Delete Season.Coord

This currently fails because a lot of World still works on references instead of lookups

MultiversalDiplomacy/Adjudicate/Decision/MovementDecisions.cs

@@ -61,25 +61,25 @@ public class MovementDecisions
                 case MoveOrder move:
                     AdvanceTimeline.Ensure(
                         move.Season,
-                        () => new(move.Season, world.OrderHistory[move.Season].Orders));
+                        () => new(move.Season, world.OrderHistory[move.Season.Designation].Orders));
                     AdvanceTimeline[move.Season].Orders.Add(move);
                     break;
 
                 case SupportHoldOrder supportHold:
                     AdvanceTimeline.Ensure(
                         supportHold.Target.Season,
-                        () => new(supportHold.Target.Season, world.OrderHistory[supportHold.Target.Season].Orders));
+                        () => new(supportHold.Target.Season, world.OrderHistory[supportHold.Target.Season.Designation].Orders));
                     AdvanceTimeline[supportHold.Target.Season].Orders.Add(supportHold);
                     break;
 
                 case SupportMoveOrder supportMove:
                     AdvanceTimeline.Ensure(
                         supportMove.Target.Season,
-                        () => new(supportMove.Target.Season, world.OrderHistory[supportMove.Target.Season].Orders));
+                        () => new(supportMove.Target.Season, world.OrderHistory[supportMove.Target.Season.Designation].Orders));
                     AdvanceTimeline[supportMove.Target.Season].Orders.Add(supportMove);
                     AdvanceTimeline.Ensure(
                         supportMove.Season,
-                        () => new(supportMove.Season, world.OrderHistory[supportMove.Season].Orders));
+                        () => new(supportMove.Season, world.OrderHistory[supportMove.Season.Designation].Orders));
                     AdvanceTimeline[supportMove.Season].Orders.Add(supportMove);
                     break;
             }

MultiversalDiplomacy/Adjudicate/MovementPhaseAdjudicator.cs

@@ -312,9 +312,9 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
 
         // All moves to a particular season in a single phase result in the same future. Keep a
         // record of when a future season has been created.
-        Dictionary<Season, Season> createdFutures = new();
-        List<Unit> createdUnits = new();
-        List<RetreatingUnit> retreats = new();
+        Dictionary<Season, Season> createdFutures = [];
+        List<Unit> createdUnits = [];
+        List<RetreatingUnit> retreats = [];
 
         // Populate createdFutures with the timeline fork decisions
         logger.Log(1, "Processing AdvanceTimeline decisions");
@@ -324,9 +324,7 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
             if (advanceTimeline.Outcome == true)
             {
                 // A timeline that doesn't have a future yet simply continues. Otherwise, it forks.
-                createdFutures[advanceTimeline.Season] = !world.GetFutures(advanceTimeline.Season).Any()
-                    ? advanceTimeline.Season.MakeNext()
-                    : advanceTimeline.Season.MakeFork();
+                createdFutures[advanceTimeline.Season] = world.ContinueOrFork(advanceTimeline.Season);
             }
         }
 
@@ -386,11 +384,11 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
         }
 
         // Record the adjudication results to the season's order history
-        Dictionary<Season, OrderHistory> newHistory = new();
+        Dictionary<string, OrderHistory> newHistory = [];
         foreach (UnitOrder unitOrder in decisions.OfType<IsDislodged>().Select(d => d.Order))
         {
-            newHistory.Ensure(unitOrder.Unit.Season, () => new());
-            OrderHistory history = newHistory[unitOrder.Unit.Season];
+            newHistory.Ensure(unitOrder.Unit.Season.Designation, () => new());
+            OrderHistory history = newHistory[unitOrder.Unit.Season.Designation];
             // TODO does this add every order to every season??
             history.Orders.Add(unitOrder);
             history.IsDislodgedOutcomes[unitOrder.Unit] = dislodges[unitOrder.Unit].Outcome == true;
@@ -401,7 +399,7 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
         }
 
