# File::Data into cvs
# Copyright 2000 2001 Richard Foley richard.foley@rfi.net
# $Id: Data.pm,v 1.12 2002/04/09 14:26:50 richard Exp $
#

package File::Data;           
use strict;
use Carp;
use Data::Dumper;
use Fcntl qw(:flock);
use FileHandle;
# use Tie::File; # <- todo
# use File::stat;
use vars qw(@ISA $VERSION $AUTOLOAD);
$VERSION = do { my @r = (q$Revision: 1.12 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r }; 
$| = 1;

=head1 NAME

File::Data - interface to file data

=head1 DESCRIPTION

Wraps all the accessing of a file into a convenient set of calls for
reading and writing data, including a simple regex interface.  

Note that the file needs to exist prior to using this module!

See L<new()>

=head1 SYNOPSIS

=over 4

	use strict;

	use File::Data;

	my $o_dat = File::Data->new('./t/example');

	$o_dat->write("complete file contents\n");

	$o_dat->prepend("first line\n"); # line 0

	$o_dat->append("original second (last) line\n");

	$o_dat->insert(2, "new second line\n"); # inc. zero!

	$o_dat->replace('line', 'LINE');

	print $o_dat->READ;

Or, perhaps more seriously :-}

	my $o_sgm = File::Data->new('./sgmlfile');

	print "new SGML data: ".$o_sgm->REPLACE(
		'\<\s*((?i)tag)\s*\>\s*((?s).*)\s*\<\s*((?i)\s*\/\s*tag)\s*\>', 
		qq|<tag>key="val"</tag>|,		
	) if $o_sgm;

See L<METHODS> and L<EXAMPLES>.

=head1 IMPORTANT

lowercase method calls return the object itself, so you can chain calls.

	my $o_obj = $o_dat->read; # ! <= object !

UPPERCASE method calls return the data relevant to the operation.

	my @data  = $o_dat->READ; # ! <= data   !

While this may occasionally be frustrating, using the B<principle of
least surprise>, it is at least consistent.

See L<do>

=head1 EXPLANATION

=over 4

The idea is to standardise accessing of files for repetitive and straight
forward tasks, and remove the repeated and therefore error prone file
access I have seen in many sites, where varying, (with equivalently
varying success), methods are used to achieve essentially the same result
- a simple search and replace and/or a regex match.

Approaches to opening and working with files vary so much, where
one person may wish to know if a file exists, another wishes to know
whether the target is a file, or if it is readable, or writable and so on.
Sometimes, in production code even (horror), file's are opened without any
checks of whether the open was succesful.  Then there's a loop through
each line to find the first or many patterns to read and/or replace.
With a failure, normally the only message is 'permission denied', is
that read or write access, does the file even exist? etc.

This module attempts to provide a plain/generic interface to accessing
a file's data.  This will not suit every situation, but I have included
some examples which will hopefully demonstrate that it may be used
in situations where people would normally go through varying and
inconsistent, (and therefore error-prone),  procedures - to get at the
same data.

Theoretically you can mix and match your read and writes so long as you
don't open read-only.

	my $o_dat  = File::Data->new($file);

	my $i_snrd = $o_dat->append($append)->REPLACE($search, $replace);

	print $o_dat->READ;

One last thing - I'm sure this could be made much more efficient,
and I'll be very interested to try and incorporate any suggestions
to that effect.  Note though that the intention has been to create a
simple moderately consistent interface, rather than a complicated one.
Sometimes it's better to roll your own, and sometimes you don't have to
reinvent the wheel - TMTOWTDI.

=back

=cut

# Methods we like:
# ================================================================
# 
my @_METHODS = qw(append insert prepend read replace return search write);
my $_METHODS = join('|', @_METHODS);

=head1 METHODS

=over 4

=item new

Create a new File::Data object (default read-write).

	my $o_rw = File::Data->new($filename); # read-write

	my $o_ro = File::Data->new($filename, 'ro'); # read-only

Each file should have it's own discrete object.

Note that if you open a file read-only and then attempt to write to it,
that will be regarded as an error, even if you change the permissions
in the meantime.

Further: The file B<must> exist before succesful use of this method
is possible.  This is B<not> a replacement for modules which create and
delete files, this is purely designed as an interface to the B<data>
of existing files.  A B<create> function is a future possibility.

