8 files changed, 178 insertions, 78 deletions

diff --git a/src/main/java/cuchaz/enigma/gui/Gui.java b/src/main/java/cuchaz/enigma/gui/Gui.java
index 92c68ac..3e85920 100644
--- a/src/main/java/cuchaz/enigma/gui/Gui.java
+++ b/src/main/java/cuchaz/enigma/gui/Gui.java
@@ -29,6 +29,7 @@ import cuchaz.enigma.gui.panels.PanelDeobf;
 import cuchaz.enigma.gui.panels.PanelEditor;
 import cuchaz.enigma.gui.panels.PanelIdentifier;
 import cuchaz.enigma.gui.panels.PanelObf;
+import cuchaz.enigma.gui.util.History;
 import cuchaz.enigma.throwables.IllegalNameException;
 import cuchaz.enigma.translation.mapping.AccessModifier;
 import cuchaz.enigma.translation.representation.entry.*;
@@ -54,7 +55,8 @@ public class Gui {
 
         private final MenuBar menuBar;
         // state
-        public EntryReference<Entry<?>, Entry<?>> reference;
+        public History<EntryReference<Entry<?>, Entry<?>>> referenceHistory;
+        public EntryReference<Entry<?>, Entry<?>> cursorReference;
         private boolean shouldNavigateOnClick;
 
         public FileDialog jarFileChooser;
@@ -162,11 +164,11 @@ public class Gui {
                                         Object node = path.getLastPathComponent();
                                         if (node instanceof ClassInheritanceTreeNode) {
                                                 ClassInheritanceTreeNode classNode = (ClassInheritanceTreeNode) node;
-                                                navigateTo(new ClassEntry(classNode.getObfClassName()));
+                                                controller.navigateTo(new ClassEntry(classNode.getObfClassName()));
                                         } else if (node instanceof MethodInheritanceTreeNode) {
                                                 MethodInheritanceTreeNode methodNode = (MethodInheritanceTreeNode) node;
                                                 if (methodNode.isImplemented()) {
-                                                        navigateTo(methodNode.getMethodEntry());
+                                                        controller.navigateTo(methodNode.getMethodEntry());
                                                 }
                                         }
                                 }
@@ -195,10 +197,10 @@ public class Gui {
                                         Object node = path.getLastPathComponent();
                                         if (node instanceof ClassImplementationsTreeNode) {
                                                 ClassImplementationsTreeNode classNode = (ClassImplementationsTreeNode) node;
-                                                navigateTo(classNode.getClassEntry());
+                                                controller.navigateTo(classNode.getClassEntry());
                                         } else if (node instanceof MethodImplementationsTreeNode) {
                                                 MethodImplementationsTreeNode methodNode = (MethodImplementationsTreeNode) node;
-                                                navigateTo(methodNode.getMethodEntry());
+                                                controller.navigateTo(methodNode.getMethodEntry());
                                         }
                                 }
                         }
@@ -225,9 +227,9 @@ public class Gui {
                                         if (node instanceof ReferenceTreeNode) {
                                                 ReferenceTreeNode<Entry<?>, Entry<?>> referenceNode = ((ReferenceTreeNode<Entry<?>, Entry<?>>) node);
                                                 if (referenceNode.getReference() != null) {
-                                                        navigateTo(referenceNode.getReference());
+                                                        controller.navigateTo(referenceNode.getReference());
                                                 } else {
-                                                        navigateTo(referenceNode.getEntry());
+                                                        controller.navigateTo(referenceNode.getEntry());
                                                 }
                                         }
                                 }
@@ -433,13 +435,13 @@ public class Gui {
                 }
         }
 
-        private void showReference(EntryReference<Entry<?>, Entry<?>> reference) {
+        private void showCursorReference(EntryReference<Entry<?>, Entry<?>> reference) {
                 if (reference == null) {
                         infoPanel.clearReference();
                         return;
                 }
 
-                this.reference = reference;
+                this.cursorReference = reference;
 
                 EntryReference<Entry<?>, Entry<?>> translatedReference = controller.getDeobfuscator().deobfuscate(reference);
 
@@ -526,12 +528,12 @@ public class Gui {
                 Token token = this.controller.getToken(pos);
                 boolean isToken = token != null;
 
