using OpenTK.Mathematics;
using VoxelEngine.Core;
using VoxelEngine.World.Blocks;
using VoxelEngine.World.Chunk;
using VoxelEngine.World.WorldGen;
using Xunit;

namespace VoxelEngine.Tests.WorldGen;

public class CaveCarverTests
{
    private static readonly BlockRegistry Blocks = new();
    private static readonly Configuration Cfg = new();

    private static Chunk MakeStoneChunk()
    {
        Chunk c = new();
        for (int x = 0; x < Chunk.Size; x++)
        for (int y = 0; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
            c[x, y, z] = Blocks.Stone.Id;
        return c;
    }

    [Fact]
    public void Carve_IsNoOpOnAirChunk()
    {
        var carver = new CaveCarver(seed: 42, Blocks, Cfg);
        Chunk c = new(); // all-air by default

        carver.Carve(c, new Vector3i(0, 4, 0));

        for (int x = 0; x < Chunk.Size; x++)
        for (int y = 0; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
            Assert.Equal(Blocks.Air.Id, c[x, y, z]);
    }

    [Fact]
    public void NoiseCaves_OnlyConvertsSolidToAir_NeverWaterNeverOtherBlocks()
    {
        var carver = new CaveCarver(seed: 42, Blocks, Cfg);
        Chunk c = MakeStoneChunk();

        // Plant some water and air voxels we expect untouched.
        c[1, 1, 1] = Blocks.Water.Id;
        c[2, 2, 2] = Blocks.Air.Id;

        carver.CarveNoiseCaves(c, new Vector3i(0, 4, 0));

        Assert.Equal(Blocks.Water.Id, c[1, 1, 1]); // water survived
        Assert.Equal(Blocks.Air.Id,   c[2, 2, 2]); // air survived

        // Spot-check that everywhere else is either Stone or Air (no other blocks).
        for (int x = 0; x < Chunk.Size; x++)
        for (int y = 0; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
        {
            ushort id = c[x, y, z];
            Assert.True(
                id == Blocks.Stone.Id || id == Blocks.Air.Id || id == Blocks.Water.Id,
                $"unexpected block id {id} at ({x},{y},{z})");
        }
    }

    [Fact]
    public void NoiseCaves_IsDeterministic_ForSameSeedAndChunkPos()
    {
        var carver1 = new CaveCarver(seed: 1234, Blocks, Cfg);
        var carver2 = new CaveCarver(seed: 1234, Blocks, Cfg);
        Chunk a = MakeStoneChunk();
        Chunk b = MakeStoneChunk();

        carver1.CarveNoiseCaves(a, new Vector3i(2, 4, 3));
        carver2.CarveNoiseCaves(b, new Vector3i(2, 4, 3));

        for (int x = 0; x < Chunk.Size; x++)
        for (int y = 0; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
            Assert.Equal(a[x, y, z], b[x, y, z]);
    }

    [Fact]
    public void NoiseCaves_RespectsBedrockFloor_DoesNotCarveBelowY1()
    {
        // ChunkPos.Y = 0 means worldY ranges 0..15. We require Y=0 stays solid.
        var carver = new CaveCarver(seed: 42, Blocks, Cfg);
        Chunk c = MakeStoneChunk();

        carver.CarveNoiseCaves(c, new Vector3i(0, 0, 0));

        for (int x = 0; x < Chunk.Size; x++)
        for (int z = 0; z < Chunk.Size; z++)
            Assert.Equal(Blocks.Stone.Id, c[x, 0, z]); // worldY = 0 is bedrock
    }

    [Fact]
    public void NoiseCaves_SeamContinuity_AdjacentChunksAgreeAtBoundary()
    {
        var carver = new CaveCarver(seed: 7, Blocks, Cfg);
        Chunk c1 = MakeStoneChunk();
        Chunk c2 = MakeStoneChunk();

        carver.CarveNoiseCaves(c1, new Vector3i(0, 4, 0));
        carver.CarveNoiseCaves(c2, new Vector3i(1, 4, 0));

        int airAtSeamC1 = 0, airAtSeamC2 = 0;
        for (int y = 1; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
        {
            if (c1[15, y, z] == Blocks.Air.Id) airAtSeamC1++;
            if (c2[0,  y, z] == Blocks.Air.Id) airAtSeamC2++;
        }
        // Sanity: noise threshold = -0.3 yields some carved cells in each.
        Assert.True(airAtSeamC1 > 0, "c1 seam column had no air — carve too sparse?");
        Assert.True(airAtSeamC2 > 0, "c2 seam column had no air — carve too sparse?");
    }

