JAL-1645 Version-Rel Version 2.9 Year-Rel 2015 Licensing glob
[jalview.git] / src / jalview / commands / EditCommand.java
index 9413ba8..1cd6fcc 100644 (file)
 /*
- * Jalview - A Sequence Alignment Editor and Viewer (Version 2.7)
- * Copyright (C) 2011 J Procter, AM Waterhouse, J Engelhardt, LM Lui, G Barton, M Clamp, S Searle
- *
+ * Jalview - A Sequence Alignment Editor and Viewer (Version 2.9)
+ * Copyright (C) 2015 The Jalview Authors
+ * 
  * This file is part of Jalview.
- *
+ * 
  * Jalview is free software: you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
- *
- * Jalview 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
+ * modify it under the terms of the GNU General Public License 
+ * as published by the Free Software Foundation, either version 3
+ * of the License, or (at your option) any later version.
+ *  
+ * Jalview 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 for more details.
- *
- * You should have received a copy of the GNU General Public License along with Jalview.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with Jalview.  If not, see <http://www.gnu.org/licenses/>.
+ * The Jalview Authors are detailed in the 'AUTHORS' file.
  */
 package jalview.commands;
 
-import java.util.*;
-
-import jalview.datamodel.*;
+import jalview.datamodel.AlignmentAnnotation;
+import jalview.datamodel.AlignmentI;
+import jalview.datamodel.Annotation;
+import jalview.datamodel.Sequence;
+import jalview.datamodel.SequenceFeature;
+import jalview.datamodel.SequenceI;
+import jalview.util.ReverseListIterator;
+import jalview.util.StringUtils;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.Map;
 
 /**
- *
+ * 
  * <p>
  * Title: EditCommmand
  * </p>
- *
+ * 
  * <p>
  * Description: Essential information for performing undo and redo for cut/paste
  * insert/delete gap which can be stored in the HistoryList
  * </p>
- *
+ * 
  * <p>
  * Copyright: Copyright (c) 2006
  * </p>
- *
+ * 
  * <p>
  * Company: Dundee University
  * </p>
- *
+ * 
  * @author not attributable
  * @version 1.0
  */
 public class EditCommand implements CommandI
 {
-  public static final int INSERT_GAP = 0;
-
-  public static final int DELETE_GAP = 1;
-
-  public static final int CUT = 2;
-
-  public static final int PASTE = 3;
-
-  public static final int REPLACE = 4;
-
-  public static final int INSERT_NUC=5;
+  public enum Action
+  {
+    INSERT_GAP
+    {
+      @Override
+      public Action getUndoAction()
+      {
+        return DELETE_GAP;
+      }
+    },
+    DELETE_GAP
+    {
+      @Override
+      public Action getUndoAction()
+      {
+        return INSERT_GAP;
+      }
+    },
+    CUT
+    {
+      @Override
+      public Action getUndoAction()
+      {
+        return PASTE;
+      }
+    },
+    PASTE
+    {
+      @Override
+      public Action getUndoAction()
+      {
+        return CUT;
+      }
+    },
+    REPLACE
+    {
+      @Override
+      public Action getUndoAction()
+      {
+        return REPLACE;
+      }
+    },
+    INSERT_NUC
+    {
+      @Override
+      public Action getUndoAction()
+      {
+        return null;
+      }
+    };
+    public abstract Action getUndoAction();
+  };
 
-  Edit[] edits;
+  private List<Edit> edits = new ArrayList<Edit>();
 
   String description;
 
@@ -70,32 +127,150 @@ public class EditCommand implements CommandI
     this.description = description;
   }
 
