using System.Collections.Generic;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// D8 (2026-06-24): verify that <see cref="PhysicsDataCache.RemoveCellsForLandblock"/>
/// evicts every cached cell belonging to the given landblock prefix and leaves
/// cells belonging to other landblocks untouched — symmetric with
/// <see cref="PhysicsDataCache.RemoveBuildingsForLandblock"/> (#146).
/// </summary>
public class RemoveCellsForLandblockTests
{
    /// <summary>
    /// Build the absolute minimum <see cref="CellPhysics"/> that satisfies the
    /// <c>required</c> init property. BSP is left null because the test exercises
    /// only the cache-eviction key logic, not BSP traversal.
    /// </summary>
    private static CellPhysics BuildMinimalCell() => new()
    {
        Resolved = new Dictionary<ushort, ResolvedPolygon>(),
    };

    [Fact]
    public void RemoveCellsForLandblock_EvictsOnlyMatchingPrefix()
    {
        var cache = new PhysicsDataCache();

        // Two cells from landblock 0xAAAA0000 and one from 0xBBBB0000.
        cache.RegisterCellStructForTest(0xAAAA0100u, BuildMinimalCell());
        cache.RegisterCellStructForTest(0xAAAA0200u, BuildMinimalCell());
        cache.RegisterCellStructForTest(0xBBBB0100u, BuildMinimalCell());

        cache.RemoveCellsForLandblock(0xAAAA0000u);

        // Both AAAA cells must be gone.
        Assert.Null(cache.GetCellStruct(0xAAAA0100u));
        Assert.Null(cache.GetCellStruct(0xAAAA0200u));

        // The BBBB cell must survive.
        Assert.NotNull(cache.GetCellStruct(0xBBBB0100u));
    }

    [Fact]
    public void RemoveCellsForLandblock_EmptyCache_DoesNotThrow()
    {
        // Must be a no-op on an empty cache.
        var cache = new PhysicsDataCache();
        cache.RemoveCellsForLandblock(0xAAAA0000u);
        Assert.Equal(0, cache.CellStructCount);
    }

    [Fact]
    public void RemoveCellsForLandblock_NoMatchingCells_LeavesOthersIntact()
    {
        var cache = new PhysicsDataCache();
        cache.RegisterCellStructForTest(0xBBBB0100u, BuildMinimalCell());

        // Evicting a prefix that has no cached entries should not disturb others.
        cache.RemoveCellsForLandblock(0xAAAA0000u);

        Assert.NotNull(cache.GetCellStruct(0xBBBB0100u));
        Assert.Equal(1, cache.CellStructCount);
    }
}