#!perl6

class Person { ... }
class Thing { ... }
class Container { ... }
class Place { ... }
class Nowhere { ... }

class Entity {
    use JSON::Tiny;
    my %cache;

    has $.id is rw;

    method Str { self.id }

    method load(Entity: $id) {
        return Nowhere if $id eq 'nowhere';
        return %cache{$id} if %cache{$id}:exists;

        my %hash = from-json slurp "$id.json";
        my $class = %hash<class>:delete;

        if (%hash<location>:exists) {
            %hash<location> = Entity.load(%hash<location>);
        }
        %hash<id> = $id;

        %cache{$id} = sub ($_) {
            return Person.new(|%hash)    when 'Person';
            return Place.new(|%hash)     when 'Place';
            return Container.new(|%hash) when 'Container';
            return Thing.new(|%hash)     when 'Thing';
        }($class);
        warn "still here";

        return %cache{$id};
    }

    method json {
        my %hash;
        for self.^attributes -> $a {
            try {
                # Fails on undefined $.location, with
                # «Invocant requires an instance of type <anon>, but a type object was passed.
                # Did you forget a .new?»
                %hash{ $a.Str.substr(2) } = $a.get_value(self).Str
            }
        };
        %hash<class> = self.^name;
        return to-json %hash;
    }
}

class Place is Entity {
    has Entity $.location is rw where Place;
}

class Person is Entity {
    has Entity $.location is rw where Place = Nowhere;
}

class Container is Entity {
    has Entity $.location is rw where Place|Container = Nowhere;
}

class Thing is Entity {
    has Entity $.location is rw where Place|Container|Person = Nowhere;
}

class Nowhere is Place {
    submethod Str { "nowhere" }
}


#my $t = Thing.new;
my $t = Entity.load("foo");
#$t.location = Place.new(id => "lhq");
say $t.perl;
say $t.json;
say $t.location.json;