-  public EditCommand(String description, int command, SequenceI[] seqs,
+  public EditCommand(String description, Action command, SequenceI[] seqs,
           int position, int number, AlignmentI al)
   {
     this.description = description;
-    if (command == CUT || command == PASTE)
+    if (command == Action.CUT || command == Action.PASTE)
     {
-      edits = new Edit[]
-      { new Edit(command, seqs, position, number, al) };
+      setEdit(new Edit(command, seqs, position, number, al));
     }
 
     performEdit(0, null);
   }
 
-  public EditCommand(String description, int command, String replace,
+  public EditCommand(String description, Action command, String replace,
           SequenceI[] seqs, int position, int number, AlignmentI al)
   {
     this.description = description;
-    if (command == REPLACE)
+    if (command == Action.REPLACE)
     {
-      edits = new Edit[]
-      { new Edit(command, seqs, position, number, al, replace) };
+      setEdit(new Edit(command, seqs, position, number, al, replace));
     }
 
     performEdit(0, null);
   }
 
+  /**
+   * Set the list of edits to the specified item (only).
+   * 
+   * @param e
+   */
+  protected void setEdit(Edit e)
+  {
+    edits.clear();
+    edits.add(e);
+  }
+
+  /**
+   * Add the given edit command to the stored list of commands. If simply
+   * expanding the range of the last command added, then modify it instead of
+   * adding a new command.
+   * 
+   * @param e
+   */
+  public void addEdit(Edit e)
+  {
+    if (!expandEdit(edits, e))
+    {
+      edits.add(e);
+    }
+  }
+
+  /**
+   * Returns true if the new edit is incorporated by updating (expanding the
+   * range of) the last edit on the list, else false. We can 'expand' the last
+   * edit if the new one is the same action, on the same sequences, and acts on
+   * a contiguous range. This is the case where a mouse drag generates a series
+   * of contiguous gap insertions or deletions.
+   * 
+   * @param edits
+   * @param e
+   * @return
+   */
+  protected static boolean expandEdit(List<Edit> edits, Edit e)
+  {
+    if (edits == null || edits.isEmpty())
+    {
+      return false;
+    }
+    Edit lastEdit = edits.get(edits.size() - 1);
+    Action action = e.command;
+    if (lastEdit.command != action)
+    {
+      return false;
+    }
+
+    /*
+     * Both commands must act on the same sequences - compare the underlying
+     * dataset sequences, rather than the aligned sequences, which change as
+     * they are edited.
+     */
+    if (lastEdit.seqs.length != e.seqs.length)
+    {
+      return false;
+    }
+    for (int i = 0; i < e.seqs.length; i++)
+    {
+      if (lastEdit.seqs[i].getDatasetSequence() != e.seqs[i]
+              .getDatasetSequence())
+      {
+        return false;
+      }
+    }
+
+    /**
+     * Check a contiguous edit; either
+     * <ul>
+     * <li>a new Insert <n> positions to the right of the last <insert n>, or</li>
+     * <li>a new Delete <n> gaps which is <n> positions to the left of the last
+     * delete.</li>
+     * </ul>
+     */
+    boolean contiguous = (action == Action.INSERT_GAP && e.position == lastEdit.position
+            + lastEdit.number)
+            || (action == Action.DELETE_GAP && e.position + e.number == lastEdit.position);
+    if (contiguous)
+    {
+      /*
+       * We are just expanding the range of the last edit. For delete gap, also
+       * moving the start position left.
+       */
+      lastEdit.number += e.number;
+      lastEdit.seqs = e.seqs;
+      if (action == Action.DELETE_GAP)
+      {
+        lastEdit.position--;
+      }
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Clear the list of stored edit commands.
+   * 
+   */
+  protected void clearEdits()
+  {
+    edits.clear();
+  }
+
+  /**
+   * Returns the i'th stored Edit command.
+   * 
+   * @param i
+   * @return
+   */
+  protected Edit getEdit(int i)
+  {
+    if (i >= 0 && i < edits.size())
+    {
+      return edits.get(i);
+    }
+    return null;
+  }
+
   @Override
   final public String getDescription()
   {
@@ -105,12 +280,17 @@ public class EditCommand implements CommandI
   @Override
   public int getSize()
   {
-    return edits == null ? 0 : edits.length;
+    return edits.size();
   }
 
