package org.opentrafficsim.editor;
   
   import java.util.ArrayDeque;
   import java.util.Deque;
   import java.util.Iterator;
   import java.util.LinkedList;
   import java.util.function.Consumer;
   
   import javax.swing.AbstractButton;
  
  import org.djutils.event.Event;
  import org.djutils.event.EventListener;
  import org.djutils.exceptions.Throw;
  import org.opentrafficsim.editor.decoration.validation.CoupledValidator;
  
  /**
   * Undo unit for the OTS editor. This class stores an internal queue of actions. Changes to XsdTreeNodes should be grouped per
   * single user input in an action. All actions need to be initiated externally using {@code startAction()}. This class will
   * itself listen to all relevant changes in the tree and add incoming sub-actions under the started action.
   * <p>
   * Copyright (c) 2023-2026 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * @author Wouter Schakel
   */
  public class Undo implements EventListener
  {
  
      /** Maximum number of undo actions stored. */
      private static final int MAX_UNDO = 50;
  
      /** Queue of actions. */
      private LinkedList<Action> queue = new LinkedList<>();
  
      /** Location of most recent undo action. */
      private int cursor = -1;
  
      /** Current queue of sub-actions from a single user input. */
      private Deque<SubAction> currentSet;
  
      /** OTS editor. */
      private final OtsEditor editor;
  
      /** Undo GUI item. */
      private final AbstractButton undoItem;
  
      /** Redo GUI item. */
      private final AbstractButton redoItem;
  
      /** Boolean to ignore changes during undo/redo, so no new undo/redo is made. */
      private boolean ignoreChanges = false;
  
      /** Allocated next action to make concrete on first actual change. */
      private Action nextAction;
  
      /**
       * Constructor.
       * @param editor editor.
       * @param undoItem undo GUI item.
       * @param redoItem redo GUI item.
       */
      public Undo(final OtsEditor editor, final AbstractButton undoItem, final AbstractButton redoItem)
      {
          this.editor = editor;
          this.undoItem = undoItem;
          this.redoItem = redoItem;
          this.undoItem.setEnabled(false);
          this.redoItem.setEnabled(false);
          editor.addListener(this, OtsEditor.NEW_FILE);
      }
  
      /**
       * Clears the entire queue, suitable for when a new tree is loaded. Also sets ignore changes to false.
       */
      public void clear()
      {
          this.ignoreChanges = false;
          this.currentSet = null;
          this.cursor = -1;
          this.queue = new LinkedList<>();
          this.undoItem.setEnabled(false);
          this.redoItem.setEnabled(false);
      }
  
      /**
       * Tells the undo unit to ignore all changes. Reset this by calling {@code clear()}. Useful during file loading.
       * @param ignore ignore changes.
       */
      public void setIgnoreChanges(final boolean ignore)
      {
          this.ignoreChanges = ignore;
      }
  
      /**
       * Returns whether undo is ignoring changes.
       * @return whether undo is ignoring changes
       */
      public boolean isIgnoreChanges()
      {
         return this.ignoreChanges;
     }
 
     /**
      * Starts a new action, which groups all sub-actions until a new action is started. This method can be called without being
      * sure concrete changes will be made. Internal listeners listen to all changes and will combine them in to one undo action,
      * up to the point the next action is started with this method. If no actual changes were made in between, the former start
      * of an action does not result in anything the user can undo or redo. When the user has stepped back a few undo actions,
      * and then makes a new change, rolled back undo steps can no longer be redone. Clearing rolled back undo steps is performed
      * lazily on the first concrete change by a sub-action. Starting a new action does not clear rolled back undo steps by
      * itself.
      * @param type action type.
      * @param node node on which the action is applied, i.e. node that should be selected on undo/redo.
      * @param attribute attribute name, may be {@code null} for actions that are not an attribute value change.
      */
     public void startAction(final ActionType type, final XsdTreeNode node, final String attribute)
     {
         if (this.ignoreChanges)
         {
             return;
         }
         // allocate a next action with the right type, nodes and attribute, but with an empty set of sub-actions for now
         // this does not yet represent an actual undoable action until any sub-action is added to it
         this.nextAction = new Action(type, new ArrayDeque<>(), node, node.parent, attribute);
     }
 
     /**
      * Adds sub-action to current action.
      * @param subAction sub-action.
      */
     private void add(final SubAction subAction)
     {
         if (this.ignoreChanges)
         {
             return;
         }
         // make allocated next action a concrete next action in the queue
         if (this.nextAction != null)
         {
             // remove any possible redos fresher in the queue than our current pointer (i.e. rolled back undo steps)
             while (this.cursor < this.queue.size() - 1)
             {
                 this.queue.pollLast();
             }
             this.currentSet = this.nextAction.subActions;
             this.queue.add(this.nextAction);
             while (this.queue.size() > MAX_UNDO)
             {
                 this.queue.pollFirst();
             }
             this.nextAction = null;
             this.cursor = this.queue.size() - 1;
             updateButtons();
         }
         Throw.when(this.currentSet == null, IllegalStateException.class,
                 "Adding undo action without having called startUndoAction()");
         this.currentSet.add(subAction);
     }
 
