# COSUpdateState.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.cos;

    /**
     * A {@link COSUpdateState} instance manages update states for a {@link COSUpdateInfo}. Such states are used to create
     * a {@link COSIncrement} for the incremental saving of a {@link COSDocument}.
     *
     * @author Christian Appl
     * @see COSDocumentState
     * @see COSUpdateInfo
     * @see COSIncrement
     */
    public class COSUpdateState
    {

        /**
         * The {@link COSUpdateInfo} the {@link COSUpdateState} does manage update states for.
         */
        private final COSUpdateInfo updateInfo;
        /**
         * The {@link COSDocumentState} the {@link #updateInfo} is linked to.
         */
        private COSDocumentState originDocumentState = null;
        /**
         * The actual update state of {@link #updateInfo}.
         * <ul>
         * <li>{@code true}, if {@link #updateInfo} has been updated after the document completed parsing.</li>
         * <li>{@code false}, if {@link #updateInfo} has remained unaltered since the document completed parsing.</li>
         * </ul>
         */
        private boolean updated = false;

        /**
         * Creates a new {@link COSUpdateState} for the given {@link COSUpdateInfo}.
         *
         * @param updateInfo The {@link COSUpdateInfo}, that shall be managed by this {@link COSUpdateState}.
         */
        public COSUpdateState(COSUpdateInfo updateInfo)
        {
            this.updateInfo = updateInfo;
        }

        /**
         * <p>
         * Links the given {@link COSDocumentState} to the {@link #updated} state of the managed {@link #updateInfo}.<br>
         * </p>
         * <p>
         * This shall also initialize {@link #updated} accordingly and will also set the same {@link COSDocumentState} for
         * all possibly contained substructures.
         * </p>
         * <p>
         * Should {@link #originDocumentState} already have been set, by a prior call to this method, this shall deny to
         * overwrite it.
         * </p>
         * <p>
         * {@link COSDocumentState#isAcceptingUpdates()} shall determine, whether updates to {@link #updateInfo} are
         * allowed.
         * </p>
         * <p>
         * As long as no {@link COSDocumentState} is linked to this {@link COSUpdateState}, it shall not accept updates.
         * </p>
         *
         * @param originDocumentState The {@link COSDocumentState} that shall be linked to this {@link COSUpdateState}.
         * @see #originDocumentState
         * @see #updated
         */
        public void setOriginDocumentState(COSDocumentState originDocumentState)
        {
            setOriginDocumentState(originDocumentState, false);
        }

        /**
         * <p>
         * Links the given {@link COSDocumentState} to the {@link #updated} state of the managed {@link #updateInfo}.<br>
         * </p>
         * <p>
         * This shall also initialize {@link #updated} accordingly and will also set the same {@link COSDocumentState} for
         * all possibly contained substructures.
         * </p>
         * <p>
         * Should {@link #originDocumentState} already have been set, by a prior call to this method, this shall deny to
         * overwrite it.
         * </p>
         * <p>
         * {@link COSDocumentState#isAcceptingUpdates()} shall determine, whether updates to {@link #updateInfo} are
         * allowed.
         * </p>
         * <p>
         * As long as no {@link COSDocumentState} is linked to this {@link COSUpdateState}, it shall not accept updates.
         * </p>
         * <p>
         * Additionally to {@link #setOriginDocumentState(COSDocumentState)}, this shall also deny changing
         * {@link #updated}, should the flag {@code dereferencing} indicate, that this is caused by dereferencing a
         * {@link COSObject}.
         * </p>
         *
         * @param originDocumentState The {@link COSDocumentState} that shall be linked to this {@link COSUpdateState}.
         * @param dereferencing       {@code true}, if this update of the {@link COSDocumentState} is caused by
         *                            dereferencing a {@link COSObject}.
         * @see #originDocumentState
         * @see #updated
         */
        private void setOriginDocumentState(COSDocumentState originDocumentState, boolean dereferencing)
        {
            if(this.originDocumentState != null || originDocumentState == null)
            {
                return;
            }
            this.originDocumentState = originDocumentState;
            if(!dereferencing)
            {
                update();
            }

            if(updateInfo instanceof COSDictionary)
            {
                COSDictionary dictionary = (COSDictionary) updateInfo;
                for(COSBase entry : dictionary.getValues())
                {
                    if (entry instanceof COSUpdateInfo)
                    {
                        ((COSUpdateInfo) entry).getUpdateState().setOriginDocumentState(originDocumentState, dereferencing);
                    }
                }
            }
            else if(updateInfo instanceof COSArray)
            {
                COSArray array = (COSArray) updateInfo;
                for(COSBase entry : array)
                {
                    if (entry instanceof COSUpdateInfo)
                    {
                        ((COSUpdateInfo) entry).getUpdateState().setOriginDocumentState(originDocumentState, dereferencing);
                    }
                }
            }
            else if(updateInfo instanceof COSObject)
            {
                COSObject object = (COSObject) updateInfo;
                COSBase reference;
                if(object.isDereferenced() && (reference = object.getObject()) instanceof COSUpdateInfo)
                {
                    ((COSUpdateInfo) reference).getUpdateState().setOriginDocumentState(originDocumentState, dereferencing);
                }
            }
        }