+  /**
+   * Return the alignment for the first edit (or null if no edit).
+   * 
+   * @return
+   */
   final public AlignmentI getAlignment()
   {
-    return edits[0].al;
+    return (edits.isEmpty() ? null : edits.get(0).al);
   }
 
   /**
@@ -118,7 +298,7 @@ public class EditCommand implements CommandI
    * operation affects more alignment objects than the one referenced in al (for
    * example, cut or pasting whole sequences). Use the form with an additional
    * AlignmentI[] views parameter.
-   *
+   * 
    * @param command
    * @param seqs
    * @param position
@@ -126,8 +306,8 @@ public class EditCommand implements CommandI
    * @param al
    * @param performEdit
    */
-  final public void appendEdit(int command, SequenceI[] seqs, int position,
-          int number, AlignmentI al, boolean performEdit)
+  final public void appendEdit(Action command, SequenceI[] seqs,
+          int position, int number, AlignmentI al, boolean performEdit)
   {
     appendEdit(command, seqs, position, number, al, performEdit, null);
   }
@@ -135,7 +315,7 @@ public class EditCommand implements CommandI
   /**
    * append a new edit command with a set of alignment views that may be
    * operated on
-   *
+   * 
    * @param command
    * @param seqs
    * @param position
@@ -144,8 +324,9 @@ public class EditCommand implements CommandI
    * @param performEdit
    * @param views
    */
-  final public void appendEdit(int command, SequenceI[] seqs, int position,
-          int number, AlignmentI al, boolean performEdit, AlignmentI[] views)
+  final public void appendEdit(Action command, SequenceI[] seqs,
+          int position, int number, AlignmentI al, boolean performEdit,
+          AlignmentI[] views)
   {
     Edit edit = new Edit(command, seqs, position, number,
             al.getGapCharacter());
@@ -155,52 +336,87 @@ public class EditCommand implements CommandI
       edit.fullAlignmentHeight = true;
     }
 
-    if (edits != null)
+    addEdit(edit);
+
+    if (performEdit)
     {
-      Edit[] temp = new Edit[edits.length + 1];
-      System.arraycopy(edits, 0, temp, 0, edits.length);
-      edits = temp;
-      edits[edits.length - 1] = edit;
+      performEdit(edit, views);
     }
-    else
+  }
+
+  /**
+   * Overloaded method that accepts an Edit object with additional parameters.
+   * 
+   * @param edit
+   * @param al
+   * @param performEdit
+   * @param views
+   */
+  final public void appendEdit(Edit edit, AlignmentI al,
+          boolean performEdit, AlignmentI[] views)
+  {
+    if (al.getHeight() == edit.seqs.length)
     {
-      edits = new Edit[]
-      { edit };
+      edit.al = al;
+      edit.fullAlignmentHeight = true;
     }
 
+    addEdit(edit);
+
     if (performEdit)
     {
-      performEdit(edits.length - 1, views);
+      performEdit(edit, views);
     }
   }
 
-  final void performEdit(int commandIndex, AlignmentI[] views)
+  /**
+   * Execute all the edit commands, starting at the given commandIndex
+   * 
+   * @param commandIndex
+   * @param views
+   */
+  public final void performEdit(int commandIndex, AlignmentI[] views)
   {
-    int eSize = edits.length;
-    for (int e = commandIndex; e < eSize; e++)
+    ListIterator<Edit> iterator = edits.listIterator(commandIndex);
+    while (iterator.hasNext())
     {
-      switch (edits[e].command)
-      {
-      case INSERT_GAP:
-        insertGap(edits[e]);
-        break;
-      case DELETE_GAP:
-        deleteGap(edits[e]);
-        break;
-      case CUT:
-        cut(edits[e], views);
-        break;
-      case PASTE:
-        paste(edits[e], views);
-        break;
-      case REPLACE:
-        replace(edits[e]);
-        break;
-        //TODO:add deleteNuc for UNDO
-//      case INSERT_NUC:
-//     insertNuc(edits[e]);
-//     break;
-      }
+      Edit edit = iterator.next();
+      performEdit(edit, views);
+    }
+  }
+
+  /**
+   * Execute one edit command in all the specified alignment views
+   * 
+   * @param edit
+   * @param views
+   */
+  protected static void performEdit(Edit edit, AlignmentI[] views)
+  {
+    switch (edit.command)
+    {
+    case INSERT_GAP:
+      insertGap(edit);
+      break;
+    case DELETE_GAP:
+      deleteGap(edit);
+      break;
+    case CUT:
+      cut(edit, views);
+      break;
+    case PASTE:
+      paste(edit, views);
+      break;
+    case REPLACE:
+      replace(edit);
+      break;
+    case INSERT_NUC:
+      // TODO:add deleteNuc for UNDO
+      // case INSERT_NUC:
+      // insertNuc(edits[e]);
+      break;
+    default:
+      break;
     }
   }
 
