Merge branch 'main' into import-exportimport-export

# Conflicts:
#	data/personaldb.json
#	src/main/java/design/controller/userinput/menus/MainMenu.java
#	src/main/java/design/persistence/JSONLeagueDatabase.java
#	src/main/java/design/persistence/JSONPersonalDatabase.java
#	src/test/java/design/model/ClubTest.java
#	src/test/java/design/model/GolferTest.java

19 files changed, 560 insertions, 71 deletions

diff --git a/src/main/java/design/controller/userinput/UndoActions.java b/src/main/java/design/controller/userinput/UndoActions.java
new file mode 100644
index 0000000..6417284
--- /dev/null
+++ b/src/main/java/design/controller/userinput/UndoActions.java
@@ -0,0 +1,51 @@
+package design.controller.userinput;
+
+import design.model.undo.UndoManager;
+import design.persistence.PersonalDatabase;
+import design.runtime.Session;
+import java.io.IOException;
+
+public final class UndoActions {
+
+    private UndoActions() {
+    }
+
+    public static void undoWithSave() {
+        UndoManager um = UndoManager.instance();
+        if (!um.canUndo()) {
+            System.out.println("Nothing to undo.");
+            return;
+        }
+
+        String label = um.peekUndoLabel();
+        um.undo();
+        System.out.println("Undo: " + label);
+
+        saveCurrentGolfer();
+    }
+
+    public static void redoWithSave() {
+        UndoManager um = UndoManager.instance();
+        if (!um.canRedo()) {
+            System.out.println("Nothing to redo.");
+            return;
+        }
+
+        String label = um.peekRedoLabel();
+        um.redo();
+        System.out.println("Redo: " + label);
+
+        saveCurrentGolfer();
+    }
+
+    private static void saveCurrentGolfer() {
+        try {
+            var g = Session.getCurrentGolfer();
+            if (g != null) {
+                PersonalDatabase.instance().updateGolfer(g);
+            }
+        } catch (IOException e) {
+            System.err.println("Failed to save after undo/redo: " + e.getMessage());
+        }
+    }
+}
diff --git a/src/main/java/design/controller/userinput/menus/CourseSearch.java b/src/main/java/design/controller/userinput/menus/CourseSearch.java
index b84247a..4dd2cad 100644
--- a/src/main/java/design/controller/userinput/menus/CourseSearch.java
+++ b/src/main/java/design/controller/userinput/menus/CourseSearch.java
@@ -9,6 +9,7 @@ import design.model.course_search.CurrentSearchQuery;
 import design.model.course_search.ICourse;
 import design.persistence.PersonalDatabase;
 import design.runtime.Session;
+import design.model.undo.UndoManager;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -71,7 +72,7 @@ public class CourseSearch extends Menu {
     }
 
     // recursively go through tree structure of courselist to make menu options.
-    // this is all for displaying the menu options, not the actual sorting. 
+    // this is all for displaying the menu options, not the actual sorting.
     private void addCoursesRecursive(List<MenuOption> menuOptions, CourseList list) {
         for (ICourse icourse : list.getCourses()) {
             // if we find a leaf (course), display it as a menu option
@@ -79,6 +80,8 @@ public class CourseSearch extends Menu {
                 var name = String.format("%s, %s, Difficulty: %s, %s holes, %s total par",
                         c.getName(), c.getLocation(), c.getDifficultyRating(), c.getHoleCount(), c.getTotalPar());
                 menuOptions.add(new MenuOption(name, () -> {
+                    UndoManager.instance().capture(golfer, "Add course " + c.getName());
+
                     // add the course, try to save to DB.
                     golfer.addCourse(c);
                     try {
@@ -89,8 +92,7 @@ public class CourseSearch extends Menu {
 
                     System.out.println("\n Course added to profile. \n");
                     new MainMenu().present();
-                }
-                ));
+                }));
             }
             // if not, we need to traverse another courselist
             else if (icourse instanceof CourseList sublist) {
diff --git a/src/main/java/design/controller/userinput/menus/HolePlayMenu.java b/src/main/java/design/controller/userinput/menus/HolePlayMenu.java
index e0d1572..6651500 100644
--- a/src/main/java/design/controller/userinput/menus/HolePlayMenu.java
+++ b/src/main/java/design/controller/userinput/menus/HolePlayMenu.java
@@ -3,12 +3,15 @@ package design.controller.userinput.menus;
 import design.controller.userinput.Menu;
 import design.controller.userinput.MenuOption;
 import design.model.Course;
+import design.model.Golfer;
 import design.model.Hole;
 import design.runtime.Session;
 import design.model.Club;
 import design.model.Round;
 import design.model.holeplay.HolePlayContext;
 import design.persistence.PersonalDatabase;
+import design.model.undo.UndoManager;
+import design.controller.userinput.UndoActions;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -18,10 +21,11 @@ public class HolePlayMenu extends Menu {
 
     private final Round round;
     private final HolePlayContext ctx;
+    private final Golfer golfer = Session.getCurrentGolfer();
 
     public HolePlayMenu() {
         this.round = createRound();
-        this.ctx = new HolePlayContext(Session.getCurrentGolfer(), round, PersonalDatabase.instance());
+        this.ctx = new HolePlayContext(this.golfer, round, PersonalDatabase.instance());
     }
 