         // Log the new order history
-        foreach ((Season season, OrderHistory history) in newHistory)
+        foreach ((string season, OrderHistory history) in newHistory)
         {
             string verb = world.OrderHistory.ContainsKey(season) ? "Updating" : "Adding";
             logger.Log(1, "{0} history for {1}", verb, season);
@@ -411,7 +409,7 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
             }
         }
 
-        IEnumerable<KeyValuePair<Season, OrderHistory>> updatedHistory = world.OrderHistory
+        IEnumerable<KeyValuePair<string, OrderHistory>> updatedHistory = world.OrderHistory
             .Where(kvp => !newHistory.ContainsKey(kvp.Key))
             .Concat(newHistory);
 
@@ -496,7 +494,7 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
         IEnumerable<MoveOrder> newIncomingMoves = decision.Orders
             .OfType<MoveOrder>()
             .Where(order => order.Season == decision.Season
-                && !world.OrderHistory[order.Season].DoesMoveOutcomes.ContainsKey(order));
+                && !world.OrderHistory[order.Season.Designation].DoesMoveOutcomes.ContainsKey(order));
         foreach (MoveOrder moveOrder in newIncomingMoves)
         {
             DoesMove doesMove = decisions.DoesMove[moveOrder];
@@ -513,7 +511,7 @@ public class MovementPhaseAdjudicator : IPhaseAdjudicator
         // 1. The outcome of a dislodge decision is changed,
         // 2. The outcome of an intra-timeline move decision is changed, or
         // 3. The outcome of an inter-timeline move decision with that season as the destination is changed.
-        OrderHistory history = world.OrderHistory[decision.Season];
+        OrderHistory history = world.OrderHistory[decision.Season.Designation];
         bool anyUnresolved = false;
         foreach (UnitOrder order in decision.Orders)
         {

MultiversalDiplomacy/CommandLine/ImageOptions.cs

@@ -0,0 +1,15 @@
+using CommandLine;
+
+namespace MultiversalDiplomacy.CommandLine;
+
+[Verb("image", HelpText = "Generate an image of a game state.")]
+public class ImageOptions
+{
+    [Value(0, HelpText = "Input file describing the game state to visualize, or - to read from stdin.")]
+    public string? InputFile { get; set; }
+
+    public static void Execute(ImageOptions args)
+    {
+        throw new NotImplementedException();
+    }
+}

MultiversalDiplomacy/CommandLine/ReplOptions.cs

@@ -0,0 +1,18 @@
+using CommandLine;
+
+namespace MultiversalDiplomacy.CommandLine;
+
+[Verb("repl", HelpText = "Begin an interactive 5dplomacy session.")]
+public class ReplOptions
+{
+    [Option('i', "input", HelpText = "Begin the repl session by executing the commands in this file.")]
+    public string? InputFile { get; set; }
+
+    [Option('o', "output", HelpText = "Echo the repl session to this file. Specify a directory to autogenerate a filename.")]
+    public string? OutputFile { get; set; }
+
+    public static void Execute(ReplOptions args)
+    {
+        throw new NotImplementedException();
+    }
+}

MultiversalDiplomacy/Model/Location.cs

@@ -1,3 +1,5 @@
+using System.Text.Json.Serialization;
+
 namespace MultiversalDiplomacy.Model;
 
 /// <summary>
@@ -9,8 +11,12 @@ public class Location
 {
     /// <summary>
     /// The province to which this location belongs.
+    /// </summary>
+    [JsonIgnore]
     public Province Province { get; }
 
+    public string ProvinceName => Province.Name;
+
     /// <summary>
     /// The location's full human-readable name.
     /// </summary>
@@ -29,6 +35,7 @@ public class Location
     /// <summary>
     /// The locations that border this location.
     /// </summary>
+    [JsonIgnore]
     public IEnumerable<Location> Adjacents => this.AdjacentList;
     private List<Location> AdjacentList { get; set; }
 

