/*
 * DSS - Digital Signature Services
 *
 * Copyright (C) 2013 European Commission, Directorate-General Internal Market and Services (DG MARKT), B-1049 Bruxelles/Brussel
 *
 * Developed by: 2013 ARHS Developments S.A. (rue Nicolas Bové 2B, L-1253 Luxembourg) http://www.arhs-developments.com
 *
 * This file is part of the "DSS - Digital Signature Services" project.
 *
 * "DSS - Digital Signature Services" is free software: you can redistribute it and/or modify it under the terms of
 * the GNU Lesser General Public License as published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 *
 * DSS 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with
 * "DSS - Digital Signature Services".  If not, see <http://www.gnu.org/licenses/>.
 */
package eu.europa.ec.markt.dss;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;

/**
 * A class for namespace context management. It is used by XPath queries.
 */
public final class NamespaceContextMap implements NamespaceContext {

	private final Map<String, String> prefixMap;
	private final Map<String, Set<String>> namespaceMap;

	/**
	 * This is the default constructor
	 */
	public NamespaceContextMap() {

		prefixMap = new HashMap<String, String>();
		namespaceMap = new HashMap<String, Set<String>>();
	}

	/**
	 * This method allows to register a namespace and associated prefix. If the prefix exists already it is replaced.
	 *
	 * @param prefix    namespace prefix
	 * @param namespace namespace
	 * @return true if this map did not already contain the specified element
	 */
	public boolean registerNamespace(final String prefix, final String namespace) {

		final String put = prefixMap.put(prefix, namespace);
		createNamespace(prefix, namespace);
		return put == null;
	}

	private void createNamespace(final String prefix, final String namespace) {

		Set<String> prefixes = namespaceMap.get(namespace);
		if (prefixes == null) {

			prefixes = new HashSet<String>();
			namespaceMap.put(namespace, prefixes);
		}
		prefixes.add(prefix);
	}

	@Override
	public String getNamespaceURI(String prefix) {

		checkNotNull(prefix);
		String nsURI = prefixMap.get(prefix);
		return nsURI == null ? XMLConstants.NULL_NS_URI : nsURI;
	}

	@Override
	public String getPrefix(String namespaceURI) {

		checkNotNull(namespaceURI);
		Set<String> set = namespaceMap.get(namespaceURI);
		return set == null ? null : set.iterator().next();
	}

	@Override
	public Iterator<String> getPrefixes(String namespaceURI) {

		checkNotNull(namespaceURI);
		Set<String> set = namespaceMap.get(namespaceURI);
		return set.iterator();
	}

	private void checkNotNull(String value) {

		if (value == null) {
			throw new IllegalArgumentException("null");
		}
	}
}