Implement climate and weather features in world simulation; enhance API with weather retrieval and climate selection options, update UI to support climate selection during world creation, and improve weather display in the game interface.

tests/TheLivingWorld.Tests/WorldSimulationTests.cs

@@ -100,13 +100,113 @@ public sealed class WorldSimulationTests
     }
 
     [Fact]
-    public void OverlayForApi_strips_last_ticked_at()
+    public void OverlayForApi_strips_storage_only_state_and_adds_live_weather()
     {
         using var simulation = WorldSimulation.Create(ReadySummary(), catchUp: false);
         var overlaid = simulation.OverlayForApi(ReadySummary());
 
         Assert.NotNull(overlaid.Clock);
         Assert.Null(overlaid.LastTickedAt);
+        Assert.Null(overlaid.WeatherState);
+
+        Assert.Equal(ClimateKind.CentralEuropean, overlaid.Climate);
+        Assert.NotNull(overlaid.Weather);
+        Assert.InRange(overlaid.Weather.Humidity, 0, 1);
+        Assert.InRange(overlaid.Weather.CloudCover, 0, 1);
+        Assert.InRange(overlaid.Weather.WindDirectionDeg, 0, 360);
+    }
+
+    [Fact]
+    public void Climate_defaults_to_the_latitude_when_the_world_never_picked_one()
+    {
+        var summary = ReadySummary() with { Latitude = 78.22, Climate = null };
+        using var simulation = WorldSimulation.Create(summary, catchUp: false);
+
+        Assert.Equal(ClimateKind.Tundra, simulation.Climate);
+    }
+
+    [Fact]
+    public void ApplyTo_persists_the_climate_and_the_drifting_pressure_systems()
+    {
+        using var simulation = WorldSimulation.Create(ReadySummary(), catchUp: false);
+        simulation.Tick(TimeSpan.FromSeconds(30));
+
+        var stored = simulation.ApplyTo(ReadySummary());
+
+        Assert.Equal(ClimateKind.CentralEuropean, stored.Climate);
+        Assert.NotNull(stored.WeatherState);
+        Assert.NotEmpty(stored.WeatherState.Systems);
+        Assert.NotEqual(0ul, stored.WeatherState.RngState);
+        // Weather itself is derived, so it has no business in the file.
+        Assert.Null(stored.Weather);
+    }
+
+    [Fact]
+    public void A_restart_resumes_the_sky_it_had_rather_than_rolling_a_new_one()
+    {
+        using var before = WorldSimulation.Create(ReadySummary(), catchUp: false);
+        before.Tick(TimeSpan.FromSeconds(45));
+
+        var persisted = before.ApplyTo(ReadySummary());
+        var weatherBefore = before.SnapshotWeather();
+
+        using var after = WorldSimulation.Create(persisted with { LastTickedAt = null }, catchUp: false);
+        var weatherAfter = after.SnapshotWeather();
+
+        Assert.Equal(weatherBefore.PressureHpa, weatherAfter.PressureHpa, 1);
+        Assert.Equal(weatherBefore.Condition, weatherAfter.Condition);
+    }
+
+    [Fact]
+    public void A_long_absence_rolls_a_fresh_sky_instead_of_stepping_through_it()
+    {
+        // Six real hours is roughly two and a half game months - the systems that were drifting are long gone.
+        var summary = ReadySummary() with { LastTickedAt = DateTimeOffset.UtcNow - TimeSpan.FromHours(6) };
+
+        using var simulation = WorldSimulation.Create(summary, catchUp: true);
+        var stored = simulation.ApplyTo(summary);
+
+        Assert.NotNull(stored.WeatherState);
+        Assert.Equal(ClimateCatalog.CentralEuropean.Storminess, stored.WeatherState.Systems.Count);
+
+        // A reseeded pool is caught mid-life over the map, not parked at age zero off the edge.
+        Assert.Contains(stored.WeatherState.Systems, static system => system.AgeHours > 0f);
+    }
+
+    [Fact]
+    public void The_weather_field_covers_the_whole_map_and_varies_across_it()
+    {
+        using var simulation = WorldSimulation.Create(ReadySummary(), catchUp: false);
+
+        var field = simulation.SnapshotWeatherField();
+
+        Assert.Equal(ClimateKind.CentralEuropean, field.Climate);
+        Assert.Equal(WorldSimulation.WeatherGridSize, field.Size);
+        Assert.Equal(field.Size * field.Size, field.Nodes.Count);
+
+        // A drifting pressure system means the corners cannot all read the same pressure.
+        var pressures = field.Nodes.Select(static node => node.PressureHpa).Distinct().Count();
+        Assert.True(pressures > 1, "The field is uniform - the pressure systems are not being sampled.");
+    }
+
+    [Fact]
+    public void Neighbouring_field_nodes_stay_close_together()
+    {
+        using var simulation = WorldSimulation.Create(ReadySummary(), catchUp: false);
+        var field = simulation.SnapshotWeatherField();
+
+        // Gaussian bumps are smooth, so a coarse grid is safe to interpolate between on the client.
+        for (var row = 0; row < field.Size; row++)
+        {
+            for (var column = 1; column < field.Size; column++)
+            {
+                var left = field.Nodes[(row * field.Size) + column - 1];
+                var right = field.Nodes[(row * field.Size) + column];
+                Assert.True(
+                    Math.Abs(left.TemperatureC - right.TemperatureC) < 6,
+                    $"Nodes {column - 1} and {column} of row {row} jump by more than six degrees.");
+            }
+        }
     }
 
     private static WorldSummaryDto ReadySummary() => new()
@@ -119,6 +219,7 @@ public sealed class WorldSimulationTests
         Status = WorldStatus.Ready,
         CreatedAt = DateTimeOffset.UtcNow,
         Clock = WorldSimulation.DefaultClock(),
+        Climate = ClimateKind.CentralEuropean,
         LastTickedAt = DateTimeOffset.UtcNow,
     };
 }