@@ -210,59 +426,81 @@ public class EditCommand implements CommandI
     performEdit(0, views);
   }
 
+  /**
+   * Undo the stored list of commands, in reverse order.
+   */
   @Override
   final public void undoCommand(AlignmentI[] views)
   {
-    int e = 0, eSize = edits.length;
-    for (e = eSize - 1; e > -1; e--)
+    ListIterator<Edit> iterator = edits.listIterator(edits.size());
+    while (iterator.hasPrevious())
     {
-      switch (edits[e].command)
+      Edit e = iterator.previous();
+      switch (e.command)
       {
       case INSERT_GAP:
-        deleteGap(edits[e]);
+        deleteGap(e);
         break;
       case DELETE_GAP:
-        insertGap(edits[e]);
+        insertGap(e);
         break;
       case CUT:
-        paste(edits[e], views);
+        paste(e, views);
         break;
       case PASTE:
-        cut(edits[e], views);
+        cut(e, views);
         break;
       case REPLACE:
-        replace(edits[e]);
+        replace(e);
+        break;
+      case INSERT_NUC:
+        // not implemented
         break;
-       }
+      default:
+        break;
+      }
     }
   }
 
-  final void insertGap(Edit command)
+  /**
+   * Insert gap(s) in sequences as specified by the command, and adjust
+   * annotations.
+   * 
+   * @param command
+   */
+  final private static void insertGap(Edit command)
   {
 
     for (int s = 0; s < command.seqs.length; s++)
     {
       command.seqs[s].insertCharAt(command.position, command.number,
               command.gapChar);
-//      System.out.println("pos: "+command.position+" number: "+command.number);
+      // System.out.println("pos: "+command.position+" number: "+command.number);
     }
 
     adjustAnnotations(command, true, false, null);
   }
-//
-//  final void insertNuc(Edit command)
-//  {
-//
-//    for (int s = 0; s < command.seqs.length; s++)
-//    {
-//        System.out.println("pos: "+command.position+" number: "+command.number);
-//     command.seqs[s].insertCharAt(command.position, command.number,'A');
-//    }
-//
-//    adjustAnnotations(command, true, false, null);
-//  }
-
-  final void deleteGap(Edit command)
+
+  //
+  // final void insertNuc(Edit command)
+  // {
+  //
+  // for (int s = 0; s < command.seqs.length; s++)
+  // {
+  // System.out.println("pos: "+command.position+" number: "+command.number);
+  // command.seqs[s].insertCharAt(command.position, command.number,'A');
+  // }
+  //
+  // adjustAnnotations(command, true, false, null);
+  // }
+
+  /**
+   * Delete gap(s) in sequences as specified by the command, and adjust
+   * annotations.
+   * 
+   * @param command
+   */
+  final static private void deleteGap(Edit command)
   {
     for (int s = 0; s < command.seqs.length; s++)
     {
@@ -273,36 +511,44 @@ public class EditCommand implements CommandI
     adjustAnnotations(command, false, false, null);
   }
 