MultiversalDiplomacy/Model/Map.cs

@@ -5,7 +5,13 @@ namespace MultiversalDiplomacy.Model;
 /// <summary>
 /// Encapsulation of the world map and playable powers constituting a Diplomacy variant.
 /// </summary>
-public class Map {
+public class Map
+{
+    /// <summary>
+    /// The map type.
+    /// </summary>
+    public MapType Type { get; }
+
     /// <summary>
     /// The game map.
     /// </summary>
@@ -16,7 +22,7 @@ public class Map {
     /// </summary>
     public ReadOnlyCollection<Power> Powers { get; }
 
-    private Map(IEnumerable<Province> provinces, IEnumerable<Power> powers)
+    private Map(MapType type, IEnumerable<Province> provinces, IEnumerable<Power> powers)
     {
         Provinces = new(provinces.ToList());
         Powers = new(powers.ToList());
@@ -102,7 +108,7 @@ public class Map {
         Power a = new("Alpha");
         Power b = new("Beta");
 
-        return new([lef, cen, rig], [a, b]);
+        return new(MapType.Test, [lef, cen, rig], [a, b]);
     });
 
     public static Map Classical => _Classical.Value;
@@ -553,7 +559,7 @@ public class Map {
             new("Turkey"),
         ];
 
-        return new(provinces, powers);
+        return new(MapType.Classical, provinces, powers);
     });
 
 #endregion Variants

MultiversalDiplomacy/Model/ModelExtensions.cs

@@ -20,4 +20,10 @@ public static class ModelExtensions
     {
         return $"{coord.season.Timeline}-{coord.province.Abbreviations[0]}@{coord.season.Turn}";
     }
+
+    public static World ContinueOrFork(this World world, Season season, out Season future)
+    {
+        future = world.ContinueOrFork(season);
+        return world.Update(seasons: world.Seasons.Append(future));
+    }
 }

MultiversalDiplomacy/Model/OrderHistory.cs

@@ -13,7 +13,7 @@ public class OrderHistory
     public Dictionary<MoveOrder, bool> DoesMoveOutcomes;
 
     public OrderHistory()
-        : this(new(), new(), new())
+        : this([], [], [])
     {}
 
     public OrderHistory(

MultiversalDiplomacy/Model/Season.cs

@@ -5,10 +5,10 @@ namespace MultiversalDiplomacy.Model;
 /// <summary>
 /// Represents a state of the map produced by a set of move orders on a previous season.
 /// </summary>
-public class Season
+public class Season(string? past, int turn, string timeline)
 {
     /// <summary>
-    /// The first turn number.
+    /// The first turn number. This is defined to reduce confusion about whether the first turn is 0 or 1.
     /// </summary>
     public const int FIRST_TURN = 0;
 
@@ -17,19 +17,19 @@ public class Season
     /// If this season is an alternate timeline root, the past is from the origin timeline.
     /// The initial season does not have a past.
     /// </summary>
-    public string? Past { get; }
+    public string? Past { get; } = past;
 
     /// <summary>
     /// The current turn, beginning at 0. Each season (spring and fall) is one turn.
     /// Phases that only occur after the fall phase occur when Turn % 2 == 1.
     /// The current year is (Turn / 2) + 1901.
     /// </summary>
-    public int Turn { get; }
+    public int Turn { get; } = turn;
 
     /// <summary>
     /// The timeline to which this season belongs.
     /// </summary>
-    public string Timeline { get; }
+    public string Timeline { get; } = timeline;
 
     /// <summary>
     /// The multiversal designation of this season.
@@ -37,50 +37,5 @@ public class Season
     [JsonIgnore]
     public string Designation => $"{this.Timeline}{this.Turn}";
 
