/*
 * 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;

import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Objects;

/**
 * Abstract superclass for class file attributes
 */
public abstract class Attribute extends ClassFileEntry {

    /**
     * The attribute name.
     */
    protected final CPUTF8 attributeName;

    private int attributeNameIndex;

    /**
     * Constructs a new instance for an attribute name.
     *
     * @param attributeName an attribute name.
     */
    public Attribute(final CPUTF8 attributeName) {
        this.attributeName = attributeName;
    }

    @Override
    protected void doWrite(final DataOutputStream dos) throws IOException {
        dos.writeShort(attributeNameIndex);
        dos.writeInt(getLength());
        writeBody(dos);
    }

    @Override
    public boolean equals(final Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null || this.getClass() != obj.getClass()) {
            return false;
        }
        final Attribute other = (Attribute) obj;
        return Objects.equals(attributeName, other.attributeName);
    }

    /**
     * Gets the attribute name.
     *
     * @return the attribute name.
     */
    protected CPUTF8 getAttributeName() {
        return attributeName;
    }

    /**
     * Gets the length.
     *
     * @return the length.
     */
    protected abstract int getLength();

    /**
     * Answer the length of the receiver including its header (the u2 for the attribute name and the u4 for the attribute length). This is relevant when
     * attributes are nested within other attributes - the outer attribute needs to take the inner attribute headers into account when calculating its length.
     *
     * @return int adjusted length
     */
    protected int getLengthIncludingHeader() {
        return getLength() + 2 + 4;
    }

    @Override
    protected ClassFileEntry[] getNestedClassFileEntries() {
        return new ClassFileEntry[] { getAttributeName() };
    }

    /**
     * Answer true if the receiver needs to have BCI renumbering applied to it; otherwise answer false.
     *
     * @return boolean BCI renumbering required
     */
    public boolean hasBCIRenumbering() {
        return false;
    }

    @Override
    public int hashCode() {
        return Objects.hash(attributeName);
    }

    /**
     * Answer true if the receiver is a source file attribute (which gets special handling when the class is built); otherwise answer false.
     *
     * @return boolean source file attribute
     */
    public boolean isSourceFileAttribute() {
        return false;
    }

    @Override
    protected void resolve(final ClassConstantPool pool) {
        super.resolve(pool);
        attributeNameIndex = pool.indexOf(attributeName);
    }

    /**
     * Writes this body to the given output stream.
     *
     * @param out the output stream.
     * @throws IOException if an I/O error occurs.
     */
    protected abstract void writeBody(DataOutputStream out) throws IOException;

}