-  void cut(Edit command, AlignmentI[] views)
+  /**
+   * Carry out a Cut action. The cut characters are saved in case Undo is
+   * requested.
+   * 
+   * @param command
+   * @param views
+   */
+  static void cut(Edit command, AlignmentI[] views)
   {
     boolean seqDeleted = false;
     command.string = new char[command.seqs.length][];
 
     for (int i = 0; i < command.seqs.length; i++)
     {
-      if (command.seqs[i].getLength() > command.position)
+      final SequenceI sequence = command.seqs[i];
+      if (sequence.getLength() > command.position)
       {
-        command.string[i] = command.seqs[i].getSequence(command.position,
+        command.string[i] = sequence.getSequence(command.position,
                 command.position + command.number);
-        SequenceI oldds = command.seqs[i].getDatasetSequence();
+        SequenceI oldds = sequence.getDatasetSequence();
         if (command.oldds != null && command.oldds[i] != null)
         {
           // we are redoing an undone cut.
-          command.seqs[i].setDatasetSequence(null);
+          sequence.setDatasetSequence(null);
         }
-        command.seqs[i].deleteChars(command.position, command.position
+        sequence.deleteChars(command.position, command.position
                 + command.number);
         if (command.oldds != null && command.oldds[i] != null)
         {
           // oldds entry contains the cut dataset sequence.
-          command.seqs[i].setDatasetSequence(command.oldds[i]);
+          sequence.setDatasetSequence(command.oldds[i]);
           command.oldds[i] = oldds;
         }
         else
         {
           // modify the oldds if necessary
-          if (oldds != command.seqs[i].getDatasetSequence()
-                  || command.seqs[i].getSequenceFeatures() != null)
+          if (oldds != sequence.getDatasetSequence()
+                  || sequence.getSequenceFeatures() != null)
           {
             if (command.oldds == null)
             {
@@ -312,16 +558,16 @@ public class EditCommand implements CommandI
             adjustFeatures(
                     command,
                     i,
-                    command.seqs[i].findPosition(command.position),
-                    command.seqs[i].findPosition(command.position
-                            + command.number), false);
+                    sequence.findPosition(command.position),
+                    sequence.findPosition(command.position + command.number),
+                    false);
           }
         }
       }
 
-      if (command.seqs[i].getLength() < 1)
+      if (sequence.getLength() < 1)
       {
-        command.al.deleteSequence(command.seqs[i]);
+        command.al.deleteSequence(sequence);
         seqDeleted = true;
       }
     }
@@ -329,7 +575,14 @@ public class EditCommand implements CommandI
     adjustAnnotations(command, false, seqDeleted, views);
   }
 
-  void paste(Edit command, AlignmentI[] views)
+  /**
+   * Perform the given Paste command. This may be to add cut or copied sequences
+   * to an alignment, or to undo a 'Cut' action on a region of the alignment.
+   * 
+   * @param command
+   * @param views
+   */
+  static void paste(Edit command, AlignmentI[] views)
   {
     StringBuffer tmp;
     boolean newDSNeeded;
@@ -345,12 +598,16 @@ public class EditCommand implements CommandI
       if (command.seqs[i].getLength() < 1)
       {
         // ie this sequence was deleted, we need to
-        // read it to the alignment
+        // readd it to the alignment
         if (command.alIndex[i] < command.al.getHeight())
         {
           List<SequenceI> sequences;
-          synchronized (sequences=command.al.getSequences()) {
-            sequences.add(command.alIndex[i], command.seqs[i]);
+          synchronized (sequences = command.al.getSequences())
+          {
+            if (!(command.alIndex[i] < 0))
+            {
+              sequences.add(command.alIndex[i], command.seqs[i]);
+            }
           }
         }
         else
@@ -393,9 +650,13 @@ public class EditCommand implements CommandI
                       + command.number);
             }
             if (command.seqs[i].getStart() == start)
+            {
               newstart--;
+            }
             else
+            {
               newend++;
+            }
           }
         }
         command.string[i] = null;
@@ -439,7 +700,7 @@ public class EditCommand implements CommandI
     command.string = null;
   }
 
