/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  Licensed 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.generic;

import org.apache.bcel.Constants;
import org.apache.bcel.classfile.LocalVariable;

/**
 * This class represents a local variable within a method. It contains its
 * scope, name and type. The generated LocalVariable object can be obtained with
 * getLocalVariable which needs the instruction list and the constant pool as
 * parameters.
 * 
 * @version $Id: LocalVariableGen.java 386056 2006-03-15 11:31:56Z tcurdt $
 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 * @see LocalVariable
 * @see MethodGen
 */
public class LocalVariableGen implements InstructionTargeter, NamedAndTyped,
		Cloneable, java.io.Serializable {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private int index;
	private String name;
	private Type type;
	private InstructionHandle start, end;

	/**
	 * Generate a local variable that with index `index'. Note that double and
	 * long variables need two indexs. Index indices have to be provided by the
	 * user.
	 * 
	 * @param index
	 *            index of local variable
	 * @param name
	 *            its name
	 * @param type
	 *            its type
	 * @param start
	 *            from where the instruction is valid (null means from the
	 *            start)
	 * @param end
	 *            until where the instruction is valid (null means to the end)
	 */
	public LocalVariableGen(int index, String name, Type type,
			InstructionHandle start, InstructionHandle end) {
		if ((index < 0) || (index > Constants.MAX_SHORT)) {
			throw new ClassGenException("Invalid index index: " + index);
		}
		this.name = name;
		this.type = type;
		this.index = index;
		setStart(start);
		setEnd(end);
	}

	/**
	 * Get LocalVariable object.
	 * 
	 * This relies on that the instruction list has already been dumped to byte
	 * code or or that the `setPositions' methods has been called for the
	 * instruction list.
	 * 
	 * Note that for local variables whose scope end at the last instruction of
	 * the method's code, the JVM specification is ambiguous: both a
	 * start_pc+length ending at the last instruction and start_pc+length ending
	 * at first index beyond the end of the code are valid.
	 * 
	 * @param cp
	 *            constant pool
	 */
	public LocalVariable getLocalVariable(ConstantPoolGen cp) {
		int start_pc = start.getPosition();
		int length = end.getPosition() - start_pc;
		if (length > 0) {
			length += end.getInstruction().getLength();
		}
		int name_index = cp.addUtf8(name);
		int signature_index = cp.addUtf8(type.getSignature());
		return new LocalVariable(start_pc, length, name_index, signature_index,
				index, cp.getConstantPool());
	}

	public void setIndex(int index) {
		this.index = index;
	}

	public int getIndex() {
		return index;
	}

	@Override
	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String getName() {
		return name;
	}

	@Override
	public void setType(Type type) {
		this.type = type;
	}

	@Override
	public Type getType() {
		return type;
	}

	public InstructionHandle getStart() {
		return start;
	}

	public InstructionHandle getEnd() {
		return end;
	}

	public void setStart(InstructionHandle start) {
		BranchInstruction.notifyTarget(this.start, start, this);
		this.start = start;
	}

	public void setEnd(InstructionHandle end) {
		BranchInstruction.notifyTarget(this.end, end, this);
		this.end = end;
	}

	/**
	 * @param old_ih
	 *            old target, either start or end
	 * @param new_ih
	 *            new target
	 */
	@Override
	public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
		boolean targeted = false;
		if (start == old_ih) {
			targeted = true;
			setStart(new_ih);
		}
		if (end == old_ih) {
			targeted = true;
			setEnd(new_ih);
		}
		if (!targeted) {
			throw new ClassGenException("Not targeting " + old_ih + ", but {"
					+ start + ", " + end + "}");
		}
	}

	/**
	 * @return true, if ih is target of this variable
	 */
	@Override
	public boolean containsTarget(InstructionHandle ih) {
		return (start == ih) || (end == ih);
	}

	/**
	 * @return a hash code value for the object.
	 */
	@Override
	public int hashCode() {
		// If the user changes the name or type, problems with the targeter
		// hashmap will occur
		int hc = index ^ name.hashCode() ^ type.hashCode();
		return hc;
	}

	/**
	 * We consider to local variables to be equal, if the use the same index and
	 * are valid in the same range.
	 */
	@Override
	public boolean equals(Object o) {
		if (!(o instanceof LocalVariableGen)) {
			return false;
		}
		LocalVariableGen l = (LocalVariableGen) o;
		return (l.index == index) && (l.start == start) && (l.end == end);
	}

	@Override
	public String toString() {
		return "LocalVariableGen(" + name + ", " + type + ", " + start + ", "
				+ end + ")";
	}

	@Override
	public Object clone() {
		try {
			return super.clone();
		} catch (CloneNotSupportedException e) {
			System.err.println(e);
			return null;
		}
	}
}