-    /// <summary>
-    /// The season's multiversal location as a timeline-turn tuple for convenience.
-    /// </summary>
-    [JsonIgnore]
-    public (string Timeline, int Turn) Coord => (this.Timeline, this.Turn);
-
-    /// <summary>
-    /// The shared timeline number generator.
-    /// </summary>
-    [JsonIgnore]
-    private TimelineFactory Timelines { get; }
-
-    private Season(Season? past, int turn, string timeline, TimelineFactory factory)
-    {
-        this.Past = past?.ToString();
-        this.Turn = turn;
-        this.Timeline = timeline;
-        this.Timelines = factory;
-    }
-
     public override string ToString() => Designation;
-
-    /// <summary>
-    /// Create a root season at the beginning of time.
-    /// </summary>
-    public static Season MakeRoot()
-    {
-        TimelineFactory factory = new TimelineFactory();
-        return new Season(
-            past: null,
-            turn: FIRST_TURN,
-            timeline: factory.NextTimeline(),
-            factory: factory);
-    }
-
-    /// <summary>
-    /// Create a season immediately after this one in the same timeline.
-    /// </summary>
-    public Season MakeNext()
-        => new(this, Turn + 1, Timeline, Timelines);
-
-    /// <summary>
-    /// Create a season immediately after this one in a new timeline.
-    /// </summary>
-    public Season MakeFork()
-        => new(this, Turn + 1, Timelines.NextTimeline(), Timelines);
 }

MultiversalDiplomacy/Model/TimelineFactory.cs

@@ -3,7 +3,7 @@ namespace MultiversalDiplomacy.Model;
 /// <summary>
 /// A shared counter for handing out new timeline designations.
 /// </summary>
-internal class TimelineFactory
+public class TimelineFactory
 {
     private static readonly char[] Letters = [
         'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',

MultiversalDiplomacy/Model/Unit.cs

@@ -1,3 +1,5 @@
+using System.Text.Json.Serialization;
+
 namespace MultiversalDiplomacy.Model;
 
 /// <summary>
@@ -18,6 +20,7 @@ public class Unit
     /// <summary>
     /// The province where the unit is.
     /// </summary>
+    [JsonIgnore]
     public Province Province => this.Location.Province;
 
     /// <summary>
@@ -59,11 +62,11 @@ public class Unit
     /// method after accepting a build order.
     /// </summary>
     public static Unit Build(Location location, Season season, Power power, UnitType type)
-        => new Unit(past: null, location, season, power, type);
+        => new(past: null, location, season, power, type);
 
     /// <summary>
     /// Advance this unit's timeline to a new location and season.
     /// </summary>
     public Unit Next(Location location, Season season)
-        => new Unit(past: this, location, season, this.Power, this.Type);
+        => new(past: this, location, season, this.Power, this.Type);
 }

MultiversalDiplomacy/Model/World.cs

@@ -1,6 +1,5 @@
 using System.Collections.ObjectModel;
-
-using MultiversalDiplomacy.Orders;
+using System.Text.Json.Serialization;
 
 namespace MultiversalDiplomacy.Model;
 
@@ -12,16 +11,24 @@ public class World
     /// <summary>
     /// The map variant of the game.
     /// </summary>
-    public readonly Map Map;
+    [JsonIgnore]
+    public Map Map { get; }
+
+    /// <summary>
+    /// The map variant of the game.
+    /// </summary>
+    public MapType MapType => this.Map.Type;
 
     /// <summary>
     /// The game map.
     /// </summary>
+    [JsonIgnore]
     public ReadOnlyCollection<Province> Provinces => this.Map.Provinces;
 
     /// <summary>
     /// The game powers.
     /// </summary>
+    [JsonIgnore]
     public ReadOnlyCollection<Power> Powers => this.Map.Powers;
 
     /// <summary>
@@ -32,11 +39,13 @@ public class World
     /// <summary>
     /// Lookup for seasons by designation.
     /// </summary>
+    [JsonIgnore]
     public ReadOnlyDictionary<string, Season> SeasonLookup { get; }
 
     /// <summary>
     /// The first season of the game.
     /// </summary>
+    [JsonIgnore]
     public Season RootSeason => GetSeason("a0");
 
