/*

 * Copyright (c) 2015, 2021, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package javax.xml.xpath;

import java.util.Objects;

import javax.xml.namespace.QName;

import org.w3c.dom.Node;

/**

 * The {@code XPathEvaluationResult} interface represents the result of the

 * evaluation of an XPath expression within the context of a particular node.

 * The evaluation of an XPath expression can result in various result types as

 * defined in XML Path Language (XPath) Version 1.0.

 *

 * @param <T> the object type returned by the XPath evaluation.

 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version

 * 1.0</a>

 *

 * @since 9

 */

public interface XPathEvaluationResult<T> {

    /**

     * XPathResultType represents possible return types of an XPath evaluation.

     * Provided as an enum type, it allows the use of switch statement. At the

     * same time, a mapping is provided between the original QName types in

     * {@link XPathConstants} and class types used in the generic methods.

     */

    public static enum XPathResultType {

        /**

         * Any type that represents any of the 5 other types listed below.

         * Maps to {@link XPathEvaluationResult}.

         */

        ANY(new QName("http://www.w3.org/1999/XSL/Transform", "any"), XPathEvaluationResult.class),

        /**

         * The XPath 1.0 boolean data type. Maps to Java {@link Boolean}.

         */

        BOOLEAN(XPathConstants.BOOLEAN, Boolean.class),

        /**

         * The XPath 1.0 Number data type. Maps to Java {@link Number}. Of the

         * subtypes of Number, only Double, Integer and Long are required.

         */

        NUMBER(XPathConstants.NUMBER, Number.class),

        /**

         * The XPath 1.0 String data type. Maps to Java {@link String}.

         */

        STRING(XPathConstants.STRING, String.class),

        /**

         * The XPath 1.0 NodeSet data type. Maps to {@link XPathNodes}.

         */

        NODESET(XPathConstants.NODESET, XPathNodes.class),

        /**

         * The XPath 1.0 Node data type. Maps to {@link org.w3c.dom.Node}.

         */

        NODE(XPathConstants.NODE, Node.class);

        final QName qnameType;

        final Class<?> clsType;

        XPathResultType(QName qnameType, Class<?> clsType) {

            this.qnameType = qnameType;

            this.clsType = clsType;

        }

        /**

         * Compares this type to the specified class type.

         * @param clsType class type

         * @return true if the argument is not null and is a class type or accepted subtype that

         * matches that this type represents, false otherwise.

         */

        private boolean equalsClassType(Class<?> clsType) {

            if (Objects.nonNull(clsType) && this.clsType.isAssignableFrom(clsType)) {

                if (this.clsType == Number.class) {

                    return isAcceptedNumberSubType(clsType);

                }

                return true;

            }

            return false;

        }

        /**

         * Compares the specified class type to accepted subtypes of number.

         * @param clsType class type

         * @return true if class type is an accepted subtype of Number, false otherwise

         */

        private boolean isAcceptedNumberSubType(Class<?> clsType) {

            return clsType.isAssignableFrom(Double.class) ||

                    clsType.isAssignableFrom(Integer.class) ||

                    clsType.isAssignableFrom(Long.class);

        }

        /**

         * Returns the QName type as specified in {@link XPathConstants} that

         * corresponds to the specified class type.

         * @param clsType a class type that the enum type supports

         * @return the QName type that matches with the specified class type,

         * null if there is no match

         */

            static public QName getQNameType(Class<?> clsType) {

            for (XPathResultType type : XPathResultType.values()) {

                if (type.equalsClassType(clsType)) {

                    return type.qnameType;

                }

            }

            return null;

        }

    }

    /**

     * Return the result type as an enum specified by {@code XPathResultType}

     * @return the result type

     */

    public XPathResultType type();

    /**

     * Returns the value of the result as the type {@code <T>} specified for the class.

     *

     * @return The value of the result.

     */

    public T value();

}