/***** 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
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 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
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 * Copyright (C) 2002-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2004-2006 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
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package org.jruby;

import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.util.cli.Options;
import org.jruby.util.log.Logger;
import org.jruby.util.log.LoggerFactory;

import static org.jruby.api.Access.classClass;
import static org.jruby.api.Error.typeError;

public final class MetaClass extends RubyClass {

    /**
     * rb_class_boot for meta classes ({@link #makeMetaClass(ThreadContext, RubyClass)})
     */
    MetaClass(Ruby runtime, RubyClass superClass, RubyBasicObject attached) {
        super(runtime, superClass, false);
        metaClassInit(superClass, attached);

        if (LOG_SINGLETONS || LOG_SINGLETONS_VERBOSE) {
            logSingleton(runtime, superClass, attached);
        }
    }

    /**
     * This is an internal API only used by Ruby constructor before ThreadContext exists.  This is for bootstrapping
     * only.
     * @param runtime
     * @param superClass
     * @param Class
     * @param attached
     */
    MetaClass(Ruby runtime, RubyClass superClass, RubyClass Class, RubyBasicObject attached) {
        super(runtime, superClass, Class);
        metaClassInit(superClass, attached);
    }

    private void metaClassInit(RubyClass superClass, RubyBasicObject attached) {
        this.attached = attached;
        // use same ClassIndex as metaclass, since we're technically still of that type
        classIndex(superClass.getClassIndex());
        superClass.addSubclass(this);
    }

    private static void logSingleton(Ruby runtime, RubyClass superClass, RubyBasicObject attached) {
        if (runtime.isBooting()) return; // don't log singleton created during boot

        String attachedString = attached == null ? "null object" : "object of type " + attached.getMetaClass();
        LOG.info("singleton class created for type " + superClass + " attached to " + attachedString);

        if (LOG_SINGLETONS_VERBOSE) {
            LOG.info(new Exception("singleton creation stack trace"));
        }
    }

    @Override
    public final IRubyObject allocate(ThreadContext context) {
        throw typeError(context, "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(ThreadContext context, RubyClass superClass) {
        MetaClass klass = new MetaClass(context.runtime, getSuperSingletonMetaClass(context), this);
        setMetaClass(klass);

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

        return klass;
    }

    private RubyClass getSuperSingletonMetaClass(ThreadContext context) {
        if (attached instanceof RubyClass att) {
            RubyClass superClass = att.superClass();
            if (superClass != null) superClass = superClass.getRealClass();
            // #<Class:BasicObject>'s singleton class == Class.singleton_class
            // Context should be safe here as we never make a metaclass from a metaclass before first TC is made.
            return superClass == null ?
                    classClass(context).singletonClass(context) :
                    superClass.getMetaClass().singletonClass(context);
        }

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

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

    @Override
    public IRubyObject attached_object(ThreadContext context) {
        return attached;
    }

    public RubyBasicObject getAttached() {
        return attached;
    }

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

    private RubyBasicObject attached;

    private static final Logger LOG = LoggerFactory.getLogger(MetaClass.class);
    private static final boolean LOG_SINGLETONS = Options.LOG_SINGLETONS.load();
    private static final boolean LOG_SINGLETONS_VERBOSE = Options.LOG_SINGLETONS_VERBOSE.load();

}