/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.wst.jsdt.core.dom;

import java.util.ArrayList;
import java.util.List;

/**
 * Simple or qualified "this" AST node type.
 *
 * <pre>
 * ThisExpression:
 *     [ ClassName <b>.</b> ] <b>this</b>
 * </pre>
 * <p>
 * See <code>FieldAccess</code> for guidelines on handling other expressions
 * that resemble qualified names.
 * </p>
 *
 * @see FieldAccess
 * 
 * Provisional API: This class/interface is part of an interim API that is still under development and expected to 
 * change significantly before reaching stability. It is being made available at this early stage to solicit feedback 
 * from pioneering adopters on the understanding that any code that uses this API will almost certainly be broken 
 * (repeatedly) as the API evolves.
 */
public class ThisExpression extends Expression {

	/**
	 * The "qualifier" structural property of this node type.
	 *  
	 */
	public static final ChildPropertyDescriptor QUALIFIER_PROPERTY =
		new ChildPropertyDescriptor(ThisExpression.class, "qualifier", Name.class, OPTIONAL, NO_CYCLE_RISK); //$NON-NLS-1$

	/**
	 * A list of property descriptors (element type:
	 * {@link StructuralPropertyDescriptor}),
	 * or null if uninitialized.
	 */
	private static final List PROPERTY_DESCRIPTORS;

	static {
		List propertyList = new ArrayList(2);
		createPropertyList(ThisExpression.class, propertyList);
		addProperty(QUALIFIER_PROPERTY, propertyList);
		PROPERTY_DESCRIPTORS = reapPropertyList(propertyList);
	}

	/**
	 * Returns a list of structural property descriptors for this node type.
	 * Clients must not modify the result.
	 *
	 * @param apiLevel the API level; one of the
	 * <code>AST.JLS*</code> constants
	 * @return a list of property descriptors (element type:
	 * {@link StructuralPropertyDescriptor})
	 *  
	 */
	public static List propertyDescriptors(int apiLevel) {
		return PROPERTY_DESCRIPTORS;
	}

	/**
	 * The optional qualifier; <code>null</code> for none; defaults to none.
	 */
	private Name optionalQualifier = null;

	/**
	 * Creates a new AST node for a "this" expression owned by the
	 * given AST. By default, there is no qualifier.
	 *
	 * @param ast the AST that is to own this node
	 */
	ThisExpression(AST ast) {
		super(ast);
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	final List internalStructuralPropertiesForType(int apiLevel) {
		return propertyDescriptors(apiLevel);
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	final ASTNode internalGetSetChildProperty(ChildPropertyDescriptor property, boolean get, ASTNode child) {
		if (property == QUALIFIER_PROPERTY) {
			if (get) {
				return getQualifier();
			} else {
				setQualifier((Name) child);
				return null;
			}
		}
		// allow default implementation to flag the error
		return super.internalGetSetChildProperty(property, get, child);
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	final int getNodeType0() {
		return THIS_EXPRESSION;
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	ASTNode clone0(AST target) {
		ThisExpression result = new ThisExpression(target);
		result.setSourceRange(this.getStartPosition(), this.getLength());
		result.setQualifier((Name) ASTNode.copySubtree(target, getQualifier()));
		return result;
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	final boolean subtreeMatch0(ASTMatcher matcher, Object other) {
		// dispatch to correct overloaded match method
		return matcher.match(this, other);
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	void accept0(ASTVisitor visitor) {
		boolean visitChildren = visitor.visit(this);
		if (visitChildren) {
			acceptChild(visitor, getQualifier());
		}
		visitor.endVisit(this);
	}

	/**
	 * Returns the qualifier of this "this" expression, or
	 * <code>null</code> if there is none.
	 *
	 * @return the qualifier name node, or <code>null</code> if there is none
	 */
	public Name getQualifier() {
		return this.optionalQualifier;
	}

	/**
	 * Sets or clears the qualifier of this "this" expression.
	 *
	 * @param name the qualifier name node, or <code>null</code> if
	 *    there is none
	 * @exception IllegalArgumentException if:
	 * <ul>
	 * <li>the node belongs to a different AST</li>
	 * <li>the node already has a parent</li>
	 * </ul>
	 */
	public void setQualifier(Name name) {
		ASTNode oldChild = this.optionalQualifier;
		preReplaceChild(oldChild, name, QUALIFIER_PROPERTY);
		this.optionalQualifier = name;
		postReplaceChild(oldChild, name, QUALIFIER_PROPERTY);
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	int memSize() {
		// treat Operator as free
		return BASE_NODE_SIZE + 1 * 4;
	}

	/* (omit javadoc for this method)
	 * Method declared on ASTNode.
	 */
	int treeSize() {
		return
			memSize()
			+ (this.optionalQualifier == null ? 0 : getQualifier().treeSize());
	}
}