Look in L<EXAMPLES> for a more complete explanation of possible arguments
to the B<new()> method

=cut

sub new {
	my $class = shift;
	my $file  = shift;
	my $perms = shift || $File::Data::PERMISSIONS; 
	my $h_err = shift || {};

	my $self = bless({
		'_err'	=> {},
		'_var'	=> {
			'backup'	=> 0,
			'limbo'		=> '',
			'state'	    => 'init',
			'writable'	=> 0,
		},
	}, $class);

	$self->_debug("file($file), perm($perms), h_err($h_err)") if $File::Data::DEBUG;
	my $i_ok = $self->_init($file, $perms, $h_err);

	return $i_ok == 1 ? $self : undef;
}

=item read

Read all data from file

	$o_dat = $o_dat->read; # !

	my @data = $o_dat->READ;

=cut

sub READ {
	my $self = shift;

	$self->_enter('read');
	$self->_debug('in: ') if $File::Data::DEBUG;

	my @ret = $self->_read;

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('read');

	return @ret;
};

sub _read { # 
	my $self = shift;

	my $FH = $self->_fh;
	$FH->seek(0, 0);
	#
	my @ret = <$FH>;	

	return ($File::Data::REFERENCE) ? \@ret : @ret;
};

=item write

Write data to file

	my $o_dat = $o_dat->WRITE; # !

	my @written = $o_dat->write;

=cut

sub WRITE {
	my $self = shift;
	my @args = @_;
	my @ret  = ();

	$self->_enter('write');
	$self->_debug('in: '.Dumper(\@args)) if $File::Data::DEBUG;

	if ($self->_writable) {
		my $FH = $self->_fh;
		$FH->truncate(0);
		$FH->seek(0, 0);
		@ret = $self->_write(@args);
	}

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('write');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
};

sub _write { # 
	my $self = shift;
	my @ret  = ();

	my $FH = $self->_fh;
	my $pos = $FH->tell;
	$self->_debug("writing at curpos: $pos") if $File::Data::DEBUG;
	foreach (@_) {
		push(@ret, $_) if print $FH $_;
        $self->_debug("wrote -->$_<--") if $File::Data::DEBUG;
	}

	return ($File::Data::REFERENCE) ? \@ret : @ret;
};

=item prepend

Prepend to file

	my $o_dat = $o_dat->prepen(\@lines); # !

	my @prepended = $o_dat->prepend(\@lines);

=cut

sub PREPEND {
	my $self = shift;
	my @ret  = ();

	$self->_enter('prepend');
	$self->_debug('in: '.Dumper(@_)) if $File::Data::DEBUG;

	if ($self->_writable) {
		my $FH = $self->_fh;
		$FH->seek(0, 0);
		my @data = <$FH>;
		$FH->truncate(0);
		$FH->seek(0, 0);
		@ret = @_ if $self->_write(@_, @data);
	}

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('prepend');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
};

=item insert

Insert data at line number, starting from '0'

	my $o_dat = $o_dat->insert($i_lineno, \@lines); # !

	my @inserted = $o_dat->INSERT($i_lineno, \@lines);

=cut

sub INSERT {
	my $self = shift;
	my $line = shift;
	my @ret  = ();

	$self->_enter('insert');
	$self->_debug('in: '.Dumper(\@_)) if $File::Data::DEBUG;

	if ($line !~ /^\d+$/) {
		$self->_error("can't go to non-numeric line($line)");
	} else {
		if ($self->_writable) {
			my $FH = $self->_fh;
			$FH->seek(0, 0);
			my $i_cnt = -1;
			my @pre  = ();
			my @post = ();
			while (<$FH>) {
				$i_cnt++; # 0..n
				my $pos = $FH->tell;
				if ($i_cnt < $line) {
					push(@pre, $_);
				} elsif ($i_cnt >= $line) {
					push(@post, $_);
				}	
			}
			$i_cnt++;
			if (!($i_cnt >= $line)) {
				my $s = ($i_cnt == 1) ? '' : 's';
				$self->_error("couldn't insert($line, ...) while only $i_cnt line$s in file");	
			} else {
				$FH->truncate(0);
				$FH->seek(0, 0);
				@ret = @_ if $self->_write(@pre, @_, @post);
			}
		}
	}

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('insert');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
}

=item append

Append to file

	my $o_dat = $o_dat->append(\@lines); # !

	my @appended = $o_dat->APPEND(\@lines);

=cut

sub APPEND {
	my $self = shift;
	my @ret  = ();

	$self->_enter('append');
	$self->_debug('in: '.Dumper(\@_)) if $File::Data::DEBUG;

	if ($self->_writable) {
		my $FH = $self->_fh;
		$FH->seek(0, 2);
		@ret = @_ if $self->_write(@_);
	}

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('append');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
};

=item search

Retrieve data out of a file, simple list of all matches found are returned.