     /**
      * Returns whether an undo is available.
      * @return whether an undo is available.
      */
     public boolean canUndo()
     {
         return this.cursor >= 0;
     }
 
     /**
      * Returns whether a redo is available.
      * @return whether a redo is available.
      */
     public boolean canRedo()
     {
         return this.cursor < this.queue.size() - 1;
     }
 
     /**
      * Performs an undo.
      */
     public synchronized void undo()
     {
         if (this.ignoreChanges)
         {
             return;
         }
         this.ignoreChanges = true;
 
         Action action = this.queue.get(this.cursor);
         if (action.type.equals(ActionType.ACTIVATE))
         {
             this.editor.collapse(action.node);
         }
         // In case of Java 21: action.subActions.reversed().forEach((a) -> a.undo());
         Iterator<SubAction> iterator = action.subActions.descendingIterator();
         while (iterator.hasNext())
         {
             iterator.next().undo();
         }
         if (action.type.equals(ActionType.REMOVE))
         {
             /*
              * CoupledValidators expect VALUE_CHANGED or ATTRIBUTE_CHANGED events to validate and couple. A NODE_CREATED event
              * as caused by an undo of a node removal, will simply place the node back in to the tree. Therefore we need to
              * invalidate the whole tree.
              */
             action.node.getRoot().invalidateAll();
         }
         else
         {
             action.parent.children.forEach((n) -> n.invalidate());
             action.parent.invalidate();
         }
         this.editor.show(action.node, action.attribute);
         this.cursor--;
         updateButtons();
         this.ignoreChanges = false;
     }
 
     /**
      * Performs a redo.
      */
     public synchronized void redo()
     {
         if (this.ignoreChanges)
         {
             return;
         }
         this.ignoreChanges = true;
         this.cursor++;
         Action action = this.queue.get(this.cursor);
         action.subActions.forEach((a) -> a.redo());
         action.parent.children.forEach((n) -> n.invalidate());
         action.parent.invalidate();
         this.editor.show(action.postActionShowNode, action.attribute);
         updateButtons();
         this.ignoreChanges = false;
     }
 
     /**
      * Update the enabled state and text of the undo and redo button.
      */
     public void updateButtons()
     {
         this.undoItem.setEnabled(canUndo());
         this.undoItem.setText(canUndo() ? ("Undo " + this.queue.get(this.cursor).type) : "Undo");
         this.redoItem.setEnabled(canRedo());
         this.redoItem.setText(canRedo() ? ("Redo " + this.queue.get(this.cursor + 1).type) : "Redo");
     }
 
     @Override
     @SuppressWarnings("methodlength")
     public void notify(final Event event)
     {
         listenAndUnlisten(event);
 
         // ignore any changes during an undo or redo; these should not result in another undo or redo
         if (this.ignoreChanges)
         {
             return;
         }
 
