Traits.pm

package CatalystX::Component::Traits;

use namespace::autoclean;
use Moose::Role;
use Moose::Autobox;
use Carp;
use List::MoreUtils qw/firstidx any uniq/;
use Scalar::Util 'reftype';
with 'MooseX::Traits::Pluggable' => { excludes => ['_find_trait'] };

=head1 NAME

CatalystX::Component::Traits - Automatic Trait Loading and Resolution for
Catalyst Components

=head1 VERSION

Version 0.07

=cut

our $VERSION   = '0.07';
our $AUTHORITY = 'id:RKITOVER';

=head1 SYNOPSIS

    package Catalyst::Model::SomeModel;
    with 'CatalystX::Component::Traits';

    package MyApp::Model::MyModel;
    use parent 'Catalyst::Model::SomeModel';

    package MyApp;

    __PACKAGE__->config('Model::MyModel' => {
        traits => ['SearchedForTrait', '+Fully::Qualified::Trait']
    });

=head1 DESCRIPTION

Adds a L<Catalyst::Component/COMPONENT> method to your L<Catalyst> component
base class that reads the optional C<traits> parameter from app and component
config and instantiates the component subclass with those traits using
L<MooseX::Traits/new_with_traits> from L<MooseX::Traits::Pluggable>.

=head1 TRAIT SEARCH

Trait names qualified with a C<+> are taken to be full package names.

Unqualified names are searched for, using the algorithm described below.

=head2 EXAMPLE

Suppose your inheritance hierarchy is:

    MyApp::Model::MyModel
    Catalyst::Model::CatModel
    Catalyst::Model
    Catalyst::Component
    Moose::Object

The configuration is:

    traits => ['Foo']

The package search order for C<Foo> will be:

    MyApp::TraitFor::Model::CatModel::Foo
    Catalyst::TraitFor::Model::CatModel::Foo

=head2 A MORE PATHOLOGICAL EXAMPLE

For:

    My::App::Controller::AController
    CatalystX::Something::ControllerBase::SomeController
    Catalyst::Controller
    Catalyst::Model
    Catalyst::Component
    Moose::Object

With:

    traits => ['Foo']

Search order for C<Foo> will be:

    My::App::TraitFor::Controller::SomeController::Foo
    CatalystX::Something::TraitFor::Controller::SomeController::Foo

The C<Base> after (M|V|C) is automatically removed.

=head1 TRAIT MERGING

Traits from component class config and app config are automatically merged if
you set the C<_trait_merge> attribute default, e.g.:

    has '+_trait_merge' => (default => 1);

You can remove component class config traits by prefixing their names with a
C<-> in the app config traits.

For example:

    package Catalyst::Model::Foo;
    has '+_trait_merge' => (default => 1);
    __PACKAGE__->config->{traits} = [qw/Foo Bar/];

    package MyApp;
    __PACKAGE__->config->{'Model::Foo'}{traits} = [qw/-Foo Baz/];

Will load the traits:

    Bar Baz

=cut

# override MX::Traits attribute
has '_trait_namespace' => (
    init_arg => undef,
    isa      => 'Str',
    (Moose->VERSION >= 0.84 ) ? (is => 'bare') : (),
    default  => '+Trait',
);

has '_trait_merge' => (
    init_arg => undef,
    isa      => 'Str',
    (Moose->VERSION >= 0.84 ) ? (is => 'bare') : (),
    default  => 0,
);

sub COMPONENT {
    my ($class, $app, $args) = @_;

    my %class_config = %{ $class->config };
    my %app_config   = %$args;

    my $traits = $class->_merge_traits(
	delete $class_config{traits},
	delete $app_config{traits},
    );

    $args = $class->merge_config_hashes(\%class_config, \%app_config);

    if ($traits) {
	return $class->new_with_traits($app, {
	    traits => $traits,
	    %$args
	});
    }

    return $class->new($app, $args);
}

sub _merge_traits {
    my $class        = shift;
    my $left_traits  = shift || [];
    my $right_traits = shift || [];

    my $should_merge =
	eval { $class->meta->find_attribute_by_name('_trait_merge')->default };
    $should_merge = $should_merge->()
	if ref($should_merge) && reftype($should_merge) eq 'CODE';

    unless ($should_merge) {
	return $right_traits || $left_traits;
    }

    my (@left_traits, @right_traits, @to_remove);

    for my $trait (@$right_traits) {
	if ($trait =~ /^-(.*)/) {
	    push @to_remove, $1;
	} else {
	    push @right_traits, $trait;
	}
    }
    @left_traits = @$left_traits;

    my @traits = grep {
	my $trait = $_;
	not any { $trait eq $_ } @to_remove;
    } (@left_traits, @right_traits);

    return [ uniq @traits ];
}

sub _find_trait {
    my ($class, $base, $name) = @_;

    my @tried; # FIXME - This sux, use load_first_existing_class ?
    for my $trait ($class->_trait_search_order($base, $name)) {
        push @tried, $trait;
        return $trait if eval { Class::MOP::load_class($trait) };
    }

    croak "Could not find a class for trait: $name (tried " . join(',', @tried) . ")";
}

sub _trait_search_order {
    my ($class, $base, $name) = @_;

    my @search_ns = $class->meta->class_precedence_list;

    my $MVCC = qr/(?:Model|View|Controller|Component)/;

    my $parent_idx    = firstidx { /^CatalystX?::/ } @search_ns;
    my $parent        = $search_ns[$parent_idx];

    my ($parent_name) = $parent =~ /($MVCC(?:Base)?.+)/;

    (my $resolved_parent_name = $parent_name) =~ s/($MVCC)Base\b/$1/;

    my ($parent_part) = $parent =~ /($MVCC)(?:Base)?::/;

    my @res;

    for my $ns (@search_ns[0 .. $parent_idx]) {
	my $find_part = $parent_part;

	my ($part) = $ns =~ /^(.+?)::$parent_part/;
	push @res, "${part}::${base}For::${resolved_parent_name}::$name";
    }

    @res;
}

# we'll come back to this later...
#    for my $ns (@search_ns[($parent_idx+1) .. $#search_ns]) {
#	my ($part, $rest) = split /::/, $ns, 2;
#
#	# no non-core crap in the Moose:: namespace
#	$part = 'MooseX' if $part eq 'Moose';
#
#	push @res, "${part}::${base}For::${rest}::$name";
#    }
#
#    @res;
#}

=head1 AUTHOR

Rafael Kitover, C<< <rkitover@cpan.org> >>

=head1 CONTRIBUTORS

Tomas Doran, C<< <bobtfish@bobtfish.net> >>

=head1 BUGS

Please report any bugs or feature requests to C<bug-catalystx-component-traits
at rt.cpan.org>, or through the web interface at
L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=CatalystX-Component-Traits>.  I
will be notified, and then you'll automatically be notified of progress on your
bug as I make changes.

=head1 SUPPORT

More information at:

=over 4

=item * RT: CPAN's request tracker

L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=CatalystX-Component-Traits>

=item * AnnoCPAN: Annotated CPAN documentation

L<http://annocpan.org/dist/CatalystX-Component-Traits>

=item * CPAN Ratings

L<http://cpanratings.perl.org/d/CatalystX-Component-Traits>

=item * Search CPAN

L<http://search.cpan.org/dist/CatalystX-Component-Traits/>

=back

=head1 ACKNOWLEDGEMENTS

Matt S. Trout and Tomas Doran helped me with the current design.

=head1 COPYRIGHT & LICENSE

Copyright (c) 2009, Rafael Kitover

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

=cut

1; # End of CatalystX::Component::Traits