using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;
using AcDream.Core.Physics;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Options;
using Xunit;
using Env = System.Environment;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// Tests for <see cref="CellTransit"/> portal-graph expansion.
///
/// <para>
/// History: A6.P5 (2026-05-25) widened the collision cell set on exit-
/// portal TOPOLOGY (outdoor cells added whenever an overlapped cell had a
/// 0xFFFF portal) so outdoor-registered doors stayed findable from indoor
/// cells under the flat registry query. BR-7 / A6.P4 C4 (2026-06-11)
/// removed the widening: outdoor cells enter the array only on the retail
/// STRADDLE gate (|dist| &lt; radius + F_EPSILON vs the exterior portal
/// plane — CEnvCell::find_transit_cells, Ghidra 0x0052c820, live-binary
/// verified), and doors are found per-cell via registration-time
/// membership instead. These tests pin BOTH halves of the retail
/// semantics on real Holtburg dat geometry.
/// </para>
/// </summary>
public class CellTransitTests
{
    [Fact]
    public void DeepInteriorSphere_NoStraddle_AddsNoOutdoorCells()
    {
        var datDir = ResolveDatDir();
        if (datDir is null) return;

        // Hydrate the cells in the portal chain.
        //   0xA9B4013F — deep interior cell (the old over-penetration tick)
        //   0xA9B40150 — alcove cell adjacent to the doorway (exit portal)
        var cache = new PhysicsDataCache();
        HydrateCell(cache, datDir, 0xA9B4013Fu);
        HydrateCell(cache, datDir, 0xA9B40150u);

        Assert.NotNull(cache.GetCellStruct(0xA9B4013Fu));
        Assert.NotNull(cache.GetCellStruct(0xA9B40150u));

        // Sphere deep in 0x13F's volume — no path sphere straddles
        // 0x150's exit portal plane from here (the A6.P5 pin's own
        // message documented exactly that). Retail adds NO outdoor cells
        // in this state; the door (outdoor 0xA9B40029) is reached only
        // when the sphere actually straddles the threshold — pinned by
        // the alcove test below and the tick-13558 door pin.
        var sphereWorld = new Vector3(132.5935f, 16.350428f, 94.48f);
        const float sphereRadius = 0.48f;
        const uint startCellId = 0xA9B4013Fu;

        _ = CellTransit.FindCellSet(
            cache,
            sphereWorld,
            sphereRadius,
            startCellId,
            out var cellSet);

        Assert.DoesNotContain(cellSet, c => (c & 0xFFFFu) < 0x0100u);
        Assert.Contains(startCellId, cellSet);
    }

    [Fact]
    public void AlcoveSphere_StraddlesExitPortal_ReachesDoorOutdoorCell()
    {
        var datDir = ResolveDatDir();
        if (datDir is null) return;

        // The alcove cell 0xA9B40150 IS the cell with the exit portal, and
        // at this captured position the foot sphere straddles its plane
        // (|dist| < 0.48 + ε — same geometry the tick-13558 straddle pin
        // proves). Retail admits the outdoor cells exactly here, which is
        // how the indoor-side sphere reaches the outdoor-registered door's
        // per-cell shadow list.
        var cache = new PhysicsDataCache();
        HydrateCell(cache, datDir, 0xA9B40150u);

        var sphereWorld = new Vector3(132.4014f, 16.761757f, 94.48f);
        const float sphereRadius = 0.48f;

        _ = CellTransit.FindCellSet(
            cache,
            sphereWorld,
            sphereRadius,
            0xA9B40150u,
            out var cellSet);

        Assert.True(
            cellSet.Contains(0xA9B40029u),
            $"Straddle-gated outside-add: the alcove sphere straddles " +
            $"0xA9B40150's exit portal, so the door's outdoor cell " +
            $"0xA9B40029 must enter the set (retail " +
            $"CEnvCell::find_transit_cells straddle, Ghidra 0x0052c820). " +
            $"Actual: {string.Join(",", cellSet.Select(c => $"0x{c:X8}"))}");
    }

    // -------------------------------------------------------------------------
    // Helpers
    // -------------------------------------------------------------------------

    private static string? ResolveDatDir()
    {
        var datDir = Env.GetEnvironmentVariable("ACDREAM_DAT_DIR")
            ?? Path.Combine(Env.GetFolderPath(Env.SpecialFolder.UserProfile),
                            "Documents", "Asheron's Call");
        return Directory.Exists(datDir) ? datDir : null;
    }

    private static void HydrateCell(PhysicsDataCache cache, string datDir, uint cellId)
    {
        const uint EnvCellPrefix = 0x0D000000u;
        using var dats = new DatCollection(datDir, DatAccessType.Read);

        var envCell = dats.Get<EnvCell>(cellId);
        if (envCell is null)
            throw new InvalidOperationException(
                $"Cell 0x{cellId:X8} missing from dat at {datDir}.");

        var environment = dats.Get<DatReaderWriter.DBObjs.Environment>(
            EnvCellPrefix | envCell.EnvironmentId);
        if (environment is null)
            throw new InvalidOperationException(
                $"Environment 0x{EnvCellPrefix | envCell.EnvironmentId:X8} missing.");

        if (!environment.Cells.TryGetValue(envCell.CellStructure, out var cellStruct))
            throw new InvalidOperationException(
                $"CellStructure {envCell.CellStructure} missing in environment.");

        var worldTransform =
            Matrix4x4.CreateFromQuaternion(envCell.Position.Orientation) *
            Matrix4x4.CreateTranslation(envCell.Position.Origin);

        cache.CacheCellStruct(cellId, envCell, cellStruct, worldTransform);
    }
}