Note - you must use capturing parentheses for this to work!

	my $o_dat = $o_dat->search('/^(.*\@.*)$/'); # !

	my @addrs = $o_dat->SEARCH('/^(.*\@.*)$/');

	my @names = $o_dat->SEARCH('/^(?:[^:]:){4}([^:]+):/');

=cut

sub SEARCH {
	my $self   = shift;
	my $search = shift; 
	my @ret    = ();

	$self->_enter('search');
	$self->_debug("in: $search") if $File::Data::DEBUG;

	if ($search !~ /.+/) {
		$self->_error("no search($search) given");
	} else {
		my $file = $self->_var('filename');
		my $FH = $self->_fh;
		$FH->seek(0, 0);
		my $i_cnt = 0;
		if ($File::Data::STRING) {       # default
			my $orig = $/;    $/ = undef; # slurp
			my $data = <$FH>; $/ = $orig;
			$self->_debug("looking at data($data)") if $File::Data::DEBUG;
			@ret = ($data =~ /$search/g);
			$i_cnt = ($data =~ tr/\n/\n/);
		} else {
			while (<$FH>) {
				$self->_debug("looking at line($_)") if $File::Data::DEBUG;
				my $line = $_;
				push(@ret, ($line =~ /$search/));
				$i_cnt++;
			}
		}
		if (scalar(@ret) >= 1) {
			$self->_debug("search($search) failed(@ret) in file($file) lines($i_cnt)");
		}	
	}

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('search');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
}

=item replace 

Replace data in a 'search and replace' manner, returns the final data.

	my $o_dat = $o_dat->replace($search, $replace); # !

	my @data = $o_dat->REPLACE($search, $replace);

	my @data = $o_dat->REPLACE(
		q|\<a href=(['"])([^$1]+)?$1| => q|'my.sales.com'|,
	);

This is B<simple>, in that you can do almost anything in the B<search> side, 
but the B<replace> side is a bit more restricted, as we can't effect the 
replacement modifiers on the fly.  

If you really need this, perhaps B<(?{})> can help?

=cut

sub REPLACE {
	my $self = shift;
	my %args = @_;
	my @ret  = ();

	$self->_enter('replace');
	$self->_debug('in: '.Dumper(\%args)) if $File::Data::DEBUG;

	if ($self->_writable) {
		my $file = $self->_var('filename');
		my $FH = $self->_fh;
		$FH->seek(0, 0);
		my $i_cnt = 0;
		SEARCH:
		foreach my $search (keys %args) {
			my $replace = $args{$search};
			if ($File::Data::STRING) {       # default
				my $orig = $/;    $/ = undef; # slurp
				my $data = <$FH>; $/ = $orig;
				$self->_debug("initial ($data)") if $File::Data::DEBUG;
				if (($i_cnt = ($data =~ s/$search/$replace/g))) {
					@ret = $data; 
				} else {
					print "unable($i_cnt) to search($search) and replace($replace)\n";
				}
			} else {
				while (<$FH>) {
					$self->_debug("initial line($_)") if $File::Data::DEBUG;
					my $line = $_;
					if ($line =~ s/$search/$replace/) {
						$i_cnt++;
					}
					push(@ret, $line);
				}
			}
            if (scalar(@ret) >= 1) {
                $FH->seek(0, 0);
                $FH->truncate(0);
                $FH->seek(0, 0);
                @ret = $self->_write(@ret); 
            }
			if (!($i_cnt >= 1)) {
				$self->_debug("nonfulfilled search($search) and replace($replace) in file($file)");
			}
		}
	}

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('replace');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
}

=item xreturn

Returns the product of the given (or last) B<do()>, undef on failure.

    my $o_dat = $o_dat->prepend($A)->append($b)->return('prepend'); # !

    my @prepended = $o_dat->prepend($A)->append($b)->RETURN('prepend');

    my @appended  = $o_dat->prepend($A)->append($b)->RETURN; # like read()

