/*
 * Copyright 2015 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * 
 *      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 org.eclipse.webdav.dom;

import java.util.Enumeration;
import java.util.NoSuchElementException;
import org.eclipse.webdav.Policy;
import org.w3c.dom.*;

/**
 * An element editor for the WebDAV propertyupdate element. See RFC2518
 * section 12.13 for the element's definition.
 * <p>
 * <b>Note:</b> This class/interface is part of an interim API that is still under 
 * development and expected to change significantly before reaching stability. 
 * It is being made available at this early stage to solicit feedback from pioneering 
 * adopters on the understanding that any code that uses this API will almost 
 * certainly be broken (repeatedly) as the API evolves.
 * </p>
 *
 * @see Prop
 */
public class PropertyUpdate extends ElementEditor {
    /**
     * An editor for a generic element that is a child of a WebDAV prop
     * element, which, in turn, is a child of a WebDAV set or remove
     * element.
     */
    public class Directive extends ElementEditor {

        /**
         * Creates a new editor on the given element.
         *
         * @param element a generic element
         * @throws        MalformedElementException if there is reason
         *                to believe that this editor's underlying
         *                element is not well formed
         */
        public Directive(Element element) throws MalformedElementException {
            super(element);
            Node parent = element.getParentNode();
            ensureDAVElement(parent, "prop", Policy.bind("ensure.expectingPropElmt")); //$NON-NLS-1$ //$NON-NLS-2$
            Node grandparent = parent.getParentNode();
            ensure(isDAVElement(grandparent, "remove") || isDAVElement(grandparent, "set"), //$NON-NLS-1$ //$NON-NLS-2$
                    Policy.bind("ensure.expectingRemoveOrSetElmt")); //$NON-NLS-1$
        }

        /**
         * Returns this editor's underlying element, which may be any
         * generic element.
         *
         * @return this editor's underlying element
         */
        public Element getProperty() throws MalformedElementException {
            return root;
        }

        /**
         * Returns <code>true</code> if this directive's property
         * decends from a WebDAV remove element and <code>false</code>
         * if it decends from a WebDAV set element.
         *
         * @return a boolean indicating whether this directive is a
         *           remove or not
         * @throws MalformedElementException if there is reason to
         *         believe that this editor's underlying element is not
         *         well formed
         */
        public boolean isRemove() throws MalformedElementException {
            Node parent = root.getParentNode();
            ensureDAVElement(parent, "prop", Policy.bind("ensure.expectingPropElmt")); //$NON-NLS-1$ //$NON-NLS-2$
            Node grandparent = parent.getParentNode();
            return isDAVElement(grandparent, "remove"); //$NON-NLS-1$
        }

        /**
         * Returns <code>true</code> if this directive's property
         * decends from a WebDAV set element and <code>false</code>
         * if it decends from a WebDAV remove element.
         *
         * @return a boolean indicating whether this directive is a
         *           set or not
         * @throws MalformedElementException if there is reason to
         *         believe that this editor's underlying element is not
         *         well formed
         */
        public boolean isSet() throws MalformedElementException {
            Node parent = root.getParentNode();
            ensureDAVElement(parent, "prop", Policy.bind("ensure.expectingPropElmt")); //$NON-NLS-1$ //$NON-NLS-2$
            Node grandparent = parent.getParentNode();
            return isDAVElement(grandparent, "set"); //$NON-NLS-1$
        }
    }

    /**
     * Creates a new editor on the given WebDAV propertyupdate element. The
     * element is assumed to be well formed.
     *
     * @param root a propertyupdate element
     * @throws        MalformedElementException if there is reason to
     *                believe that the element is not well formed
     */
    public PropertyUpdate(Element root) throws MalformedElementException {
        super(root, "propertyupdate"); //$NON-NLS-1$
    }

    /**
     * Adds a remove to the given propertyupdate and returns an editor on
     * its prop.
     *
     * @return an editor on a new prop
     */
    public Prop addRemove() {
        Element remove = appendChild(root, "remove"); //$NON-NLS-1$
        Element prop = appendChild(remove, "prop"); //$NON-NLS-1$
        Prop result = null;
        try {
            result = new Prop(prop);
        } catch (MalformedElementException e) {
            Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
        }
        return result;
    }

    /**
     * Adds a set to the given propertyupdate and returns an editor on its
     * prop.
     *
     * @return an editor on a new prop
     */
    public Prop addSet() {
        Element set = appendChild(root, "set"); //$NON-NLS-1$
        Element prop = appendChild(set, "prop"); //$NON-NLS-1$
        try {
            return new Prop(prop);
        } catch (MalformedElementException e) {
            Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
            return null; // Never reached.
        }
    }

    /**
     * Creates a new WebDAV propertyupdate element and sets it as the root
     * of the given document. Returns an editor on the new propertyupdate
     * element. The document must not be <code>null</code>, and must not
     * already have a root element.
     *
     * @param document the document that will become the root of a new
     *                 propertyupdate element
     * @return         an element editor on a propertyupdate element
     */
    public static PropertyUpdate create(Document document) {
        Assert.isNotNull(document);
        Assert.isTrue(document.getDocumentElement() == null);
        Element element = create(document, "propertyupdate"); //$NON-NLS-1$
        PropertyUpdate result = null;
        try {
            result = new PropertyUpdate(element);
        } catch (MalformedElementException e) {
            Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
        }
        return result;
    }

    /**
     * Returns an <code>Enumeration</code> over this propertyupdate's set
     * and remove property elements.
     *
     * @return an <code>Enumeration</code> of
     *         <code>PropertyUpdate.Directive</code>s
     * @throws MalformedElementException if there is reason to believe that
     *         this editor's underlying element is not well formed
     */
    public Enumeration getSetsAndRemoves() throws MalformedElementException {

        Node setOrRemove = getFirstChild(root, new String[] {"remove", "set"}); //$NON-NLS-1$ //$NON-NLS-2$
        ensureNotNull(Policy.bind("ensure.missingRemoveOrSetElmt"), setOrRemove); //$NON-NLS-1$
        Node property = null;

        while (setOrRemove != null && property == null) {
            Node prop = getFirstChild((Element) setOrRemove, "prop"); //$NON-NLS-1$
            ensureNotNull(Policy.bind("ensure.missingPropElmt"), prop); //$NON-NLS-1$
            property = getChildElement((Element) prop, true);

            if (property == null)
                setOrRemove = getNextSibling((Element) setOrRemove, new String[] {"remove", "set"}); //$NON-NLS-1$ //$NON-NLS-2$
        }

        final Node a = setOrRemove;
        final Node c = property;

        Enumeration e = new Enumeration() {
            Node currentSetOrRemove = a;
            Node currentProperty = c;

            public boolean hasMoreElements() {

                return currentProperty != null;
            }

            public Object nextElement() {

                if (!hasMoreElements())
                    throw new NoSuchElementException();
                Directive result = null;
                try {
                    result = new Directive((Element) currentProperty);
                } catch (MalformedElementException ex) {
                    Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
                }
                currentProperty = getNextSibling((Element) currentProperty);
                while (currentSetOrRemove != null && currentProperty == null) {
                    currentSetOrRemove = getNextSibling((Element) currentSetOrRemove, new String[] {"remove", "set"}); //$NON-NLS-1$ //$NON-NLS-2$
                    if (currentSetOrRemove != null) {
                        Node prop = getFirstChild((Element) currentSetOrRemove, "prop"); //$NON-NLS-1$
                        if (prop != null)
                            currentProperty = getChildElement((Element) prop, true);
                    }
                }
                return result;
            }
        };

        return e;
    }
}