-                reference = this.controller.getReference(token);
-                Entry<?> referenceEntry = reference != null ? reference.entry : null;
+                cursorReference = this.controller.getReference(token);
+                Entry<?> referenceEntry = cursorReference != null ? cursorReference.entry : null;
 
                 if (referenceEntry != null && shouldNavigateOnClick) {
                         shouldNavigateOnClick = false;
-                        navigateTo(referenceEntry);
+                        this.controller.navigateTo(referenceEntry);
                         return;
                 }
 
@@ -540,10 +542,10 @@ public class Gui {
                 boolean isMethodEntry = isToken && referenceEntry instanceof MethodEntry && !((MethodEntry) referenceEntry).isConstructor();
                 boolean isConstructorEntry = isToken && referenceEntry instanceof MethodEntry && ((MethodEntry) referenceEntry).isConstructor();
                 boolean isInJar = isToken && this.controller.entryIsInJar(referenceEntry);
-                boolean isRenamable = isToken && this.controller.getDeobfuscator().isRenamable(reference);
+                boolean isRenamable = isToken && this.controller.getDeobfuscator().isRenamable(cursorReference);
 
                 if (isToken) {
-                        showReference(reference);
+                        showCursorReference(cursorReference);
                 } else {
                         infoPanel.clearReference();
                 }
@@ -554,7 +556,8 @@ public class Gui {
                 this.popupMenu.showCallsMenu.setEnabled(isClassEntry || isFieldEntry || isMethodEntry || isConstructorEntry);
                 this.popupMenu.showCallsSpecificMenu.setEnabled(isMethodEntry);
                 this.popupMenu.openEntryMenu.setEnabled(isInJar && (isClassEntry || isFieldEntry || isMethodEntry || isConstructorEntry));
-                this.popupMenu.openPreviousMenu.setEnabled(this.controller.hasPreviousLocation());
+                this.popupMenu.openPreviousMenu.setEnabled(this.controller.hasPreviousReference());
+                this.popupMenu.openNextMenu.setEnabled(this.controller.hasNextReference());
                 this.popupMenu.toggleMappingMenu.setEnabled(isRenamable);
 
                 if (isToken && this.controller.getDeobfuscator().isRemapped(referenceEntry)) {
@@ -564,33 +567,12 @@ public class Gui {
                 }
         }
 
-        public void navigateTo(Entry<?> entry) {
-                if (!this.controller.entryIsInJar(entry)) {
-                        // entry is not in the jar. Ignore it
-                        return;
-                }
-                if (reference != null) {
-                        this.controller.savePreviousReference(reference);
-                }
-                this.controller.openDeclaration(entry);
-        }
-
-        private void navigateTo(EntryReference<Entry<?>, Entry<?>> reference) {
-                if (!this.controller.entryIsInJar(reference.getLocationClassEntry())) {
-                        return;
-                }
-                if (this.reference != null) {
-                        this.controller.savePreviousReference(this.reference);
-                }
-                this.controller.openReference(reference);
-        }
-
         public void startRename() {
 
                 // init the text box
                 final JTextField text = new JTextField();
 
-                EntryReference<Entry<?>, Entry<?>> translatedReference = controller.getDeobfuscator().deobfuscate(reference);
+                EntryReference<Entry<?>, Entry<?>> translatedReference = controller.getDeobfuscator().deobfuscate(cursorReference);
                 text.setText(translatedReference.getNameableName());
 
                 text.setPreferredSize(new Dimension(360, text.getPreferredSize().height));
@@ -631,7 +613,7 @@ public class Gui {
                 String newName = text.getText();
                 if (saveName && newName != null && !newName.isEmpty()) {
                         try {
-                                this.controller.rename(reference, newName, true);
+                                this.controller.rename(cursorReference, newName, true);
                         } catch (IllegalNameException ex) {
                                 text.setBorder(BorderFactory.createLineBorder(Color.red, 1));
                                 text.setToolTipText(ex.getReason());
@@ -643,7 +625,7 @@ public class Gui {
                 // abort the rename
                 JPanel panel = (JPanel) infoPanel.getComponent(0);
                 panel.remove(panel.getComponentCount() - 1);
-                panel.add(Utils.unboldLabel(new JLabel(reference.getNameableName(), JLabel.LEFT)));
+                panel.add(Utils.unboldLabel(new JLabel(cursorReference.getNameableName(), JLabel.LEFT)));
 
                 this.editor.grabFocus();
 
@@ -652,24 +634,24 @@ public class Gui {
 
         public void showInheritance() {
 
-                if (reference == null) {
+                if (cursorReference == null) {
                         return;
                 }
 
                 inheritanceTree.setModel(null);
 
