package Perl::Critic::Policy::BuiltinFunctions::RequireSimpleSortBlock;

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

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

our $VERSION = '1.125';

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

Readonly::Scalar my $DESC => q{Sort blocks should have a single statement};
Readonly::Scalar my $EXPL => [ 149 ];

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

sub supported_parameters { return ()                                   }
sub default_severity     { return $SEVERITY_MEDIUM                     }
sub default_themes       { return qw( core pbp maintenance complexity) }
sub applies_to           { return 'PPI::Token::Word'                   }

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

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

    return if $elem ne 'sort';
    return if ! is_function_call($elem);

    my $sib = $elem->snext_sibling();
    return if !$sib;

    my $arg = $sib;
    if ( $arg->isa('PPI::Structure::List') ) {
        $arg = $arg->schild(0);
        # Forward looking: PPI might change in v1.200 so schild(0) is a PPI::Statement::Expression
        if ( $arg && $arg->isa('PPI::Statement::Expression') ) {
            $arg = $arg->schild(0);
        }
    }
    return if !$arg || !$arg->isa('PPI::Structure::Block');

    # If we get here, we found a sort with a block as the first arg
    return if ( 1 >= $arg->schildren() );

    # more than one child statements
    return $self->violation( $DESC, $EXPL, $elem );
}

1;

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

__END__

=pod

=head1 NAME

Perl::Critic::Policy::BuiltinFunctions::RequireSimpleSortBlock - Sort blocks should have a single statement.


=head1 AFFILIATION

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


=head1 DESCRIPTION

Conway advises that sort functions should be simple.  Any complicated
operations on list elements should be computed and cached (perhaps via
a Schwartzian Transform) before the sort, rather than computed inside
the sort block, because the sort block is called C<N log N> times
instead of just C<N> times.

This policy prohibits the most blatant case of complicated sort
blocks: multiple statements.  Future policies may wish to examine the
sort block in more detail -- looking for subroutine calls or large
numbers of operations.


=head1 CONFIGURATION

This Policy is not configurable except for the standard options.


=head1 AUTHOR

Chris Dolan <cdolan@cpan.org>

=head1 COPYRIGHT

Copyright (c) 2006-2011 Chris Dolan.

This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut

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