     @Override
@@ -34,17 +38,37 @@ public class HolePlayMenu extends Menu {
     public List<MenuOption> getMenuOptions() {
         List<MenuOption> opts = new ArrayList<>();
 
+        // End round (always shown) 1
+        opts.add(new MenuOption("end round", () -> {
+            UndoManager.instance().capture(golfer, "End round on " + round.getCourse().getName());
+            ctx.endRoundNow();
+            System.out.println("Round ended.");
+            new MainMenu().present();
+        }));
+
+        // 2
+        opts.add(new MenuOption("undo", () -> {
+            UndoActions.undoWithSave();
+            this.present();
+        }));
+
+        // 3
+        opts.add(new MenuOption("redo", () -> {
+            UndoActions.redoWithSave();
+            this.present();
+        }));
+
         boolean inSetup = (ctx.getCurrentPlay() == null);
 
         if (inSetup) {
-            // 0) Start hole
+            // 4) Start hole
             opts.add(new MenuOption("start hole", () -> {
                 ctx.startHole();
                 System.out.println("Started hole " + round.getCurrentHole().getNumber() + ".");
                 this.present();
             }));
         } else {
-            // 0) Take a shot
+            // 4) Take a shot
             opts.add(new MenuOption("take a shot", () -> {
                 var selector = new SelectClub();
                 selector.present();
@@ -60,6 +84,8 @@ public class HolePlayMenu extends Menu {
                     dist = Integer.parseInt(ds);
                 }
 
+                UndoManager.instance().capture(ctx, "Shot with " + club.getNickname() + " for " + dist + " yds");
+
                 // Records shot
                 ctx.recordShot(club, dist);
                 System.out.println("Shot recorded: " + dist + " yds with " + club.getNickname());
@@ -67,23 +93,19 @@ public class HolePlayMenu extends Menu {
                 this.present();
             }));
 
-            // 1) Hole out
+            // 5) Hole out
             opts.add(new MenuOption("hole out", () -> {
                 // Precedes to next hole
                 int prev = round.getCurrentHole().getNumber();
+
+                UndoManager.instance().capture(golfer, "Hole out on " + prev + " at " + round.getCourse().getName());
+
                 ctx.holeOut();
                 System.out.println("Holed out on " + prev + ". Next: " + round.getCurrentHole().getNumber());
                 this.present();
             }));
         }
 
-        // End round (always shown)
-        opts.add(new MenuOption("end round", () -> {
-            ctx.endRoundNow();
-            System.out.println("Round ended.");
-            new MainMenu().present();
-        }));
-
         return opts;
     }
 
@@ -118,6 +140,8 @@ public class HolePlayMenu extends Menu {
         // Starts round and sends user to HolePlayMenu
         Hole startHole = course.getHoles().get(startHoleNum - 1);
         Round r = new Round(course, Session.getDateTime(), startHole);
+        // Undo puts golfer back to before round existed.
+        UndoManager.instance().capture(golfer, "Start round on " + course.getName() + " (hole " + startHoleNum + ")");
         golfer.addRound(r);
         return r;
     }
diff --git a/src/main/java/design/controller/userinput/menus/LeageMenu.java b/src/main/java/design/controller/userinput/menus/LeageMenu.java
new file mode 100644
index 0000000..d9afa91
--- /dev/null
+++ b/src/main/java/design/controller/userinput/menus/LeageMenu.java
@@ -0,0 +1,30 @@
+package design.controller.userinput.menus;
+
+import design.controller.userinput.Menu;
+import design.controller.userinput.MenuOption;
+import design.model.League;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class LeageMenu extends Menu {
+    private final League league;
+
+    public LeageMenu(League league) {
+        this.league = league;
+    }
+
+    @Override
+    public String getTitle() {
+        return "League Menu";
+    }
+
+    @Override
+    public List<MenuOption> getMenuOptions() {
+        List<MenuOption> options = new ArrayList<>();
+        options.add(new MenuOption("statistics...", () -> {}));
+        options.add(new MenuOption("leaderboard...", () -> {}));
+        options.add(new MenuOption("log round...", () -> {}));
+        return options;
+    }
+}
diff --git a/src/main/java/design/controller/userinput/menus/MainMenu.java b/src/main/java/design/controller/userinput/menus/MainMenu.java
index 9d5204f..0c42422 100644
--- a/src/main/java/design/controller/userinput/menus/MainMenu.java
+++ b/src/main/java/design/controller/userinput/menus/MainMenu.java
@@ -2,6 +2,8 @@ package design.controller.userinput.menus;
 