-                if (reference.entry instanceof ClassEntry) {
+                if (cursorReference.entry instanceof ClassEntry) {
                         // get the class inheritance
-                        ClassInheritanceTreeNode classNode = this.controller.getClassInheritance((ClassEntry) reference.entry);
+                        ClassInheritanceTreeNode classNode = this.controller.getClassInheritance((ClassEntry) cursorReference.entry);
 
                         // show the tree at the root
                         TreePath path = getPathToRoot(classNode);
                         inheritanceTree.setModel(new DefaultTreeModel((TreeNode) path.getPathComponent(0)));
                         inheritanceTree.expandPath(path);
                         inheritanceTree.setSelectionRow(inheritanceTree.getRowForPath(path));
-                } else if (reference.entry instanceof MethodEntry) {
+                } else if (cursorReference.entry instanceof MethodEntry) {
                         // get the method inheritance
-                        MethodInheritanceTreeNode classNode = this.controller.getMethodInheritance((MethodEntry) reference.entry);
+                        MethodInheritanceTreeNode classNode = this.controller.getMethodInheritance((MethodEntry) cursorReference.entry);
 
                         // show the tree at the root
                         TreePath path = getPathToRoot(classNode);
@@ -685,7 +667,7 @@ public class Gui {
 
         public void showImplementations() {
 
-                if (reference == null) {
+                if (cursorReference == null) {
                         return;
                 }
 
@@ -694,11 +676,11 @@ public class Gui {
                 DefaultMutableTreeNode node = null;
 
                 // get the class implementations
-                if (reference.entry instanceof ClassEntry)
-                        node = this.controller.getClassImplementations((ClassEntry) reference.entry);
+                if (cursorReference.entry instanceof ClassEntry)
+                        node = this.controller.getClassImplementations((ClassEntry) cursorReference.entry);
                 else // get the method implementations
-                        if (reference.entry instanceof MethodEntry)
-                                node = this.controller.getMethodImplementations((MethodEntry) reference.entry);
+                        if (cursorReference.entry instanceof MethodEntry)
+                                node = this.controller.getMethodImplementations((MethodEntry) cursorReference.entry);
 
                 if (node != null) {
                         // show the tree at the root
@@ -714,18 +696,18 @@ public class Gui {
         }
 
         public void showCalls(boolean recurse) {
-                if (reference == null) {
+                if (cursorReference == null) {
                         return;
                 }
 
-                if (reference.entry instanceof ClassEntry) {
-                        ClassReferenceTreeNode node = this.controller.getClassReferences((ClassEntry) reference.entry);
+                if (cursorReference.entry instanceof ClassEntry) {
+                        ClassReferenceTreeNode node = this.controller.getClassReferences((ClassEntry) cursorReference.entry);
                         callsTree.setModel(new DefaultTreeModel(node));
-                } else if (reference.entry instanceof FieldEntry) {
-                        FieldReferenceTreeNode node = this.controller.getFieldReferences((FieldEntry) reference.entry);
+                } else if (cursorReference.entry instanceof FieldEntry) {
+                        FieldReferenceTreeNode node = this.controller.getFieldReferences((FieldEntry) cursorReference.entry);
                         callsTree.setModel(new DefaultTreeModel(node));
-                } else if (reference.entry instanceof MethodEntry) {
-                        MethodReferenceTreeNode node = this.controller.getMethodReferences((MethodEntry) reference.entry, recurse);
+                } else if (cursorReference.entry instanceof MethodEntry) {
+                        MethodReferenceTreeNode node = this.controller.getMethodReferences((MethodEntry) cursorReference.entry, recurse);
                         callsTree.setModel(new DefaultTreeModel(node));
                 }
 
@@ -735,10 +717,10 @@ public class Gui {
         }
 
         public void toggleMapping() {
-                if (this.controller.getDeobfuscator().isRemapped(reference.entry)) {
-                        this.controller.removeMapping(reference);
+                if (this.controller.getDeobfuscator().isRemapped(cursorReference.entry)) {
+                        this.controller.removeMapping(cursorReference);
                 } else {
-                        this.controller.markAsDeobfuscated(reference);
+                        this.controller.markAsDeobfuscated(cursorReference);
                 }
         }
 
