/*******************************************************************************
 * Copyright (c) 2000, 2019 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Microsoft Corporation - copied to jdt.core.manipulation
 *******************************************************************************/
package org.eclipse.jdt.internal.corext.dom;

import org.eclipse.core.runtime.Assert;

import org.eclipse.jdt.core.dom.ASTNode;
import org.eclipse.jdt.core.dom.ASTVisitor;
import org.eclipse.jdt.core.dom.BodyDeclaration;
import org.eclipse.jdt.core.dom.FieldDeclaration;
import org.eclipse.jdt.core.dom.IVariableBinding;
import org.eclipse.jdt.core.dom.Initializer;
import org.eclipse.jdt.core.dom.MethodDeclaration;
import org.eclipse.jdt.core.dom.SingleVariableDeclaration;
import org.eclipse.jdt.core.dom.VariableDeclarationFragment;


public class LocalVariableIndex extends ASTVisitor {

	private int fTopIndex;

	/**
	 * Computes the maximum number of local variable declarations in the
	 * given body declaration.
	 *
	 * @param declaration the body declaration. Must either be a method
	 *  declaration, or an initializer, or a field declaration.
	 * @return the maximum number of local variables
	 */
	public static int perform(BodyDeclaration declaration) {
		Assert.isTrue(declaration != null);
		switch (declaration.getNodeType()) {
			case ASTNode.METHOD_DECLARATION:
			case ASTNode.FIELD_DECLARATION:
			case ASTNode.INITIALIZER:
				return internalPerform(declaration);
			default:
				throw new IllegalArgumentException(declaration.toString());
		}
	}

	private static int internalPerform(BodyDeclaration methodOrInitializer) {
		// we have to find the outermost method/initializer/field declaration since a local or anonymous
		// type can reference final variables from the outer scope.
		BodyDeclaration target= methodOrInitializer;
		ASTNode parent= target.getParent();
		while (parent != null) {
			if (parent instanceof MethodDeclaration || parent instanceof Initializer || parent instanceof FieldDeclaration) {
				target= (BodyDeclaration)parent;
			}
			parent= parent.getParent();
		}

		return doPerform(target);
	}

	private static int doPerform(BodyDeclaration node) {
		LocalVariableIndex counter= new LocalVariableIndex();
		node.accept(counter);
		return counter.fTopIndex;
	}

	@Override
	public boolean visit(SingleVariableDeclaration node) {
		handleVariableBinding(node.resolveBinding());
		return true;
	}

	@Override
	public boolean visit(VariableDeclarationFragment node) {
		handleVariableBinding(node.resolveBinding());
		return true;
	}

	private void handleVariableBinding(IVariableBinding binding) {
		if (binding == null)
			return;
		fTopIndex= Math.max(fTopIndex, binding.getVariableId());
	}
}