     /// <summary>
@@ -52,7 +61,12 @@ public class World
     /// <summary>
     /// Orders given to units in each season.
     /// </summary>
-    public ReadOnlyDictionary<Season, OrderHistory> OrderHistory { get; }
+    public ReadOnlyDictionary<string, OrderHistory> OrderHistory { get; }
+
+    /// <summary>
+    /// The shared timeline number generator.
+    /// </summary>
+    public TimelineFactory Timelines { get; }
 
     /// <summary>
     /// Immutable game options.
@@ -67,7 +81,8 @@ public class World
         ReadOnlyCollection<Season> seasons,
         ReadOnlyCollection<Unit> units,
         ReadOnlyCollection<RetreatingUnit> retreatingUnits,
-        ReadOnlyDictionary<Season, OrderHistory> orderHistory,
+        ReadOnlyDictionary<string, OrderHistory> orderHistory,
+        TimelineFactory timelines,
         Options options)
     {
         this.Map = map;
@@ -75,6 +90,7 @@ public class World
         this.Units = units;
         this.RetreatingUnits = retreatingUnits;
         this.OrderHistory = orderHistory;
+        this.Timelines = timelines;
         this.Options = options;
 
         this.SeasonLookup = new(Seasons.ToDictionary(season => $"{season.Timeline}{season.Turn}"));
@@ -88,7 +104,7 @@ public class World
         ReadOnlyCollection<Season>? seasons = null,
         ReadOnlyCollection<Unit>? units = null,
         ReadOnlyCollection<RetreatingUnit>? retreatingUnits = null,
-        ReadOnlyDictionary<Season, OrderHistory>? orderHistory = null,
+        ReadOnlyDictionary<string, OrderHistory>? orderHistory = null,
         Options? options = null)
         : this(
             previous.Map,
@@ -96,6 +112,7 @@ public class World
             units ?? previous.Units,
             retreatingUnits ?? previous.RetreatingUnits,
             orderHistory ?? previous.OrderHistory,
+            previous.Timelines,
             options ?? previous.Options)
     {
     }
@@ -105,12 +122,14 @@ public class World
     /// </summary>
     public static World WithMap(Map map)
     {
+        TimelineFactory timelines = new();
         return new World(
             map,
-            new([Season.MakeRoot()]),
+            new([new(past: null, Season.FIRST_TURN, timelines.NextTimeline())]),
             new([]),
             new([]),
-            new(new Dictionary<Season, OrderHistory>()),
+            new(new Dictionary<string, OrderHistory>()),
+            timelines,
             new Options());
     }
 
@@ -124,7 +143,7 @@ public class World
         IEnumerable<Season>? seasons = null,
         IEnumerable<Unit>? units = null,
         IEnumerable<RetreatingUnit>? retreats = null,
-        IEnumerable<KeyValuePair<Season, OrderHistory>>? orders = null)
+        IEnumerable<KeyValuePair<string, OrderHistory>>? orders = null)
         => new(
             previous: this,
             seasons: seasons == null
@@ -200,28 +219,17 @@ public class World
     }
 
     /// <summary>
-    /// Create a season immediately after this one in the same timeline.
+    /// Create a continuation of this season if it has no futures, otherwise ceate a fork.
     /// </summary>
-    public World ContinueSeason(string season)
-        => Update(seasons: Seasons.Append(SeasonLookup[season].MakeNext()));
-
-    /// <summary>
-    /// Create a season immediately after this one in the same timeline.
-    /// </summary>
-    public World ContinueSeason(Season season) => ContinueSeason(season.ToString());
-
-    /// <summary>
-    /// Create a season immediately after this one in a new timeline.
-    /// </summary>
-    public World ForkSeason(string season)
-        => Update(seasons: Seasons.Append(SeasonLookup[season].MakeFork()));
+    public Season ContinueOrFork(Season season)
+        => GetFutures(season).Any()
+        ? new(season.Designation, season.Turn + 1, Timelines.NextTimeline())
+        : new(season.Designation, season.Turn + 1, season.Timeline);
 
     /// <summary>
     /// A standard Diplomacy game setup.
     /// </summary>
-    public static World Standard => World
-        .WithStandardMap()
-        .AddStandardUnits();
+    public static World Standard => WithStandardMap().AddStandardUnits();
 
