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/*
 * Copyright 2010-2012 Craig S. Dickson (http://craigsdickson.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.squeakysand.commons.xml;

import com.squeakysand.commons.lang.ToStringHelper;
import com.squeakysand.commons.util.CollectionUtils;

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

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Implementation of the {@link NamespaceContext} interface that takes care of the basic namespace mappings (xml, xmlns)
 * and allows developers to just bind any additional namespaces as necessary.
 *
 * @author Craig S. Dickson
 */
public class SimpleNamespaceContext implements NamespaceContext {

    private static final Logger LOG = LoggerFactory.getLogger(SimpleNamespaceContext.class);

    private Map mappings;

    /**
     * Constructs a {@link NamespaceContext} that can handle the basic XML namespaces.
     */
    public SimpleNamespaceContext() {
        mappings = new HashMap();
        mappings.put(XMLConstants.DEFAULT_NS_PREFIX, XMLConstants.NULL_NS_URI);
        mappings.put(XMLConstants.XML_NS_PREFIX, XMLConstants.XML_NS_URI);
        mappings.put(XMLConstants.XMLNS_ATTRIBUTE, XMLConstants.XMLNS_ATTRIBUTE_NS_URI);
        if (LOG.isDebugEnabled()) {
            LOG.debug("mappings = {}", ToStringHelper.toString(mappings));
        }
    }

    /**
     * Constructs a {@link NamespaceContext} that can handle the basic XML namespaces and also binds a URI to
     * the default prefix.
     *
     * @param defaultNamespaceURI the URI to use, cannot be null.
     */
    public SimpleNamespaceContext(String defaultNamespaceURI) {
        this();
        if (defaultNamespaceURI == null) {
            throw new IllegalArgumentException("defaultNamespaceURI cannot be null");
        } else {
            mappings.put(XMLConstants.DEFAULT_NS_PREFIX, defaultNamespaceURI);
        }
        if (LOG.isDebugEnabled()) {
            LOG.debug("mappings = {}", ToStringHelper.toString(mappings));
        }
    }

    /**
     * Adds an additional namespace mapping to the context.
     *
     * @param prefix the prefix to use, cannot be null.
     * @param namespaceURI the URI to use, cannot be null.
     */
    public void bind(String prefix, String namespaceURI) {
        if (prefix == null) {
            throw new IllegalArgumentException("prefix cannot be null");
        } else if (namespaceURI == null) {
            throw new IllegalArgumentException("namespaceURI cannot be null");
        } else {
            mappings.put(prefix, namespaceURI);
        }
        if (LOG.isDebugEnabled()) {
            LOG.debug("mappings = {}", ToStringHelper.toString(mappings));
        }
    }

    /**
     * Binds a URI to the default prefix.
     *
     * @param namespaceURI the URI to use, cannot be null.
     */
    public void bindDefaultNamespace(String namespaceURI) {
        if (namespaceURI == null) {
            throw new IllegalArgumentException("namespaceURI cannot be null");
        } else {
            mappings.put(XMLConstants.DEFAULT_NS_PREFIX, namespaceURI);
        }
        if (LOG.isDebugEnabled()) {
            LOG.debug("mappings = {}", ToStringHelper.toString(mappings));
        }
    }

    @Override
    public String getNamespaceURI(String prefix) {
        if (prefix == null) {
            throw new IllegalArgumentException("prefix cannot be null");
        }
        String result = XMLConstants.NULL_NS_URI;
        if (mappings.containsKey(prefix)) {
            result = mappings.get(prefix);
        }
        LOG.debug("returning namespaceURL '{}' for prefix '{}'", result, prefix);
        return result;
    }

    @Override
    public String getPrefix(String namespaceURI) {
        if (namespaceURI == null) {
            throw new IllegalArgumentException("namespaceURI cannot be null");
        }
        String result = CollectionUtils.getKeyByValue(mappings, namespaceURI);
        LOG.debug("returning prefix '{}' for namespaceURI '{}'", result, namespaceURI);
        return result;
    }

    @Override
    public Iterator getPrefixes(String string) {
        return mappings.keySet().iterator();
    }

}