using OpenTK.Mathematics;

namespace VoxelEngine.World.Persistence;

public sealed class InMemoryChunkModificationStore : IChunkModificationStore
{
    private readonly Dictionary<Vector3i, Dictionary<int, ushort>> _diffs = new();

    public bool TryGetDiff(Vector3i chunkPos, out IReadOnlyDictionary<int, ushort>? diff)
    {
        if (this._diffs.TryGetValue(chunkPos, out Dictionary<int, ushort>? d))
        {
            // Returned snapshot: callers may safely retain and enumerate even
            // after concurrent RecordEdit on the same chunk.
            diff = new Dictionary<int, ushort>(d);
            return true;
        }
        diff = null;
        return false;
    }

    public void RecordEdit(Vector3i chunkPos, int localIndex, ushort blockId)
    {
        if (!this._diffs.TryGetValue(chunkPos, out Dictionary<int, ushort>? d))
        {
            d = new Dictionary<int, ushort>();
            this._diffs[chunkPos] = d;
        }
        d[localIndex] = blockId;
    }

    public void ClearDiff(Vector3i chunkPos) => this._diffs.Remove(chunkPos);

    public bool HasDiff(Vector3i chunkPos) => this._diffs.ContainsKey(chunkPos);
}