     /// <summary>
     /// Get a season by coordinate. Throws if the season is not found.
@@ -288,11 +296,10 @@ public class World
     /// <summary>
     /// Returns a unit in a province. Throws if there are duplicate units.
     /// </summary>
-    public Unit GetUnitAt(string provinceName, (string timeline, int turn)? seasonCoord = null)
+    public Unit GetUnitAt(string provinceName, Season? season = null)
     {
         Province province = Map.GetProvince(provinceName);
-        seasonCoord ??= (this.RootSeason.Timeline, this.RootSeason.Turn);
-        Season season = GetSeason(seasonCoord.Value.timeline, seasonCoord.Value.turn);
+        season ??= RootSeason;
         Unit? foundUnit = this.Units.SingleOrDefault(
             u => u!.Province == province && u.Season == season,
             null)

MultiversalDiplomacy/Program.cs

@@ -9,9 +9,15 @@ internal class Program
     static void Main(string[] args)
     {
         var parser = Parser.Default;
-        var parseResult = parser.ParseArguments<AdjudicateOptions>(args);
+        var parseResult = parser.ParseArguments(
+            args,
+            typeof(AdjudicateOptions),
+            typeof(ImageOptions),
+            typeof(ReplOptions));
 
         parseResult
-            .WithParsed(AdjudicateOptions.Execute);
+            .WithParsed<AdjudicateOptions>(AdjudicateOptions.Execute)
+            .WithParsed<ImageOptions>(ImageOptions.Execute)
+            .WithParsed<ReplOptions>(ReplOptions.Execute);
     }
 }

MultiversalDiplomacyTests/MDATC_A.cs

@@ -43,14 +43,14 @@ public class TimeTravelTest
 
         // Confirm that there is a unit in Tyr b1 originating from Mun a1
         Season fork = world.GetSeason("b1");
-        Unit originalUnit = world.GetUnitAt("Mun", s0.Coord);
-        Unit aMun0 = world.GetUnitAt("Mun", s1.Coord);
-        Unit aTyr = world.GetUnitAt("Tyr", fork.Coord);
+        Unit originalUnit = world.GetUnitAt("Mun", s0);
+        Unit aMun0 = world.GetUnitAt("Mun", s1);
+        Unit aTyr = world.GetUnitAt("Tyr", fork);
         Assert.That(aTyr.Past, Is.EqualTo(mun1.Order.Unit));
         Assert.That(aTyr.Past?.Past, Is.EqualTo(mun0.Order.Unit));
 
         // Confirm that there is a unit in Mun b1 originating from Mun a0
-        Unit aMun1 = world.GetUnitAt("Mun", fork.Coord);
+        Unit aMun1 = world.GetUnitAt("Mun", fork);
         Assert.That(aMun1.Past, Is.EqualTo(originalUnit));
     }
 
@@ -92,7 +92,7 @@ public class TimeTravelTest
         // Confirm that an alternate future is created.
         World world = setup.UpdateWorld();
         Season fork = world.GetSeason("b1");
-        Unit tyr1 = world.GetUnitAt("Tyr", fork.Coord);
+        Unit tyr1 = world.GetUnitAt("Tyr", fork);
         Assert.That(
             tyr1.Past,
             Is.EqualTo(mun0.Order.Unit),

MultiversalDiplomacyTests/MovementAdjudicatorTest.cs

@@ -206,7 +206,7 @@ public class MovementAdjudicatorTest
         Assert.That(s2.Turn, Is.EqualTo(s1.Turn + 1));
 