         // store action for each change
         if (event.getType().equals(XsdTreeNodeRoot.NODE_CREATED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[0];
             XsdTreeNode parent = (XsdTreeNode) content[1];
             int index = (int) content[2];
             XsdTreeNode root = node.getRoot();
             add(new SubAction(() ->
             {
                 parent.children.remove(node);
                 node.parent = null;
                 root.fireEvent(XsdTreeNodeRoot.NODE_REMOVED, new Object[] {node, parent, index});
             }, () ->
             {
                 if (index >= 0)
                 {
                     parent.setChild(index, node);
                 }
                 node.parent = parent;
                 root.fireEvent(XsdTreeNodeRoot.NODE_CREATED, new Object[] {node, parent, index});
             }, "Create " + node.getPathString()));
         }
         else if (event.getType().equals(XsdTreeNodeRoot.NODE_REMOVED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[0];
             XsdTreeNode parent = (XsdTreeNode) content[1];
             int index = (int) content[2];
             XsdTreeNode root = parent.getRoot();
             add(new SubAction(() ->
             {
                 if (index < 0)
                 {
                     // non selected choice node
                     node.parent = parent;
                     root.fireEvent(XsdTreeNodeRoot.NODE_CREATED, new Object[] {node, parent, parent.children.indexOf(node)});
                 }
                 else
                 {
                     parent.setChild(index, node);
                     root.fireEvent(XsdTreeNodeRoot.NODE_CREATED, new Object[] {node, parent, index});
                 }
             }, () ->
             {
                 node.parent.children.remove(node);
                 node.parent = null;
                 root.fireEvent(XsdTreeNodeRoot.NODE_REMOVED, new Object[] {node, parent, index});
             }, "Remove " + node.getPathString()));
         }
         else if (event.getType().equals(XsdTreeNode.VALUE_CHANGED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[0];
             String value = node.getValue();
             add(new SubAction(() ->
             {
                 node.setValue((String) content[1]); // invokes event
             }, () ->
             {
                 node.setValue(value); // invokes event
             }, "Change " + node.getPathString() + " value: " + value));
         }
         else if (event.getType().equals(XsdTreeNode.ATTRIBUTE_CHANGED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[0];
             String attribute = (String) content[1];
             String prevValue = (String) content[2];
             String value = node.getAttributeValue(attribute);
             // for include nodes, setAttributeValue will trigger addition and removal of nodes, we can ignore these events
             if (node.xsdNode.equals(XiIncludeNode.XI_INCLUDE))
             {
                 if (this.currentSet == null)
                 {
                     return;
                 }
                 this.currentSet.clear();
             }
             add(new SubAction(() ->
             {
                 node.setAttributeValue(attribute, prevValue); // invokes event
             }, () ->
             {
                 node.setAttributeValue(attribute, value); // invokes event
             }, "Create " + node.getPathString() + ".@" + attribute + ": " + value));
         }
         else if (event.getType().equals(XsdTreeNode.ACTIVATION_CHANGED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[0];
             boolean activated = (boolean) content[1];
             add(new SubAction(() ->
             {
                 node.active = !activated;
                 node.fireEvent(XsdTreeNode.ACTIVATION_CHANGED, new Object[] {node, !activated});
             }, () ->
             {
                 node.active = activated;
                 node.fireEvent(XsdTreeNode.ACTIVATION_CHANGED, new Object[] {node, activated});
             }, "Activation " + node.getPathString() + " " + activated));
         }
         else if (event.getType().equals(XsdTreeNode.OPTION_CHANGED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[1];
             XsdTreeNode previous = (XsdTreeNode) content[2];
             if (previous != null)
             {
                 add(new SubAction(() ->
                 {
                     node.setOption(previous); // invokes event
                 }, () ->
                 {
                     previous.setOption(node); // invokes event
                 }, "Set option " + node.getPathString()));
             }
         }
         else if (event.getType().equals(XsdTreeNode.MOVED))
         {
             Object[] content = (Object[]) event.getContent();
             XsdTreeNode node = (XsdTreeNode) content[0];
             int oldIndex = (int) content[1];
             int newIndex = (int) content[2];
             add(new SubAction(() ->
             {
                 node.parent.children.remove(node);
                 node.parent.children.add(oldIndex, node);
                 node.fireEvent(XsdTreeNode.MOVED, new Object[] {node, newIndex, oldIndex});
             }, () ->
             {
                 node.parent.children.remove(node);
                 node.parent.children.add(newIndex, node);
                 node.fireEvent(XsdTreeNode.MOVED, new Object[] {node, oldIndex, newIndex});
             }, "Move " + node.getPathString()));
         }
         else if (event.getType().equals(CoupledValidator.COUPLING))
         {
             if (this.currentSet == null)
             {
                 return; // We can ignore couplings created by node expansion after loading a file
             }
             Object[] content = (Object[]) event.getContent();
             CoupledValidator validator = (CoupledValidator) content[0];
             XsdTreeNode fromNode = (XsdTreeNode) content[1];
             XsdTreeNode toNode = (XsdTreeNode) content[2];
             XsdTreeNode prevToNode = (XsdTreeNode) content[3];
             Consumer<XsdTreeNode> consumer = (node) -> // this works either way, towards prevToNode (undo) or toNode (redo)
             {
                 if (node == null)
                 {
                     validator.removeCoupling(fromNode);
                 }
                 else
                 {
                     validator.addCoupling(fromNode, node);
                 }
                 fromNode.invalidate();
             };
             add(new SubAction(() -> consumer.accept(prevToNode), () -> consumer.accept(toNode),
                     "Coupling " + fromNode.getNodeName()));
         }
     }
 