 import design.controller.userinput.Menu;
 import design.controller.userinput.MenuOption;
+import design.controller.userinput.UndoActions;
+import design.runtime.Session;
 
 import java.util.List;
 
@@ -13,14 +15,33 @@ public class MainMenu extends Menu {
 
     @Override
     public List<MenuOption> getMenuOptions() {
-        return List.of(
-                new MenuOption("quit", () -> System.exit(0)),
-                new MenuOption("user settings...", () -> new UserSettings().present()),
-                new MenuOption("manage courses...", () -> new ManageCourses().present()),
-                new MenuOption("manage clubs...", () -> new ManageClubs().present()),
-                new MenuOption("statistics...", () -> new StatisticsMenu().present()),
-                new MenuOption("log round...", () -> new HolePlayMenu().present()),
-                new MenuOption("manage data...", () -> new ImportExportMenu().present())
-        );
+        boolean guest = Session.isGuest();
+        if (guest) {
+            return List.of(
+                    new MenuOption("quit", () -> System.exit(0)),
+                    new MenuOption("guest settings...", () -> new UserSettings().present()),
+                    new MenuOption("browse courses...", () -> new SearchMenu().present())
+
+            );
+        } else {
+            return List.of(
+                    new MenuOption("quit", () -> System.exit(0)),
+                    new MenuOption("undo", () -> {
+                        UndoActions.undoWithSave();
+                        this.present();
+                    }),
+                    new MenuOption("redo", () -> {
+                        UndoActions.redoWithSave();
+                        this.present();
+                    }),
+                    new MenuOption("user settings...", () -> new UserSettings().present()),
+                    new MenuOption("manage courses...", () -> new ManageCourses().present()),
+                    new MenuOption("manage clubs...", () -> new ManageClubs().present()),
+                    new MenuOption("statistics...", () -> new StatisticsMenu().present()),
+                    new MenuOption("log round...", () -> new HolePlayMenu().present()),
+                    new MenuOption("League play...", () -> new SelectLeague().present()),
+                    new MenuOption("manage data...", () -> new ImportExportMenu().present())
+            );
+        }
     }
 }
diff --git a/src/main/java/design/controller/userinput/menus/ManageClubs.java b/src/main/java/design/controller/userinput/menus/ManageClubs.java
index 6b6811b..9c23433 100644
--- a/src/main/java/design/controller/userinput/menus/ManageClubs.java
+++ b/src/main/java/design/controller/userinput/menus/ManageClubs.java
@@ -6,6 +6,7 @@ import design.model.Club;
 import design.model.Golfer;
 import design.persistence.PersonalDatabase;
 import design.runtime.Session;
+import design.model.undo.UndoManager;
 
 import java.io.IOException;
 import java.util.Arrays;
@@ -36,7 +37,11 @@ public class ManageClubs extends Menu {
         opts.add(new MenuOption("remove club...", () -> {
             var selector = new SelectClub();
             selector.present();
-            golfer.removeClub(selector.getResult());
+            Club toRemove = selector.getResult();
+
+            UndoManager.instance().capture(golfer, "Remove club " + toRemove);
+
+            golfer.removeClub(toRemove);
             try {
                 personalDB.updateGolfer(golfer);
             } catch (IOException ex) {
@@ -46,6 +51,8 @@ public class ManageClubs extends Menu {
         }));
 
         opts.add(new MenuOption("add club...", () -> {
+            UndoManager.instance().capture(golfer, "Add club");
+
             Scanner sc = new Scanner(System.in);
 