         // Confirm the unit was created in the future
-        Unit u2 = updated.GetUnitAt("Mun", s2.Coord);
+        Unit u2 = updated.GetUnitAt("Mun", s2);
         Assert.That(updated.Units.Count, Is.EqualTo(2));
         Assert.That(u2, Is.Not.EqualTo(mun1.Order.Unit));
         Assert.That(u2.Past, Is.EqualTo(mun1.Order.Unit));
@@ -228,7 +228,7 @@ public class MovementAdjudicatorTest
         // Update the world again
         updated = setup.UpdateWorld();
         Season s3 = updated.GetSeason(s2.Timeline, s2.Turn + 1);
-        Unit u3 = updated.GetUnitAt("Mun", s3.Coord);
+        Unit u3 = updated.GetUnitAt("Mun", s3);
         Assert.That(u3.Past, Is.EqualTo(mun2.Order.Unit));
     }
 
@@ -256,7 +256,7 @@ public class MovementAdjudicatorTest
         Assert.That(s2.Turn, Is.EqualTo(s1.Turn + 1));
 
         // Confirm the unit was created in the future
-        Unit u2 = updated.GetUnitAt("Tyr", s2.Coord);
+        Unit u2 = updated.GetUnitAt("Tyr", s2);
         Assert.That(updated.Units.Count, Is.EqualTo(2));
         Assert.That(u2, Is.Not.EqualTo(mun1.Order.Unit));
         Assert.That(u2.Past, Is.EqualTo(mun1.Order.Unit));
@@ -278,7 +278,7 @@ public class MovementAdjudicatorTest
         // Update the world again
         updated = setup.UpdateWorld();
         Season s3 = updated.GetSeason(s2.Timeline, s2.Turn + 1);
-        Unit u3 = updated.GetUnitAt("Mun", s3.Coord);
+        Unit u3 = updated.GetUnitAt("Mun", s3);
         Assert.That(u3.Past, Is.EqualTo(u2));
     }
 }

MultiversalDiplomacyTests/SeasonTests.cs

@@ -9,30 +9,22 @@ public class SeasonTests
     [Test]
     public void TimelineForking()
     {
-        World world = World
-            .WithMap(Map.Test)
-            .ContinueSeason("a0")
-            .ContinueSeason("a1")
-            .ContinueSeason("a2")
-            .ForkSeason("a1")
-            .ContinueSeason("b2")
-            .ForkSeason("a1")
-            .ForkSeason("a2");
+        World world = World.WithMap(Map.Test);
+        Season a0 = world.GetSeason("a0");
+        world = world
+            .ContinueOrFork(a0, out Season a1)
+            .ContinueOrFork(a1, out Season a2)
+            .ContinueOrFork(a2, out Season a3)
+            .ContinueOrFork(a1, out Season b2)
+            .ContinueOrFork(b2, out Season b3)
+            .ContinueOrFork(a1, out Season c2)
+            .ContinueOrFork(a2, out Season d3);
 
         Assert.That(
             world.Seasons.Select(season => season.ToString()),
             Is.EquivalentTo(new List<string> { "a0", "a1", "a2", "a3", "b2", "b3", "c2", "d3" }),
             "Unexpected seasons");
 
-        Season a0 = world.GetSeason("a0");
-        Season a1 = world.GetSeason("a1");
-        Season a2 = world.GetSeason("a2");
-        Season a3 = world.GetSeason("a3");
-        Season b2 = world.GetSeason("b2");
-        Season b3 = world.GetSeason("b3");
-        Season c2 = world.GetSeason("c2");
-        Season d3 = world.GetSeason("d3");
-
         Assert.That(a0.Timeline, Is.EqualTo("a"), "Unexpected trunk timeline");
         Assert.That(a1.Timeline, Is.EqualTo("a"), "Unexpected trunk timeline");
         Assert.That(a2.Timeline, Is.EqualTo("a"), "Unexpected trunk timeline");

