/*

 * Copyright (c) 1997, 2004, 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

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 */

package java.awt.dnd;

import java.awt.Component;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.Transferable;

import java.awt.datatransfer.UnsupportedFlavorException;

import java.awt.dnd.peer.DropTargetContextPeer;

import java.io.IOException;

import java.io.Serializable;

import java.util.Arrays;

import java.util.List;

/**

 * A <code>DropTargetContext</code> is created

 * whenever the logical cursor associated

 * with a Drag and Drop operation coincides with the visible geometry of

 * a <code>Component</code> associated with a <code>DropTarget</code>.

 * The <code>DropTargetContext</code> provides

 * the mechanism for a potential receiver

 * of a drop operation to both provide the end user with the appropriate

 * drag under feedback, but also to effect the subsequent data transfer

 * if appropriate.

 *

 * @since 1.2

 */

public class DropTargetContext implements Serializable {

    private static final long serialVersionUID = -634158968993743371L;

    /**

     * Construct a <code>DropTargetContext</code>

     * given a specified <code>DropTarget</code>.

     * @param dt the DropTarget to associate with

     */

    DropTargetContext(DropTarget dt) {

        super();

        dropTarget = dt;

    }

    /**

     * This method returns the <code>DropTarget</code> associated with this

     * <code>DropTargetContext</code>.

     * @return the <code>DropTarget</code> associated with this <code>DropTargetContext</code>

     */

    public DropTarget getDropTarget() { return dropTarget; }

    /**

     * This method returns the <code>Component</code> associated with

     * this <code>DropTargetContext</code>.

     * @return the Component associated with this Context

     */

    public Component getComponent() { return dropTarget.getComponent(); }

    /**

     * Called when associated with the <code>DropTargetContextPeer</code>.

     * @param dtcp the <code>DropTargetContextPeer</code>

     */

    public void addNotify(DropTargetContextPeer dtcp) {

        dropTargetContextPeer = dtcp;

    }

    /**

     * Called when disassociated with the <code>DropTargetContextPeer</code>.

     */

    public void removeNotify() {

        dropTargetContextPeer = null;

        transferable          = null;

    }

    /**

     * This method sets the current actions acceptable to

     * this <code>DropTarget</code>.

     * @param actions an <code>int</code> representing the supported action(s)

     */

    protected void setTargetActions(int actions) {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer != null) {

            synchronized (peer) {

                peer.setTargetActions(actions);

                getDropTarget().doSetDefaultActions(actions);

            }

        } else {

            getDropTarget().doSetDefaultActions(actions);

        }

    }

    /**

     * This method returns an <code>int</code> representing the

     * current actions this <code>DropTarget</code> will accept.

     * @return the current actions acceptable to this <code>DropTarget</code>

     */

    protected int getTargetActions() {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        return ((peer != null)

                        ? peer.getTargetActions()

                        : dropTarget.getDefaultActions()

        );

    }

    /**

     * This method signals that the drop is completed and

     * if it was successful or not.

     * @param success true for success, false if not

     * @throws InvalidDnDOperationException if a drop is not outstanding/extant

     */

    public void dropComplete(boolean success) throws InvalidDnDOperationException{

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer != null) {

            peer.dropComplete(success);

        }

    }

    /**

     * accept the Drag.

     * @param dragOperation the supported action(s)

     */

    protected void acceptDrag(int dragOperation) {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer != null) {

            peer.acceptDrag(dragOperation);

        }

    }

    /**

     * reject the Drag.

     */

    protected void rejectDrag() {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer != null) {

            peer.rejectDrag();

        }

    }

    /**

     * called to signal that the drop is acceptable

     * using the specified operation.

     * must be called during DropTargetListener.drop method invocation.

     * @param dropOperation the supported action(s)

     */

    protected void acceptDrop(int dropOperation) {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer != null) {

            peer.acceptDrop(dropOperation);

        }

    }

    /**

     * called to signal that the drop is unacceptable.

     * must be called during DropTargetListener.drop method invocation.

     */

    protected void rejectDrop() {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer != null) {

            peer.rejectDrop();

        }

    }

    /**

     * get the available DataFlavors of the

     * <code>Transferable</code> operand of this operation.

     * @return a <code>DataFlavor[]</code> containing the

     * supported <code>DataFlavor</code>s of the

     * <code>Transferable</code> operand.

     */

    protected DataFlavor[] getCurrentDataFlavors() {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        return peer != null ? peer.getTransferDataFlavors() : new DataFlavor[0];

    }

    /**

     * This method returns a the currently available DataFlavors

     * of the <code>Transferable</code> operand

     * as a <code>java.util.List</code>.

     * @return the currently available

     * DataFlavors as a <code>java.util.List</code>

     */

    protected List<DataFlavor> getCurrentDataFlavorsAsList() {

        return Arrays.asList(getCurrentDataFlavors());

    }

    /**

     * This method returns a <code>boolean</code>

     * indicating if the given <code>DataFlavor</code> is

     * supported by this <code>DropTargetContext</code>.

