package net.sourceforge.jeuclid.elements.support;

 import java.util.Collections;

 import java.util.Iterator;

 import javax.annotation.Nonnull;

 import javax.annotation.Nullable;

 import javax.xml.XMLConstants;

 import javax.xml.namespace.NamespaceContext;

 /**

  * Chainable implementation of a {@link NamespaceContext}.

  *

  * @version $Revision: f5d68b2c52ae $

  */

 public class NamespaceContextAdder implements NamespaceContext {

     private final String namespacePrefix;

     private final String namespaceURI;

     private final NamespaceContext delegateContext;

     /**

      * Create a new NamespaceAdder. The delegate context will be called if the

      * namespace to be checked is not the namespace given in this adder. If the

      * delegate is null, default values will be returned.

      *

      * @param ns

      *            namespace prefix.

      * @param nsuri

      *            namespace URI

      * @param delegate

      *            delegate {@link NamespaceContext}

      */

     public NamespaceContextAdder(@Nonnull final String ns,

             @Nonnull final String nsuri,

             @Nullable final NamespaceContext delegate) {

         this.namespacePrefix = ns;

         this.namespaceURI = nsuri;

         this.delegateContext = delegate;

     }

     /** {@inheritDoc} */

     public String getNamespaceURI(final String prefix) {

         String retVal;

         if (this.namespacePrefix.equals(prefix)) {

             retVal = this.namespaceURI;

         } else if (this.delegateContext == null) {

             retVal = XMLConstants.NULL_NS_URI;

         } else {

             retVal = this.delegateContext.getNamespaceURI(prefix);

         }

         return retVal;

     }

     /** {@inheritDoc} */

     public String getPrefix(final String uri) {

         String retVal;

         if (this.namespaceURI.equals(uri)) {

             retVal = this.namespacePrefix;

         } else if (this.delegateContext == null) {

             retVal = "";

         } else {

             retVal = this.delegateContext.getPrefix(uri);

         }

         return retVal;

     }

     /** {@inheritDoc} */

     @SuppressWarnings("unchecked")

     public Iterator<String> getPrefixes(final String uri) {

         Iterator<String> retVal;

         if (this.namespaceURI.equals(uri)) {

             retVal = Collections.singleton(this.namespacePrefix).iterator();

         } else if (this.delegateContext == null) {

             retVal = Collections.EMPTY_LIST.iterator();

         } else {

             retVal = this.delegateContext.getPrefixes(uri);

         }

         return retVal;

     }

 }