using NUnit.Framework;
using ProjectM.Simulation;
using Unity.Mathematics;

namespace ProjectM.Tests
{
    /// <summary>
    /// Pure-function tests for <see cref="BaseGridMath"/> (no ECS world), mirroring PlayerSpawnRingTests.
    /// Pins the locked M5 home-base grid coordinate space: planar 32x32, CellSize 1.0, corner-origin,
    /// center-returning, half-open cell bounds, floor-based world-&gt;cell. M6 placement builds on this.
    /// </summary>
    public class BaseGridMathTests
    {
        const float Eps = 1e-4f;

        // Locked config: center at (0,1,0); 32x32 cells of 1.0u => origin corner at (-16,1,-16).
        static BaseAnchor MakeAnchor()
        {
            var dims = new int2(32, 32);
            float cell = 1f;
            var anchorPos = new float3(0f, 1f, 0f);
            var gridOrigin = new float3(
                anchorPos.x - dims.x * cell * 0.5f,
                anchorPos.y,
                anchorPos.z - dims.y * cell * 0.5f);
            return new BaseAnchor { AnchorPos = anchorPos, GridOrigin = gridOrigin, CellSize = cell, GridDims = dims };
        }

        [Test]
        public void CellToWorld_Returns_Cell_Centers()
        {
            var a = MakeAnchor();
            AssertXz(BaseGridMath.CellToWorld(a, new int2(0, 0)), -15.5f, -15.5f);
            AssertXz(BaseGridMath.CellToWorld(a, new int2(31, 31)), 15.5f, 15.5f);
            AssertXz(BaseGridMath.CellToWorld(a, new int2(16, 16)), 0.5f, 0.5f);
            // Centers stay on the base plane.
            Assert.AreEqual(1f, BaseGridMath.CellToWorld(a, new int2(5, 9)).y, Eps);
        }

        [Test]
        public void RoundTrip_CellToWorld_Then_WorldToCell()
        {
            var a = MakeAnchor();
            AssertCell(BaseGridMath.WorldToCell(a, BaseGridMath.CellToWorld(a, new int2(0, 0))), 0, 0);
            AssertCell(BaseGridMath.WorldToCell(a, BaseGridMath.CellToWorld(a, new int2(31, 31))), 31, 31);
            AssertCell(BaseGridMath.WorldToCell(a, BaseGridMath.CellToWorld(a, new int2(16, 16))), 16, 16);
        }

        [Test]
        public void WorldToCell_Uses_Floor_Not_Truncation()
        {
            var a = MakeAnchor();
            // local x = worldX + 16, then floor. z = 0 -> cell.y = 16.
            Assert.AreEqual(0, BaseGridMath.WorldToCell(a, new float3(-15.6f, 1f, 0f)).x);
            Assert.AreEqual(-1, BaseGridMath.WorldToCell(a, new float3(-16.4f, 1f, 0f)).x);
            // A point exactly on a cell's lower edge belongs to the higher cell (half-open).
            Assert.AreEqual(1, BaseGridMath.WorldToCell(a, new float3(-15.0f, 1f, 0f)).x);
            Assert.AreEqual(16, BaseGridMath.WorldToCell(a, new float3(-15.6f, 1f, 0f)).y);
        }

        [Test]
        public void IsCellInPlot_Is_HalfOpen()
        {
            var a = MakeAnchor();
            Assert.IsTrue(BaseGridMath.IsCellInPlot(a, new int2(0, 0)));
            Assert.IsTrue(BaseGridMath.IsCellInPlot(a, new int2(31, 31)));
            Assert.IsFalse(BaseGridMath.IsCellInPlot(a, new int2(-1, 0)));
            Assert.IsFalse(BaseGridMath.IsCellInPlot(a, new int2(0, 32)));
            Assert.IsFalse(BaseGridMath.IsCellInPlot(a, new int2(32, 32)));
        }

        [Test]
        public void IsPointInPlot_Bounds()
        {
            var a = MakeAnchor();
            Assert.IsTrue(BaseGridMath.IsPointInPlot(a, a.AnchorPos));                    // center
            Assert.IsTrue(BaseGridMath.IsPointInPlot(a, new float3(-16f, 1f, 0f)));       // lower corner edge -> cell 0
            Assert.IsTrue(BaseGridMath.IsPointInPlot(a, new float3(15.9f, 1f, 15.9f)));   // cell (31,31)
            Assert.IsFalse(BaseGridMath.IsPointInPlot(a, new float3(-16.1f, 1f, 0f)));    // cell (-1,*) out
            Assert.IsFalse(BaseGridMath.IsPointInPlot(a, new float3(16f, 1f, 0f)));       // far edge -> cell 32 out
        }

        [Test]
        public void ClampCell_Bounds_To_Plot()
        {
            var a = MakeAnchor();
            AssertCell(BaseGridMath.ClampCell(a, new int2(-5, 99)), 0, 31);
            AssertCell(BaseGridMath.ClampCell(a, new int2(10, 10)), 10, 10);
        }

        [Test]
        public void PlotCenter_Equals_AnchorPos()
        {
            var a = MakeAnchor();
            var c = BaseGridMath.PlotCenter(a);
            Assert.AreEqual(a.AnchorPos.x, c.x, Eps);
            Assert.AreEqual(a.AnchorPos.y, c.y, Eps);
            Assert.AreEqual(a.AnchorPos.z, c.z, Eps);
        }

        static void AssertXz(float3 p, float x, float z)
        {
            Assert.AreEqual(x, p.x, Eps);
            Assert.AreEqual(z, p.z, Eps);
        }

        static void AssertCell(int2 c, int x, int y)
        {
            Assert.AreEqual(x, c.x);
            Assert.AreEqual(y, c.y);
        }
    }
}