     * @param df the <code>DataFlavor</code>

     * @return if the <code>DataFlavor</code> specified is supported

     */

    protected boolean isDataFlavorSupported(DataFlavor df) {

        return getCurrentDataFlavorsAsList().contains(df);

    }

    /**

     * get the Transferable (proxy) operand of this operation

     * @throws InvalidDnDOperationException if a drag is not outstanding/extant

     * @return the <code>Transferable</code>

     */

    protected Transferable getTransferable() throws InvalidDnDOperationException {

        DropTargetContextPeer peer = getDropTargetContextPeer();

        if (peer == null) {

            throw new InvalidDnDOperationException();

        } else {

            if (transferable == null) {

                Transferable t = peer.getTransferable();

                boolean isLocal = peer.isTransferableJVMLocal();

                synchronized (this) {

                    if (transferable == null) {

                        transferable = createTransferableProxy(t, isLocal);

                    }

                }

            }

            return transferable;

        }

    }

    /**

     * Get the <code>DropTargetContextPeer</code>

     * @return the platform peer

     */

    DropTargetContextPeer getDropTargetContextPeer() {

        return dropTargetContextPeer;

    }

    /**

     * Creates a TransferableProxy to proxy for the specified

     * Transferable.

     *

     * @param t the <tt>Transferable</tt> to be proxied

     * @param local <tt>true</tt> if <tt>t</tt> represents

     *        the result of a local drag-n-drop operation.

     * @return the new <tt>TransferableProxy</tt> instance.

     */

    protected Transferable createTransferableProxy(Transferable t, boolean local) {

        return new TransferableProxy(t, local);

    }

/****************************************************************************/

    /**

     * <code>TransferableProxy</code> is a helper inner class that implements

     * <code>Transferable</code> interface and serves as a proxy for another

     * <code>Transferable</code> object which represents data transfer for

     * a particular drag-n-drop operation.

     * <p>

     * The proxy forwards all requests to the encapsulated transferable

     * and automatically performs additional conversion on the data

     * returned by the encapsulated transferable in case of local transfer.

     */

    protected class TransferableProxy implements Transferable {

        /**

         * Constructs a <code>TransferableProxy</code> given

         * a specified <code>Transferable</code> object representing

         * data transfer for a particular drag-n-drop operation and

         * a <code>boolean</code> which indicates whether the

         * drag-n-drop operation is local (within the same JVM).

         * @param t the <code>Transferable</code> object

         * @param local <code>true</code>, if <code>t</code> represents

         *        the result of local drag-n-drop operation

         */

        TransferableProxy(Transferable t, boolean local) {

            proxy = new sun.awt.datatransfer.TransferableProxy(t, local);

            transferable = t;

            isLocal      = local;

        }

        /**

         * Returns an array of DataFlavor objects indicating the flavors

         * the data can be provided in by the encapsulated transferable.

         * @return an array of data flavors in which the data can be

         *         provided by the encapsulated transferable

         */

        public DataFlavor[] getTransferDataFlavors() {

            return proxy.getTransferDataFlavors();

        }

        /**

         * Returns whether or not the specified data flavor is supported by

         * the encapsulated transferable.

         * @param flavor the requested flavor for the data

         * @return <code>true</code> if the data flavor is supported,

         *         <code>false</code> otherwise

         */

        public boolean isDataFlavorSupported(DataFlavor flavor) {

            return proxy.isDataFlavorSupported(flavor);

        }

        /**

         * Returns an object which represents the data provided by

         * the encapsulated transferable for the requested data flavor.

         * <p>

         * In case of local transfer a serialized copy of the object

         * returned by the encapsulated transferable is provided when

         * the data is requested in application/x-java-serialized-object

         * data flavor.

         *

         * @param df the requested flavor for the data

         * @throws IOException if the data is no longer available

         *              in the requested flavor.

         * @throws UnsupportedFlavorException if the requested data flavor is

         *              not supported.

         */

        public Object getTransferData(DataFlavor df)

            throws UnsupportedFlavorException, IOException

        {

            return proxy.getTransferData(df);

        }

        /*

         * fields

         */

        // We don't need to worry about client code changing the values of

        // these variables. Since TransferableProxy is a protected class, only

        // subclasses of DropTargetContext can access it. And DropTargetContext

        // cannot be subclassed by client code because it does not have a

        // public constructor.

        /**

         * The encapsulated <code>Transferable</code> object.

         */

        protected Transferable  transferable;

        /**

         * A <code>boolean</code> indicating if the encapsulated

         * <code>Transferable</code> object represents the result

         * of local drag-n-drop operation (within the same JVM).

         */

        protected boolean       isLocal;

        private sun.awt.datatransfer.TransferableProxy proxy;

    }

/****************************************************************************/

    /*

     * fields

     */

    /**

     * The DropTarget associated with this DropTargetContext.

     *

     * @serial

     */

    private DropTarget dropTarget;

    private transient DropTargetContextPeer dropTargetContextPeer;

    private transient Transferable transferable;

}