MultiversalDiplomacyTests/SerializationTest.cs

@@ -0,0 +1,98 @@
+using System.Text.Json;
+
+using MultiversalDiplomacy.Adjudicate;
+using MultiversalDiplomacy.Model;
+
+using NUnit.Framework;
+
+namespace MultiversalDiplomacyTests;
+
+public class SerializationTest
+{
+    [Test]
+    public void SerializeRoundTrip_NewGame()
+    {
+        JsonSerializerOptions options = new() {
+            WriteIndented = true,
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        };
+
+        World world = World.WithStandardMap();
+        string serialized = JsonSerializer.Serialize(world, options);
+        Console.WriteLine(serialized);
+        World? deserialized = JsonSerializer.Deserialize<World>(serialized, options);
+        Assert.That(deserialized, Is.Not.Null, "Failed to deserialize");
+    }
+
+    [Test]
+    public void SerializeRoundTrip_MDATC_3_A_2()
+    {
+        // Set up MDATC 3.A.2
+        TestCaseBuilder setup = new(World.WithStandardMap(), MovementPhaseAdjudicator.Instance);
+        setup[("a", 0)]
+            .GetReference(out Season s0)
+            ["Germany"]
+                .Army("Mun").MovesTo("Tyr").GetReference(out var mun0)
+            ["Austria"]
+                .Army("Tyr").Holds().GetReference(out var tyr0);
+
+        setup.ValidateOrders();
+        Assert.That(mun0, Is.Valid);
+        Assert.That(tyr0, Is.Valid);
+        setup.AdjudicateOrders();
+        Assert.That(mun0, Is.Repelled);
+        Assert.That(tyr0, Is.NotDislodged);
+        setup.UpdateWorld();
+
+        // Serialize the world
+        JsonSerializerOptions options = new() {
+            WriteIndented = true,
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        };
+        JsonElement serialized = JsonSerializer.SerializeToDocument(setup.World, options).RootElement;
+
+        Assert.That(
+            serialized.EnumerateObject().Select(prop => prop.Name),
+            Is.EquivalentTo(new List<string> {
+                "mapType",
+                "seasons",
+                "units",
+                "retreatingUnits",
+                "orderHistory",
+                "options",
+            }));
+
+        // Deserialize the world
+        World reserialized = JsonSerializer.Deserialize<World>(serialized)
+            ?? throw new AssertionException("Failed to reserialize world");
+
+        // Resume the test case
+        setup = new(reserialized, MovementPhaseAdjudicator.Instance);
+        setup[("a", 1)]
+            ["Germany"]
+                .Army("Mun").Supports.Army("Mun", season: reserialized.GetSeason("a0")).MoveTo("Tyr").GetReference(out var mun1)
+            ["Austria"]
+                .Army("Tyr").Holds();
+
+        setup.ValidateOrders();
+        Assert.That(mun1, Is.Valid);
+        setup.AdjudicateOrders();
+        Assert.That(mun1, Is.NotCut);
+        Assert.That(mun0, Is.Victorious);
+        Assert.That(tyr0, Is.Dislodged);
+
+        // Confirm that an alternate future is created.
+        World world = setup.UpdateWorld();
+        Season fork = world.GetSeason("b1");
+        Unit tyr1 = world.GetUnitAt("Tyr", fork);
+        Assert.That(
+            tyr1.Past,
+            Is.EqualTo(mun0.Order.Unit),
+            "Expected A Mun a0 to advance to Tyr b1");
+        Assert.That(
+            world.RetreatingUnits.Count,
+            Is.EqualTo(1),
+            "Expected A Tyr a0 to be in retreat");
+        Assert.That(world.RetreatingUnits.First().Unit, Is.EqualTo(tyr0.Order.Unit));
+    }
+}

MultiversalDiplomacyTests/UnitTests.cs

@@ -17,12 +17,10 @@ public class UnitTests
         Season a0 = world.RootSeason;
         Unit u1 = Unit.Build(Mun, a0, pw1, UnitType.Army);
 
-        world = world.ContinueSeason(a0);
-        Season a1 = world.GetSeason("a1");
+        world = world.ContinueOrFork(a0, out Season a1);
         Unit u2 = u1.Next(Boh, a1);
 
-        world = world.ContinueSeason(a1);
-        Season a2 = world.GetSeason("a2");
+        _ = world.ContinueOrFork(a1, out Season a2);
         Unit u3 = u2.Next(Tyr, a2);
 
         Assert.That(u3.Past, Is.EqualTo(u2), "Missing unit past");