    [Fact]
    public void WormCaves_IsDeterministic_ForSameSeedAndChunkPos()
    {
        var c1 = new CaveCarver(seed: 999, Blocks, Cfg);
        var c2 = new CaveCarver(seed: 999, Blocks, Cfg);
        Chunk a = MakeStoneChunk();
        Chunk b = MakeStoneChunk();

        c1.CarveWormCaves(a, new Vector3i(0, 4, 0));
        c2.CarveWormCaves(b, new Vector3i(0, 4, 0));

        for (int x = 0; x < Chunk.Size; x++)
        for (int y = 0; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
            Assert.Equal(a[x, y, z], b[x, y, z]);
    }

    [Fact]
    public void WormCaves_OnlyConvertsSolidToAir_NeverWater()
    {
        var carver = new CaveCarver(seed: 999, Blocks, Cfg);
        Chunk c = MakeStoneChunk();
        // Set every voxel along a diagonal to water — must survive.
        for (int i = 0; i < Chunk.Size; i++)
            c[i, i, i] = Blocks.Water.Id;

        carver.CarveWormCaves(c, new Vector3i(0, 4, 0));

        for (int i = 0; i < Chunk.Size; i++)
            Assert.Equal(Blocks.Water.Id, c[i, i, i]);
    }

    [Fact]
    public void WormCaves_RespectsBedrockFloor()
    {
        var carver = new CaveCarver(seed: 999, Blocks, Cfg);
        Chunk c = MakeStoneChunk();

        carver.CarveWormCaves(c, new Vector3i(0, 0, 0)); // worldY = 0..15

        for (int x = 0; x < Chunk.Size; x++)
        for (int z = 0; z < Chunk.Size; z++)
            Assert.Equal(Blocks.Stone.Id, c[x, 0, z]); // bedrock untouched
    }

    [Fact]
    public void WormCaves_SeamContinuity_VoxelAtSharedWorldCoord_IsSame()
    {
        var carver = new CaveCarver(seed: 999, Blocks, Cfg);
        Chunk c1 = MakeStoneChunk();
        Chunk c2 = MakeStoneChunk();

        carver.CarveWormCaves(c1, new Vector3i(0, 4, 0));
        carver.CarveWormCaves(c2, new Vector3i(1, 4, 0));

        int airC1Seam = 0, airC2Seam = 0;
        for (int y = 1; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
        {
            if (c1[15, y, z] == Blocks.Air.Id) airC1Seam++;
            if (c2[0,  y, z] == Blocks.Air.Id) airC2Seam++;
        }
        bool bothEmpty = airC1Seam == 0 && airC2Seam == 0;
        bool bothCarved = airC1Seam > 0 && airC2Seam > 0;
        Assert.True(bothEmpty || bothCarved,
            $"seam mismatch: c1={airC1Seam}, c2={airC2Seam}");
    }

    [Fact]
    public void Carve_RespectsMinCaveY_NoCarvingAboveCeiling()
    {
        var cfg = new Configuration { MinCaveY = 20 };
        var carver = new CaveCarver(seed: 42, Blocks, cfg);
        Chunk c = MakeStoneChunk();

        // Chunk Y=2 → worldY 32..47, all above MinCaveY=20 → must stay solid.
        carver.Carve(c, new Vector3i(0, 2, 0));

        for (int x = 0; x < Chunk.Size; x++)
        for (int y = 0; y < Chunk.Size; y++)
        for (int z = 0; z < Chunk.Size; z++)
            Assert.Equal(Blocks.Stone.Id, c[x, y, z]);
    }
}