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

namespace AcDream.Core.Tests.Physics;

public class CellTransitAddAllOutsideCellsTests
{
    [Fact]
    public void SphereWellInsideCell_AddsOneCell()
    {
        // A6.P4 (2026-05-24): coords are LANDBLOCK-LOCAL (X/Y in [0, 192]).
        // #106 (2026-06-09): the convention is now explicit — coords are
        // world-frame and currentBlockOrigin converts them to block-local;
        // Zero origin == "current block is the anchor", the same inputs as
        // before. Player at landblock-local (12, 12, 0) → cell (0,0) in
        // landblock 0xA9B40000.
        var candidates = new HashSet<uint>();
        CellTransit.AddAllOutsideCells(
            worldSphereCenter: new Vector3(12f, 12f, 0f),
            sphereRadius: 0.5f,
            currentCellId: 0xA9B40001u,
            currentBlockOrigin: Vector3.Zero,
            candidates: candidates);

        Assert.Single(candidates);
        Assert.Contains(0xA9B40001u, candidates);
    }

    [Fact]
    public void SphereAtCellEastBoundary_AddsTwoCells()
    {
        // Player at (23.6, 12, 0) — near +X edge of cell (0,0). Sphere
        // reaches to local X = 23.6 + 0.5 = 24.1 → cell (1,0) added.
        var candidates = new HashSet<uint>();
        CellTransit.AddAllOutsideCells(
            worldSphereCenter: new Vector3(23.6f, 12f, 0f),
            sphereRadius: 0.5f,
            currentCellId: 0xA9B40001u,
            currentBlockOrigin: Vector3.Zero,
            candidates: candidates);

        Assert.Equal(2, candidates.Count);
        Assert.Contains(0xA9B40001u, candidates);
        // Cell (1,0): low-16 id = 1 * 8 + 0 + 1 = 9 → 0x0009.
        Assert.Contains(0xA9B40009u, candidates);
    }

    // ── #106: landblock crossings (retail add_all_outside_cells has no
    //    same-block clamp — LandDefs global lcoords) ─────────────────────

    [Fact]
    public void SphereJustSouthOfBlockBoundary_AddsBothBlocks()
    {
        // 0.2 m south of A9B4's southern edge: adjust_to_outside re-seats to
        // A9B3 row 7 (cell 0xA9B30038 under x=150), and the boundary check
        // (point.Y = 23.8 > maxRad 23.5) adds the A9B4 cell back as the +Y
        // neighbour. Pre-#106 this returned ZERO candidates (the freeze).
        var candidates = new HashSet<uint>();
        CellTransit.AddAllOutsideCells(
            worldSphereCenter: new Vector3(150f, -0.2f, 0f),
            sphereRadius: 0.5f,
            currentCellId: 0xA9B40031u,
            currentBlockOrigin: Vector3.Zero,
            candidates: candidates);

        Assert.Contains(0xA9B30038u, candidates);   // containing (south block)
        Assert.Contains(0xA9B40031u, candidates);   // +Y neighbour (home block)
        Assert.Equal(2, candidates.Count);
    }

    [Fact]
    public void SphereDeepInNeighbourBlock_AddsNeighbourCellOnly()
    {
        // The #106 capture geometry: ~109.65 m south of A9B4's origin =
        // ~82 m into A9B3 → cell row 3 (floor(-109.65/24) = -5 → ly 1435).
        var candidates = new HashSet<uint>();
        CellTransit.AddAllOutsideCells(
            worldSphereCenter: new Vector3(150f, -109.65f, 0f),
            sphereRadius: 0.5f,
            currentCellId: 0xA9B40031u,
            currentBlockOrigin: Vector3.Zero,
            candidates: candidates);

        Assert.Contains(0xA9B30034u, candidates);
        Assert.DoesNotContain(0xA9B40031u, candidates);
    }

    [Fact]
    public void NonAnchorBlockOrigin_ConvertsWorldFrame()
    {
        // Player's current cell is in A9B3 (one block south of the anchor,
        // world origin (0, -192)). World y = -0.2 is block-local y = 191.8 —
        // still inside A9B3 row 7, with the boundary check adding the A9B4
        // cell to the north. Exercises the origin conversion that the
        // pre-#106 code silently skipped (world frame assumed block-local).
        var candidates = new HashSet<uint>();
        CellTransit.AddAllOutsideCells(
            worldSphereCenter: new Vector3(150f, -0.2f, 0f),
            sphereRadius: 0.5f,
            currentCellId: 0xA9B30038u,
            currentBlockOrigin: new Vector3(0f, -192f, 0f),
            candidates: candidates);

        Assert.Contains(0xA9B30038u, candidates);
        Assert.Contains(0xA9B40031u, candidates);
    }
}