File::chdir

package File::chdir;
use 5.004;
use strict;
use vars qw($VERSION @ISA @EXPORT $CWD @CWD);
$VERSION = '0.1004';
$VERSION = eval $VERSION; ## no critic

require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw($CWD @CWD);

use Carp;
use Cwd;
use File::Spec::Functions qw/canonpath splitpath catpath splitdir catdir/;

tie $CWD, 'File::chdir::SCALAR' or die "Can't tie \$CWD";
tie @CWD, 'File::chdir::ARRAY'  or die "Can't tie \@CWD";

sub _abs_path { 
    # Otherwise we'll never work under taint mode.
    my($cwd) = Cwd::abs_path =~ /(.*)/;
    # Run through File::Spec, since everything else uses it 
    return canonpath($cwd);
}

# splitpath but also split directory
sub _split_cwd {
    my ($vol, $dir) = splitpath(_abs_path, 1);
    my @dirs = splitdir( $dir );
    shift @dirs; # get rid of leading empty "root" directory
    return ($vol, @dirs);
}

# catpath, but take list of directories
# restore the empty root dir and provide an empty file to avoid warnings
sub _catpath {
    my ($vol, @dirs) = @_;
    return catpath($vol, catdir(q{}, @dirs), q{});
}

sub _chdir { 
    my($new_dir) = @_;

    local $Carp::CarpLevel = $Carp::CarpLevel + 1;
    if ( ! CORE::chdir($new_dir) ) {
        croak "Failed to change directory to '$new_dir': $!";
    };
    return 1;
}

{
    package File::chdir::SCALAR;
    use Carp;

    BEGIN { 
        *_abs_path = \&File::chdir::_abs_path;
        *_chdir = \&File::chdir::_chdir;
        *_split_cwd = \&File::chdir::_split_cwd;
        *_catpath = \&File::chdir::_catpath;
    }

    sub TIESCALAR { 
        bless [], $_[0];
    }

    # To be safe, in case someone chdir'd out from under us, we always
    # check the Cwd explicitly.
    sub FETCH {
        return _abs_path;
    }

    sub STORE {
        return unless defined $_[1];
        _chdir($_[1]);
    }
}


{
    package File::chdir::ARRAY;
    use Carp;

    BEGIN { 
        *_abs_path = \&File::chdir::_abs_path; 
        *_chdir = \&File::chdir::_chdir;
        *_split_cwd = \&File::chdir::_split_cwd;
        *_catpath = \&File::chdir::_catpath;
    }

    sub TIEARRAY {
        bless {}, $_[0];
    }

    sub FETCH { 
        my($self, $idx) = @_;
        my ($vol, @cwd) = _split_cwd;
        return $cwd[$idx];
    }

    sub STORE {
        my($self, $idx, $val) = @_;

        my ($vol, @cwd) = _split_cwd;
        if( $self->{Cleared} ) {
            @cwd = ();
            $self->{Cleared} = 0;
        }

        $cwd[$idx] = $val;
        my $dir = _catpath($vol,@cwd);

        _chdir($dir);
        return $cwd[$idx];
    }

    sub FETCHSIZE { 
        my ($vol, @cwd) = _split_cwd;
        return scalar @cwd; 
    }
    sub STORESIZE {}

    sub PUSH {
        my($self) = shift;

        my $dir = _catpath(_split_cwd, @_);
        _chdir($dir);
        return $self->FETCHSIZE;
    }

    sub POP {
        my($self) = shift;

        my ($vol, @cwd) = _split_cwd;
        my $popped = pop @cwd;
        my $dir = _catpath($vol,@cwd);
        _chdir($dir);
        return $popped;
    }

    sub SHIFT {
        my($self) = shift;

        my ($vol, @cwd) = _split_cwd;
        my $shifted = shift @cwd;
        my $dir = _catpath($vol,@cwd);
        _chdir($dir);
        return $shifted;
    }

    sub UNSHIFT {
        my($self) = shift;

        my ($vol, @cwd) = _split_cwd;
        my $dir = _catpath($vol, @_, @cwd);
        _chdir($dir);
        return $self->FETCHSIZE;
    }

    sub CLEAR  {
        my($self) = shift;
        $self->{Cleared} = 1;
    }

    sub SPLICE {
        my $self = shift;
        my $offset = shift || 0;
        my $len = shift || $self->FETCHSIZE - $offset;
        my @new_dirs = @_;
        
        my ($vol, @cwd) = _split_cwd;
        my @orig_dirs = splice @cwd, $offset, $len, @new_dirs;
        my $dir = _catpath($vol, @cwd);
        _chdir($dir);
        return @orig_dirs;
    }

    sub EXTEND { }
    sub EXISTS { 
        my($self, $idx) = @_;
        return $self->FETCHSIZE >= $idx ? 1 : 0;
    }

    sub DELETE {
        my($self, $idx) = @_;
        croak "Can't delete except at the end of \@CWD"
            if $idx < $self->FETCHSIZE - 1;
        local $Carp::CarpLevel = $Carp::CarpLevel + 1;
        $self->POP;
    }
}

1;
__END__