using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.Physics;
using DatReaderWriter.Enums;
using DatReaderWriter.Types;
using Xunit;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// Conformance tests for AP-71 (Campaign P Slice P4, 2026-07-30) — retail
/// <c>CObjCell::check_entry_restrictions</c> (named-retail pc:308873-308912,
/// 0x0052b6d0), ported as <see cref="ObjectInfo.CheckEntryRestrictions"/> and
/// wired at the head of the indoor branch of
/// <c>Transition.FindEnvCollisions</c> (<c>src/AcDream.Core/Physics/
/// TransitionTypes.cs</c>).
///
/// <para>
/// Retail gate order: NPCs/props (not a player) bypass entirely; a mover
/// whose PWD bitfield grants <c>CanBypassMoveRestrictions</c> (BF_ADMIN &amp;
/// BF_IMMUNE_CELL_RESTRICTIONS) bypasses; an ordinary cell (no
/// <c>restriction_obj</c> authored) is a no-op; otherwise retail resolves
/// the restriction weenie and asks <c>CanMoveInto</c> — acdream has no
/// owner/guest-list model for that yet, so it fails CLOSED (Collided),
/// matching retail's own fallback when the restriction object can't be
/// resolved (pc:704-716).
/// </para>
/// </summary>
public sealed class Ap71EntryRestrictionGateTests
{
    private const uint RestrictionObjGuid = 0x80001234u;

    [Fact]
    public void OrdinaryCell_NoRestrictionObj_IsNoOp_ForPlayer()
    {
        var mover = new ObjectInfo { State = ObjectInfoState.IsPlayer };

        Assert.Equal(TransitionState.OK, mover.CheckEntryRestrictions(cellRestrictionObj: 0));
    }

    [Fact]
    public void OrdinaryCell_NoRestrictionObj_IsNoOp_ForNonPlayer()
    {
        // NPCs/props aren't players; confirms the gate is a genuine no-op for
        // the overwhelmingly common (non-house) content regardless of mover kind.
        var mover = new ObjectInfo { State = ObjectInfoState.None };

        Assert.Equal(TransitionState.OK, mover.CheckEntryRestrictions(cellRestrictionObj: 0));
    }

    [Fact]
    public void RestrictedCell_NonPlayerMover_Bypasses()
    {
        // Retail's (state & 0x100) == 0 -> OK early return: NPCs/props never
        // gated by house restrictions regardless of the cell's restriction_obj.
        var mover = new ObjectInfo { State = ObjectInfoState.None };

        Assert.Equal(
            TransitionState.OK,
            mover.CheckEntryRestrictions(RestrictionObjGuid));
    }

    [Fact]
    public void RestrictedCell_PlayerMover_CannotBypass_FailsClosed()
    {
        // A restricted cell, a player mover, no CanBypassMoveRestrictions bit:
        // acdream cannot resolve CanMoveInto (no guest-list model) -> Collided,
        // matching retail's own fallback when the restriction weenie can't be
        // resolved (pc:704-716 fallthrough to COLLIDED_TS).
        var mover = new ObjectInfo { State = ObjectInfoState.IsPlayer };

        Assert.Equal(
            TransitionState.Collided,
            mover.CheckEntryRestrictions(RestrictionObjGuid));
    }

    [Fact]
    public void RestrictedCell_PlayerMover_CanBypassMoveRestrictions_PassesThrough()
    {
        // BF_ADMIN & BF_IMMUNE_CELL_RESTRICTIONS both set on the mover's own
        // PWD bitfield (via EntityCollisionFlagsExt.ToMoverState) -> OK.
        var mover = new ObjectInfo
        {
            State = ObjectInfoState.IsPlayer | ObjectInfoState.CanBypassMoveRestrictions,
        };

        Assert.Equal(
            TransitionState.OK,
            mover.CheckEntryRestrictions(RestrictionObjGuid));
    }

    // ── PWD-bitfield decode (mirrors the existing EntityCollisionFlagsTests
    // pattern for IsPK/IsPKLite/IsImpenetrable) ─────────────────────────────

    [Fact]
    public void FromPwdBitfield_OnlyAdminBit_DoesNotGrantBypass()
    {
        // BF_ADMIN alone (0x100000) is not sufficient — retail ANDs both bits.
        var flags = EntityCollisionFlagsExt.FromPwdBitfield(0x100000u);
        Assert.False(flags.HasFlag(EntityCollisionFlags.CanBypassMoveRestrictions));
    }

    [Fact]
    public void FromPwdBitfield_OnlyImmuneCellRestrictionsBit_DoesNotGrantBypass()
    {
        // BF_IMMUNE_CELL_RESTRICTIONS alone (0x400000) is not sufficient either.
        var flags = EntityCollisionFlagsExt.FromPwdBitfield(0x400000u);
        Assert.False(flags.HasFlag(EntityCollisionFlags.CanBypassMoveRestrictions));
    }

    [Fact]
    public void FromPwdBitfield_BothAdminAndImmuneCellRestrictionsBits_GrantsBypass()
    {
        uint bitfield = 0x100000u | 0x400000u;
        var flags = EntityCollisionFlagsExt.FromPwdBitfield(bitfield);
        Assert.True(flags.HasFlag(EntityCollisionFlags.CanBypassMoveRestrictions));
    }

    [Fact]
    public void ToMoverState_CanBypassMoveRestrictions_TranslatesIndependently()
    {
        Assert.Equal(
            ObjectInfoState.CanBypassMoveRestrictions,
            EntityCollisionFlags.CanBypassMoveRestrictions.ToMoverState());
    }