-  void replace(Edit command)
+  static void replace(Edit command)
   {
     StringBuffer tmp;
     String oldstring;
@@ -452,18 +713,19 @@ public class EditCommand implements CommandI
     command.number = start + command.string[0].length;
     for (int i = 0; i < command.seqs.length; i++)
     {
-      boolean newDSWasNeeded = command.oldds != null && command.oldds[i] != null;
+      boolean newDSWasNeeded = command.oldds != null
+              && command.oldds[i] != null;
 
       /**
        * cut addHistoryItem(new EditCommand("Cut Sequences", EditCommand.CUT,
        * cut, sg.getStartRes(), sg.getEndRes()-sg.getStartRes()+1,
        * viewport.alignment));
-       *
+       * 
        */
       /**
        * then addHistoryItem(new EditCommand( "Add sequences",
        * EditCommand.PASTE, sequences, 0, alignment.getWidth(), alignment) );
-       *
+       * 
        */
       oldstring = command.seqs[i].getSequenceAsString();
       tmp = new StringBuffer(oldstring.substring(0, start));
@@ -500,8 +762,12 @@ public class EditCommand implements CommandI
           fullseq = osp.substring(0, ipos) + nogaprep
                   + osp.substring(ipos + nogaprep.length());
           newds.setSequence(fullseq.toUpperCase());
-          // TODO: ensure newly created dataset sequence is added to the set of
+          // TODO: JAL-1131 ensure newly created dataset sequence is added to
+          // the set of
           // dataset sequences associated with the alignment.
+          // TODO: JAL-1131 fix up any annotation associated with new dataset
+          // sequence to ensure that original sequence/annotation relationships
+          // are preserved.
           command.seqs[i].setDatasetSequence(newds);
 
         }
@@ -511,7 +777,7 @@ public class EditCommand implements CommandI
     }
   }
 
-  final void adjustAnnotations(Edit command, boolean insert,
+  final static void adjustAnnotations(Edit command, boolean insert,
           boolean modifyVisibility, AlignmentI[] views)
   {
     AlignmentAnnotation[] annotations = null;
@@ -519,7 +785,7 @@ public class EditCommand implements CommandI
     if (modifyVisibility && !insert)
     {
       // only occurs if a sequence was added or deleted.
-      command.deletedAnnotationRows = new Hashtable();
+      command.deletedAnnotationRows = new Hashtable<SequenceI, AlignmentAnnotation[]>();
     }
     if (command.fullAlignmentHeight)
     {
@@ -603,7 +869,7 @@ public class EditCommand implements CommandI
                     && command.deletedAnnotationRows
                             .containsKey(command.seqs[s]))
             {
-              AlignmentAnnotation[] revealed = (AlignmentAnnotation[]) command.deletedAnnotationRows
+              AlignmentAnnotation[] revealed = command.deletedAnnotationRows
                       .get(command.seqs[s]);
               command.seqs[s].setAlignmentAnnotation(revealed);
               if (revealed != null)
@@ -674,7 +940,7 @@ public class EditCommand implements CommandI
 
     if (!insert)
     {
-      command.deletedAnnotations = new Hashtable();
+      command.deletedAnnotations = new Hashtable<String, Annotation[]>();
     }
 
     int aSize;
@@ -694,10 +960,12 @@ public class EditCommand implements CommandI
       {
         temp = new Annotation[aSize + command.number];
         if (annotations[a].padGaps)
+        {
           for (int aa = 0; aa < temp.length; aa++)
           {
             temp[aa] = new Annotation(command.gapChar + "", null, ' ', 0);
           }
+        }
       }
       else
       {
@@ -735,7 +1003,7 @@ public class EditCommand implements CommandI
                   && command.deletedAnnotations
                           .containsKey(annotations[a].annotationId))
           {
-            Annotation[] restore = (Annotation[]) command.deletedAnnotations
+            Annotation[] restore = command.deletedAnnotations
                     .get(annotations[a].annotationId);
 
