package Perl::Critic::Policy::RegularExpressions::ProhibitSingleCharAlternation;

use 5.010001;
use strict;
use warnings;

use Readonly;

use Perl::Critic::Utils qw( :characters :severities );
use parent 'Perl::Critic::Policy';

our $VERSION = '1.152';

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

Readonly::Scalar my $EXPL => [265];

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

sub supported_parameters { return qw()                    }
sub default_severity     { return $SEVERITY_LOWEST        }
sub default_themes       { return qw( core pbp performance ) }
sub applies_to           { return qw(PPI::Token::Regexp::Match
                                     PPI::Token::Regexp::Substitute
                                     PPI::Token::QuoteLike::Regexp) }

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

sub violates {
    my ( $self, $elem, $document ) = @_;

    # optimization: don't bother parsing the regexp if there are no pipes
    return if $elem !~ m/[|]/xms;

    my $re = $document->ppix_regexp_from_element( $elem ) or return;
    $re->failures() and return;

    my @violations;
    foreach my $node ( @{ $re->find_parents( sub {
                return $_[1]->isa( 'PPIx::Regexp::Token::Operator' )
                && $_[1]->content() eq q<|>;
            } ) || [] } ) {

        my @singles;
        my @alternative;
        foreach my $kid ( $node->children() ) {
            if ( $kid->isa( 'PPIx::Regexp::Token::Operator' )
                && $kid->content() eq q<|>
            ) {
                @alternative == 1
                    and $alternative[0]->isa( 'PPIx::Regexp::Token::Literal' )
                    and push @singles, map { $_->content() } @alternative;
                @alternative = ();
            } elsif ( $kid->significant() ) {
                push @alternative, $kid;
            }
        }
        @alternative == 1
            and $alternative[0]->isa( 'PPIx::Regexp::Token::Literal' )
            and push @singles, map { $_->content() } @alternative;

        if ( 1 < @singles ) {
            my $description =
                  'Use ['
                . join( $EMPTY, @singles )
                . '] instead of '
                . join q<|>, @singles;
            push @violations, $self->violation( $description, $EXPL, $elem );
        }
    }

    return @violations;
}

1;

__END__

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

=pod

=head1 NAME

Perl::Critic::Policy::RegularExpressions::ProhibitSingleCharAlternation - Use C<[abc]> instead of C<a|b|c>.


=head1 AFFILIATION

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


=head1 DESCRIPTION

Character classes (like C<[abc]>) are significantly faster than single
character alternations (like C<(?:a|b|c)>).  This policy complains if
you have more than one instance of a single character in an
alternation.  So C<(?:a|the)> is allowed, but C<(?:a|e|i|o|u)> is not.


=head1 CONFIGURATION

This Policy is not configurable except for the standard options.


=head1 CREDITS

Initial development of this policy was supported by a grant from the
Perl Foundation.


=head1 AUTHOR

Chris Dolan <cdolan@cpan.org>


=head1 COPYRIGHT

Copyright (c) 2007-2023 Chris Dolan

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

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