using System.Collections.Concurrent;

namespace AcDream.App.Rendering.Wb;

/// <summary>
/// Thread-safe side-table mapping <c>(gfxObjId, surfaceIdx)</c> to
/// <see cref="AcSurfaceMetadata"/>. Populated when a GfxObj's mesh data
/// is extracted; queried at draw time.
///
/// <para>
/// Keyed by <c>(gfxObjId, surfaceIdx)</c> not by WB's runtime batch
/// identity because batch objects can be evicted and re-loaded by WB's
/// LRU; the (gfxObj, surface) pair is stable across cycles.
/// </para>
/// </summary>
public sealed class AcSurfaceMetadataTable
{
    private readonly ConcurrentDictionary<(ulong gfxObjId, int surfaceIdx), AcSurfaceMetadata> _table = new();

    public void Add(ulong gfxObjId, int surfaceIdx, AcSurfaceMetadata meta)
        => _table[(gfxObjId, surfaceIdx)] = meta;

    public bool TryLookup(ulong gfxObjId, int surfaceIdx, out AcSurfaceMetadata meta)
        => _table.TryGetValue((gfxObjId, surfaceIdx), out meta!);

    public void Clear() => _table.Clear();
}