diff --git a/src/main/java/cuchaz/enigma/gui/GuiController.java b/src/main/java/cuchaz/enigma/gui/GuiController.java
index 4155062..5610233 100644
--- a/src/main/java/cuchaz/enigma/gui/GuiController.java
+++ b/src/main/java/cuchaz/enigma/gui/GuiController.java
@@ -12,7 +12,6 @@
 package cuchaz.enigma.gui;
 
 import com.google.common.collect.Lists;
-import com.google.common.collect.Queues;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.strobel.decompiler.languages.java.ast.CompilationUnit;
 import cuchaz.enigma.Deobfuscator;
@@ -20,6 +19,7 @@ import cuchaz.enigma.SourceProvider;
 import cuchaz.enigma.analysis.*;
 import cuchaz.enigma.config.Config;
 import cuchaz.enigma.gui.dialog.ProgressDialog;
+import cuchaz.enigma.gui.util.History;
 import cuchaz.enigma.throwables.MappingParseException;
 import cuchaz.enigma.translation.Translator;
 import cuchaz.enigma.translation.mapping.*;
@@ -40,7 +40,6 @@ import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.nio.file.Path;
 import java.util.Collection;
-import java.util.Deque;
 import java.util.List;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -53,14 +52,13 @@ public class GuiController {
         private final Gui gui;
         private Deobfuscator deobfuscator;
         private DecompiledClassSource currentSource;
-        private Deque<EntryReference<Entry<?>, Entry<?>>> referenceStack;
+
 
         private Path loadedMappingPath;
         private MappingFormat loadedMappingFormat;
 
         public GuiController(Gui gui) {
                 this.gui = gui;
-                this.referenceStack = Queues.newArrayDeque();
         }
 
         public boolean isDirty() {
@@ -246,6 +244,10 @@ public class GuiController {
                 refreshCurrentClass(reference);
         }
 
+        /**
+         * Navigates to the declaration with respect to navigation history
+         * @param entry the entry whose declaration will be navigated to
+         */
         public void openDeclaration(Entry<?> entry) {
                 if (entry == null) {
                         throw new IllegalArgumentException("Entry cannot be null!");
@@ -253,11 +255,29 @@ public class GuiController {
                 openReference(new EntryReference<>(entry, entry.getName()));
         }
 
+        /**
+         * Navigates to the reference with respect to navigation history
+         * @param reference the reference
+         */
         public void openReference(EntryReference<Entry<?>, Entry<?>> reference) {
                 if (reference == null) {
                         throw new IllegalArgumentException("Reference cannot be null!");
                 }
+                if (this.gui.referenceHistory == null) {
+                        this.gui.referenceHistory = new History<>(reference);
+                } else {
+                        if (!reference.equals(this.gui.referenceHistory.getCurrent())) {
+                                this.gui.referenceHistory.push(reference);
+                        }
+                }
+                setReference(reference);
+        }
 
+        /**
+         * Navigates to the reference without modifying history. If the class is not currently loaded, it will be loaded.
+         * @param reference the reference
+         */
+        private void setReference(EntryReference<Entry<?>, Entry<?>> reference) {
                 // get the reference target class
                 ClassEntry classEntry = reference.getLocationClassEntry();
                 if (!this.deobfuscator.isRenamable(classEntry)) {
@@ -272,6 +292,10 @@ public class GuiController {
                 }
         }
 
+        /**
+         * Navigates to the reference without modifying history. Assumes the class is loaded.
+         * @param reference
+         */
         private void showReference(EntryReference<Entry<?>, Entry<?>> reference) {
                 EntryRemapper mapper = this.deobfuscator.getMapper();
 
@@ -289,18 +313,39 @@ public class GuiController {
                 }
         }
 
-        public void savePreviousReference(EntryReference<Entry<?>, Entry<?>> reference) {
-                this.referenceStack.push(reference);
+        public void openPreviousReference() {
+                if (hasPreviousReference()) {
+                        setReference(gui.referenceHistory.goBack());
+                }
         }
 
-        public void openPreviousReference() {
-                if (hasPreviousLocation()) {
-                        openReference(this.referenceStack.pop());
+        public boolean hasPreviousReference() {
+                return gui.referenceHistory != null && gui.referenceHistory.canGoBack();
+        }
+
+        public void openNextReference() {
+                if (hasNextReference()) {
+                        setReference(gui.referenceHistory.goForward());
                 }
         }
 
