using System.Collections;
using OpenTK.Mathematics;
using VoxelEngine.World.Blocks;

namespace VoxelEngine.World;

public sealed class World : IWorld, IEnumerable<KeyValuePair<Vector3i, Chunk.Chunk>>
{
    private readonly Dictionary<Vector3i, Chunk.Chunk> _chunks = new();
    private readonly BlockRegistry _registry;

    public World(BlockRegistry registry)
    {
        this._registry = registry;
    }
    
    public void SetChunk(Vector3i chunkPos, Chunk.Chunk chunk)
    {
        this._chunks[chunkPos] = chunk;
    }

    public Chunk.Chunk? GetChunk(Vector3i chunkPos)
    {
        return this._chunks.GetValueOrDefault(chunkPos);
    }

    public IBlock GetBlock(int worldX, int worldY, int worldZ)
    {
        Vector3i chunkPos = new(
            World.FloorDiv(worldX, Chunk.Chunk.Size),
            World.FloorDiv(worldY, Chunk.Chunk.Size),
            World.FloorDiv(worldZ, Chunk.Chunk.Size)
        );
        
        Chunk.Chunk? chunk = this.GetChunk(chunkPos);
        if (chunk == null)
        {
            return this._registry.Air;
        }
        
        int localX = worldX - chunkPos.X *  Chunk.Chunk.Size;
        int localY = worldY - chunkPos.Y *  Chunk.Chunk.Size;
        int localZ = worldZ - chunkPos.Z *  Chunk.Chunk.Size;
        
        return this._registry.Get(chunk[localX, localY, localZ]);
    }

    private static int FloorDiv(int value, int size)
    {
        int quotient = value / size;
        if (value % size != 0 && value < 0)
        {
            quotient--;
        }
        return quotient;
    }

    public IEnumerator<KeyValuePair<Vector3i, Chunk.Chunk>> GetEnumerator()
        => this._chunks.GetEnumerator();

    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();

}