=cut

sub RETURN {
	my $self = shift;
	my $call = uc(shift) || $self->_var('last');

	if ((defined($self->{'_var'}{$call}) && 
		     ref($self->{'_var'}{$call}) eq 'ARRAY'
	)) {
		return @{$self->_var($call)};
	} else {
		$self->_debug("not returning invalid call($call) ref($self->{'_var'}{$call})");
		return undef;
	}
}

=item create

placeholder - unsupported

=cut

sub create {
	my $self = shift;

	$self->_error("unsupported call: __FILE__(@_)"); 

	return ();
}

=item delete 

placeholder - unsupported

=cut

sub delete {
	my $self = shift;

	$self->_error("unsupported call: __FILE__(@_)"); 

	return ();
}

=item close 

Close the file

	my $i_closed = $o_dat->close; # 1|0

=cut

sub close {
	my $self = shift;

	return $self->_close;
}


=item info 

placeholder - unsupported

=cut

# Returns File::stat object for the file.

# 	print 'File size: '.$o_dat->stat->size;

sub xFSTAT {
	my $self = shift;
	my $file = shift || '_';

	# print "file($file) stat: ".Dumper(stat($file));

	# return stat($file);

	return ();
}

sub xfstat {
	my $self = shift;
	my $file = shift || '_';

	# print "file($file) stat: ".Dumper(stat($file));

	# stat($file);

	return ();
}

sub dummy {
	my $self = shift;
	my %args = @_;
	my @ret  = ();

	$self->_enter('dummy');
	$self->_debug('in: '.Dumper(\%args)) if $File::Data::DEBUG;

	# if ($self->_writable) {
	# rjsf
	# $FH->seek(0, 2);
	# }

	$self->_debug('out: '.Dumper(\@ret)) if $File::Data::DEBUG;
	$self->_leave('dummy');

	return ($File::Data::REFERENCE) ? \@ret : @ret;
}

=back

=cut

# ================================================================

=head1 VARIABLES

Various variables may be set affecting the behaviour of the module.

=over 4

=item $File::Data::DEBUG

Set to 0 (default) or 1 for debugging information to be printed on STDOUT.

	$File::Data::DEBUG = 1;

Alternatively  set to a regex of any of the prime methods to debug them individually.

	$File::Data::DEBUG = '(ap|pre)pend';

=cut

$File::Data::DEBUG ||= $ENV{'File_Data_DEBUG'} || 0;
# $File::Data::DEBUG = 1; # rjsf

=item $File::Data::FATAL

Will die if there is any failure in accessing the file, or reading the data.

Default = 0 (don't die - just warn);

	$File::Data::FATAL = 1;	# die

=cut

$File::Data::FATAL ||= $ENV{'File_Data_FATAL'} || 0;

=item $File::Data::REFERENCE

Will return a reference, not a list, useful with large files.

Default is 0, ie; methods normally returns a list.

Hopefully future versions of perl may return a reference if you request one, 
but as this is not supported generically yet, nor do we, so we require the 
variable to be set.  There may be an argument to make this a reference by 
default, feedback will decide.

	$File::Data::REFERENCE = 1;

	my $a_ref = $o_dat->search('.*');

	print "The log: \n".@{ $a_ref };

=cut

$File::Data::REFERENCE ||= $ENV{'File_Data_REFERENCE'} || 0;


=item $File::Data::SILENT

Set to something other than zero if you don't want error messages ?-\

	$File::Data::SILENT = 0; # per line

=cut

$File::Data::SILENT ||= $ENV{'File_Data_SILENT'} || 0;


=item $File::Data::STRING

Where regex's are used, default behaviour is to treate the entire file as a 
single scalar string, so that, for example, B<(?ms:...)> matches are effective.

Unset if you don't want this behaviour.

	$File::Data::STRING = 0; # per line

=cut

$File::Data::STRING ||= $ENV{'File_Data_STRING'} || 1;


=item $File::Data::PERMISSIONS

File will be opened read-write (B<insert()> compatible) unless this
variable is set explicitly or given via B<new()>.  In either case,
unless it is one of our valid permission B<keys> declared below,
it will be passed on to B<FileHandle> and otherwise not modified.
We don't support fancy permission sets, just read or write.

Read-only permissions may be explicitly set using one of these B<keys>:

	$File::Data::PERMISSIONS = 'ro'; # or readonly or <

Or, equivalently, for read-write (default):

	$File::Data::PERMISSIONS = 'rw'; # or readwrite or +<

Note that it makes no sense to have an 'append only' command (>>),
we'd have to disable all of write, search and replace, and insert,
etc. in that case - just use the B<append()> method only.

