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/*
 * Copyright (c) 2015, 2016 Oracle and/or its affiliates. All rights reserved. This
 * code is released under a tri EPL/GPL/LGPL license. You can use it,
 * redistribute it and/or modify it under the terms of the:
 *
 * Eclipse Public License version 1.0
 * GNU General Public License version 2
 * GNU Lesser General Public License version 2.1
 */
package org.jruby.truffle.language.methods;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.frame.Frame;
import com.oracle.truffle.api.object.DynamicObject;
import org.jruby.truffle.RubyContext;
import org.jruby.truffle.language.Visibility;
import org.jruby.truffle.language.arguments.RubyArguments;
import org.jruby.truffle.language.objects.SingletonClassNode;

/**
 * Declaration context for methods:
 * 
 * visibility
 * default definee / current module (which module to define on)
 * 
 */
public class DeclarationContext {

    /** @see http://yugui.jp/articles/846 */
    private enum DefaultDefinee {
        LEXICAL_SCOPE,
        SINGLETON_CLASS,
        SELF
    }

    public final Visibility visibility;
    public final DefaultDefinee defaultDefinee;

    public DeclarationContext(Visibility visibility, DefaultDefinee defaultDefinee) {
        this.visibility = visibility;
        this.defaultDefinee = defaultDefinee;
    }

    private static Frame lookupVisibility(Frame frame) {
        while (frame != null) {
            final Visibility visibility = RubyArguments.getDeclarationContext(frame).visibility;
            if (visibility != null) {
                return frame;
            }
            frame = RubyArguments.getDeclarationFrame(frame);
        }
        throw new UnsupportedOperationException("No declaration frame with visibility found");
    }

    public static Visibility findVisibility(Frame frame) {
        final Frame visibilityFrame = lookupVisibility(frame);
        return RubyArguments.getDeclarationContext(visibilityFrame).visibility;
    }

    public static void changeVisibility(Frame frame, Visibility newVisibility) {
        final Frame visibilityFrame = lookupVisibility(frame);
        final DeclarationContext oldDeclarationContext = RubyArguments.getDeclarationContext(visibilityFrame);
        if (newVisibility != oldDeclarationContext.visibility) {
            RubyArguments.setDeclarationContext(visibilityFrame, oldDeclarationContext.withVisibility(newVisibility));
        }
    }

    private DeclarationContext withVisibility(Visibility visibility) {
        assert visibility != null;
        return new DeclarationContext(visibility, defaultDefinee);
    }

    public DynamicObject getModuleToDefineMethods(Object self, InternalMethod method, RubyContext context, SingletonClassNode singletonClassNode) {
        switch (defaultDefinee) {
        case LEXICAL_SCOPE:
            return method.getSharedMethodInfo().getLexicalScope().getLiveModule();
        case SINGLETON_CLASS:
            return singletonClassNode.executeSingletonClass(self);
        case SELF:
            return (DynamicObject) self;
        default:
            CompilerDirectives.transferToInterpreterAndInvalidate();
            throw new UnsupportedOperationException();
        }
    }

    public static final DeclarationContext MODULE = new DeclarationContext(Visibility.PUBLIC, DefaultDefinee.LEXICAL_SCOPE);
    public static final DeclarationContext METHOD = new DeclarationContext(Visibility.PUBLIC, DefaultDefinee.LEXICAL_SCOPE);
    public static final DeclarationContext BLOCK = new DeclarationContext(null, DefaultDefinee.LEXICAL_SCOPE);
    public static final DeclarationContext TOP_LEVEL = new DeclarationContext(Visibility.PRIVATE, DefaultDefinee.LEXICAL_SCOPE);
    public static final DeclarationContext INSTANCE_EVAL = new DeclarationContext(Visibility.PUBLIC, DefaultDefinee.SINGLETON_CLASS);
    public static final DeclarationContext CLASS_EVAL = new DeclarationContext(Visibility.PUBLIC, DefaultDefinee.SELF);

}