/*
 * 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
 *
 *   https://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.apache.commons.compress.harmony.unpack200.bytecode.forms;

import org.apache.commons.compress.harmony.unpack200.bytecode.ByteCode;
import org.apache.commons.compress.harmony.unpack200.bytecode.CodeAttribute;
import org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager;

/**
 * This class implements the byte code form for those bytecodes which have label references (and only label references).
 */
public class LabelForm extends ByteCodeForm {

    protected boolean widened;

    /**
     * Constructs a new instance with the specified opcode, name, operandType and rewrite.
     *
     * @param opcode  index corresponding to the opcode's value.
     * @param name    String printable name of the opcode.
     * @param rewrite Operand positions (which will later be rewritten in ByteCodes) are indicated by -1.
     */
    public LabelForm(final int opcode, final String name, final int[] rewrite) {
        super(opcode, name, rewrite);
    }

    /**
     * Constructs a new instance with the specified opcode, name, operandType and rewrite.
     *
     * @param opcode  index corresponding to the opcode's value.
     * @param name    String printable name of the opcode.
     * @param rewrite Operand positions (which will later be rewritten in ByteCodes) are indicated by -1.
     * @param widened TODO.
     */
    public LabelForm(final int opcode, final String name, final int[] rewrite, final boolean widened) {
        this(opcode, name, rewrite);
        this.widened = widened;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.apache.commons.compress.harmony.unpack200.bytecode.forms.ByteCodeForm#fixUpByteCodeTarget(org.apache.commons.
     * compress.harmony.unpack200.bytecode.ByteCode, org.apache.commons.compress.harmony.unpack200.bytecode.CodeAttribute)
     */
    @Override
    public void fixUpByteCodeTargets(final ByteCode byteCode, final CodeAttribute codeAttribute) {
        // LabelForms need to fix up the target of label operations
        final int originalTarget = byteCode.getByteCodeTargets()[0];
        final int sourceIndex = byteCode.getByteCodeIndex();
        final int absoluteInstructionTargetIndex = sourceIndex + originalTarget;
        final int targetValue = codeAttribute.byteCodeOffsets.get(absoluteInstructionTargetIndex).intValue();
        final int sourceValue = codeAttribute.byteCodeOffsets.get(sourceIndex).intValue();
        // The operand is the difference between the source instruction
        // and the destination instruction.
        byteCode.setOperandSigned2Bytes(targetValue - sourceValue, 0);
        if (widened) {
            byteCode.setNestedPositions(new int[][] { { 0, 4 } });
        } else {
            byteCode.setNestedPositions(new int[][] { { 0, 2 } });
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see org.apache.commons.compress.harmony.unpack200.bytecode.forms.ByteCodeForm#setByteCodeOperands(org.apache.commons.
     * compress.harmony.unpack200.bytecode.ByteCode, org.apache.commons.compress.harmony.unpack200.bytecode.OperandTable,
     * org.apache.commons.compress.harmony.unpack200.SegmentConstantPool)
     */
    @Override
    public void setByteCodeOperands(final ByteCode byteCode, final OperandManager operandManager, final int codeLength) {
        byteCode.setByteCodeTargets(new int[] { operandManager.nextLabel() });
        // The byte code operands actually get set later -
        // once we have all the bytecodes - in fixUpByteCodeTarget().
    }
}