This is a KISS-compatible module remember?

=cut

$File::Data::PERMISSIONS ||= $ENV{'File_Data_PERMISSIONS'} || '+<';


=back

# ================================================================

=head1 SPECIAL

...

=over 4

=item AUTOLOAD

Any unrecognised function will be passed to the FileHandle object for final 
consideration, behaviour is then effectively 'o_dat ISA FileHandle'.

	$o_dat->truncate;

=cut

sub AUTOLOAD {
    my $self = shift;
    return if $AUTOLOAD =~ /::DESTROY$/o;    # protection

    my $meth = $AUTOLOAD;
	$meth =~ s/.+::([^:]+)$/$1/;
 
    if ($meth =~ /^($_METHODS)$/io) { 		# convenience
		$self->_debug("rerouting: $meth(@_)");
        return $self->do(uc($meth), @_);					# <- 
        # return $self->do(lc($meth), @_); 
    } else { 								# or fallback
		my $FH = $self->_fh;
		if ($FH->can($meth)) {
			return $FH->$meth(@_);							# <-
		} else {									
			$DB::single=2; # rjsf
			return $self->_error("no such method($meth)!"); # <-
		}
    }
}

=back

=cut

# ================================================================

=head1 EXAMPLES

Typical construction examples:

	my $o_rw = File::Data->new($filename, 'rw');

	my $o_ro = File::Data->new($filename, 'ro');

=over 4

=item complete

	my $o_dat = File::Data->new('./jabber');

	$o_dat->write("  Bewxre the Jabberwock my son,\n");

	$o_dat->prepend("The Jxbberwock by Lewis Cxrroll:\n");

	$o_dat->append("  the claws thxt snxtch,\n  ...\n");

	$o_dat->insert(2, "  the jaws which bite.\n");

	$o_dat->replace('x', 'a');

	print $o_dat->SEARCH('The.+\n')->REPLACE("The.+\n", '')->return('search');

	print $o_dat->READ;

=item error

Failure is indicated by an error routine being called, this will print 
out any error to STDERR, unless warnings are declared fatal, in which 
case we croak.  You can register your own error handlers for any method 
mentioned in the L<METHOD> section of this document, in addition is a 
special B<init> call for initial file opening and general setting up.

Create a read-write object with a callback for all errors:

	my $o_rw = File::Data->new($filename, 'ro', {
		'error'		=> \&myerror,
	});

Create a read-only object with a separate object handler for each error type:

	my $o_rw = File::Data->new($filename, 'rw', {
		'error'		=> $o_generic->error_handler,
		'insert'	=> $o_handler->insert_error,
		'open'		=> $o_open_handler,
		'read'		=> \&carp,
		'write'		=> \&write_error,
	});

=item commandline

From the command line:

	C<perl -MFile::Data -e "File::Data->new('./test.txt')->write('some stuff')">

And (very non-obfuscated)

  C<
  perl -MFile::Data -e "@x=sort qw(perl another hacker just);
    print map {split(\"\n\", ucfirst(\$_).\" \")}\
    File::Data->new(\"./t/japh\")->\
      write(shift(@x).\"\n\")->    \
      append(shift(@x).\"\n\")->   \
      prepend(shift(@x).\"\n\")->  \
      insert(2, shift(@x).\"\n\")->\
    READ;" 
  >

If you still have problems, mail me the output of 
		
	make test TEST_VERBOSE=1

=back

=cut

# ================================================================

=head1 PRIVATE

=over 4

Private methods not expected to be called by anybody, and completely unsupported.  

Expected to metamorphose regularly - do B<not> call these - you have been warned!

=item _var

Variable get/set method

	my $get = $o_dat->_var($key);		# get

	my $set = $o_dat->_var($key, $val);	# set	

=cut

# @_METHODS, qw(append insert prepend read replace return search write);
my $_VARS = join('|', @_METHODS, qw(
	backup error errors filename filehandle last limbo permissions state writable
));

sub _var {
	my $self = shift;
	my $key  = shift;
	my $val  = shift;
	my $ret  = '';
	
	# if (!(grep(/^_$key$/, keys %{$self{'_var'}}))) {
	if ($key !~ /^($_VARS)$/io) {
		$self->_error("No such key($key) val($val)!");
	} else {
		if (defined($val)) {
			$self->{'_var'}{$key} = $val; 
			# {"$File::Data::$key"} = $val;
			$self->_debug("set key($key) => val($val)");
		}
		$ret = $self->{'_var'}{$key};
	}

	return $ret;
}

=item _debug

Print given args on STDOUT

	$o_dat->_debug($msg) if $File::Data::DEBUG;

