using System;
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>
/// #133 (Bug A) — the validated-claim placement branch of
/// <see cref="PhysicsEngine.Resolve"/> must return the VALIDATED claim's own
/// full cell id, NOT <c>lbPrefix | (cellId &amp; 0xFFFF)</c>.
///
/// <para>
/// <c>lbPrefix</c> is found by scanning resident landblocks for one whose
/// <c>[0,192)</c> local bounds contain the candidate XY. A dungeon EnvCell's
/// local Y can be NEGATIVE relative to its own landblock (the live capture:
/// server teleport to dungeon cell <c>0x00070143</c> at local <c>(70,-60,0.01)</c>).
/// The dungeon landblock fails the <c>localY &gt;= 0</c> bounds test, so the loop
/// instead matches a still-resident NEIGHBOURING block (a Holtburg landblock
/// whose world bounds happen to contain the same XY) and sets
/// <c>lbPrefix = 0xA9B30000</c>. The old code then returned
/// <c>0xA9B30000 | 0x0143 = 0xA9B30143</c>, re-stamping the validated dungeon
/// claim with the wrong landblock — the client mis-resolved the player into
/// Holtburg and spammed ACE with rejected moves
/// (<c>movement pre-validation failed from 00070143 to A9B30143</c>).
/// </para>
///
/// <para>
/// The validated claim's prefix is authoritative; a position falling in a
/// neighbouring resident landblock must not re-stamp it. This test reproduces
/// the exact geometry of the capture (dungeon claim in landblock <c>0x0007</c>,
/// candidate XY also inside resident Holtburg <c>0xA9B3</c>) and asserts the
/// returned cell keeps its <c>0x0007</c> prefix.
/// </para>
/// </summary>
public class Issue133DungeonTeleportPrefixTests
{
    private const uint DungeonLandblock = 0x00070000u;
    private const uint DungeonCellId    = 0x00070143u;  // indoor (low 0x0143 ≥ 0x0100)
    private const uint HoltburgLandblock = 0xA9B30000u;  // a neighbouring resident block

    // The capture: dungeon cell 0x00070143 at dungeon-local (70, -60, 0.01).
    // We place the Holtburg block at world origin so its [0,192) bounds contain
    // the candidate XY, and the dungeon block at world Y-offset 130 so the SAME
    // world XY lands at dungeon-local Y = 70 - 130 = -60 (the captured negative).
    private static readonly Vector3 SpawnPos = new(70f, 70f, 0.01f);

    [Fact]
    public void ValidatedDungeonClaim_KeepsItsLandblockPrefix_NotTheNeighbour()
    {
        var engine = BuildEngine();

        // Zero delta = the snap shape (teleport arrival). cellId is the dungeon
        // claim; the candidate XY also falls inside the resident Holtburg block.
        var result = engine.Resolve(SpawnPos, DungeonCellId, delta: Vector3.Zero, stepUpHeight: 0.5f);

        Assert.True(result.IsOnGround);
        // The validated claim's prefix is authoritative — high word stays 0x0007,
        // NOT re-stamped to the neighbouring Holtburg 0xA9B3.
        Assert.Equal(DungeonCellId, result.CellId);
        Assert.Equal(DungeonLandblock, result.CellId & 0xFFFF0000u);
    }

    // ── fixture ──────────────────────────────────────────────────────────────

    private static PhysicsEngine BuildEngine()
    {
        var cache  = new PhysicsDataCache();
        var engine = new PhysicsEngine { DataCache = cache };

        // The dungeon cell: a Leaf CellBSP contains any point, so AdjustPosition
        // validates the claim (returns it with found=true). Its Resolved set has
        // one walkable floor polygon at z=0 under the spawn XY so the #111
        // validated-claim branch grounds onto it.
        cache.RegisterCellStructForTest(DungeonCellId, MakeDungeonCell());

        // Resident Holtburg block at world origin: its [0,192) bounds CONTAIN the
        // candidate XY (70,70). This is the block the lbPrefix loop wrongly matched.
        engine.AddLandblock(
            landblockId:  HoltburgLandblock,
            terrain:      FlatTerrain(),
            cells:        Array.Empty<CellSurface>(),
            portals:      Array.Empty<PortalPlane>(),
            worldOffsetX: 0f,
            worldOffsetY: 0f);

        // The dungeon's own landblock, offset so the candidate XY produces a
        // NEGATIVE dungeon-local Y (70 - 130 = -60) → it FAILS the [0,192) bounds
        // test, which is exactly why the old code fell through to the Holtburg
        // prefix. Registered so the scenario is faithful (a resident dungeon block
        // whose local bounds don't cover the EnvCell's negative-Y position).
        engine.AddLandblock(
            landblockId:  DungeonLandblock,
            terrain:      FlatTerrain(),
            cells:        Array.Empty<CellSurface>(),
            portals:      Array.Empty<PortalPlane>(),
            worldOffsetX: 0f,
            worldOffsetY: 130f);

        return engine;
    }

    /// <summary>Flat 81-vertex stub terrain (all zero heights).</summary>
    private static TerrainSurface FlatTerrain() => new(new byte[81], new float[256]);

    private static CellPhysics MakeDungeonCell()
    {
        // One floor polygon: a 200×200 square at z=0 centred so it covers the
        // spawn XY. Normal (0,0,1) → normal.Z = 1 ≥ FloorZ (0.6642) → walkable.
        // Identity transform: cell-local == world, so the plane d = 0 (z + d = 0).
        var floor = new ResolvedPolygon
        {
            Vertices = new[]
            {
                new Vector3(-100f, -100f, 0f),
                new Vector3( 200f, -100f, 0f),
                new Vector3( 200f,  200f, 0f),
                new Vector3(-100f,  200f, 0f),
            },
            Plane     = new Plane(new Vector3(0f, 0f, 1f), 0f),
            NumPoints = 4,
            SidesType = CullMode.None,
        };

        return new CellPhysics
        {
            BSP                   = new PhysicsBSPTree { Root = new PhysicsBSPNode { Type = BSPNodeType.Leaf } },
            WorldTransform        = Matrix4x4.Identity,
            InverseWorldTransform = Matrix4x4.Identity,
            Resolved              = new Dictionary<ushort, ResolvedPolygon> { [0] = floor },
            // Leaf root → point_in_cell true for any point → AdjustPosition
            // validates the claim (found=true, cell unchanged).
            CellBSP               = new CellBSPTree { Root = new CellBSPNode { Type = BSPNodeType.Leaf } },
            Portals               = Array.Empty<PortalInfo>(),
            PortalPolygons        = new Dictionary<ushort, ResolvedPolygon>(),
            VisibleCellIds        = new HashSet<uint>(),
        };
    }
}