/*
 * 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.apache.bcel.classfile;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import org.apache.bcel.Constants;
import org.apache.bcel.classfile.ConstantUtf8;

/**
 * Abstract super class for <em>Attribute</em> objects. Currently the
 * <em>ConstantValue</em>, <em>SourceFile</em>, <em>Code</em>,
 * <em>Exceptiontable</em>, <em>LineNumberTable</em>,
 * <em>LocalVariableTable</em>, <em>InnerClasses</em> and
 * <em>Synthetic</em> attributes are supported. The <em>Unknown</em>
 * attribute stands for non-standard-attributes.
 * 
 * @version $Id$
 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 * @see ConstantValue
 * @see SourceFile
 * @see Code
 * @see Unknown
 * @see ExceptionTable
 * @see LineNumberTable
 * @see LocalVariableTable
 * @see InnerClasses
 * @see Synthetic
 * @see Deprecated
 * @see Signature
 */
public abstract class Attribute implements Cloneable, Node, Serializable
{
    private static final long serialVersionUID = -1707826820310002955L;

    protected int name_index; // Points to attribute name in constant pool TODO make private (has getter & setter)

    protected int length; // Content length of attribute field TODO make private (has getter & setter)

    protected byte tag; // Tag to distinguish subclasses TODO make private & final; supposed to be immutable

    protected ConstantPool constant_pool; // TODO make private (has getter & setter)

    protected Attribute(byte tag, int name_index, int length,
            ConstantPool constant_pool)
    {
        this.tag = tag;
        this.name_index = name_index;
        this.length = length;
        this.constant_pool = constant_pool;
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitely
     * 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
     */
    public abstract void accept(Visitor v);

    /**
     * Dump attribute to file stream in binary format.
     * 
     * @param file
     *            Output file stream
     * @throws IOException
     */
    public void dump(DataOutputStream file) throws IOException
    {
        file.writeShort(name_index);
        file.writeInt(length);
    }

    private static final Map<String, AttributeReader> readers = new HashMap<String, AttributeReader>();

    /**
     * Add an Attribute reader capable of parsing (user-defined) attributes
     * named "name". You should not add readers for the standard attributes such
     * as "LineNumberTable", because those are handled internally.
     * 
     * @param name
     *            the name of the attribute as stored in the class file
     * @param r
     *            the reader object
     */
    public static void addAttributeReader(String name, AttributeReader r)
    {
        readers.put(name, r);
    }

    /**
     * Remove attribute reader
     * 
     * @param name
     *            the name of the attribute as stored in the class file
     */
    public static void removeAttributeReader(String name)
    {
        readers.remove(name);
    }