=cut

sub _debug {
	my $self = shift;

	my $state = $self->{'_var'}{'state'}; # ahem
	my $debug = $File::Data::DEBUG;

	if (($debug =~ /^(\d+)$/o && $1 >= 1) ||
	     $debug =~ /^(.+)$/o && $state =~ /$debug/
	) {
		print ("$state: ", @_, "\n");
	}

	return ();
}

=item _vars

Return dumped env and object B<key> and B<values>

	print $o_dat->_vars;

=cut

sub _vars {
	my $self  = shift;
	my $h_ret = $self;

	no strict 'refs';
	foreach my $key (keys %{File::Data::}) {
		next unless $key =~ /^[A-Z]+$/o;
		next if $key =~ /^(BEGIN|EXPORT)/o;
		my $var = "File::Data::$key";
		$$h_ret{'_pck'}{$key} = $$var;
	}

	return Dumper($h_ret);
}

=item _err 

Get/set error handling methods/objects

	my $c_sub = $o_dat->_err('insert'); # or default

=cut

sub _err {
	my $self  = shift;
	my $state = shift || $self->_var('state');

	my $err   = $self->{'_err'}{$state} || $self->{'_err'}{'default'};

	return $err;
}

=item _error

By default prints error to STDERR, will B<croak> if B<File::Data::FATAL> set, returning ().

See L<EXAMPLES> for info on how to pass your own error handlers in.

=cut

sub _error {
	my $self = shift; 
	my @err  = @_;
	my @ret  = ();

	my $state = $self->_var('state'); 
	my $c_ref = $self->_err($state ); 
	my $error = $self->_var('error'); 
	unshift(@err, "$state ERROR: ");
	my $ref   = $self->_var('errors', join("\n", @err)); 

	# $self->_debug($self->_vars) if $File::Data::DEBUG;

		if (ref($c_ref) eq 'CODE') {
			eval { @ret = &$c_ref(@err) };
			if ($@) {
			$File::Data::FATAL >= 1 
				? croak("$0 failed: $c_ref(@err)")
				: carp("$0 failed: $c_ref(@err)")
			;
		}
		} elsif (ref($c_ref) && $c_ref->can($state)) { 
			eval { @ret = $c_ref->$state(@err) };
			if ($@) {
			$File::Data::FATAL >= 1 
				? croak("$0 failed: $c_ref(@err)")
				: carp("$0 failed: $c_ref(@err)")
			;
		}
		} else {
			unless ($File::Data::SILENT) {
			($File::Data::FATAL >= 1) ? croak(@err) : carp(@err);
			}
		}

	return (); # 
}

=item _mapfile

Maps file

	my $file = $o_dat->_mapfile($filename);

=cut

sub _mapfile {
	my $self = shift;
	my $file = shift || '';

	$file =~ s/^\s*//o;
	$file =~ s/\s*$//o;

	unless ($file =~ /\w+/o) {
		$file = '';
		$self->_error("inappropriate filename($file)"); 
	} else {
		my $xfile = $self->_var('filename') || '';
		if ($xfile =~ /.+/o) {
			$file = '';
			$self->_error("can't reuse ".ref($self)." object($xfile) for another file($file)"); 
		}
	}

	return $file;
}

=item _mapperms

Maps given permissions to appropriate form for B<FileHandle>

	my $perms = $o_dat->_mapperms('+<');	

=cut

sub _mapperms {
	my $self = shift;
	my $args = shift || '';

	$args =~ s/^\s*//o;
	$args =~ s/\s*$//o;

	my %map = ( # we only recognise
		'ro'		=> '<',
		'readonly'	=> '<',
		'rw'		=> '+<',
		'readwrite'	=> '+<',
	);
	my $ret = $map{$args} || $args;

	$self->_error("Inappropriate permissions($args) - use this: ".Dumper(\%map))
		unless $ret =~ /.+/o;

	return $ret;
}

=item _maperrs

Map error handlers, if given

	my $h_errs = $o_dat->_maperrs(\%error_handlers);