             System.out.print("Manufacturer: ");
diff --git a/src/main/java/design/controller/userinput/menus/ManageCourses.java b/src/main/java/design/controller/userinput/menus/ManageCourses.java
index b592cd2..4f3efe5 100644
--- a/src/main/java/design/controller/userinput/menus/ManageCourses.java
+++ b/src/main/java/design/controller/userinput/menus/ManageCourses.java
@@ -6,6 +6,7 @@ import design.model.Course;
 import design.model.Golfer;
 import design.persistence.PersonalDatabase;
 import design.runtime.Session;
+import design.model.undo.UndoManager;
 
 import java.io.IOException;
 import java.util.List;
@@ -34,7 +35,11 @@ public class ManageCourses extends Menu {
         opts.add(new MenuOption("remove course...", () -> {
             var selector = new SelectCourse();
             selector.present();
-            golfer.removeCourse(selector.getResult());
+            Course course = selector.getResult();
+
+            UndoManager.instance().capture(golfer, "Remove course " + course.getName());
+
+            golfer.removeCourse(course);
             try {
                 personalDB.updateGolfer(golfer);
             } catch (IOException ex) {
diff --git a/src/main/java/design/controller/userinput/menus/SelectLeague.java b/src/main/java/design/controller/userinput/menus/SelectLeague.java
new file mode 100644
index 0000000..08f6c91
--- /dev/null
+++ b/src/main/java/design/controller/userinput/menus/SelectLeague.java
@@ -0,0 +1,83 @@
+package design.controller.userinput.menus;
+
+import design.controller.userinput.Menu;
+import design.controller.userinput.MenuOption;
+import design.model.Golfer;
+import design.model.League;
+import design.model.ScrambleLeague;
+import design.model.StrokeLeague;
+import design.persistence.LeagueDatabase;
+import design.runtime.Session;
+
+import java.io.IOException;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.*;
+
+public class SelectLeague extends Menu {
+    private final Golfer golfer = Session.getCurrentGolfer();
+
+    @Override
+    public String getTitle() {
+        return "Select League";
+    }
+
+    @Override
+    public List<MenuOption> getMenuOptions() {
+        List<MenuOption> options = new ArrayList<>();
+        for (League l : LeagueDatabase.instance().getLeagues()) {
+            options.add(new MenuOption(l.getName(), () -> {
+                if (l instanceof ScrambleLeague sl && sl.locateTeam(golfer) == null) {
+                    Scanner sc = new Scanner(System.in);
+                    System.out.print("You are not a member of a team for this league. Would you like to create one (Y/n): ");
+                    if (sc.next().equals("n")) {
+                        new MainMenu().present();
+                    } else {
+                        // create team
+                    }
+                } else {
+                    new LeageMenu(l).present();
+                }
+            }));
+        }
+        options.add(new MenuOption("<create>", this::createLeagueWizard));
+        return options;
+    }
+
+    private void createLeagueWizard() {
+        try {
+            Scanner scanner = new Scanner(System.in);
+            SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
+
+            System.out.print("Enter league name: ");
+            String name = scanner.nextLine();
+
+            System.out.print("Enter registration date (yyyy-MM-dd): ");
+            Date registrationDate = dateFormat.parse(scanner.nextLine());
+
+            System.out.print("Enter start date (yyyy-MM-dd): ");
+            Date startDate = dateFormat.parse(scanner.nextLine());
+
+            System.out.print("Enter end date (yyyy-MM-dd): ");
+            Date endDate = dateFormat.parse(scanner.nextLine());
+
+            Golfer owner = Session.getCurrentGolfer();
+
+            System.out.print("Enter format (stroke/scramble): ");
+            String scramble = scanner.nextLine();
+
+            League league;
+            switch (scramble) {
+                case "scramble" -> league = new ScrambleLeague(name, registrationDate, startDate, endDate, owner);
+                case "stroke" -> league = new StrokeLeague(name, registrationDate, startDate, endDate, owner);
+                default -> throw new RuntimeException();
+            }
+            LeagueDatabase.instance().addLeague(league);
+        } catch (ParseException ex) {
+            System.out.println("Invalid format");
+        } catch (IOException ex) {
+            System.out.println("Error writing to file");
+        }
+        this.present();
+    }
+}
diff --git a/src/main/java/design/controller/userinput/menus/SelectUser.java b/src/main/java/design/controller/userinput/menus/SelectUser.java
index 4b7928c..6931a4b 100644
--- a/src/main/java/design/controller/userinput/menus/SelectUser.java
+++ b/src/main/java/design/controller/userinput/menus/SelectUser.java
@@ -6,6 +6,7 @@ import design.controller.userinput.MenuOption;
 import design.model.Golfer;
 import design.runtime.Session;
 import design.persistence.PersonalDatabase;
+import design.model.undo.UndoManager;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -52,6 +53,12 @@ public class SelectUser extends Menu {
             this.present();
         }));
 
+        opts.add(new MenuOption("<guest login>", () -> {
+            Session.setCurrentGolfer(null);
+            Session.setGuest(true);
+            doAfter.onAction();
+        }));
+
         return opts;
     }
 
