package Perl::Critic::Policy::CodeLayout::ProhibitHardTabs;

use 5.006001;
use strict;
use warnings;
use Readonly;

use Perl::Critic::Utils qw{ :booleans :severities };
use base 'Perl::Critic::Policy';

our $VERSION = '1.125';

#-----------------------------------------------------------------------------

Readonly::Scalar my $DESC => q{Hard tabs used};
Readonly::Scalar my $EXPL => [ 20 ];

#-----------------------------------------------------------------------------

# The following regex should probably be "qr{^ .* [^\t]+ \t}xms" but it doesn't
# match when I expect it to.  I haven't figured out why, so I used "\S" to
# approximately mean "not a tab", and that seemed to work.

Readonly::Scalar my $NON_LEADING_TAB_REGEX => qr{^ .* \S+ \t }xms;

#-----------------------------------------------------------------------------

sub supported_parameters {
    return (
        {
            name           => 'allow_leading_tabs',
            description    => 'Allow hard tabs before first non-whitespace character.',
            default_string => '1',
            behavior       => 'boolean',
        },
    );
}

sub default_severity { return $SEVERITY_MEDIUM    }
sub default_themes   { return qw( core cosmetic pbp )   }
sub applies_to       { return 'PPI::Token'        }

#-----------------------------------------------------------------------------

sub violates {
    my ( $self, $elem, undef ) = @_;
    $elem =~ m{ \t }xms || return;

    # The __DATA__ element is exempt
    return if $elem->parent->isa('PPI::Statement::Data');

    # If allowed, permit leading tabs in situations where whitespace s not significant.
    if ( $self->_allow_leading_tabs() ) {

        return if $elem->location->[1] == 1;

        return if _is_extended_regex($elem)
            && $elem !~ $NON_LEADING_TAB_REGEX;

        return if $elem->isa('PPI::Token::QuoteLike::Words')
            && $elem !~ $NON_LEADING_TAB_REGEX;
    }

    # If we get here, then it must be a violation...
    return $self->violation( $DESC, $EXPL, $elem );
}

#-----------------------------------------------------------------------------

sub _allow_leading_tabs {
    my ( $self ) = @_;
    return $self->{_allow_leading_tabs};
}

#-----------------------------------------------------------------------------

sub _is_extended_regex {
    my ($elem) = @_;

    $elem->isa('PPI::Token::Regexp')
        || $elem->isa('PPI::Token::QuoteLike::Regexp')
            || return;

   # Look for the /x modifier near the end
   return $elem =~ m{\b [gimso]* x [gimso]* $}xms;
}

1;

__END__

#-----------------------------------------------------------------------------

=head1 NAME

Perl::Critic::Policy::CodeLayout::ProhibitHardTabs - Use spaces instead of tabs.


=head1 AFFILIATION

This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.


=head1 DESCRIPTION

Putting hard tabs in your source code (or POD) is one of the worst
things you can do to your co-workers and colleagues, especially if
those tabs are anywhere other than a leading position.  Because
various applications and devices represent tabs differently, they can
cause you code to look vastly different to other people.  Any decent
editor can be configured to expand tabs into spaces.
L<Perl::Tidy|Perl::Tidy> also does this for you.

This Policy catches all tabs in your source code, including POD,
quotes, and HEREDOCs.  The contents of the C<__DATA__> section are not
examined.


=head1 CONFIGURATION

Hard tabs in a string are always forbidden (use "\t" instead).  But
hard tabs in a leading position are allowed when they are used to indent
code statements, C<qw()> word lists, and regular expressions with the C</x>
modifier.  However, if you want to forbid all tabs everywhere, then add
this to your F<.perlcriticrc> file:

    [CodeLayout::ProhibitHardTabs]
    allow_leading_tabs = 0


=head1 NOTES

Beware that Perl::Critic may report the location of the string that
contains the tab, not the actual location of the tab, so you may need
to do some hunting.  I'll try and fix this in the future.


=head1 AUTHOR

Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>


=head1 COPYRIGHT

Copyright (c) 2005-2011 Imaginative Software Systems.  All rights reserved.

This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.  The full text of this license
can be found in the LICENSE file included with this module.

=cut

##############################################################################
# Local Variables:
#   mode: cperl
#   cperl-indent-level: 4
#   fill-column: 78
#   indent-tabs-mode: nil
#   c-indentation-style: bsd
# End:
# ex: set ts=8 sts=4 sw=4 tw=78 ft=perl expandtab shiftround :