=cut

sub _mapperrs {
	my $self   = shift;
	my $h_errs = shift || {};
	
	if (ref($h_errs) ne 'HASH') {
		$self->_error("invalid error_handlers($h_errs)");
	} else {
		foreach my $key (%{$h_errs}) {
			$self->{'_err'}{$key} = $$h_errs{$key};
		}
	}	

	return $self->{'_err'};
}

=item _enter

Mark the entering of a special section, or state

	my $entered = $o_dat->enter('search');

=cut

sub _enter {
	my $self = shift;
	my $sect = shift;
	
	my $last = $self->_var('state');
	$self->_var('last' => $last) unless $last eq 'limbo';
	my $next  = $self->_var('state' => $sect);

	# $self->_debug("vars") if $File::Data::DEBUG;

	return $next;
}

=item _leave

Mark the leaving of a special section, or state

	my $left = $o_dat->_leave('search');

=cut

sub _leave {
	my $self = shift;
	my $sect = shift;
	
	my $last = $self->_var('state');
	$self->_var('last' => $last) unless $last eq 'limbo';
	my $next  = $self->_var('state' => 'limbo');

	# $self->_debug("leaving state($last) => next($next)") if $File::Data::DEBUG;

	return $last;
}

=item _fh

Get and set B<FileHandle>.

Returns undef otherwise.

	my $FH = $o_dat->_fh($FH); 

=cut

sub _fh {
	my $self = shift;
	my $arg  = shift;

	my $FH = (defined($arg)
		? $self->_var('filehandle', $arg) 
		: $self->_var('filehandle')
	);
	$self->_error("no filehandle($FH)") unless $FH;

	return $FH;
}

=back

=cut

# ================================================================

=head1 UTILITY

Private methods not expected to be called by anybody, and completely unsupported.  

Expected to metamorphose regularly - do B<not> call these - you have been warned!

=over 4

The following utility methods return integer values

	1 = success

	0 = failure

=item _init

Setup object, open a file, with permissions.

	my $i_ok = $o_date->_init($file, $perm, $h_errs);

=cut

sub _init {
	my $self = shift; 
	my $file = shift;
	my $perm = shift;
	my $h_err= shift;
	my $i_ok = 0;

	# $self->_enter('init');
	$self->_debug("in: file($file), perm($perm), h_err($h_err)") if $File::Data::DEBUG;

	$file  = $self->_mapfile($file  );
	$perm  = $self->_mapperms($perm ) if $file;
	$h_err = $self->_mapperrs($h_err) if $file; # if $perm

	if ($file) { # unless $h_err
		$i_ok = $self->_check_access($file, $perm); 
		if ($i_ok == 1) {
			$file = $self->_var('filename', $file);
			$perm = $self->_var('permissions', $perm);
			$i_ok = $self->_open($file, $perm);
			$i_ok = $self->_backup() if $i_ok && $self->_var('backup');
		}
	}
	# $self->_error("failed for file($file) and perm($perm)") unless $i_ok == 1;

	$self->_debug("out: $i_ok") if $File::Data::DEBUG;
	$self->_leave('init');

	return $i_ok;
}

=item _check_access

Checks the args for existence and appropriate permissions etc.

	my $i_isok = $o_dat->_check_access($filename, $permissions);

=cut

sub _check_access {
	my $self = shift;
	my $file = shift;
	my $perm = shift;
	my $i_ok = 0;

	if (!($file =~ /.+/o && $perm =~ /.+/o)) {
		$self->_error("no filename($file) or permissions($perm) given!");
	} else {
		stat($file); # just once
		if (! -e _) {
			$self->_error("target($file) does not exist!");
		} else {
			if (! -f _) {
				$self->_error("target($file) is not a file!");
			} else {	
				if (!-r _) {
					$self->_error("file($file) cannot be read by effective uid($>) or gid($))!");
				} else {
					if ($perm =~ /^<$/o) { # readable
						$i_ok++;
					} else {
						if (! -w $file) {
							$self->_error("file($file) cannot be written by effective uid($>) or gid($))!");
						} else {           # writable
							$self->_var('writable' => 1);
							$i_ok++;
						}
					}
				}
			}
		}
	}

	return $i_ok;
}

=item _open

Open the file

	my $i_ok = $o_dat->_open;

