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/***** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
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 * The contents of this file are subject to the Eclipse Public
 * License Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.eclipse.org/legal/epl-v20.html
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 * rights and limitations under the License.
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 * Copyright (C) 2002-2004 Jan Arne Petersen 
 * Copyright (C) 2004-2006 Thomas E Enebo 
 * Copyright (C) 2004 Stefan Matthias Aust 
 * 
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
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package org.jruby;

import org.jruby.runtime.builtin.IRubyObject;

public final class MetaClass extends RubyClass {

    @Deprecated
    public MetaClass(Ruby runtime, RubyClass superClass, IRubyObject attached) {
        this(runtime, superClass, (RubyBasicObject) attached);
    }

    /**
     * rb_class_boot for meta classes ({@link #makeMetaClass(RubyClass)})
     */
    MetaClass(Ruby runtime, RubyClass superClass, RubyBasicObject attached) {
        super(runtime, superClass, false);
        this.attached = attached;
        // use same ClassIndex as metaclass, since we're technically still of that type
        setClassIndex(superClass.getClassIndex());
        superClass.addSubclass(this);
    }

    @Override
    public final IRubyObject allocate(){
        throw runtime.newTypeError("can't create instance of virtual class");
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

    /**
     * rb_make_metaclass
     * @param superClass
     * @return singleton-class for this (singleton) class
     */
    @Override
    public RubyClass makeMetaClass(RubyClass superClass) {
        MetaClass klass = new MetaClass(runtime, getSuperSingletonMetaClass(), this);
        setMetaClass(klass);

        // Foo.singleton_class.singleton_class: #>
        // #>'s singleton_class == #>
        klass.setMetaClass(klass);

        return klass;
    }

    private RubyClass getSuperSingletonMetaClass() {
        if (attached instanceof RubyClass) {
            RubyClass superClass = ((RubyClass) attached).getSuperClass();
            if (superClass != null) superClass = superClass.getRealClass();
            // #'s singleton class == Class.singleton_class
            if (superClass == null) return runtime.getClassClass().getSingletonClass();
            return superClass.getMetaClass().getSingletonClass();
        }

        return getSuperClass().getRealClass().getMetaClass(); // NOTE: is this correct?
    }

    @Override
    RubyClass toSingletonClass(RubyBasicObject target) {
        return attached == target ? this : super.toSingletonClass(target);
    }

    public RubyBasicObject getAttached() {
        return attached;
    }

    public void setAttached(RubyBasicObject attached) {
        this.attached = attached;
    }

    private RubyBasicObject attached;

}