/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache 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.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.codehaus.groovy.transform.sc.transformers;

import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.GroovyCodeVisitor;
import org.codehaus.groovy.ast.expr.BinaryExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.ExpressionTransformer;
import org.codehaus.groovy.classgen.AsmClassGenerator;
import org.codehaus.groovy.classgen.asm.WriterController;
import org.codehaus.groovy.syntax.Token;
import org.codehaus.groovy.syntax.Types;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

/**
 * Compares two objects using identity comparison.
 * This expression will generate bytecode using the IF_ACMPNE instruction, instead of
 * using the "equals" method that is currently mapped to "==" in Groovy.
 *
 * This expression should only be used to compare to objects, not primitives, and only
 * in the context of reference equality check.
 */
public class CompareIdentityExpression extends BinaryExpression implements Opcodes {
    private final Expression leftExpression;
    private final Expression rightExpression;

    public CompareIdentityExpression(final Expression leftExpression, final Expression rightExpression) {
        super(leftExpression, new Token(Types.COMPARE_TO, "==", -1, -1), rightExpression);
        this.leftExpression = leftExpression;
        this.rightExpression = rightExpression;
    }

    @Override
    public Expression transformExpression(final ExpressionTransformer transformer) {
        return this;
    }

    @Override
    public void visit(final GroovyCodeVisitor visitor) {
        if (visitor instanceof AsmClassGenerator) {
            AsmClassGenerator acg = (AsmClassGenerator) visitor;
            WriterController controller = acg.getController();
            controller.getTypeChooser().resolveType(leftExpression, controller.getClassNode());
            controller.getTypeChooser().resolveType(rightExpression, controller.getClassNode());
            MethodVisitor mv = controller.getMethodVisitor();
            leftExpression.visit(acg);
            controller.getOperandStack().box();
            rightExpression.visit(acg);
            controller.getOperandStack().box();
            Label l1 = new Label();
            mv.visitJumpInsn(IF_ACMPNE, l1);
            mv.visitInsn(ICONST_1);
            Label l2 = new Label();
            mv.visitJumpInsn(GOTO, l2);
            mv.visitLabel(l1);
            mv.visitInsn(ICONST_0);
            mv.visitLabel(l2);
            controller.getOperandStack().replace(ClassHelper.boolean_TYPE, 2);
        } else {
            super.visit(visitor);
        }
    }
}
