ts3java/ts3-client/swing/src/main/java/com/ts3client/ui/ServerTreeDragAndDrop.java

package com.ts3client.ui;

import com.ts3client.net.ChannelNode;
import com.ts3client.net.ClientEntry;
import com.ts3client.net.ServerModel;
import com.ts3client.text.TsLink;

import javax.swing.JComponent;
import javax.swing.JTree;
import javax.swing.TransferHandler;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.util.function.Function;

/**
 * Drag-and-drop for the {@link ServerTreePanel} tree: dragging a client onto a
 * channel moves it there, dragging a channel reorders/reparents it, and dropping
 * either outside the tree yields its TS3 link BBCode, which the chat input accepts
 * as plain text.
 */
final class ServerTreeDragAndDrop {

    /** Carries the dragged node inside this JVM; drops elsewhere get the BBCode text. */
    private static final DataFlavor NODE_FLAVOR = new DataFlavor(
            DataFlavor.javaJVMLocalObjectMimeType + ";class=java.lang.Object",
            "TeamSpeak tree node");

    private final ServerModel model;
    private final ServerTreePanel.Actions actions;
    private final DropIndicatorTree tree;
    /** Looks up the tree path currently showing a given channel/client, or {@code null}. */
    private final Function<Object, TreePath> pathOf;

    ServerTreeDragAndDrop(ServerModel model, ServerTreePanel.Actions actions, DropIndicatorTree tree,
                           Function<Object, TreePath> pathOf) {
        this.model = model;
        this.actions = actions;
        this.tree = tree;
        this.pathOf = pathOf;
    }

    TransferHandler transferHandler() {
        return new TreeTransferHandler();
    }

    private static DefaultMutableTreeNode nodeOf(TreePath path) {
        return path == null ? null : (DefaultMutableTreeNode) path.getLastPathComponent();
    }

    /**
     * The channel a dragged client would land in, or {@code null} if the drop makes
     * no sense (outside a channel, or the channel the client is already in).
     */
    private ChannelNode resolveClientDrop(JTree.DropLocation loc, ClientEntry dragged) {
        DefaultMutableTreeNode target = nodeOf(loc.getPath());
        if (target == null) return null;
        Object obj = target.getUserObject();
        ChannelNode channel = null;
        if (obj instanceof ChannelNode) {
            channel = (ChannelNode) obj;
        } else if (obj instanceof ClientEntry) {
            channel = model.getChannel(((ClientEntry) obj).channelId);
        }
        if (channel == null || Spacers.isSpacer(channel.name)) return null;
        if (channel.id == dragged.channelId) return null;
        return channel;
    }

    /**
     * The new parent and predecessor for a dragged channel as {@code {cpid, order}},
     * or {@code null} if this drop is not a legal (or meaningful) move.
     */
    private int[] resolveChannelDrop(JTree.DropLocation loc, ChannelNode dragged) {
        DefaultMutableTreeNode target = nodeOf(loc.getPath());
        if (target == null) return null;

        DefaultMutableTreeNode parentNode;
        int insertIndex;
        if (loc.getChildIndex() >= 0) {
            parentNode = target;
            insertIndex = loc.getChildIndex();
        } else {
            // Dropped onto a node: become its last subchannel.
            parentNode = target.getUserObject() instanceof ClientEntry
                    ? (DefaultMutableTreeNode) target.getParent() : target;
            if (parentNode == null) return null;
            insertIndex = parentNode.getChildCount();
        }

        int parentId = 0;
        Object parentObj = parentNode.getUserObject();
        if (parentObj instanceof ChannelNode) {
            ChannelNode parent = (ChannelNode) parentObj;
            if (Spacers.isSpacer(parent.name)) return null;
            if (isSelfOrDescendant(parent, dragged)) return null; // would detach the subtree
            parentId = parent.id;
        } else if (parentNode.getParent() != null) {
            return null;
        }

        int predecessorId = 0;
        for (int i = 0; i < insertIndex && i < parentNode.getChildCount(); i++) {
            Object o = ((DefaultMutableTreeNode) parentNode.getChildAt(i)).getUserObject();
            if (o instanceof ChannelNode && ((ChannelNode) o).id != dragged.id) {
                predecessorId = ((ChannelNode) o).id;
            }
        }
        if (parentId == dragged.parentId && predecessorId == dragged.order) return null; // no-op
        return new int[]{parentId, predecessorId};
    }

