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Structr is an open source framework based on the popular Neo4j graph database.
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/**
 * Copyright (C) 2010-2016 Structr GmbH
 *
 * This file is part of Structr .
 *
 * Structr is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * Structr is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with Structr.  If not, see .
 */
package org.structr.web.diff;

import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import org.structr.common.error.FrameworkException;
import org.structr.core.app.App;
import org.structr.web.entity.dom.DOMNode;
import org.structr.web.entity.dom.Page;
import org.structr.web.entity.dom.relationship.DOMChildren;

/**
 *
 *
 */
public abstract class InvertibleModificationOperation implements Comparable {

	protected Map hashMappedExistingNodes = new LinkedHashMap<>();

	public abstract void apply(final App app, final Page sourcePage, final Page newPage) throws FrameworkException;
	public abstract InvertibleModificationOperation revert();
	public abstract Integer getPosition();

	public InvertibleModificationOperation(final Map hashMappedExistingNodes) {
		this.hashMappedExistingNodes = hashMappedExistingNodes;
	}

	protected InsertPosition findInsertPosition(final Page sourcePage, final String parentHash, final List siblingHashes, final DOMNode newNode) {

		final DOMNode newParent  = hashMappedExistingNodes.get(parentHash);
		DOMNode newSibling       = null;

		// we need to check the whole list of siblings here because
		// when inserting the first element of a list of elements,
		// the "next sibling" element is not there yet, so we have
		// to use the one after
		for (final String siblingHash : siblingHashes) {

			newSibling = hashMappedExistingNodes.get(siblingHash);
			if (newSibling != null) {
				break;
			}
		}

		if (newParent == null) {

			// new parent did not exist in source document, what do?
			// System.out.println("TODO: new parent not found in source document.");
		}

		return new InsertPosition(newParent, newSibling);
	}

	public static void collectNodes(final DOMNode node, final Map indexMappedNodes, final Map hashMappedNodes, final Map depthMap) {

		collectNodes(node, indexMappedNodes, hashMappedNodes, depthMap, 0, new LinkedHashMap());
	}

	public static void collectNodes(final Page page, final Map indexMappedNodes, final Map hashMappedNodes, final Map depthMap) {

		collectNodes(page, indexMappedNodes, hashMappedNodes, depthMap, 0, new LinkedHashMap());
	}

	private static void collectNodes(final DOMNode node, final Map indexMappedNodes, final Map hashMappedNodes, final Map depthMap, final int depth, final Map childIndexMap) {

		// early exit
		if (node == null) {
			return;
		}
		
		Integer pos  = childIndexMap.get(depth);
		if (pos == null) {

			pos = 0;
		}

		int position = pos;
		childIndexMap.put(depth, ++position);

		// store node with its tree index
		final String hash = "[" + depth + ":" + position + "]";
		indexMappedNodes.put(hash, node);

		// store node with its data hash
		String dataHash = node.getProperty(DOMNode.dataHashProperty);
		if (dataHash == null) {
			dataHash = node.getIdHash();
		}

		hashMappedNodes.put(dataHash, node);
		depthMap.put(node, depth);

		// recurse
		for (final DOMChildren childRel : node.getChildRelationships()) {

			collectNodes(childRel.getTargetNode(), indexMappedNodes, hashMappedNodes, depthMap, depth+1, childIndexMap);
		}

	}

	@Override
	public int compareTo(final InvertibleModificationOperation op) {
		return getPosition().compareTo(op.getPosition());
	}

	protected static class InsertPosition {

		private DOMNode parent = null;
		private DOMNode sibling = null;

		public InsertPosition(final DOMNode parent, final DOMNode sibling) {
			this.parent  = parent;
			this.sibling = sibling;
		}

		public DOMNode getParent() {
			return parent;
		}

		public DOMNode getSibling() {
			return sibling;
		}
	}
}