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 WorldGeneratorTests
{
    private static BlockRegistry Blocks => new();

    [Fact]
    public void BlockAt_AboveTerrainAndSea_IsAir()
    {
        var blocks = Blocks;
        var biomes = new BiomeRegistry(1, blocks);
        ushort id = WorldGenerator.BlockAt(300, surfaceHeight: 290, biomes.Plains, blocks);
        Assert.Equal(blocks.Air.Id, id); // 300 > 290 (above surface) and 300 > SeaLevel(256)
    }

    [Fact]
    public void BlockAt_AboveTerrainBelowSea_IsWater()
    {
        var blocks = Blocks;
        var biomes = new BiomeRegistry(1, blocks);
        ushort id = WorldGenerator.BlockAt(60, surfaceHeight: 50, biomes.Plains, blocks);
        Assert.Equal(blocks.Water.Id, id); // 60 > 50 but 60 <= SeaLevel(64)
    }

    [Fact]
    public void BlockAt_Surface_IsBiomeTop()
    {
        var blocks = Blocks;
        var biomes = new BiomeRegistry(1, blocks);
        ushort id = WorldGenerator.BlockAt(70, surfaceHeight: 70, biomes.Desert, blocks);
        Assert.Equal(blocks.Sand.Id, id);
    }

    [Fact]
    public void BlockAt_FillerBand_IsBiomeFiller()
    {
        var blocks = Blocks;
        var biomes = new BiomeRegistry(1, blocks);
        ushort id = WorldGenerator.BlockAt(68, surfaceHeight: 70, biomes.Plains, blocks);
        Assert.Equal(blocks.Dirt.Id, id); // within 3 of surface
    }

    [Fact]
    public void BlockAt_Deep_IsStone()
    {
        var blocks = Blocks;
        var biomes = new BiomeRegistry(1, blocks);
        ushort id = WorldGenerator.BlockAt(40, surfaceHeight: 70, biomes.Plains, blocks);
        Assert.Equal(blocks.Stone.Id, id);
    }

    [Fact]
    public void Generate_IsDeterministic()
    {
        var gen1 = new WorldGenerator(99, Blocks, new Configuration());
        var gen2 = new WorldGenerator(99, Blocks, new Configuration());
        Chunk a = gen1.Generate(new Vector3i(0, 4, 0));
        Chunk b = gen2.Generate(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 Generate_AppliesCaves_ProducesAirVoxelsBelowSurface()
    {
        var gen = new WorldGenerator(seed: 12345, Blocks, new Configuration());
        // A chunk well below typical surface height — guaranteed mostly stone before carving.
        Chunk c = gen.Generate(new Vector3i(0, 1, 0)); // worldY = 16..31

        int airCount = 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++)
            if (c[x, y, z] == Blocks.Air.Id) airCount++;

        Assert.True(airCount > 0,
            "Deep chunk had zero air voxels after generation — caves not running?");
    }

    [Fact]
    public void Generate_PreservesBedrockFloor_Y0_IsStone()
    {
        var gen = new WorldGenerator(seed: 12345, Blocks, new Configuration());
        Chunk c = gen.Generate(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]);
    }
}