=cut

sub _open {
	my $self = shift;
	my $file = $self->_var('filename');
	my $perm = $self->_var('permissions');
	my $i_ok = 0;
	
	my $open = "$perm $file";
	$self->_debug("using open($open)");

	my $FH = FileHandle->new("$perm $file") || '';
	my @file = ();
	# my $FH = tie(@file, 'Tie::File', $file) or '';
	if (!$FH) {
		$self->_error("Can't get handle($FH) for file($file) with permissions($perm)! $!");
	} else {
		# $FH = $self->_fh(\@file);
		$FH = $self->_fh($FH);
		if ($FH) {
			$i_ok++;
			$i_ok = $self->_lock(); # if $self->_writable; 
		}
		$self->_debug("FH($FH) => i_ok($i_ok)");
	}

	return $i_ok;
};

=item _lock

Lock the file

	my $i_ok = $o_dat->_lock;

=cut

sub _lock {
	my $self = shift;
	my $FH   = $self->_fh;
	my $i_ok = 0;

	if ($FH) {
		my $file = $self->_var('filename');
		# $DB::single=2; # rjsf
		if ($self->_writable) {
			# if ($FH->flock(LOCK_EX | LOCK_NB)) {
			if (flock($FH, LOCK_EX | LOCK_NB)) {
				$i_ok++;
			} else {
				$self->_error("Can't overlock file($file) handle($FH)!");
			}
		} else {
			# if ($FH->flock(LOCK_SH | LOCK_NB)) {
			if (flock($FH, LOCK_SH | LOCK_NB)) {
				$i_ok++;
			} else {
				$self->_error("Can't lock shared file($file) handle($FH)!");
			}
		}
	}

	return $i_ok;
};

=item _unlock

Unlock the file

	my $i_ok = $o_dat->_unlock;

=cut

sub _unlock {
	my $self = shift;
	my $FH   = $self->_fh;
	my $i_ok = 0;

	if ($FH) {
		# if (flock($FH, LOCK_UN)) { apparently there's a race, perl does it better - see close :) }
		$i_ok++;
	} else {
		my $file = $self->_var('filename');
		$self->_error("Can't unlock file($file) handle($FH)!");
	}

	return $i_ok;
}

=item _close

Close the filehandle

	my $i_ok = $o_dat->_close;

=cut

sub _close {
	my $self = shift;
	my $FH   = $self->_fh if $self->_var('filehandle');
	my $i_ok = 0;

	if ($FH) {
		# $FH->untie;
		if ($FH->close) { # perl unlocks it better than we can (race)
			$i_ok++;
		} else {
			$DB::single=2; # rjsf
			my $file = $self->_var('filename');
			$self->_error("Can't close file($file) handle($FH)!");
		}
	}

	return $i_ok;
}

sub _writable {
	my $self = shift;

	my $i_ok = $self->_var('writable');

	if ($i_ok != 1) {
		my $file  = $self->_var('filename');
		my $perms = $self->_var('permissions');
		$self->_debug("$file not writable($i_ok) with permissions($perms)"); 
	}

	return $i_ok;
}

=back

=cut

# ================================================================

sub DESTROY {
	my $self = shift;
	$self->_close;
}

=head1 AUTHOR

Richard Foley <C> richard.foley@rfi.net 2001

For those that are interested, the docs and tests were (mostly) written
before the code, which was helpful in keeping it tidy.

=cut

1;

=item do

Simple wrapper for method calls, returning the content.

    my @inserted = $o_dat->do('insert', @this);

    my @appended = $o_dat->do('append', @this);

An addendum to this method, and to make life generally easier, is that
you can also call any of the above methods in uppercase, to call via
B<do()> eg;

    my @data = $o_dat->WRITE($this)->APPEND->($that)->read;

First argument is the method to call, followed by the arguments that
method expects.

    perl -MFile::Data -e "print File::Data->new($file)->INSERT(3,
    \"third line\n\")->READ";

If you want to get at the output of a particular called method see
L<return()>

=cut

sub DO {
	my $self = shift;
	my $call = shift;
	my @res  = ();
	
	$self->_enter('do');
	$self->_debug('in: '.Dumper([$call, @_])) if $File::Data::DEBUG;

	if ($call !~ /^($_METHODS)$/io) {
		$self->_error("unsupported method($call)");
	} else {
		$call = uc($call);
		$self->_var($call => []);
		my @res = $self->$call(@_);
		$self->_var($call => (ref($res[0]) ? $res[0] : \@res));
	}

	$self->_debug('out: $self') if $File::Data::DEBUG;
	$self->_leave('do');

	return @res;
}

sub do {
	my $self = shift;
	
	$self->DO(@_);

	return $self;
}