# PDThreadBead.java

    /*
     * Licensed to the Apache Software Foundation (ASF) under one or more
     * contributor license agreements.  See the NOTICE file distributed with
     * this work for additional information regarding copyright ownership.
     * The ASF licenses this file to You under the Apache License, Version 2.0
     * (the "License"); you may not use this file except in compliance with
     * the License.  You may obtain a copy of the License at
     *
     *      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.apache.pdfbox.pdmodel.interactive.pagenavigation;

    import org.apache.pdfbox.cos.COSArray;
    import org.apache.pdfbox.cos.COSDictionary;
    import org.apache.pdfbox.cos.COSName;

    import org.apache.pdfbox.pdmodel.PDPage;
    import org.apache.pdfbox.pdmodel.common.COSObjectable;
    import org.apache.pdfbox.pdmodel.common.PDRectangle;

    /**
     * This a single bead in a thread in a PDF document.
     *
     * @author Ben Litchfield
     */
    public class PDThreadBead implements COSObjectable
    {

        private final COSDictionary bead;

        /**
         * Constructor that is used for a preexisting dictionary.
         *
         * @param b The underlying dictionary.
         */
        public PDThreadBead( COSDictionary b )
        {
            bead = b;
        }

        /**
         * Default constructor.
         *
         */
        public PDThreadBead()
        {
            bead = new COSDictionary();
            bead.setItem(COSName.TYPE, COSName.BEAD);
            setNextBead( this );
            setPreviousBead( this );
        }

        /**
         * This will get the underlying dictionary that this object wraps.
         *
         * @return The underlying info dictionary.
         */
        @Override
        public COSDictionary getCOSObject()
        {
            return bead;
        }

        /**
         * This will get the thread that this bead is part of.  This is only required
         * for the first bead in a thread, so other beads 'may' return null.
         *
         * @return The thread that this bead is part of.
         */
        public PDThread getThread()
        {
            COSDictionary dic = bead.getCOSDictionary(COSName.T);
            return dic != null ? new PDThread(dic) : null;
        }

        /**
         * Set the thread that this bead is part of.  This is only required for the
         * first bead in a thread.  Note: This property is set for you by the PDThread.setFirstBead() method.
         *
         * @param thread The thread that this bead is part of.
         */
        public void setThread( PDThread thread )
        {
            bead.setItem(COSName.T, thread);
        }

        /**
         * This will get the next bead.  If this bead is the last bead in the list then this
         * will return the first bead.
         *
         * @return The next bead in the list or the first bead if this is the last bead.
         */
        public PDThreadBead getNextBead()
        {
            return new PDThreadBead(bead.getCOSDictionary(COSName.N));
        }

        /**
         * Set the next bead in the thread.
         *
         * @param next The next bead.
         */
        protected final void setNextBead( PDThreadBead next )
        {
            bead.setItem(COSName.N, next);
        }

        /**
         * This will get the previous bead.  If this bead is the first bead in the list then this
         * will return the last bead.
         *
         * @return The previous bead in the list or the last bead if this is the first bead.
         */
        public PDThreadBead getPreviousBead()
        {
            return new PDThreadBead(bead.getCOSDictionary(COSName.V));
        }

        /**
         * Set the previous bead in the thread.
         *
         * @param previous The previous bead.
         */
        protected final void setPreviousBead( PDThreadBead previous )
        {
            bead.setItem(COSName.V, previous);
        }

        /**
         * Append a bead after this bead.  This will correctly set the next/previous beads in the
         * linked list.
         *
         * @param append The bead to insert.
         */
        public void appendBead( PDThreadBead append )
        {
            PDThreadBead nextBead = getNextBead();
            nextBead.setPreviousBead( append );
            append.setNextBead( nextBead );
            setNextBead( append );
            append.setPreviousBead( this );
        }

        /**
         * Get the page that this bead is part of.
         *
         * @return The page that this bead is part of.
         */
        public PDPage getPage()
        {
            COSDictionary dic = bead.getCOSDictionary(COSName.P);
            return dic != null ? new PDPage(dic) : null;
        }

        /**
         * Set the page that this bead is part of.  This is a required property and must be
         * set when creating a new bead.  The PDPage object also has a list of beads in the natural
         * reading order.  It is recommended that you add this object to that list as well.
         *
         * @param page The page that this bead is on.
         */
        public void setPage( PDPage page )
        {
            bead.setItem(COSName.P, page);
        }

        /**
         * The rectangle on the page that this bead is part of.
         *
         * @return The part of the page that this bead covers.
         */
        public PDRectangle getRectangle()
        {
            COSArray array = bead.getCOSArray(COSName.R);
            return array != null ? new PDRectangle(array) : null;
        }

        /**
         * Set the rectangle on the page that this bead covers.
         *
         * @param rect The portion of the page that this bead covers.
         */
        public void setRectangle( PDRectangle rect )
        {
            bead.setItem( COSName.R, rect );
        }
    }