/*
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 */
/*
 * $Id: XPathType.java,v 1.4 2005/05/10 16:40:17 mullan Exp $
 */
package javax.xml.crypto.dsig.spec;

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

/**
 * The XML Schema Definition of the <code>XPath</code> element as defined in the
 * <a href="http://www.w3.org/TR/xmldsig-filter2">
 * W3C Recommendation for XML-Signature XPath Filter 2.0</a>:
 * <pre><code>
 * <schema xmlns="http://www.w3.org/2001/XMLSchema"
 *         xmlns:xf="http://www.w3.org/2002/06/xmldsig-filter2"
 *         targetNamespace="http://www.w3.org/2002/06/xmldsig-filter2"
 *         version="0.1" elementFormDefault="qualified">
 *
 * <element name="XPath"
 *          type="xf:XPathType"/>
 *
 * <complexType name="XPathType">
 *   <simpleContent>
 *     <extension base="string">
 *       <attribute name="Filter">
 *         <simpleType>
 *           <restriction base="string">
 *             <enumeration value="intersect"/>
 *             <enumeration value="subtract"/>
 *             <enumeration value="union"/>
 *           </restriction>
 *         </simpleType>
 *       </attribute>
 *     </extension>
 *   </simpleContent>
 * </complexType>
 * </code></pre>
 *
 * @author Sean Mullan
 * @author JSR 105 Expert Group
 * @since 1.6
 * @see XPathFilter2ParameterSpec
 */
public class XPathType {

    /**
     * Represents the filter set operation.
     */
    public static class Filter {
        private final String operation;

        private Filter(String operation) {
            this.operation = operation;
        }

        /**
         * Returns the string form of the operation.
         *
         * @return the string form of the operation
         */
        public String toString() {
            return operation;
        }

        /**
         * The intersect filter operation.
         */
        public static final Filter INTERSECT = new Filter("intersect");

        /**
         * The subtract filter operation.
         */
        public static final Filter SUBTRACT = new Filter("subtract");

        /**
         * The union filter operation.
         */
        public static final Filter UNION = new Filter("union");
    }

    private final String expression;
    private final Filter filter;
    private Map nsMap;

    /**
     * Creates an <code>XPathType</code> instance with the specified XPath
     * expression and filter.
     *
     * @param expression the XPath expression to be evaluated
     * @param filter the filter operation ({@link Filter#INTERSECT},
     *    {@link Filter#SUBTRACT}, or {@link Filter#UNION})
     * @throws NullPointerException if <code>expression</code> or
     *    <code>filter</code> is <code>null</code>
     */
    public XPathType(String expression, Filter filter) {
        if (expression == null) {
            throw new NullPointerException("expression cannot be null");
        }
        if (filter == null) {
            throw new NullPointerException("filter cannot be null");
        }
        this.expression = expression;
        this.filter = filter;
        this.nsMap = Collections.EMPTY_MAP;
    }

    /**
     * Creates an <code>XPathType</code> instance with the specified XPath
     * expression, filter, and namespace map. The map is copied to protect
     * against subsequent modification.
     *
     * @param expression the XPath expression to be evaluated
     * @param filter the filter operation ({@link Filter#INTERSECT},
     *    {@link Filter#SUBTRACT}, or {@link Filter#UNION})
     * @param namespaceMap the map of namespace prefixes. Each key is a
     *    namespace prefix <code>String</code> that maps to a corresponding
     *    namespace URI <code>String</code>.
     * @throws NullPointerException if <code>expression</code>,
     *    <code>filter</code> or <code>namespaceMap</code> are
     *    <code>null</code>
     * @throws ClassCastException if any of the map's keys or entries are
     *    not of type <code>String</code>
     */
    public XPathType(String expression, Filter filter, Map namespaceMap) {
        this(expression, filter);
        if (namespaceMap == null) {
            throw new NullPointerException("namespaceMap cannot be null");
        }
        nsMap = new HashMap(namespaceMap);
        Iterator entries = nsMap.entrySet().iterator();
        while (entries.hasNext()) {
            Map.Entry me = (Map.Entry) entries.next();
            if (!(me.getKey() instanceof String) ||
                !(me.getValue() instanceof String)) {
                throw new ClassCastException("not a String");
            }
        }
        nsMap = Collections.unmodifiableMap(nsMap);
    }

    /**
     * Returns the XPath expression to be evaluated.
     *
     * @return the XPath expression to be evaluated
     */
    public String getExpression() {
        return expression;
    }

    /**
     * Returns the filter operation.
     *
     * @return the filter operation
     */
    public Filter getFilter() {
        return filter;
    }

    /**
     * Returns a map of namespace prefixes. Each key is a namespace prefix
     * <code>String</code> that maps to a corresponding namespace URI
     * <code>String</code>.
     * <p>
     * This implementation returns an {@link Collections#unmodifiableMap
     * unmodifiable map}.
     *
     * @return a <code>Map</code> of namespace prefixes to namespace URIs
     *    (may be empty, but never <code>null</code>)
     */
    public Map getNamespaceMap() {
        return nsMap;
    }
}