package Class::Accessor::Fast::WithBuilder;

=head1 NAME

Class::Accessor::Fast::WithBuilder - Class::Accessor::Fast with lazy defaults

=head1 VERSION

0.01

=head1 DESCRIPTION

This module will require builders for each attribute defined. This means
that adding attributes with this module, is something like this code
from L<Moose>:

    has age => (
        is => "ro", # or rw
        lazy => 1,
        builder => "_build_age",
    );

NOTE: All builders will be called as late as possible.

=head1 SYNOPSIS

    package Foo;
    use base qw(Class::Accessor::Fast::WithBuilder);

    Foo->mk_accessors(qw( name age ));

    sub _build_name { $_[0]->_croak("'name' attribute cannot be built!") }
    sub _build_age { 0 }

    print Foo->new->name; # BOOM!
    print Foo->new->age; # Will print "0"
    print Foo->new({ age => 123 })->age; # Will print "123"

=cut

use strict;
use warnings;
use base 'Class::Accessor::Fast'; # overriding all ::Fast methods, but...

our $VERSION = eval '0.01';

=head1 METHODS

=head2 make_accessor

See L<Class::Accessor/make_accessor>

=cut

sub make_accessor {
    my($class, $field) = @_;
    my $builder = "_build_$field";

    return sub {
        return $_[0]->{$field} = @_ == 2 ? $_[1] : [@_[1..$#_]] if @_ > 1;
        exists $_[0]->{$field} or $_[0]->{$field} = $_[0]->$builder;
        return $_[0]->{$field} if @_ == 1;
    };
}

=head2 make_ro_accessor

See L<Class::Accessor/make_ro_accessor>

=cut

sub make_ro_accessor {
    my($class, $field) = @_;
    my $builder = "_build_$field";

    return sub {
        exists $_[0]->{$field} or $_[0]->{$field} = $_[0]->$builder;
        return $_[0]->{$field} if @_ == 1;
        my $caller = caller;
        $_[0]->_croak("'$caller' cannot alter the value of '$field' on objects of class '$class'");
    };
}

=head2 make_wo_accessor

This is not implemented. (See L<Class::Accessor/make_wo_accessor>)

=cut

sub make_wo_accessor {
    $_[0]->_croak('not implemented');
}

# used to check if _build_foo() methods are defined
sub _mk_accessors {
    my $class = shift;
    my($type, @fields) = @_;

    for my $f (@fields) {
        unless($class->can("_build_$f")) {
            $class->_croak("$class\::_build_$f() is required!");
        }
    }

    return $class->SUPER::_mk_accessors(@_);
}

=head1 COPYRIGHT & LICENSE

=head1 AUTHOR

Jan Henning Thorsen C<< jhthorsen at cpan.org >>

=cut

1;