/*******************************************************************************

 * Copyright (c) 2000, 2005 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.core.internal.watson;

import java.io.DataInput;

import java.io.IOException;

import org.eclipse.core.internal.dtree.DeltaDataTree;

/** <code>ElementTreeReader_1</code> is an implementation

 * of the <code>ElementTreeReader</code> for format version 1.

 *

 * <p>Instances of this reader read only format 1

 * of a saved element tree (they do not deal with

 * compatibility issues).

 *

 * @see ElementTreeReader

 */

/* package */class ElementTreeReaderImpl_1 extends ElementTreeReader {

	/** 

	 * Constructs a new element tree reader that works for

	 * the given element info factory.

	 */

	ElementTreeReaderImpl_1(IElementInfoFlattener factory) {

		super(factory);

	}

	/**

	 * Reads an element tree delta from the input stream, and

	 * reconstructs it as a delta on the given tree.

	 */

	public ElementTree readDelta(ElementTree parentTree, DataInput input) throws IOException {

		DeltaDataTree complete = parentTree.getDataTree();

		DeltaDataTree delta = dataTreeReader.readTree(complete, input);

		//if the delta is empty, just return the parent

		if (delta.isEmptyDelta())

			return parentTree;

		ElementTree tree = new ElementTree(delta);

		//copy the user data forward

		IElementTreeData data = parentTree.getTreeData();

		if (data != null) {

			tree.setTreeData((IElementTreeData) data.clone());

		}

		//make the underlying data tree immutable

		//can't call immutable() on the ElementTree because

		//this would attempt to reroot.

		delta.immutable();

		return tree;

	}

	/**

	 * Reads a chain of ElementTrees from the given input stream.

	 * @return A chain of ElementTrees, where the first tree in the list is

	 * complete, and all other trees are deltas on the previous tree in the list.

	 */

	public ElementTree[] readDeltaChain(DataInput input) throws IOException {

		/* read the number of trees */

		int treeCount = readNumber(input);

		ElementTree[] results = new ElementTree[treeCount];

		if (treeCount <= 0) {

			return results;

		}

		/* read the sort order */

		int[] order = new int[treeCount];

		for (int i = 0; i < treeCount; i++) {

			order[i] = readNumber(input);

		}

		/* read the complete tree */

		results[order[0]] = super.readTree(input);

		/* reconstitute each of the remaining trees from their written deltas */

		for (int i = 1; i < treeCount; i++) {

			results[order[i]] = super.readDelta(results[order[i - 1]], input);

		}

		return results;

	}

	/** Part of <code>ElementTreeReader</code> interface.

	 * @see ElementTreeReader

	 */

	public ElementTree readTree(DataInput input) throws IOException {

		/* The format version number has already been consumed

		 * by ElementTreeReader#readFrom.

		 */

		ElementTree result = new ElementTree(dataTreeReader.readTree(null, input));

		return result;

	}

}