using OpenTK.Mathematics;
using VoxelEngine.Core;
using VoxelEngine.World.Blocks;
using VoxelChunk = VoxelEngine.World.Chunk.Chunk;

namespace VoxelEngine.World.WorldGen;

public sealed class WorldGenerator
{
    private const int FillerDepth = 3;
    private const float CellSize = 96f;

    private readonly BlockRegistry _blocks;
    private readonly BiomeMap _biomeMap;
    private readonly TerrainSampler _terrain;
    private readonly CaveCarver _caves;

    public WorldGenerator(int seed, BlockRegistry blocks, Configuration cfg)
    {
        this._blocks = blocks;
        NoiseSource noise = new(seed);
        VoronoiCells cells = new(seed, WorldGenerator.CellSize);
        BiomeRegistry biomes = new(seed, blocks);
        this._biomeMap = new BiomeMap(noise, cells, biomes);
        this._terrain = new TerrainSampler(noise, this._biomeMap);
        this._caves = new CaveCarver(seed, blocks, cfg);
    }

    public int SurfaceHeightAt(int worldX, int worldZ) => this._terrain.HeightAt(worldX, worldZ);

    public VoxelChunk Generate(Vector3i chunkPos)
    {
        VoxelChunk chunk = new();
        int baseX = chunkPos.X * VoxelChunk.Size;
        int baseY = chunkPos.Y * VoxelChunk.Size;
        int baseZ = chunkPos.Z * VoxelChunk.Size;

        for (int x = 0; x < VoxelChunk.Size; x++)
        for (int z = 0; z < VoxelChunk.Size; z++)
        {
            int worldX = baseX + x;
            int worldZ = baseZ + z;
            int height = this._terrain.HeightAt(worldX, worldZ);
            IBiome biome = this._biomeMap.BiomeAt(worldX, worldZ);

            for (int y = 0; y < VoxelChunk.Size; y++)
            {
                int worldY = baseY + y;
                chunk[x, y, z] = WorldGenerator.BlockAt(worldY, height, biome, this._blocks);
            }
        }

        this._caves.Carve(chunk, chunkPos);
        return chunk;
    }

    public static ushort BlockAt(int worldY, int surfaceHeight, IBiome biome, BlockRegistry blocks)
    {
        if (worldY > surfaceHeight)
            return worldY <= WorldConstants.SeaLevel ? blocks.Water.Id : blocks.Air.Id;
        if (worldY == surfaceHeight)
            return biome.TopBlock(worldY).Id;
        if (worldY >= surfaceHeight - WorldGenerator.FillerDepth)
            return biome.Surface.Filler.Id;
        return biome.Surface.Under.Id;
    }
}