BEGIN LICENSE BLOCK *****
Version: EPL 2.0/GPL 2.0/LGPL 2.1
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
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.
Copyright (C) 2001 Alan Moore 
Copyright (C) 2001-2004 Jan Arne Petersen 
Copyright (C) 2002-2004 Anders Bengtsson 
Copyright (C) 2004 Thomas E Enebo 
Copyright (C) 2004 Charles O Nutter 
Copyright (C) 2004 Stefan Matthias Aust 
Alternatively, the contents of this file may be used under the terms of
either of the GNU General Public License Version 2 or later (the "GPL"),
or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
in which case the provisions of the GPL or the LGPL are applicable instead
of those above. If you wish to allow use of your version of this file only
under the terms of either the GPL or the LGPL, and not to allow others to
use your version of this file under the terms of the EPL, indicate your
decision by deleting the provisions above and replace them with the notice
and other provisions required by the GPL or the LGPL. If you do not delete
the provisions above, a recipient may use your version of this file under
the terms of any one of the EPL, the GPL or the LGPL.
END LICENSE BLOCK /***** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * 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
 *
 * 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.
 *
 * Copyright (C) 2001 Alan Moore <alan_moore@gmx.net>
 * Copyright (C) 2001-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2002-2004 Anders Bengtsson <ndrsbngtssn@yahoo.se>
 * Copyright (C) 2004 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2004 Charles O Nutter <headius@headius.com>
 * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the EPL, the GPL or the LGPL.
 ***** END LICENSE BLOCK *****/

package org.jruby;

import org.jcodings.specific.USASCIIEncoding;
import org.jruby.anno.JRubyMethod;
import org.jruby.anno.JRubyClass;
import org.jruby.compiler.Constantizable;
import org.jruby.runtime.ClassIndex;
import org.jruby.runtime.ObjectAllocator;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.runtime.opto.OptoFactory;
import org.jruby.util.ByteList;

Author:
 jpetersen/**
 *
 * @author  jpetersen
 */
@JRubyClass(name="NilClass")
public class RubyNil extends RubyObject implements Constantizable {

    private final int hashCode;
    private final Object constant;

    public RubyNil(Ruby runtime) {
        super(runtime, runtime.getNilClass(), false);
        flags |= NIL_F | FALSE_F | FROZEN_F;

        if (RubyInstanceConfig.CONSISTENT_HASHING_ENABLED) {
            // default to a fixed value
            this.hashCode = 34;
        } else {
            // save the object id based hash code;
            this.hashCode = System.identityHashCode(this);
        }

        constant = OptoFactory.newConstantWrapper(IRubyObject.class, this);
    }
    
    public static final ObjectAllocator NIL_ALLOCATOR = new ObjectAllocator() {
        @Override
        public IRubyObject allocate(Ruby runtime, RubyClass klass) {
            throw runtime.newTypeError("allocator undefined for NilClass");
        }
    };
    
    public static RubyClass createNilClass(Ruby runtime) {
        RubyClass nilClass = runtime.defineClass("NilClass", runtime.getObject(), NIL_ALLOCATOR);
        runtime.setNilClass(nilClass);
        nilClass.setClassIndex(ClassIndex.NIL);
        nilClass.setReifiedClass(RubyNil.class);
        
        nilClass.defineAnnotatedMethods(RubyNil.class);
        
        nilClass.getMetaClass().undefineMethod("new");
        
        // FIXME: This is causing a verification error for some reason
        //nilClass.dispatcher = callbackFactory.createDispatcher(nilClass);
        
        return nilClass;
    }
    
    @Override
    public ClassIndex getNativeClassIndex() {
        return ClassIndex.NIL;
    }

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

    @Override
    public RubyClass getSingletonClass() {
        return metaClass;
    }
    
    @Override
    public Class<?> getJavaClass() {
        return void.class;
    }

    
See Also:
Constantizable/**
     * @see org.jruby.compiler.Constantizable
     */
    @Override
    public Object constant() {
        return constant;
    }

