/* The contents of this file are subject to the license and copyright terms
 * detailed in the license directory at the root of the source tree (also 
 * available online at http://fedora-commons.org/license/).
 */

package fedora.common.xml.namespace;

/**
 * An XML namespace.
 * 
 * @author Chris Wilper
 * @version $Id$
 */
public class XMLNamespace {
    
    /**
     * Namespace URI to use to represent that there is no Namespace. 
     * Defined by the Namespace specification to be "".
     */
    public static final String NULL_NS_URI = "";
    
    /** The URI of this namespace. */
    public final String uri;

    /**
     * The preferred prefix for this namespace when used in instance documents.
     */
    public final String prefix;

    /**
     * Constructs an instance.
     * 
     * @param uri
     *        the URI of the namespace.
     * @param prefix
     *        the preferred prefix.
     * @throws IllegalArgumentException
     *         if either parameter is null.
     */
    public XMLNamespace(String uri, String prefix) {
        if (uri == null) {
            throw new IllegalArgumentException("uri cannot be null");
        }
        if (prefix == null) {
            throw new IllegalArgumentException("prefix cannot be null");
        }
        this.uri = uri;
        this.prefix = prefix;
    }

    //---
    // Object overrides
    //---

    /**
     * Returns the URI of the namespace. {@inheritDoc}
     */
    @Override
    public String toString() {
        return uri;
    }

    /**
     * Returns true iff the given object is an instance of this class and has
     * the same URI. {@inheritDoc}
     */
    @Override
    public boolean equals(Object o) {
        if (o instanceof XMLNamespace
                && o.getClass().getName().equals(this.getClass().getName())) {
            XMLNamespace n = (XMLNamespace) o;
            return uri.equals(n.uri);
        } else {
            return false;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        return uri.hashCode();
    }

}