             System.arraycopy(restore, 0, temp, command.position,
@@ -753,7 +1021,7 @@ public class EditCommand implements CommandI
                   && command.deletedAnnotations
                           .containsKey(annotations[a].annotationId))
           {
-            Annotation[] restore = (Annotation[]) command.deletedAnnotations
+            Annotation[] restore = command.deletedAnnotations
                     .get(annotations[a].annotationId);
 
             temp = new Annotation[annotations[a].annotations.length
@@ -776,8 +1044,10 @@ public class EditCommand implements CommandI
           int copylen = Math.min(command.position,
                   annotations[a].annotations.length);
           if (copylen > 0)
+          {
             System.arraycopy(annotations[a].annotations, 0, temp, 0,
                     copylen); // command.position);
+          }
 
           Annotation[] deleted = new Annotation[command.number];
           if (copylen >= command.position)
@@ -831,7 +1101,7 @@ public class EditCommand implements CommandI
     }
   }
 
-  final void adjustFeatures(Edit command, int index, int i, int j,
+  final static void adjustFeatures(Edit command, int index, int i, int j,
           boolean insert)
   {
     SequenceI seq = command.seqs[index];
@@ -846,8 +1116,7 @@ public class EditCommand implements CommandI
       if (command.editedFeatures != null
               && command.editedFeatures.containsKey(seq))
       {
-        sequence.setSequenceFeatures((SequenceFeature[]) command.editedFeatures
-                .get(seq));
+        sequence.setSequenceFeatures(command.editedFeatures.get(seq));
       }
 
       return;
@@ -902,28 +1171,132 @@ public class EditCommand implements CommandI
 
     if (command.editedFeatures == null)
     {
-      command.editedFeatures = new Hashtable();
+      command.editedFeatures = new Hashtable<SequenceI, SequenceFeature[]>();
     }
 
     command.editedFeatures.put(seq, oldsf);
 
   }
 
-  class Edit
+  /**
+   * Returns the list of edit commands wrapped by this object.
+   * 
+   * @return
+   */
+  public List<Edit> getEdits()
+  {
+    return this.edits;
+  }
+
+  /**
+   * Returns a map whose keys are the dataset sequences, and values their
+   * aligned sequences before the command edit list was applied. The aligned
+   * sequences are copies, which may be updated without affecting the originals.
+   * 
+   * The command holds references to the aligned sequences (after editing). If
+   * the command is an 'undo',then the prior state is simply the aligned state.
+   * Otherwise, we have to derive the prior state by working backwards through
+   * the edit list to infer the aligned sequences before editing.
+   * 
+   * Note: an alternative solution would be to cache the 'before' state of each
+   * edit, but this would be expensive in space in the common case that the
+   * original is never needed (edits are not mirrored).
+   * 
+   * @return
+   * @throws IllegalStateException
+   *           on detecting an edit command of a type that can't be unwound
+   */
+  public Map<SequenceI, SequenceI> priorState(boolean forUndo)
+  {
+    Map<SequenceI, SequenceI> result = new HashMap<SequenceI, SequenceI>();
+    if (getEdits() == null)
+    {
+      return result;
+    }
+    if (forUndo)
+    {
+      for (Edit e : getEdits())
+      {
+        for (SequenceI seq : e.getSequences())
+        {
+          SequenceI ds = seq.getDatasetSequence();
+          SequenceI preEdit = result.get(ds);
+          if (preEdit == null)
+          {
+            preEdit = new Sequence("", seq.getSequenceAsString());
+            preEdit.setDatasetSequence(ds);
+            result.put(ds, preEdit);
+          }
+        }
+      }
+      return result;
+    }
+
+    /*
+     * Work backwards through the edit list, deriving the sequences before each
+     * was applied. The final result is the sequence set before any edits.
+     */
+    Iterator<Edit> edits = new ReverseListIterator<Edit>(getEdits());
+    while (edits.hasNext())
+    {
+      Edit oldEdit = edits.next();
+      Action action = oldEdit.getAction();
+      int position = oldEdit.getPosition();
+      int number = oldEdit.getNumber();
+      final char gap = oldEdit.getGapCharacter();
+      for (SequenceI seq : oldEdit.getSequences())
+      {
+        SequenceI ds = seq.getDatasetSequence();
+        SequenceI preEdit = result.get(ds);
+        if (preEdit == null)
+        {
+          preEdit = new Sequence("", seq.getSequenceAsString());
+          preEdit.setDatasetSequence(ds);
+          result.put(ds, preEdit);
+        }
+        /*
+         * 'Undo' this edit action on the sequence (updating the value in the
+         * map).
+         */
+        if (ds != null)
+        {
+          if (action == Action.DELETE_GAP)
+          {
+            preEdit.setSequence(new String(StringUtils.insertCharAt(
+                    preEdit.getSequence(), position, number, gap)));
+          }
+          else if (action == Action.INSERT_GAP)
+          {
+            preEdit.setSequence(new String(StringUtils.deleteChars(
+                    preEdit.getSequence(), position, position + number)));
+          }
+          else
+          {
+            System.err.println("Can't undo edit action " + action);
+            // throw new IllegalStateException("Can't undo edit action " +
+            // action);
+          }
+        }
+      }
+    }
+    return result;
+  }
+
+  public class Edit
   {
     public SequenceI[] oldds;
 