    /** Whether {@code candidate} is {@code ancestor} itself or sits below it. */
    private boolean isSelfOrDescendant(ChannelNode candidate, ChannelNode ancestor) {
        ChannelNode c = candidate;
        for (int guard = 0; c != null && guard < 64; guard++) {
            if (c.id == ancestor.id) return true;
            c = model.getChannel(c.parentId);
        }
        return false;
    }

    private final class TreeTransferHandler extends TransferHandler {
        @Override
        public int getSourceActions(JComponent c) {
            return COPY | MOVE;
        }

        @Override
        protected Transferable createTransferable(JComponent c) {
            TreePath path = tree.getSelectionPath();
            if (path == null) return null;
            Object obj = nodeOf(path).getUserObject();
            if (obj instanceof ClientEntry) {
                ClientEntry cl = (ClientEntry) obj;
                return new NodeTransferable(cl, TsLink.clientBBCode(cl.id, cl.uniqueId, cl.nickname));
            }
            if (obj instanceof ChannelNode) {
                ChannelNode ch = (ChannelNode) obj;
                // Spacers have no meaningful link text, but can still be re-ordered.
                return new NodeTransferable(ch, Spacers.isSpacer(ch.name)
                        ? null : TsLink.channelBBCode(ch.id, ch.name));
            }
            return null;
        }

        @Override
        public boolean canImport(TransferSupport support) {
            if (!support.isDrop() || !support.isDataFlavorSupported(NODE_FLAVOR)) {
                tree.highlightChannel(null);
                return false;
            }
            if ((support.getSourceDropActions() & MOVE) == MOVE) support.setDropAction(MOVE);
            Object resolved = resolve(support);
            // A client always lands *inside* a channel, so mark that channel instead of
            // drawing a line that would suggest a position among its clients.
            tree.highlightChannel(resolved instanceof ChannelNode
                    ? pathOf.apply(resolved) : null);
            // The indicator spans the full width, past the row rectangles Swing
            // repaints on its own when the drop location moves.
            tree.repaint();
            return resolved != null;
        }

        @Override
        protected void exportDone(JComponent source, Transferable data, int action) {
            tree.highlightChannel(null);
            tree.repaint();
        }

        @Override
        public boolean importData(TransferSupport support) {
            if (!canImport(support)) return false;
            Object dragged = draggedNode(support);
            Object resolved = resolve(support);
            tree.highlightChannel(null);
            if (dragged instanceof ClientEntry) {
                actions.moveClientToChannel((ClientEntry) dragged, (ChannelNode) resolved);
            } else if (dragged instanceof ChannelNode) {
                int[] place = (int[]) resolved;
                actions.moveChannel((ChannelNode) dragged, place[0], place[1]);
            }
            return true;
        }

        /** The destination for this drop: a ChannelNode, an {@code {cpid, order}} pair, or null. */
        private Object resolve(TransferSupport support) {
            Object dragged = draggedNode(support);
            if (!(support.getDropLocation() instanceof JTree.DropLocation)) return null;
            JTree.DropLocation loc = (JTree.DropLocation) support.getDropLocation();
            if (dragged instanceof ClientEntry) return resolveClientDrop(loc, (ClientEntry) dragged);
            if (dragged instanceof ChannelNode) return resolveChannelDrop(loc, (ChannelNode) dragged);
            return null;
        }

        private Object draggedNode(TransferSupport support) {
            try {
                return support.getTransferable().getTransferData(NODE_FLAVOR);
            } catch (Exception e) {
                return null;
            }
        }
    }

    /** Offers the dragged node locally and its TS3 link BBCode to other applications. */
    private static final class NodeTransferable implements Transferable {
        private final Object node;
        private final String text;

        NodeTransferable(Object node, String text) {
            this.node = node;
            this.text = text;
        }

        @Override
        public DataFlavor[] getTransferDataFlavors() {
            return text == null ? new DataFlavor[]{NODE_FLAVOR}
                    : new DataFlavor[]{NODE_FLAVOR, DataFlavor.stringFlavor};
        }

        @Override
        public boolean isDataFlavorSupported(DataFlavor flavor) {
            return NODE_FLAVOR.equals(flavor) || (text != null && DataFlavor.stringFlavor.equals(flavor));
        }

        @Override
        public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException {
            if (NODE_FLAVOR.equals(flavor)) return node;
            if (text != null && DataFlavor.stringFlavor.equals(flavor)) return text;
            throw new UnsupportedFlavorException(flavor);
        }
    }
}