
static char *
_make_toplevel (void)
{
    size_t len;
    int status;
#ifdef __MINGW32__
    char *defaulthomedir = "c:";
    char *homedir = getenv ( "HOME" );
#else    
    uid_t me;
    struct passwd *my_passwd;
#endif    
    struct stat buf;
    char *path;

    errno = 0;

    /* Query whatever database to get user's home dir */
#ifdef __MINGW32__
    if ( NULL == homedir ) {
        homedir = defaulthomedir;
    }
    
    len = strlen ( homedir ) + 8; /* + "/.grass\0" */
    if ( NULL == ( path = G_calloc ( 1, len ) ) ) {
        return NULL;
    }
    sprintf ( path, "%s%s", homedir, "/.grass" );
#else
    me = getuid();
    my_passwd = getpwuid (me);
    if (my_passwd == NULL)
        return NULL;

    len = strlen (my_passwd->pw_dir) + 8; /* + "/.grass\0" */
    if (NULL == (path = G_calloc (1, len)))
        return NULL;

    sprintf (path, "%s%s", my_passwd->pw_dir, "/.grass");
#endif

    status = G_lstat (path, &buf);

    /* If errno == ENOENT, the directory doesn't exist */
    if (status != 0)
    {
        if (errno == ENOENT)
        {
            status = G_mkdir (path);
    
            if (status != 0)  /* mkdir failed */
            {
                G_free (path);
                return NULL;
            }
            
            /* override umask settings, if possible */
            chmod (path, S_IRWXU);

            /* otherwise mkdir succeeded, we're done here */
            return path;
        }
        
        /* other errors should not be defined ??? give up */
        G_free (path);
        return NULL;
    }
    /* implicit else */

    /* Examine the stat "buf" */
    /* It better be a directory */
    if (!S_ISDIR(buf.st_mode)) /* File, link, something else */
    {
        errno = ENOTDIR; /* element is not a directory, but should be */
        G_free (path);
        return NULL;
    }

    /* No read/write/execute ??? */
    if (!(
          (S_IRUSR & buf.st_mode) &&
          (S_IWUSR & buf.st_mode) &&
          (S_IXUSR & buf.st_mode)
         )
       )
    {
        errno = EACCES;  /* Permissions error */
        G_free (path);
        return NULL;
    }

    /* We'll assume that if the user grants greater permissions
     * than we would, that they know what they're doing
     * -- so we're done here...
     */

    return path;
}


/**************************************************************************
 * _elem_count_split: Does a couple things:
 * 1) Counts the number of elements in "elems"
 * 2) Replaces occurrences of '/' with '\0'
 * 3) Checks that no element begins with a '.'
 * 4) Checks there are no '//'
 *
 * Therefore, THE STRING THAT IS PASSED IN IS MODIFIED
 * Returns 0 if there are no elements, or an element
 * beginning with a '.' or containing a '//' is found.
 *************************************************************************/
static int
_elem_count_split (char *elems)
{
    int i;
    size_t len;
    char *begin, *end;
    
    /* Some basic assertions */
    assert (elems != NULL);
    assert ((len = strlen(elems)) > 0);
    assert (*elems != '/');
    
    begin = elems;
    for (i = 0; begin != NULL && len > begin - elems; i++)
    {
        /* check '.' condition */
        if (*begin == '.')
            return 0;
        end = strchr (begin, '/');
        /* check '//' condition */
        if (end != NULL && end == begin)
            return 0;
        /* okay, change '/' into '\0' */
        begin = end;
        if (begin != NULL)
        {
            *begin = '\0';  /* begin points at '/', change it */
            begin++;        /* increment begin to next char */
        }
    }

    /* That's it */
    return i;
}
    

/**************************************************************************
 * _make_sublevels(): creates subelements as necessary from the passed
 * "elems" string.  It returns the full path if successful or NULL
 * if it fails.  "elems" must not be NULL, zero length, or have any
 * elements that begin with a '.' or any occurrences of '//'.
 *************************************************************************/
static char *
_make_sublevels(const char *elems)
{
    int i, status;
    char *cp, *path, *top, *ptr;
    struct stat buf;

    /* Get top level path */
    if (NULL == (top = _make_toplevel()))
        return NULL;

    /* Make a copy of elems */
    if (NULL == (cp = G_store (elems)))
    {
        G_free (top);
        return NULL;
    }
    
    /* Do element count, sanity checking and "splitting" */
    if ((i = _elem_count_split (cp)) < 1)
    {
        G_free (cp);
        G_free (top);
        return NULL;
    }

    /* Allocate our path to be large enough */
    if ((path = G_calloc (1, strlen(top) + strlen(elems) + 2)) == NULL)
    {
        G_free (top);
        G_free (cp);
        return NULL;
    }
    
    /* Now loop along adding directories if they don't exist
     * make sure the thing is a directory as well.
     * If there was a trailing '/' in the original "elem", it doesn't
     * make it into the returned path.
     */
    for (; i > 0; i--)
    {
        sprintf (path, "%s/%s", top, cp);
        errno = 0;
        status = G_lstat (path, &buf);
        if (status != 0)
        {
            /* the element doesn't exist */
            status = G_mkdir (path);
            if (status != 0)
            {
                /* Some kind of problem... */
                G_free (top);
                G_free (cp);
                return NULL;
            }
            /* override umask settings, if possible */
            chmod (path, S_IRWXU);
        }
        else
        {
            /* Examine the stat "buf" */
            /* It better be a directory */
            if (!S_ISDIR(buf.st_mode)) /* File, link, something else */
            {
                errno = ENOTDIR; /* element is not a directory, but should be */
                G_free (path);
                return NULL;
            }

            /* No read/write/execute ??? */
            if (!(
                  (S_IRUSR & buf.st_mode) &&
                  (S_IWUSR & buf.st_mode) &&
                  (S_IXUSR & buf.st_mode)
                 )
               )
            {
                errno = EACCES;  /* Permissions error */
                G_free (path);
                return NULL;
            }

            /* okay continue ... */
        }

        ptr = strchr (cp, '\0');
        *ptr = '/';
    }

    /* All done, free memory */
    G_free (top);
    G_free (cp);

    return path;
}

    
/**
 * \brief Returns path to <b>element</b> and <b>item</b>.
 *
 * Either <b>element</b> or <b>item</b> can be NULL, but not both.  If 
 * <b>element</b> is NULL, then the file is assumed to live at the top 
 * level. If file is NULL, then it is assumed the caller is not 
 * interested in the file.  If the element or rc dir do not exist, they 
 * are created. However, the file is never checked for.
 *
 * \param[in] element
 * \param[in] item
 * \return Pointer to string path
 */

char *
G_rc_path (const char *element, const char *item)
{
    size_t len;
    char *path, *ptr;

    assert (!(element == NULL && item == NULL));

    /* Simple item in top-level */
    if (element == NULL)
    {
        path = _make_toplevel();
    }
    else if (item == NULL)
    {
        return _make_sublevels (element);
    }
    else
    {
        path = _make_sublevels (element);
    }
   

    assert (*item != '.');
    assert (path != NULL);
    ptr = strchr (item, '/'); /* should not have slashes */
    assert (ptr == NULL);
    len = strlen(path) + strlen(item) + 2;
    if ((ptr = G_realloc (path, len)) == NULL)
    {
        G_free (path);
        return NULL;
    }
    path = ptr;
    ptr = strchr (path, '\0');
    sprintf (ptr, "/%s", item);

    return path;
} /* G_rc_path */
       

/* vim: set softtabstop=4 shiftwidth=4 expandtab: */
#endif