-        public boolean hasPreviousLocation() {
-                return !this.referenceStack.isEmpty();
+        public boolean hasNextReference() {
+                return gui.referenceHistory != null && gui.referenceHistory.canGoForward();
+        }
+
+        public void navigateTo(Entry<?> entry) {
+                if (!entryIsInJar(entry)) {
+                        // entry is not in the jar. Ignore it
+                        return;
+                }
+                openDeclaration(entry);
+        }
+
+        public void navigateTo(EntryReference<Entry<?>, Entry<?>> reference) {
+                if (!entryIsInJar(reference.getLocationClassEntry())) {
+                        return;
+                }
+                openReference(reference);
         }
 
         private void refreshClasses() {
@@ -390,7 +435,7 @@ public class GuiController {
 
         public void modifierChange(ItemEvent event) {
                 if (event.getStateChange() == ItemEvent.SELECTED) {
-                        deobfuscator.changeModifier(gui.reference.entry, (AccessModifier) event.getItem());
+                        deobfuscator.changeModifier(gui.cursorReference.entry, (AccessModifier) event.getItem());
                         refreshCurrentClass();
                 }
         }
diff --git a/src/main/java/cuchaz/enigma/gui/dialog/SearchDialog.java b/src/main/java/cuchaz/enigma/gui/dialog/SearchDialog.java
index da09c52..a122bd8 100644
--- a/src/main/java/cuchaz/enigma/gui/dialog/SearchDialog.java
+++ b/src/main/java/cuchaz/enigma/gui/dialog/SearchDialog.java
@@ -125,7 +125,7 @@ public class SearchDialog {
                         .filter(classEntry -> classEntry.getSimpleName().equals(classList.getSelectedValue())).
                         findFirst()
                         .ifPresent(classEntry -> {
-                                parent.navigateTo(classEntry);
+                                parent.getController().navigateTo(classEntry);
                                 parent.getDeobfPanel().deobfClasses.setSelectionClass(classEntry);
                         });
         }
diff --git a/src/main/java/cuchaz/enigma/gui/elements/PopupMenuBar.java b/src/main/java/cuchaz/enigma/gui/elements/PopupMenuBar.java
index 32f9172..fbf39ac 100644
--- a/src/main/java/cuchaz/enigma/gui/elements/PopupMenuBar.java
+++ b/src/main/java/cuchaz/enigma/gui/elements/PopupMenuBar.java
@@ -15,6 +15,7 @@ public class PopupMenuBar extends JPopupMenu {
         public final JMenuItem showCallsSpecificMenu;
         public final JMenuItem openEntryMenu;
         public final JMenuItem openPreviousMenu;
+        public final JMenuItem openNextMenu;
         public final JMenuItem toggleMappingMenu;
 
         public PopupMenuBar(Gui gui) {
@@ -60,14 +61,14 @@ public class PopupMenuBar extends JPopupMenu {
                 }
                 {
                         JMenuItem menu = new JMenuItem("Go to Declaration");
-                        menu.addActionListener(event -> gui.navigateTo(gui.reference.entry));
+                        menu.addActionListener(event -> gui.getController().navigateTo(gui.cursorReference.entry));
                         menu.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, 0));
                         menu.setEnabled(false);
                         this.add(menu);
                         this.openEntryMenu = menu;
                 }
                 {
-                        JMenuItem menu = new JMenuItem("Go to previous");
+                        JMenuItem menu = new JMenuItem("Go back");
                         menu.addActionListener(event -> gui.getController().openPreviousReference());
                         menu.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_P, 0));
                         menu.setEnabled(false);
@@ -75,6 +76,14 @@ public class PopupMenuBar extends JPopupMenu {
                         this.openPreviousMenu = menu;
                 }
                 {
+                        JMenuItem menu = new JMenuItem("Go forward");
+                        menu.addActionListener(event -> gui.getController().openNextReference());
+                        menu.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_E, 0));
+                        menu.setEnabled(false);
+                        this.add(menu);
+                        this.openNextMenu = menu;
+                }
+                {
                         JMenuItem menu = new JMenuItem("Mark as deobfuscated");
                         menu.addActionListener(event -> gui.toggleMapping());
                         menu.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O, 0));
diff --git a/src/main/java/cuchaz/enigma/gui/panels/PanelDeobf.java b/src/main/java/cuchaz/enigma/gui/panels/PanelDeobf.java
index 68cc8e1..2a4e2d7 100644
--- a/src/main/java/cuchaz/enigma/gui/panels/PanelDeobf.java
+++ b/src/main/java/cuchaz/enigma/gui/panels/PanelDeobf.java
@@ -15,7 +15,7 @@ public class PanelDeobf extends JPanel {
                 this.gui = gui;
 