@@ -61,6 +68,7 @@ public class SelectUser extends Menu {
         if (g.checkPassword(password)) {
             // Sets user in Session too
             Session.setCurrentGolfer(g);
+            UndoManager.instance().purge();
             System.out.printf("Loaded user: %s%n", g);
             doAfter.onAction();
         } else {
diff --git a/src/main/java/design/controller/userinput/menus/UserSettings.java b/src/main/java/design/controller/userinput/menus/UserSettings.java
index 47b0a5b..1b2082d 100644
--- a/src/main/java/design/controller/userinput/menus/UserSettings.java
+++ b/src/main/java/design/controller/userinput/menus/UserSettings.java
@@ -12,6 +12,8 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Scanner;
 
+import design.model.undo.UndoManager;
+
 public class UserSettings extends Menu {
 
     private final Golfer golfer = Session.getCurrentGolfer();
@@ -25,6 +27,8 @@ public class UserSettings extends Menu {
 
     @Override
     public List<MenuOption> getMenuOptions() {
+        boolean guest = Session.isGuest();
+
         var opts = new ArrayList<MenuOption>();
 
         opts.add(new MenuOption("return to main menu", () -> new MainMenu().present()));
@@ -34,31 +38,37 @@ public class UserSettings extends Menu {
             new SelectUser(doAfter).present();
         }));
 
-        opts.add(new MenuOption("set password...", () -> {
-            System.out.print("Enter password: ");
-            var password = scanner.nextLine();
-
-            golfer.setPassword(password);
-            try {
-                personalDatabase.updateGolfer(golfer);
-            } catch (IOException ex) {
-                throw new RuntimeException(ex);
-            }
-            this.present();
-        }));
+        if (!guest) {
+            opts.add(new MenuOption("set password...", () -> {
+                UndoManager.instance().capture(golfer, "Change password for @" + golfer.getUsername());
 
-        opts.add(new MenuOption("set full name...", () -> {
-            System.out.print("Enter full name: ");
-            var fullName = scanner.nextLine();
-
-            golfer.setFullName(fullName);
-            try {
-                personalDatabase.updateGolfer(golfer);
-            } catch (IOException ex) {
-                throw new RuntimeException(ex);
-            }
-            this.present();
-        }));
+                System.out.print("Enter password: ");
+                var password = scanner.nextLine();
+
+                golfer.setPassword(password);
+                try {
+                    personalDatabase.updateGolfer(golfer);
+                } catch (IOException ex) {
+                    throw new RuntimeException(ex);
+                }
+                this.present();
+            }));
+
+            opts.add(new MenuOption("set full name...", () -> {
+                UndoManager.instance().capture(golfer, "Change full name for @" + golfer.getUsername());
+
+                System.out.print("Enter full name: ");
+                var fullName = scanner.nextLine();
+
+                golfer.setFullName(fullName);
+                try {
+                    personalDatabase.updateGolfer(golfer);
+                } catch (IOException ex) {
+                    throw new RuntimeException(ex);
+                }
+                this.present();
+            }));
+        }
 
         return opts;
     }
diff --git a/src/main/java/design/model/Golfer.java b/src/main/java/design/model/Golfer.java
index 1c4e669..84f7396 100644
--- a/src/main/java/design/model/Golfer.java
+++ b/src/main/java/design/model/Golfer.java
@@ -7,8 +7,11 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 import java.util.ArrayList;
 import java.util.List;
 
+import design.model.undo.Memento;
+import design.model.undo.Originator;
+
 @JsonPropertyOrder({ "clubs", "nextClubId" })
-public class Golfer {
+public class Golfer implements Originator {
     private String username;
     private int passwordHash;
     private String fullName;
@@ -16,20 +19,18 @@ public class Golfer {
     private final List<Round> rounds;
     private final List<Club> clubs; // Keep track of golfer's clubs
     private int nextClubId;
-    private final List<Invite> invites;
 
 
     
     @JsonCreator
     private Golfer(String username, int passwordHash, String fullName, List<Course> courses, List<Round> rounds,
-            List<Club> clubs, List<Invite> invites) {
+            List<Club> clubs) {
         this.username = username;
         this.passwordHash = passwordHash;
         this.fullName = fullName;
         this.courses = courses;
         this.rounds = rounds;
         this.clubs = clubs;
-        this.invites = invites != null ? invites : new ArrayList<>();
         this.nextClubId = this.clubs.stream().mapToInt(Club::getId).max().orElse(0) + 1;
     }
 
@@ -40,7 +41,6 @@ public class Golfer {
         this.courses = new ArrayList<>();
         this.rounds = new ArrayList<>();
         this.clubs = new ArrayList<>();
-        this.invites = new ArrayList<>();
         this.nextClubId = 1;
     }
 
