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[gitmo/Moose.git] / lib / Moose / Meta / TypeConstraint / Union.pm

package Moose::Meta::TypeConstraint::Union;

use strict;
use warnings;
use metaclass;

use Moose::Meta::TypeCoercion::Union;

use List::Util qw(first);

our $AUTHORITY = 'cpan:STEVAN';

use base 'Moose::Meta::TypeConstraint';

__PACKAGE__->meta->add_attribute('type_constraints' => (
    accessor  => 'type_constraints',
    default   => sub { [] }
));

sub new {
    my ($class, %options) = @_;

    my $name = join '|' => sort { $a cmp $b }
        map { $_->name } @{ $options{type_constraints} };

    my $self = $class->SUPER::new(
        name => $name,
        %options,
    );

    $self->_set_constraint(sub { $self->check($_[0]) });

    return $self;
}

# XXX - this is a rather gross implementation of laziness for the benefit of
# MX::Types. If we try to call ->has_coercion on the objects during object
# construction, this does not work when defining a recursive constraint with
# MX::Types.
sub coercion {
    my $self = shift;

    return $self->{coercion} if exists $self->{coercion};

    # Using any instead of grep here causes a weird error with some corner
    # cases when MX::Types is in use. See RT #61001.
    if ( grep { $_->has_coercion } @{ $self->type_constraints } ) {
        return $self->{coercion} = Moose::Meta::TypeCoercion::Union->new(
            type_constraint => $self );
    }
    else {
        return $self->{coercion} = undef;
    }
}

sub has_coercion {
    return defined $_[0]->coercion;
}

sub _actually_compile_type_constraint {
    my $self = shift;

    my @constraints = @{ $self->type_constraints };

    return sub {
        my $value = shift;
        foreach my $type (@constraints) {
            return 1 if $type->check($value);
        }
        return undef;
    };
}


sub equals {
    my ( $self, $type_or_name ) = @_;

    my $other = Moose::Util::TypeConstraints::find_type_constraint($type_or_name);

    return unless $other->isa(__PACKAGE__);

    my @self_constraints  = @{ $self->type_constraints };
    my @other_constraints = @{ $other->type_constraints };

    return unless @self_constraints == @other_constraints;

    # FIXME presort type constraints for efficiency?
    constraint: foreach my $constraint ( @self_constraints ) {
        for ( my $i = 0; $i < @other_constraints; $i++ ) {
            if ( $constraint->equals($other_constraints[$i]) ) {
                splice @other_constraints, $i, 1;
                next constraint;
            }
        }
    }

    return @other_constraints == 0;
}

sub parents {
    my $self = shift;
    $self->type_constraints;
}

sub validate {
    my ($self, $value) = @_;
    my $message;
    foreach my $type (@{$self->type_constraints}) {
        my $err = $type->validate($value);
        return unless defined $err;
        $message .= ($message ? ' and ' : '') . $err
            if defined $err;
    }
    return ($message . ' in (' . $self->name . ')') ;
}

sub find_type_for {
    my ($self, $value) = @_;

    return first { $_->check($value) } @{ $self->type_constraints };
}

sub is_a_type_of {
    my ($self, $type_name) = @_;
    foreach my $type (@{$self->type_constraints}) {
        return 1 if $type->is_a_type_of($type_name);
    }
    return 0;
}

sub is_subtype_of {
    my ($self, $type_name) = @_;
    foreach my $type (@{$self->type_constraints}) {
        return 1 if $type->is_subtype_of($type_name);
    }
    return 0;
}

sub create_child_type {
    my ( $self, %opts ) = @_;

    my $constraint
        = Moose::Meta::TypeConstraint->new( %opts, parent => $self );

    # if we have a type constraint union, and no
    # type check, this means we are just aliasing
    # the union constraint, which means we need to
    # handle this differently.
    # - SL
    if ( not( defined $opts{constraint} )
        && $self->has_coercion ) {
        $constraint->coercion(
            Moose::Meta::TypeCoercion::Union->new(
                type_constraint => $self,
            )
        );
    }

    return $constraint;
}

1;

# ABSTRACT: A union of Moose type constraints

__END__

=pod

=head1 DESCRIPTION

This metaclass represents a union of type constraints. A union takes
multiple type constraints, and is true if any one of its member
constraints is true.

=head1 INHERITANCE

C<Moose::Meta::TypeConstraint::Union> is a subclass of
L<Moose::Meta::TypeConstraint>.

=over 4

=item B<< Moose::Meta::TypeConstraint::Union->new(%options) >>

This creates a new class type constraint based on the given
C<%options>.

It takes the same options as its parent. It also requires an
additional option, C<type_constraints>. This is an array reference
containing the L<Moose::Meta::TypeConstraint> objects that are the
members of the union type. The C<name> option defaults to the names
all of these member types sorted and then joined by a pipe (|).

The constructor sets the implementation of the constraint so that is
simply calls C<check> on the newly created object.

Finally, the constructor also makes sure that the object's C<coercion>
attribute is a L<Moose::Meta::TypeCoercion::Union> object.

=item B<< $constraint->type_constraints >>

This returns the array reference of C<type_constraints> provided to
the constructor.

=item B<< $constraint->parents >>

This returns the same constraint as the C<type_constraints> method.

=item B<< $constraint->check($value) >>

=item B<< $constraint->validate($value) >>

These two methods simply call the relevant method on each of the
member type constraints in the union. If any type accepts the value,
the value is valid.

With C<validate> the error message returned includes all of the error
messages returned by the member type constraints.

=item B<< $constraint->equals($type_name_or_object) >>

A type is considered equal if it is also a union type, and the two
unions have the same member types.

=item B<< $constraint->find_type_for($value) >>

This returns the first member type constraint for which C<check($value)> is
true, allowing you to determine which of the Union's member type constraints
a given value matches.

=item B<< $constraint->is_a_type_of($type_name_or_object) >>

This returns true if any of the member type constraints return true
for the C<is_a_type_of> method.

=item B<< $constraint->is_subtype_of >>

This returns true if any of the member type constraints return true
for the C<is_a_subtype_of> method.

=item B<< $constraint->create_child_type(%options) >>

This returns a new L<Moose::Meta::TypeConstraint> object with the type
as its parent.

=back

=head1 BUGS

See L<Moose/BUGS> for details on reporting bugs.

=cut