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After compilation and installation of C<fuse> kernel module and C<Fuse> perl
bindings for it, you will have to load C<fuse> module into kernel. For that,
you will have to be root. If you are not administrator on particular
machine, ask your admin to install and load C<fuse> module for you.

If you used C<fusermount> command before running this script, module will be
already loaded.

=head2 unsupported operations

There is no support for creation of new templates, renaming, or deleting.
Although those operations map nicely to file system semantics there are still
possible only using WebGUI web interface.

=head2 unlink to invalidate cache

Unlink command (C<rm>) is implemented on files with special function: it
will remove in-memory cache of particular template and reload it from
database. That enables usage of web interface to make small changes and then
continuing editing using this script without restarting it.

In-memory cache is populated with data about available templates when you
start this script. Currently only way to refresh template list (after you
create copy of template through web interface) is to remove directory using
C<rmdir> or C<rm -rf>.

B<Don't panic!> Destructive operations in filesystem (C<rm> and C<rmdir>)
just invalidate in-memory cache and re-read data from database (this will
also change ctime of file, so your editor will probably notice that file has
changed).

In-memory cache is used to speed up operations like grep on templates. If it
wasn't there, grep wouldn't be useful at all. I think this is acceptable
compromise.

=head2 invalidating of on-disk templates

Every write operation will erase all templates on disk (so that next reload
on browser will show your changes). It would be better if just changed
template is erased, but this works well enough. You might notice performance
penalty of this simplification if you are running very loaded production
site.

You have to have write permission on C<uploads/temp/templates/> directory
for your WebGUI instance for this to work. If you don't C<Fuse::DBI> will
complain.

=head2 supported databases

This script have embedded SQL queries for MySQL and PostgreSQL. Other databases
could be supported easily. Contributions are welcomed.

=head2 database transactions

C<Fuse::DBI> uses transactions (if your database supports them) to prevent
accidental corruption of data by reading old version. Depending on type of
database back-end, MySQL users might be out of luck.

=head2 recovering from errors

B<Transport endpoint is not connected> is very often error when Fuse perl
bindings exit without clean umount (through C<Fuse::DBI> C<umount> method or
with C<fusermount -u /mnt> command).

This script will automatically run C<fusermount -u /mnt> if it receives
above error on startup. If it fails, mount point is still in use (that
happens if you changed directory to mount point in other shell). Solution is
simple, just change directory in other back to C<$HOME> (with just C<cd>)
and re-run this script.

=head2 missing Data::Config

If this script complains about missing C<Data::Config> module, you will have
to point path at top which points to lib directory of WebGUI installation.
By default it points to C</data/WebGUI>:

 use lib '/data/WebGUI/lib/';

=cut

my ($config_file,$mount) = @ARGV;

unless ($config_file && $mount) {
	print STDERR <<_USAGE_;
usage: $0 /data/WebGUI/etc/webgui.conf /mnt

For more information see perldoc webgui.pl
_USAGE_
	exit 1;
}

system "fusermount -u $mount" unless (-w $mount);

unless (-w $mount) {
	print STDERR "Current user doesn't have permission on mount point $mount: $!";
	exit 1;
}

my $config = new Data::Config $config_file || "can't open config $config_file: $!";

my $sql = {
	'pg' => {
		'filenames' => q{
			select
				oid as id,
				namespace||'/'||name||' ['||oid||']' as filename,
				length(template) as size,
				iseditable as writable
			from template ;
		},
		'read' => q{
			select template
				from template
				where oid = ?;
		},
		'update' => q{
			update template
				set template = ?	
				where oid = ?;
		},
	},