    // Methods of the Nil Class (nil_*):
    
    
nil_to_i
/** nil_to_i
     *
     */
    @JRubyMethod
    public static RubyFixnum to_i(ThreadContext context, IRubyObject recv) {
        return RubyFixnum.zero(context.runtime);
    }
    
    
nil_to_f
/**
     * nil_to_f
     *
     */
    @JRubyMethod
    public static RubyFloat to_f(ThreadContext context, IRubyObject recv) {
        return RubyFloat.newFloat(context.runtime, 0.0D);
    }
    
    
nil_to_s
/** nil_to_s
     *
     */
    @JRubyMethod
    public static RubyString to_s(ThreadContext context, IRubyObject recv) {
        return RubyString.newEmptyString(context.runtime);
    }
    
    
nil_to_a
/** nil_to_a
     *
     */
    @JRubyMethod
    public static RubyArray to_a(ThreadContext context, IRubyObject recv) {
        return context.runtime.newEmptyArray();
    }
    
    @JRubyMethod
    public static RubyHash to_h(ThreadContext context, IRubyObject recv) {
        return RubyHash.newSmallHash(context.runtime);
    }

    
nil_inspect
/** nil_inspect
     *
     */
    @Override
    @JRubyMethod
    public IRubyObject inspect() {
        return RubyNil.inspect(getRuntime());
    }

    static final byte[] nilBytes = new byte[] { 'n','i','l' }; // RubyString.newUSASCIIString(runtime, "nil")
    private static final ByteList nil = new ByteList(nilBytes, USASCIIEncoding.INSTANCE);

    static RubyString inspect(Ruby runtime) {
        return RubyString.newStringShared(runtime, runtime.getString(), nil);
    }

    
nil_and
/** nil_and
     *
     */
    @JRubyMethod(name = "&", required = 1)
    public static RubyBoolean op_and(ThreadContext context, IRubyObject recv, IRubyObject obj) {
        return context.fals;
    }
    
    
nil_or
/** nil_or
     *
     */
    @JRubyMethod(name = "|", required = 1)
    public static RubyBoolean op_or(ThreadContext context, IRubyObject recv, IRubyObject obj) {
        return context.runtime.newBoolean(obj.isTrue());
    }
    
    
nil_xor
/** nil_xor
     *
     */
    @JRubyMethod(name = "^", required = 1)
    public static RubyBoolean op_xor(ThreadContext context, IRubyObject recv, IRubyObject obj) {
        return context.runtime.newBoolean(obj.isTrue());
    }

    @JRubyMethod(name = "nil?")
    public IRubyObject nil_p() {
        return getRuntime().getTrue();
    }

    @JRubyMethod
    public RubyFixnum hash(ThreadContext context) {
        return context.runtime.newFixnum(hashCode());
    }

    @Override
    public int hashCode() {
        return hashCode;
    }

    @Override
    public RubyFixnum id() {
        return getRuntime().newFixnum(8);
    }
    
    @Override
    public IRubyObject taint(ThreadContext context) {
        return this;
    }

    
nilclass_to_c
/** nilclass_to_c
     * 
     */
    @JRubyMethod
    public static IRubyObject to_c(ThreadContext context, IRubyObject recv) {
        return RubyComplex.newComplexCanonicalize(context, RubyFixnum.zero(context.runtime));
    }
    
    
nilclass_to_r
/** nilclass_to_r
     * 
     */
    @JRubyMethod
    public static IRubyObject to_r(ThreadContext context, IRubyObject recv) {
        return RubyRational.newRationalCanonicalize(context, 0);
    }

    
nilclass_rationalize
/** nilclass_rationalize
     *
     */
    @JRubyMethod(optional = 1)
    public static IRubyObject rationalize(ThreadContext context, IRubyObject recv, IRubyObject[] args) {
        return to_r(context, recv);
    }

    @Override
    public <T> T toJava(Class<T> target) {
        if (target.isPrimitive()) {
            if (target == boolean.class) {
                return (T) Boolean.FALSE;
            } else if (target == char.class) {
                return (T) (Character) '\0';
            } else {
                switch (target.getSimpleName().charAt(0)) {
                    case 'b': return (T) (Byte) (byte) 0;
                    case 's': return (T) (Short) (short) 0;
                    case 'i': return (T) (Integer) 0;
                    case 'l': return (T) (Long) 0L;
                    case 'f': return (T) (Float) 0.0F;
                    case 'd': return (T) (Double) 0.0;
                }
            }
        }
        return null;
    }
}