@@ -93,8 +93,8 @@ public class Golfer {
     }
 
     public Club addClub(Club c) {
-        c.setId(nextClubId++);
         clubs.add(c);
+        c.setId(nextClubId++);
         return c;
     }
 
@@ -119,15 +119,49 @@ public class Golfer {
         clubs.remove(c);
     }
 
-    public boolean addInvite(Invite invite) {
-        return invites.add(invite);
+    // Takes a snapshot of the golfer
+    private static class GolferMemento implements Memento {
+        private final String username;
+        private final int passwordHash;
+        private final String fullName;
+        private final List<Course> courses;
+        private final List<Round> rounds;
+        private final List<Club> clubs;
+        private final int nextClubId;
+
+        GolferMemento(Golfer g) {
+            this.username = g.username;
+            this.passwordHash = g.passwordHash;
+            this.fullName = g.fullName;
+            this.courses = new ArrayList<>(g.courses);
+            this.rounds = new ArrayList<>(g.rounds);
+            this.clubs = new ArrayList<>(g.clubs);
+            this.nextClubId = g.nextClubId;
+        }
     }
 
-    public boolean removeInvite(Invite o) {
-        return invites.remove(o);
+    @Override
+    public Memento createMemento() {
+        return new GolferMemento(this);
     }
 
-    public Invite[] getInvites() {
-        return invites.toArray(Invite[]::new);
+    @Override
+    public void restore(Memento memento) {
+        GolferMemento gm = (GolferMemento) memento;
+
+        this.username = gm.username;
+        this.passwordHash = gm.passwordHash;
+        this.fullName = gm.fullName;
+
+        this.courses.clear();
+        this.courses.addAll(gm.courses);
+
+        this.rounds.clear();
+        this.rounds.addAll(gm.rounds);
+
+        this.clubs.clear();
+        this.clubs.addAll(gm.clubs);
+
+        this.nextClubId = gm.nextClubId;
     }
 }
diff --git a/src/main/java/design/model/League.java b/src/main/java/design/model/League.java
index 0252f89..881e25f 100644
--- a/src/main/java/design/model/League.java
+++ b/src/main/java/design/model/League.java
@@ -1,9 +1,22 @@
 package design.model;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
 
+import java.util.ArrayList;
 import java.util.Date;
+import java.util.List;
 
+@JsonTypeInfo(
+        use = JsonTypeInfo.Id.NAME,
+        include = JsonTypeInfo.As.PROPERTY,
+        property = "type"
+)
+@JsonSubTypes({
+        @JsonSubTypes.Type(value = ScrambleLeague.class, name = "scramble"),
+        @JsonSubTypes.Type(value = StrokeLeague.class, name = "stroke")
+})
 public abstract class League {
     private int id;
     private final String name;
@@ -11,15 +24,17 @@ public abstract class League {
     private final Date startDate;
     private final Date endDate;
     private final Golfer owner;
+    private final List<Match> schedule;
 
     @JsonCreator
-    protected League(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner) {
+    protected League(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner, List<Match> schedule) {
         this.id = id;
         this.name = name;
         this.registrationDate = registrationDate;
         this.startDate = startDate;
         this.endDate = endDate;
         this.owner = owner;
+        this.schedule = schedule != null ? schedule : new ArrayList<>();
     }
 
     public League(String name, Date registrationDate, Date startDate, Date endDate, Golfer owner) {
@@ -29,6 +44,7 @@ public abstract class League {
         this.startDate = startDate;
         this.endDate = endDate;
         this.owner = owner;
+        this.schedule = new ArrayList<>();
     }
 
     public int getId() {
@@ -55,6 +71,18 @@ public abstract class League {
         return owner;
     }
 
+    public Match[] getSchedule() {
+        return schedule.toArray(Match[]::new);
+    }
+
+    public void addMatchToSchedule(Match match) {
+        Date date = match.getDateScheduled();
+        if(date.after(endDate)){
+            throw new IllegalArgumentException("Cannot create match after league has ended");
+        }
+        schedule.add(match);
+    }
+
     public void setId(int id) {
         assert this.id == -1;
         this.id = id;
diff --git a/src/main/java/design/model/ScrambleLeague.java b/src/main/java/design/model/ScrambleLeague.java
index 7ff966e..d372264 100644
--- a/src/main/java/design/model/ScrambleLeague.java
+++ b/src/main/java/design/model/ScrambleLeague.java
@@ -1,22 +1,25 @@
 package design.model;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Date;
 import java.util.List;
 
+@JsonTypeName("scramble")
 public class ScrambleLeague extends League {
     private final List<Team> participants;
 