    [Fact]
    public void FromPwdBitfield_ThenToMoverState_EndToEnd_AdminBypassesRestriction()
    {
        // Full pipeline: a wire bitfield with BF_PLAYER | BF_ADMIN |
        // BF_IMMUNE_CELL_RESTRICTIONS decodes through FromPwdBitfield ->
        // ToMoverState -> ORs into moverFlags -> ObjectInfo.State ->
        // CheckEntryRestrictions passes through a restricted cell.
        uint bitfield = 0x8u | 0x100000u | 0x400000u;
        ObjectInfoState moverState =
            ObjectInfoState.IsPlayer | EntityCollisionFlagsExt.FromPwdBitfield(bitfield).ToMoverState();

        var mover = new ObjectInfo { State = moverState };

        Assert.Equal(
            TransitionState.OK,
            mover.CheckEntryRestrictions(RestrictionObjGuid));
    }

    // ── CellPhysics.RestrictionObj plumbing (ordinary-cell no-op proof) ────

    [Fact]
    public void CellPhysics_DefaultRestrictionObj_IsZero()
    {
        // Default-constructed CellPhysics (the shape every existing test
        // fixture builds) carries RestrictionObj == 0 — the exact "ordinary
        // cell" no-op input CheckEntryRestrictions expects. Proves the new
        // field cannot silently flip any existing fixture's behavior.
        var cellPhysics = new CellPhysics
        {
            WorldTransform = System.Numerics.Matrix4x4.Identity,
            InverseWorldTransform = System.Numerics.Matrix4x4.Identity,
            Resolved = new System.Collections.Generic.Dictionary<ushort, ResolvedPolygon>(),
        };

        Assert.Equal(0u, cellPhysics.RestrictionObj);
    }

    // ── End-to-end: the gate wired into Transition.FindEnvCollisions ──────
    // A single indoor cell with an EMPTY physics BSP (no walls of its own) —
    // the ONLY thing that can stop the sphere here is the entry-restriction
    // gate. Proves the wiring at the top of FindEnvCollisions's indoor
    // branch, not just the pure CheckEntryRestrictions logic above.

    private const uint CellId = 0xA9B40157u;

    private static CellPhysics MakeIndoorCell(uint restrictionObj) => new()
    {
        BSP = new PhysicsBSPTree
        {
            Root = new PhysicsBSPNode
            {
                Type = BSPNodeType.Leaf,
                BoundingSphere = new Sphere { Origin = Vector3.Zero, Radius = 10f },
            },
        },
        WorldTransform = Matrix4x4.Identity,
        InverseWorldTransform = Matrix4x4.Identity,
        Resolved = new Dictionary<ushort, ResolvedPolygon>(),
        CellBSP = new CellBSPTree { Root = new CellBSPNode { Type = BSPNodeType.Leaf } },
        RestrictionObj = restrictionObj,
    };

    private static PhysicsEngine MakeEngine(CellPhysics cellPhysics)
    {
        var engine = new PhysicsEngine();
        engine.DataCache = new PhysicsDataCache();
        engine.DataCache.RegisterCellStructForTest(CellId, cellPhysics);
        return engine;
    }

    [Fact]
    public void EndToEnd_RestrictedCell_PlayerCannotBypass_TransitionHaltsAtOrigin()
    {
        var engine = MakeEngine(MakeIndoorCell(restrictionObj: 0xABCDu));

        var from = new Vector3(0.1f, 0f, 0.2f);
        var to = new Vector3(0.7f, 0f, 0.2f);
        var t = BSPStepUpFixtures.MakeGroundedTransition(from, to, cellId: CellId);
        t.ObjectInfo.State |= ObjectInfoState.IsPlayer;

        t.FindTransitionalPosition(engine);

        Assert.True(
            System.MathF.Abs(t.SpherePath.CurPos.X - from.X) < 1e-4f,
            $"Restricted cell must halt the player at the origin; CurPos.X={t.SpherePath.CurPos.X:F4}");
    }

    [Fact]
    public void EndToEnd_RestrictedCell_PlayerCanBypass_TransitionReachesTarget()
    {
        var engine = MakeEngine(MakeIndoorCell(restrictionObj: 0xABCDu));

        var from = new Vector3(0.1f, 0f, 0.2f);
        var to = new Vector3(0.7f, 0f, 0.2f);
        var t = BSPStepUpFixtures.MakeGroundedTransition(from, to, cellId: CellId);
        t.ObjectInfo.State |= ObjectInfoState.IsPlayer | ObjectInfoState.CanBypassMoveRestrictions;

        t.FindTransitionalPosition(engine);

        Assert.True(
            System.MathF.Abs(t.SpherePath.CurPos.X - to.X) < 1e-4f,
            $"An admin/bypass-flagged player must pass through unimpeded; CurPos.X={t.SpherePath.CurPos.X:F4}");
    }

    [Fact]
    public void EndToEnd_OrdinaryCell_NoRestrictionObj_PlayerUnaffected()
    {
        // Zero-behavior-change proof: an ordinary (non-house) cell, empty BSP,
        // reaches the target exactly like it did before AP-71 landed.
        var engine = MakeEngine(MakeIndoorCell(restrictionObj: 0u));

        var from = new Vector3(0.1f, 0f, 0.2f);
        var to = new Vector3(0.7f, 0f, 0.2f);
        var t = BSPStepUpFixtures.MakeGroundedTransition(from, to, cellId: CellId);
        t.ObjectInfo.State |= ObjectInfoState.IsPlayer;

        t.FindTransitionalPosition(engine);

        Assert.True(
            System.MathF.Abs(t.SpherePath.CurPos.X - to.X) < 1e-4f,
            $"Ordinary cell must be a complete no-op; CurPos.X={t.SpherePath.CurPos.X:F4}");
    }
}