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

namespace VoxelEngine.World;

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

    public IChunkModificationStore ModificationStore { get; } = modStore;

    public void SetChunk(Vector3i chunkPos, Chunk.Chunk chunk) => this._chunks[chunkPos] = chunk;

    public void RemoveChunk(Vector3i chunkPos) => this._chunks.Remove(chunkPos);

    public Chunk.Chunk? GetChunk(Vector3i chunkPos) => this._chunks.GetValueOrDefault(chunkPos);

    public IBlock GetBlock(int worldX, int worldY, int worldZ)
    {
        Vector3i chunkPos = new(
            ChunkMath.FloorDiv(worldX, Chunk.Chunk.Size),
            ChunkMath.FloorDiv(worldY, Chunk.Chunk.Size),
            ChunkMath.FloorDiv(worldZ, Chunk.Chunk.Size));

        Chunk.Chunk? chunk = this.GetChunk(chunkPos);
        if (chunk == null) return 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 registry.Get(chunk[localX, localY, localZ]);
    }

    public bool SetBlock(int worldX, int worldY, int worldZ, ushort blockId)
    {
        Vector3i chunkPos = new(
            ChunkMath.FloorDiv(worldX, Chunk.Chunk.Size),
            ChunkMath.FloorDiv(worldY, Chunk.Chunk.Size),
            ChunkMath.FloorDiv(worldZ, Chunk.Chunk.Size));

        Chunk.Chunk? chunk = this.GetChunk(chunkPos);

        int localX = worldX - chunkPos.X * Chunk.Chunk.Size;
        int localY = worldY - chunkPos.Y * Chunk.Chunk.Size;
        int localZ = worldZ - chunkPos.Z * Chunk.Chunk.Size;
        int localIndex = (localX * Chunk.Chunk.Size + localY) * Chunk.Chunk.Size + localZ;

        // For a loaded chunk, no-op writes shouldn't pollute the diff store.
        if (chunk != null && chunk[localX, localY, localZ] == blockId) return true;

        this.ModificationStore.RecordEdit(chunkPos, localIndex, blockId);

        if (chunk == null) return false;

        chunk[localX, localY, localZ] = blockId;
        return true;
    }

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

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