    /*
     * Class method reads one attribute from the input data stream. This method
     * must not be accessible from the outside. It is called by the Field and
     * Method constructor methods.
     * 
     * @see Field
     * @see Method @param file Input stream @param constant_pool Array of
     *      constants @return Attribute @throws IOException @throws
     *      ClassFormatException
     */
    public static Attribute readAttribute(DataInputStream file,
            ConstantPool constant_pool) throws IOException,
            ClassFormatException
    {
        ConstantUtf8 c;
        String name;
        int name_index;
        int length;
        byte tag = Constants.ATTR_UNKNOWN; // Unknown attribute
        // Get class name from constant pool via `name_index' indirection
        name_index = file.readUnsignedShort();
        c = (ConstantUtf8) constant_pool.getConstant(name_index,
                Constants.CONSTANT_Utf8);
        name = c.getBytes();
        // Length of data in bytes
        length = file.readInt();
        // Compare strings to find known attribute
        // System.out.println(name);
        for (byte i = 0; i < Constants.KNOWN_ATTRIBUTES; i++)
        {
            if (name.equals(Constants.ATTRIBUTE_NAMES[i]))
            {
                tag = i; // found!
                break;
            }
        }
        // Call proper constructor, depending on `tag'
        switch (tag)
        {
        case Constants.ATTR_UNKNOWN:
            AttributeReader r = readers.get(name);
            if (r != null)
            {
                return r.createAttribute(name_index, length, file,
                        constant_pool);
            }
            return new Unknown(name_index, length, file, constant_pool);
        case Constants.ATTR_CONSTANT_VALUE:
            return new ConstantValue(name_index, length, file, constant_pool);
        case Constants.ATTR_SOURCE_FILE:
            return new SourceFile(name_index, length, file, constant_pool);
        case Constants.ATTR_CODE:
            return new Code(name_index, length, file, constant_pool);
        case Constants.ATTR_EXCEPTIONS:
            return new ExceptionTable(name_index, length, file, constant_pool);
        case Constants.ATTR_LINE_NUMBER_TABLE:
            return new LineNumberTable(name_index, length, file, constant_pool);
        case Constants.ATTR_LOCAL_VARIABLE_TABLE:
            return new LocalVariableTable(name_index, length, file,
                    constant_pool);
        case Constants.ATTR_INNER_CLASSES:
            return new InnerClasses(name_index, length, file, constant_pool);
        case Constants.ATTR_SYNTHETIC:
            return new Synthetic(name_index, length, file, constant_pool);
        case Constants.ATTR_DEPRECATED:
            return new Deprecated(name_index, length, file, constant_pool);
        case Constants.ATTR_PMG:
            return new PMGClass(name_index, length, file, constant_pool);
        case Constants.ATTR_SIGNATURE:
            return new Signature(name_index, length, file, constant_pool);
        case Constants.ATTR_STACK_MAP:
            return new StackMap(name_index, length, file, constant_pool);
        case Constants.ATTR_RUNTIME_VISIBLE_ANNOTATIONS:
            return new RuntimeVisibleAnnotations(name_index, length, file,
                    constant_pool);
        case Constants.ATTR_RUNTIME_INVISIBLE_ANNOTATIONS:
            return new RuntimeInvisibleAnnotations(name_index, length, file,
                    constant_pool);
        case Constants.ATTR_RUNTIME_VISIBLE_PARAMETER_ANNOTATIONS:
            return new RuntimeVisibleParameterAnnotations(name_index, length,
                    file, constant_pool);
        case Constants.ATTR_RUNTIME_INVISIBLE_PARAMETER_ANNOTATIONS:
            return new RuntimeInvisibleParameterAnnotations(name_index, length,
                    file, constant_pool);
        case Constants.ATTR_ANNOTATION_DEFAULT:
            return new AnnotationDefault(name_index, length, file,
                    constant_pool);
        case Constants.ATTR_LOCAL_VARIABLE_TYPE_TABLE:
            return new LocalVariableTypeTable(name_index, length, file,
                    constant_pool);
        case Constants.ATTR_ENCLOSING_METHOD:
            return new EnclosingMethod(name_index, length, file, constant_pool);
        case Constants.ATTR_STACK_MAP_TABLE:
            return new StackMapTable(name_index, length, file, constant_pool);
        case Constants.ATTR_BOOTSTRAP_METHODS:
            return new BootstrapMethods(name_index, length, file, constant_pool);
        case Constants.ATTR_METHOD_PARAMETERS:
                return new MethodParameters(name_index, length, file, constant_pool);
        default: // Never reached
            throw new IllegalStateException("Unrecognized attribute type tag parsed: " + tag);
        }
    }

    /**
     * @return Name of attribute
     */
    public String getName()
    {
        ConstantUtf8 c = (ConstantUtf8) constant_pool.getConstant(name_index,
                Constants.CONSTANT_Utf8);
        return c.getBytes();
    }

    /**
     * @return Length of attribute field in bytes.
     */
    public final int getLength()
    {
        return length;
    }

    /**
     * @param length
     *            length in bytes.
     */
    public final void setLength(int length)
    {
        this.length = length;
    }

    /**
     * @param name_index
     *            of attribute.
     */
    public final void setNameIndex(int name_index)
    {
        this.name_index = name_index;
    }

    /**
     * @return Name index in constant pool of attribute name.
     */
    public final int getNameIndex()
    {
        return name_index;
    }

    /**
     * @return Tag of attribute, i.e., its type. Value may not be altered, thus
     *         there is no setTag() method.
     */
    public final byte getTag()
    {
        return tag;
    }

    /**
     * @return Constant pool used by this object.
     * @see ConstantPool
     */
    public final ConstantPool getConstantPool()
    {
        return constant_pool;
    }

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

    /**
     * Use copy() if you want to have a deep copy(), i.e., with all references
     * copied correctly.
     * 
     * @return shallow copy of this attribute
     */
    @Override
    public Object clone()
    {
        Attribute attr = null;
        try
        {
            attr = (Attribute) super.clone();
        }
        catch (CloneNotSupportedException e)
        {
            throw new Error("Clone Not Supported"); // never happens
        }
        return attr;
    }

    /**
     * @return deep copy of this attribute
     */
    public abstract Attribute copy(ConstantPool _constant_pool);

    /**
     * @return attribute name.
     */
    @Override
    public String toString()
    {
        return Constants.ATTRIBUTE_NAMES[tag];
    }
}