     /**
      * Listen and un-listen to all possible changes.
      * @param event event
      */
     private void listenAndUnlisten(final Event event)
     {
         if (event.getType().equals(OtsEditor.NEW_FILE))
         {
             XsdTreeNodeRoot root = (XsdTreeNodeRoot) event.getContent();
             root.addListener(this, XsdTreeNodeRoot.NODE_CREATED);
             root.addListener(this, XsdTreeNodeRoot.NODE_REMOVED);
             root.addListener(this, CoupledValidator.COUPLING);
         }
         else if (event.getType().equals(XsdTreeNodeRoot.NODE_CREATED))
         {
             XsdTreeNode node = (XsdTreeNode) ((Object[]) event.getContent())[0];
             node.addListener(this, XsdTreeNode.VALUE_CHANGED);
             node.addListener(this, XsdTreeNode.ATTRIBUTE_CHANGED);
             node.addListener(this, XsdTreeNode.OPTION_CHANGED);
             node.addListener(this, XsdTreeNode.ACTIVATION_CHANGED);
             node.addListener(this, XsdTreeNode.MOVED);
         }
         else if (event.getType().equals(XsdTreeNodeRoot.NODE_REMOVED))
         {
             XsdTreeNode node = (XsdTreeNode) ((Object[]) event.getContent())[0];
             node.removeListener(this, XsdTreeNode.VALUE_CHANGED);
             node.removeListener(this, XsdTreeNode.ATTRIBUTE_CHANGED);
             node.removeListener(this, XsdTreeNode.OPTION_CHANGED);
             node.removeListener(this, XsdTreeNode.ACTIVATION_CHANGED);
             node.removeListener(this, XsdTreeNode.MOVED);
         }
     }
 
     /**
      * Sets the node to show in the tree after the action. This is for example useful to set the selection on the duplicate of a
      * duplicated node when redoing the duplication. Note that the node of the action that is otherwise shown would be the
      * duplicated node, rather than the duplicate.
      * @param node node to show in the tree after the action.
      */
     public void setPostActionShowNode(final XsdTreeNode node)
     {
         this.queue.get(this.cursor).postActionShowNode = node;
     }
 
     /**
      * Class that groups information around an action.
      */
     private class Action
     {
         // can't be a record due to mutable postActionShowNode
 
         /** Name of the action, as presented with the undo/redo buttons. */
         private final ActionType type;
 
         /** Queue of sub-actions. */
         private final Deque<SubAction> subActions;
 
         /** Node involved in the action. */
         private final XsdTreeNode node;
 
         /** Parent node of the node involved in the action. */
         private final XsdTreeNode parent;
 
         /** Attribute for an attribute change, {@code null} otherwise. */
         private final String attribute;
 
         /** Node to gain focus after the action. */
         private XsdTreeNode postActionShowNode;
 
         /**
          * Constructor.
          * @param type type of the action, as presented with the undo/redo buttons.
          * @param subActions queue of sub-actions.
          * @param node node involved in the action.
          * @param parent parent node of the node involved in the action.
          * @param attribute attribute for an attribute change, {@code null} otherwise.
          */
         Action(final ActionType type, final Deque<SubAction> subActions, final XsdTreeNode node, final XsdTreeNode parent,
                 final String attribute)
         {
             this.type = type;
             this.subActions = subActions;
             this.node = node;
             this.parent = parent;
             this.attribute = attribute;
             this.postActionShowNode = node;
         }
     }
 
     /**
      * Type of actions for undo.
      */
     public enum ActionType
     {
         /** Node activated. */
         ACTIVATE,
 
         /** Node added. */
         ADD,
 
         /** Attribute changed. */
         ATTRIBUTE_CHANGE,
 
         /** Cut. */
         CUT,
 
         /** Node duplicated. */
         DUPLICATE,
 
         /** Id changed. */
         ID_CHANGE,
 
         /** INSERT. */
         INSERT,
 
         /** Node moved. */
         MOVE,
 
         /** Option set. */
         OPTION,
 
         /** Paste. */
         PASTE,
 
         /** Node removed. */
         REMOVE,
 
         /** Node value changed. */
         VALUE_CHANGE,
 
         /** Action on node, by custom decoration. */
         ACTION;
 
         @Override
         public String toString()
         {
             return name().toLowerCase().replace("_", " ");
         }
     }
 
     /**
      * Sub-action defined by using two {@link Runnable}'s, definable as a lambda expression.
      */
     private static class SubAction
     {
         /** Undo runnable. */
         private Runnable undo;
 
         /** Redo runnable. */
         private Runnable redo;
 
         /** String representation of this sub-action. */
         private String string;
 
         /**
          * Constructor.
          * @param undo undo runnable.
          * @param redo redo runnable.
          * @param string string representation of this sub-action.
          */
         SubAction(final Runnable undo, final Runnable redo, final String string)
         {
             this.undo = undo;
             this.redo = redo;
             this.string = string;
         }
 
         /**
          * Undo the sub-action.
          */
         public void undo()
         {
             this.undo.run();
         }
 
         /**
          * Redo the sub-action.
          */
         public void redo()
         {
             this.redo.run();
         }
 
         @Override
         public String toString()
         {
             return this.string;
         }
     }
 
 }