        /**
         * <p>
         * Returns the {@link #originDocumentState}, that is linked to the managed {@link #updateInfo}.
         * </p>
         * <p>
         * {@link COSDocumentState#isAcceptingUpdates()} shall determine, whether updates to {@link #updateInfo} are
         * allowed.
         * </p>
         * <p>
         * As long as no {@link COSDocumentState} is linked to this {@link COSUpdateState}, it shall not accept updates.
         * </p>
         *
         * @return The {@link COSDocumentState} linked to this {@link COSUpdateState}.
         * @see #setOriginDocumentState(COSDocumentState)
         */
        public COSDocumentState getOriginDocumentState()
        {
            return originDocumentState;
        }

        /**
         * Returns {@code true}, if the linked {@link #originDocumentState} {@link COSDocumentState#isAcceptingUpdates()}
         * and such a {@link COSDocumentState} has been linked to this {@link COSUpdateState}.
         *
         * @return {@code true}, if the linked {@link #originDocumentState} {@link COSDocumentState#isAcceptingUpdates()}
         * and such a {@link COSDocumentState} has been linked to this {@link COSUpdateState}.
         * @see #originDocumentState
         * @see COSDocumentState#isAcceptingUpdates()
         */
        boolean isAcceptingUpdates()
        {
            return originDocumentState != null && originDocumentState.isAcceptingUpdates();
        }

        /**
         * Returns the actual {@link #updated} state of the managed {@link #updateInfo}.
         *
         * @return The actual {@link #updated} state of the managed {@link #updateInfo}
         * @see #updated
         */
        public boolean isUpdated()
        {
            return updated;
        }

        /**
         * Calls {@link #update(boolean)} with {@code true} as the new update state.<br>
         * This shall only then have an effect, if {@link #isAcceptingUpdates()} returns {@code true}.
         *
         * @see #update(boolean)
         * @see #updated
         * @see #isAcceptingUpdates()
         */
        void update()
        {
            update(true);
        }

        /**
         * Sets the {@link #updated} state of the managed {@link #updateInfo} to the given state.<br>
         * This shall only then have an effect, if {@link #isAcceptingUpdates()} returns {@code true}.
         *
         * @param updated The state to set for {@link #updated}.
         * @see #update(boolean)
         * @see #updated
         * @see #isAcceptingUpdates()
         */
        void update(boolean updated)
        {
            if(isAcceptingUpdates())
            {
                this.updated = updated;
            }
        }

        /**
         * <p>
         * Shall call {@link #update()} for this {@link COSUpdateState} and shall
         * {@link #setOriginDocumentState(COSDocumentState)} for the given child, initializing it´s {@link #updated} state
         * and {@link #originDocumentState}.
         * </p>
         * <p>
         * This shall have no effect for a child, that is not an instance of {@link COSUpdateInfo}.
         * </p>
         *
         * @param child The child that shall also be updated.
         * @see #update()
         * @see #setOriginDocumentState(COSDocumentState)
         */
        void update(COSBase child)
        {
            update();
            if(child instanceof COSUpdateInfo)
            {
                ((COSUpdateInfo) child).getUpdateState().setOriginDocumentState(originDocumentState);
            }
        }

        /**
         * <p>
         * Shall call {@link #update()} for this {@link COSUpdateState} and shall
         * {@link #setOriginDocumentState(COSDocumentState)} for the given children, initializing their {@link #updated}
         * state and {@link #originDocumentState}.
         * </p>
         * <p>
         * This shall have no effect for a child, that is not an instance of {@link COSUpdateInfo}.
         * </p>
         *
         * @param children The children that shall also be updated.
         * @see #update()
         * @see #setOriginDocumentState(COSDocumentState)
         */
        void update(COSArray children)
        {
            update((Iterable<COSBase>) children);
        }

        /**
         * <p>
         * Shall call {@link #update()} for this {@link COSUpdateState} and shall
         * {@link #setOriginDocumentState(COSDocumentState)} for the given children, initializing their {@link #updated}
         * state and {@link #originDocumentState}.
         * </p>
         * <p>
         * This shall have no effect for a child, that is not an instance of {@link COSUpdateInfo}.
         * </p>
         *
         * @param children The children that shall also be updated.
         * @see #update()
         * @see #setOriginDocumentState(COSDocumentState)
         */
        void update(Iterable<COSBase> children)
        {
            update();
            if(children == null)
            {
                return;
            }
            for(COSBase child : children)
            {
                if(child instanceof COSUpdateInfo)
                {
                    ((COSUpdateInfo) child).getUpdateState().setOriginDocumentState(originDocumentState);
                }
            }
        }

        /**
         * This shall {@link #setOriginDocumentState(COSDocumentState, boolean)}  for the dereferenced child,
         * initializing it´s {@link #originDocumentState}.
         * </p>
         * <p>
         * This shall have no effect for a child, that is not an instance of {@link COSUpdateInfo} and will never change
         * the child´s {@link #updated} state.
         * </p>
         *
         * @param child The child, that has been dereferenced.
         * @see #setOriginDocumentState(COSDocumentState, boolean)
         */
        void dereferenceChild(COSBase child)
        {
            if(child instanceof COSUpdateInfo)
            {
                ((COSUpdateInfo) child).getUpdateState().setOriginDocumentState(originDocumentState, true);
            }
        }

        /**
         * Uses the managed {@link #updateInfo} as the base object of a new {@link COSIncrement}.
         *
         * @return A {@link COSIncrement} based on the managed {@link #updateInfo}.
         * @see COSUpdateInfo
         * @see COSIncrement
         */
        COSIncrement toIncrement()
        {
            return new COSIncrement(updateInfo);
        }

    }