package LaTeX::TikZ::Meta::TypeConstraint::Autocoerce;

use strict;
use warnings;

=head1 NAME

LaTeX::TikZ::Meta::TypeConstraint::Autocoerce - Type constraint metaclass that autoloads type coercions.

=head1 VERSION

Version 0.01

=cut

our $VERSION = '0.01';

use Scalar::Util qw/blessed/;

use Sub::Name ();

use Any::Moose;
use Any::Moose 'Util' => [ 'find_meta' ];

extends any_moose('Meta::TypeConstraint');

=head1 ATTRIBUTES

=head2 C<mapper>

A code reference that maps an object class name to the name of the package in which the coercion can be found, or C<undef> to disable coercion for this class name.
It is called with the type constraint object as first argument, followed by the class name.

=cut

has 'mapper' => (
 is       => 'ro',
 isa      => 'CodeRef',
 required => 1,
);

=head2 C<parent>

=cut

has 'parent' => (
 is       => 'ro',
 isa      => any_moose('Meta::TypeConstraint'),
 required => 1,
);

=head2 C<user_constraint>

=cut

has 'user_constraint' => (
 is       => 'ro',
 isa      => 'Maybe[CodeRef]',
 required => 1,
);

=head1 METHODS

=cut

around 'new' => sub {
 my ($orig, $class, %args) = @_;

 unless (exists $args{mapper}) {
  $args{mapper} = sub { join '::', $_[0]->parent->name, $_[1] };
 }

 my $parent = delete $args{parent};
 unless (blessed $parent) {
  $parent = find_meta($parent)->type_constraint;
 }
 __PACKAGE__->meta->find_attribute_by_name('parent')
                  ->type_constraint->assert_valid($parent);
 $args{parent} = $parent;

 $args{user_constraint} = delete $args{constraint};

 if (any_moose() eq 'Moose') {
  $args{coercion} = Moose::Meta::TypeCoercion->new;
 }

 my $tc;
 $args{constraint} = Sub::Name::subname('_constraint' => sub {
  my ($thing) = @_;

  # Remember that when ->check is called inside coerce, a return value of 0
  # means that coercion should take place, while 1 signifies that the value is
  # already OK.

  # First, try a possible user defined constraint
  my $user = $tc->user_constraint;
  if (defined $user) {
   my $ok = $user->($thing);
   return 1 if $ok;
  }

  # Then, it's valid if and only if it passes the parent type constraint
  return $tc->parent->check($thing);
 });

 $tc = $class->$orig(%args);
};

around 'coerce' => sub {
 my ($orig, $tc, $thing) = @_;

 # The original coerce gets an hold onto the type coercions *before* calling
 # the constraint. Thus, we have to force the loading before recalling into
 # $orig.

 # First, check whether $thing is already of the right kind.
 return $thing if $tc->check($thing);

 # If $thing isn't even an object, don't bother trying to autoload a coercion
 my $class = blessed($thing);
 if (defined $class) {
  $class = $tc->mapper->($tc, $class);

  if (defined $class) {
   # Find the file to autoload
   (my $pm = $class) =~ s{::}{/}g;
   $pm .= '.pm';

   unless ($INC{$pm}) { # Not loaded yet
    local $@;
    eval {
     # We die often here, even though we're not really interested in the error.
     # However, if a die handler is set (e.g. to \&Carp::confess), this can get
     # very slow. Resetting the handler shows a 10% total time improvement for
     # the geodyn app.
     local $SIG{__DIE__};
     require $pm;
    };
   }
  }
 }

 $tc->$orig($thing);
};

__PACKAGE__->meta->make_immutable(
 inline_constructor => 0,
);

=head1 AUTHOR

Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.

You can contact me by mail or on C<irc.perl.org> (vincent).

=head1 BUGS

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

=head1 SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc LaTeX::TikZ

=head1 COPYRIGHT & LICENSE

Copyright 2010 Vincent Pit, all rights reserved.

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

=cut

1; # End of LaTeX::TikZ::Meta::TypeConstraint::Autocoerce