     @JsonCreator
-    private ScrambleLeague(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner, List<Team> participants) {
-        super(id, name, registrationDate, startDate, endDate, owner);
+    private ScrambleLeague(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner, List<Team> participants, List<Match> schedule) {
+        super(id, name, registrationDate, startDate, endDate, owner, schedule);
         this.participants = participants;
     }
 
-    public ScrambleLeague(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner) {
-        super(id, name, registrationDate, startDate, endDate, owner);
+    public ScrambleLeague(String name, Date registrationDate, Date startDate, Date endDate, Golfer owner) {
+        super(name, registrationDate, startDate, endDate, owner);
         this.participants = new ArrayList<>();
     }
 
@@ -31,4 +34,13 @@ public class ScrambleLeague extends League {
     public Team[] getParticipants() {
         return participants.toArray(Team[]::new);
     }
+
+    public Team locateTeam(Golfer golfer) {
+        for (Team participant : participants) {
+            if (List.of(participant.getMembers()).contains(golfer)) {
+                return participant;
+            }
+        }
+        return null;
+    }
 }
diff --git a/src/main/java/design/model/StrokeLeague.java b/src/main/java/design/model/StrokeLeague.java
index 6bdde0a..2b787b5 100644
--- a/src/main/java/design/model/StrokeLeague.java
+++ b/src/main/java/design/model/StrokeLeague.java
@@ -1,22 +1,24 @@
 package design.model;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
 
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
 
+@JsonTypeName("stroke")
 public class StrokeLeague extends League {
     private final List<Golfer> participants;
 
     @JsonCreator
-    private StrokeLeague(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner, List<Golfer> participants) {
-        super(id, name, registrationDate, startDate, endDate, owner);
+    private StrokeLeague(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner, List<Golfer> participants, List<Match> schedule) {
+        super(id, name, registrationDate, startDate, endDate, owner, schedule);
         this.participants = participants;
     }
 
-    public StrokeLeague(int id, String name, Date registrationDate, Date startDate, Date endDate, Golfer owner) {
-        super(id, name, registrationDate, startDate, endDate, owner);
+    public StrokeLeague(String name, Date registrationDate, Date startDate, Date endDate, Golfer owner) {
+        super(name, registrationDate, startDate, endDate, owner);
         this.participants = new ArrayList<>();
     }
 
diff --git a/src/main/java/design/model/holeplay/HolePlayContext.java b/src/main/java/design/model/holeplay/HolePlayContext.java
index 7a5d8ef..71fba32 100644
--- a/src/main/java/design/model/holeplay/HolePlayContext.java
+++ b/src/main/java/design/model/holeplay/HolePlayContext.java
@@ -6,7 +6,10 @@ import java.util.ArrayList;
 import design.model.*;
 import design.persistence.PersonalDatabase;
 
