feat(bake): extract each EnvCell geometry once

tests/AcDream.Bake.Tests/EnvCellBakeCatalogTests.cs

@@ -0,0 +1,85 @@
+namespace AcDream.Bake.Tests;
+
+public sealed class EnvCellBakeCatalogTests
+{
+    [Fact]
+    public void Build_GroupsEqualGeometryAndPreservesEverySortedFileId()
+    {
+        var catalog = EnvCellBakeCatalog.Build(
+        [
+            new(0x2222_0102, 7, 3, new ushort[] { 10, 20 }),
+            new(0x1111_0100, 7, 3, new ushort[] { 10, 20 }),
+            new(0x1111_0101, 7, 4, new ushort[] { 10, 20 }),
+            new(0x2222_0100, 7, 3, new ushort[] { 10, 20 }),
+        ]);
+
+        Assert.Equal(4, catalog.CellCount);
+        Assert.Equal(2, catalog.UniqueGeometryCount);
+        Assert.Equal(2, catalog.AliasCount);
+        Assert.Equal(
+            new uint[] { 0x1111_0100, 0x2222_0100, 0x2222_0102 },
+            catalog.Groups[0].FileIds);
+        Assert.Equal(new uint[] { 0x1111_0101 }, catalog.Groups[1].FileIds);
+    }
+
+    [Fact]
+    public void Build_IsDeterministicAcrossSourceOrder()
+    {
+        EnvCellBakeSource[] sources =
+        [
+            new(4, 9, 2, new ushort[] { 5, 6 }),
+            new(2, 9, 2, new ushort[] { 5, 6 }),
+            new(3, 1, 8, new ushort[] { 7 }),
+        ];
+
+        var forward = EnvCellBakeCatalog.Build(sources);
+        var reverse = EnvCellBakeCatalog.Build(sources.Reverse());
+
+        Assert.Equal(forward.Groups, reverse.Groups, GroupComparer.Instance);
+    }
+
+    [Fact]
+    public void Build_RejectsIdentityCollisionWithDifferentTuple()
+    {
+        EnvCellBakeSource[] sources =
+        [
+            new(1, 10, 20, new ushort[] { 30 }),
+            new(2, 11, 20, new ushort[] { 30 }),
+        ];
+
+        var exception = Assert.Throws<InvalidDataException>(
+            () => EnvCellBakeCatalog.Build(sources, (_, _, _) => 0x2_0000_0000));
+
+        Assert.Contains("collision", exception.Message);
+        Assert.Contains("0x00000001", exception.Message);
+        Assert.Contains("0x00000002", exception.Message);
+    }
+
+    [Fact]
+    public void Build_RejectsDuplicateFileId()
+    {
+        EnvCellBakeSource[] sources =
+        [
+            new(1, 10, 20, Array.Empty<ushort>()),
+            new(1, 10, 20, Array.Empty<ushort>()),
+        ];
+
+        Assert.Throws<InvalidDataException>(() => EnvCellBakeCatalog.Build(sources));
+    }
+
+    private sealed class GroupComparer : IEqualityComparer<EnvCellGeometryGroup>
+    {
+        public static GroupComparer Instance { get; } = new();
+
+        public bool Equals(EnvCellGeometryGroup? x, EnvCellGeometryGroup? y) =>
+            x is not null &&
+            y is not null &&
+            x.GeometryId == y.GeometryId &&
+            x.EnvironmentId == y.EnvironmentId &&
+            x.CellStructure == y.CellStructure &&
+            x.Surfaces.AsSpan().SequenceEqual(y.Surfaces) &&
+            x.FileIds.AsSpan().SequenceEqual(y.FileIds);
+
+        public int GetHashCode(EnvCellGeometryGroup obj) => obj.GeometryId.GetHashCode();
+    }
+}