using AcDream.Core.Physics;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Options;

namespace AcDream.Content.Tests;

/// <summary>
/// AP-22 reachability proof. The deleted Setup-radius collision fallback fired
/// only for a Setup with no CylSphere, no Sphere, and a nonzero summary
/// Radius. This sweeps every Setup in the installed client_portal.dat and
/// asserts no such Setup exists, so the deletion cannot remove collision from
/// any real object.
/// </summary>
public sealed class InstalledSetupCollisionReachabilityTests
{
    // Positive controls. These are EXTERNAL constants, measured on 2026-08-06
    // by an independent raw client_portal.dat parse (B-tree directory walk +
    // Setup record decode) that validated itself by byte accounting: all
    // 5,935 records consumed with an exact residual tail of
    // 20 + 48 * numLights and zero unexplained bytes.
    //
    // They are deliberately NOT derived from FlatCollisionAssetBuilder. A
    // broken enumeration, a wrong dat path, or a silently-empty flatten all
    // satisfy the negative claim vacuously and are caught only here.
    private const int ExpectedSetups = 5935;
    private const int ExpectedWithCylinder = 678;
    private const int ExpectedSphereOnlyNoCylinder = 3605;
    private const int ExpectedWithoutAnyPrimitive = 1652;
    private const int ExpectedWithSummaryRadius = 4282;

    [Fact]
    public void InstalledSetups_NeverReachTheDeletedRadiusFallback()
    {
        string? datDir = ContentConformanceDats.ResolveDatDir();
        if (datDir is null)
            return;

        using var dats = new DatCollection(datDir, DatAccessType.Read);

        int total = 0;
        int withCylinder = 0;
        int sphereOnly = 0;
        int withoutPrimitive = 0;
        int withRadius = 0;
        var fallbackReachable = new List<uint>();
        var fallbackReachableWideGuard = new List<uint>();

        foreach (uint id in dats.GetAllIdsOfType<Setup>())
        {
            if (!dats.Portal.TryGet<Setup>(id, out Setup? setup)
                || setup is null)
            {
                continue;
            }

            FlatSetupCollision flat =
                FlatCollisionAssetBuilder.FlattenSetup(setup);
            total++;

            bool hasCylinder = flat.Cylinders.Length > 0;
            bool hasSphere = flat.Spheres.Length > 0;
            if (hasCylinder)
                withCylinder++;
            else if (hasSphere)
                sphereOnly++;
            else
                withoutPrimitive++;

            if (flat.Radius > 0.0001f)
                withRadius++;

            // BOTH guard variants the deleted copies used — they are not the
            // same predicate. Site 1 (LiveEntityCollisionBuilder) tested
            // `Radius > 0.0001f`; sites 2 and 3 (LandblockPhysicsPublisher,
            // LandblockPhysicsContentBuilder — the headless-reachable one)
            // tested the strictly wider `Radius > 0f`. Corrected 2026-08-06 at
            // the AP-22 architecture review, which measured that the two
            // genuinely differ over the installed DAT by exactly one Setup:
            // 0x02001657, whose radius is the denormal 1.3e-39. Asserting only
            // the narrow guard would have claimed coverage of two deletions it
            // never evaluated.
            if (!hasCylinder && !hasSphere && flat.Radius > 0.0001f)
                fallbackReachable.Add(id);
            if (!hasCylinder && !hasSphere && flat.Radius > 0f)
                fallbackReachableWideGuard.Add(id);
        }

        // (b) Positive controls first: if the enumeration is broken, fail here
        // rather than passing (a) for the wrong reason.
        Assert.Equal(ExpectedSetups, total);
        Assert.Equal(ExpectedWithCylinder, withCylinder);
        Assert.Equal(ExpectedSphereOnlyNoCylinder, sphereOnly);
        Assert.Equal(ExpectedWithoutAnyPrimitive, withoutPrimitive);
        Assert.Equal(ExpectedWithSummaryRadius, withRadius);

        // (a) The negative claim the deletion rests on.
        Assert.Empty(fallbackReachable);
        // The wider guard sites 2 and 3 actually used. Zero here is what makes
        // the headless-reachable deletion safe; the narrow guard above does
        // not evaluate it.
        Assert.Empty(fallbackReachableWideGuard);
    }
}