-public class HolePlayContext {
+import design.model.undo.Memento;
+import design.model.undo.Originator;
+
+public class HolePlayContext implements Originator {
     private final Golfer golfer;
     private final Round round;
     private final PersonalDatabase pdb;
@@ -109,4 +112,60 @@ public class HolePlayContext {
     void setStrokes(int s) {
         this.strokes = s;
     }
+
+    // Captures current State, current play (hole# + swings), and stroke counter
+    private static class HolePlayMemento implements Memento {
+        private final String stateName;
+        private final Play currentPlayCopy;
+        private final int strokesCopy;
+
+        HolePlayMemento(HolePlayContext ctx) {
+            this.stateName = ctx.state.name();
+
+            // Copy currentPlay if it exists
+            Play src = ctx.currentPlay;
+            if (src != null) {
+                var copySwings = new ArrayList<Swing>();
+                for (Swing s : src.getSwings()) {
+                    copySwings.add(new Swing(s.getDistance(), s.getClubUsed()));
+                }
+                this.currentPlayCopy = new Play(src.getHoleNumber(), copySwings);
+            } else {
+                this.currentPlayCopy = null;
+            }
+
+            this.strokesCopy = ctx.strokes;
+        }
+    }
+
+    @Override
+    public Memento createMemento() {
+        return new HolePlayMemento(this);
+    }
+
+    @Override
+    public void restore(Memento m) {
+        HolePlayMemento hm = (HolePlayMemento) m;
+
+        // restore strokes
+        this.strokes = hm.strokesCopy;
+
+        // restore currentPlay
+        if (hm.currentPlayCopy == null) {
+            this.currentPlay = null;
+        } else {
+            var copySwings = new ArrayList<Swing>();
+            for (Swing s : hm.currentPlayCopy.getSwings()) {
+                copySwings.add(new Swing(s.getDistance(), s.getClubUsed()));
+            }
+            this.currentPlay = new Play(hm.currentPlayCopy.getHoleNumber(), copySwings);
+        }
+
+        // restore state based on name
+        switch (hm.stateName) {
+            case "SetupState" -> this.state = new SetupState();
+            case "PlayState" -> this.state = new PlayState();
+            case "HoleCompleteState" -> this.state = new HoleCompleteState();
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/design/model/undo/Memento.java b/src/main/java/design/model/undo/Memento.java
new file mode 100644
index 0000000..162c3f3
--- /dev/null
+++ b/src/main/java/design/model/undo/Memento.java
@@ -0,0 +1,4 @@
+package design.model.undo;
+
+public interface Memento {
+}
diff --git a/src/main/java/design/model/undo/Originator.java b/src/main/java/design/model/undo/Originator.java
new file mode 100644
index 0000000..63eac38
--- /dev/null
+++ b/src/main/java/design/model/undo/Originator.java
@@ -0,0 +1,7 @@
+package design.model.undo;
+
+public interface Originator {
+    Memento createMemento();
+
+    void restore(Memento memento);
+}
\ No newline at end of file
diff --git a/src/main/java/design/model/undo/UndoManager.java b/src/main/java/design/model/undo/UndoManager.java
new file mode 100644
index 0000000..5c6a4a0
--- /dev/null
+++ b/src/main/java/design/model/undo/UndoManager.java
@@ -0,0 +1,91 @@
+package design.model.undo;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.List;
+import java.util.stream.Collectors;
+
+// Singleton caretaker that handles undo and redo stacks.
+public final class UndoManager {
+
+    private static final UndoManager INSTANCE = new UndoManager();
+
+    public static UndoManager instance() {
+        return INSTANCE;
+    }
+
+    private UndoManager() {
+    }
+
+    // Stack entry
+    private static class Entry {
+        final Originator originator;
+        final Memento memento;
+        final String label;
+
+        Entry(Originator originator, Memento memento, String label) {
+            this.originator = originator;
+            this.memento = memento;
+            this.label = label;
+        }
+    }
+
+    private final Deque<Entry> undoStack = new ArrayDeque<>();
+    private final Deque<Entry> redoStack = new ArrayDeque<>();
+
+    // Capture state
+    public void capture(Originator originator, String label) {
+        undoStack.push(new Entry(originator, originator.createMemento(), label));
+        redoStack.clear();
+    }
+
+    // Undo / Redo ops
+    public boolean canUndo() {
+        return !undoStack.isEmpty();
+    }
+
+    public boolean canRedo() {
+        return !redoStack.isEmpty();
+    }
+
+    public String peekUndoLabel() {
+        return canUndo() ? undoStack.peek().label : null;
+    }
+
+    public String peekRedoLabel() {
+        return canRedo() ? redoStack.peek().label : null;
+    }
+
+    public List<String> getUndoHistoryLabels() {
+        return undoStack.stream()
+                .map(e -> e.label)
+                .collect(Collectors.toList());
+    }
+
+    public void undo() {
+        if (!canUndo()) {
+            System.out.println("Nothing to undo.");
+            return;
+        }
+
+        Entry entry = undoStack.pop();
+        redoStack.push(new Entry(entry.originator, entry.originator.createMemento(), entry.label));
+        entry.originator.restore(entry.memento);
+    }
+
+    public void redo() {
+        if (!canRedo()) {
+            System.out.println("Nothing to redo.");
+            return;
+        }
+
+        Entry entry = redoStack.pop();
+        undoStack.push(new Entry(entry.originator, entry.originator.createMemento(), entry.label));
+        entry.originator.restore(entry.memento);
+    }
+
+    public void purge() {
+        undoStack.clear();
+        redoStack.clear();
+    }
+}
diff --git a/src/main/java/design/runtime/Session.java b/src/main/java/design/runtime/Session.java
index 59d31d8..5b00e67 100644
--- a/src/main/java/design/runtime/Session.java
+++ b/src/main/java/design/runtime/Session.java
@@ -7,12 +7,14 @@ import java.time.LocalDateTime;
 public final class Session {
     private static Golfer currentGolfer;
     private static LocalDateTime timeOverride;
+    private static boolean isGuest = false;
 
     public static Golfer getCurrentGolfer() {
         return currentGolfer;
     }
 
     public static void setCurrentGolfer(Golfer currentGolfer) {
+        Session.setGuest(false);
         Session.currentGolfer = currentGolfer;
     }
 
@@ -23,4 +25,13 @@ public final class Session {
     public static void setTimeOverride(LocalDateTime timeOverride) {
         Session.timeOverride = timeOverride;
     }
+
+    public static boolean isGuest() {
+        return isGuest;
+    }
+
+    public static void setGuest(boolean g) {
+        isGuest = g;
+    }
+
 }