                 this.deobfClasses = new ClassSelector(gui, ClassSelector.DEOBF_CLASS_COMPARATOR, true);
-                this.deobfClasses.setSelectionListener(gui::navigateTo);
+                this.deobfClasses.setSelectionListener(gui.getController()::navigateTo);
                 this.deobfClasses.setRenameSelectionListener(gui::onPanelRename);
 
                 this.setLayout(new BorderLayout());
diff --git a/src/main/java/cuchaz/enigma/gui/panels/PanelEditor.java b/src/main/java/cuchaz/enigma/gui/panels/PanelEditor.java
index f766743..f19d98f 100644
--- a/src/main/java/cuchaz/enigma/gui/panels/PanelEditor.java
+++ b/src/main/java/cuchaz/enigma/gui/panels/PanelEditor.java
@@ -21,8 +21,19 @@ public class PanelEditor extends JEditorPane {
                 this.addMouseListener(new MouseAdapter() {
                         @Override
                         public void mouseReleased(MouseEvent e) {
-                                if (e.getButton() == MouseEvent.BUTTON3)
-                                        self.setCaretPosition(self.viewToModel(e.getPoint()));
+                                switch (e.getButton()) {
+                                        case MouseEvent.BUTTON3: // Right click
+                                                self.setCaretPosition(self.viewToModel(e.getPoint()));
+                                                break;
+
+                                        case 4: // Back navigation
+                                                gui.getController().openPreviousReference();
+                                                break;
+
+                                        case 5: // Forward navigation
+                                                gui.getController().openNextReference();
+                                                break;
+                                }
                         }
                 });
                 this.addKeyListener(new KeyAdapter() {
@@ -49,6 +60,10 @@ public class PanelEditor extends JEditorPane {
                                                 gui.popupMenu.openPreviousMenu.doClick();
                                                 break;
 
+                                        case KeyEvent.VK_E:
+                                                gui.popupMenu.openNextMenu.doClick();
+                                                break;
+
                                         case KeyEvent.VK_C:
                                                 gui.popupMenu.showCallsMenu.doClick();
                                                 break;
diff --git a/src/main/java/cuchaz/enigma/gui/panels/PanelObf.java b/src/main/java/cuchaz/enigma/gui/panels/PanelObf.java
index ccdc9f8..8ee564b 100644
--- a/src/main/java/cuchaz/enigma/gui/panels/PanelObf.java
+++ b/src/main/java/cuchaz/enigma/gui/panels/PanelObf.java
@@ -26,7 +26,7 @@ public class PanelObf extends JPanel {
                 };
 
                 this.obfClasses = new ClassSelector(gui, obfClassComparator, false);
-                this.obfClasses.setSelectionListener(gui::navigateTo);
+                this.obfClasses.setSelectionListener(gui.getController()::navigateTo);
                 this.obfClasses.setRenameSelectionListener(gui::onPanelRename);
 
                 this.setLayout(new BorderLayout());
diff --git a/src/main/java/cuchaz/enigma/gui/util/History.java b/src/main/java/cuchaz/enigma/gui/util/History.java
new file mode 100644
index 0000000..94f3105
--- /dev/null
+++ b/src/main/java/cuchaz/enigma/gui/util/History.java
@@ -0,0 +1,49 @@
+package cuchaz.enigma.gui.util;

+

+import com.google.common.collect.Queues;

+

+import java.util.Deque;

+

+public class History<T> {

+        private final Deque<T> previous = Queues.newArrayDeque();

+        private final Deque<T> next = Queues.newArrayDeque();

+        private T current;

+

+        public History(T initial) {

+                current = initial;

+        }

+

+        public T getCurrent() {

+                return current;

+        }

+

+        public void push(T value) {

+                previous.addLast(current);

+                current = value;

+                next.clear();

+        }

+

+        public void replace(T value) {

+                current = value;

+        }

+

+        public boolean canGoBack() {

+                return !previous.isEmpty();

+        }

+

+        public T goBack() {

+                next.addFirst(current);

+                current = previous.removeLast();

+                return current;

+        }

+

+        public boolean canGoForward() {

+                return !next.isEmpty();

+        }

+

+        public T goForward() {

+                previous.addLast(current);

+                current = next.removeFirst();

+                return current;

+        }

+}