     boolean fullAlignmentHeight = false;
 
-    Hashtable deletedAnnotationRows;
+    Hashtable<SequenceI, AlignmentAnnotation[]> deletedAnnotationRows;
 
-    Hashtable deletedAnnotations;
+    Hashtable<String, Annotation[]> deletedAnnotations;
 
-    Hashtable editedFeatures;
+    Hashtable<SequenceI, SequenceFeature[]> editedFeatures;
 
     AlignmentI al;
 
-    int command;
+    Action command;
 
     char[][] string;
 
@@ -935,7 +1308,7 @@ public class EditCommand implements CommandI
 
     char gapChar;
 
-    Edit(int command, SequenceI[] seqs, int position, int number,
+    public Edit(Action command, SequenceI[] seqs, int position, int number,
             char gapChar)
     {
       this.command = command;
@@ -945,7 +1318,7 @@ public class EditCommand implements CommandI
       this.gapChar = gapChar;
     }
 
-    Edit(int command, SequenceI[] seqs, int position, int number,
+    Edit(Action command, SequenceI[] seqs, int position, int number,
             AlignmentI al)
     {
       this.gapChar = al.getGapCharacter();
@@ -964,7 +1337,7 @@ public class EditCommand implements CommandI
       fullAlignmentHeight = (al.getHeight() == seqs.length);
     }
 
-    Edit(int command, SequenceI[] seqs, int position, int number,
+    Edit(Action command, SequenceI[] seqs, int position, int number,
             AlignmentI al, String replace)
     {
       this.command = command;
@@ -981,5 +1354,49 @@ public class EditCommand implements CommandI
 
       fullAlignmentHeight = (al.getHeight() == seqs.length);
     }
+
+    public SequenceI[] getSequences()
+    {
+      return seqs;
+    }
+
+    public int getPosition()
+    {
+      return position;
+    }
+
+    public Action getAction()
+    {
+      return command;
+    }
+
+    public int getNumber()
+    {
+      return number;
+    }
+
+    public char getGapCharacter()
+    {
+      return gapChar;
+    }
+  }
+
+  /**
+   * Returns an iterator over the list of edit commands which traverses the list
+   * either forwards or backwards.
+   * 
+   * @param forwards
+   * @return
+   */
+  public Iterator<Edit> getEditIterator(boolean forwards)
+  {
+    if (forwards)
+    {
+      return getEdits().iterator();
+    }
+    else
+    {
+      return new ReverseListIterator<Edit>(getEdits());
+    }
   }
 }