/*
 * 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.bcel.classfile;

import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.bcel.Const;

/**
 * This class represents the type of a local variable or item on stack used in the StackMap entries.
 *
 * @see StackMapEntry
 * @see StackMap
 * @see Const
 */
public final class StackMapType implements Node, Cloneable {

    /**
     * Empty array constant.
     */
    public static final StackMapType[] EMPTY_ARRAY = {}; // BCELifier code generator writes calls to constructor translating null to EMPTY_ARRAY

    private byte type;
    private int index = -1; // Index to CONSTANT_Class or offset
    private ConstantPool constantPool;

    /**
     * Constructs a StackMapType.
     *
     * @param type type tag as defined in the Constants interface.
     * @param index index to constant pool, or byte code offset.
     * @param constantPool The constant pool.
     */
    public StackMapType(final byte type, final int index, final ConstantPool constantPool) {
        this.type = checkType(type);
        this.index = index;
        this.constantPool = constantPool;
    }

    /**
     * Constructs object from file stream.
     *
     * @param file Input stream.
     * @param constantPool The constant pool.
     * @throws IOException Thrown if an I/O error occurs.
     */
    StackMapType(final DataInput file, final ConstantPool constantPool) throws IOException {
        this(file.readByte(), -1, constantPool);
        if (hasIndex()) {
            this.index = file.readUnsignedShort();
        }
        this.constantPool = constantPool;
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object.
     * @since 6.8.0
     */
    @Override
    public void accept(final Visitor v) {
        v.visitStackMapType(this);
    }

    private byte checkType(final byte type) {
        if (type < Const.ITEM_Bogus || type > Const.ITEM_NewObject) {
            throw new ClassFormatException("Illegal type for StackMapType: " + type);
        }
        return type;
    }

    /**
     * Creates a deep copy of this object.
     *
     * @return deep copy of this object.
     */
    public StackMapType copy() {
        try {
            return (StackMapType) clone();
        } catch (final CloneNotSupportedException e) {
            // TODO should this throw?
        }
        return null;
    }

    /**
     * Dumps type entries to file.
     *
     * @param file Output file stream.
     * @throws IOException Thrown if an I/O error occurs.
     */
    public void dump(final DataOutputStream file) throws IOException {
        file.writeByte(type);
        if (hasIndex()) {
            file.writeShort(getIndex());
        }
    }

    /**
     * Gets the class name of this StackMapType from the constant pool at index position.
     *
     * @return The fully qualified name of the class for this StackMapType.
     * @since 6.8.0
     */
    public String getClassName() {
        return constantPool.constantToString(index, Const.CONSTANT_Class);
    }

    /**
     * Gets the constant pool.
     *
     * @return Constant pool used by this object.
     */
    public ConstantPool getConstantPool() {
        return constantPool;
    }

    /**
     * Gets the index.
     *
     * @return index to constant pool if type == ITEM_Object, or offset in byte code, if type == ITEM_NewObject, and -1
     *         otherwise.
     */
    public int getIndex() {
        return index;
    }

    /**
     * Gets the type.
     *
     * @return The type.
     */
    public byte getType() {
        return type;
    }

    /**
     * Checks if this type has an index.
     *
     * @return true, if type is either ITEM_Object or ITEM_NewObject.
     */
    public boolean hasIndex() {
        return type == Const.ITEM_Object || type == Const.ITEM_NewObject;
    }

    private String printIndex() {
        if (type == Const.ITEM_Object) {
            if (index < 0) {
                return ", class=<unknown>";
            }
            return ", class=" + getClassName();
        }
        if (type == Const.ITEM_NewObject) {
            return ", offset=" + index;
        }
        return "";
    }

    /**
     * Sets the constant pool.
     *
     * @param constantPool Constant pool to be used for this object.
     */
    public void setConstantPool(final ConstantPool constantPool) {
        this.constantPool = constantPool;
    }

    /**
     * Sets the index.
     *
     * @param index The index.
     */
    public void setIndex(final int index) {
        this.index = index;
    }

    /**
     * Sets the type.
     *
     * @param type The type.
     */
    public void setType(final byte type) {
        this.type = checkType(type);
    }

    /**
     * @return String representation.
     */
    @Override
    public String toString() {
        return "(type=" + Const.getItemName(type) + printIndex() + ")";
    }
}