acdream/src/AcDream.App/RuntimeDatCollectionFactory.cs

using DatReaderWriter;
using DatReaderWriter.Options;
using AcDream.Content;
using DatReaderWriter.Lib.IO;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;

namespace AcDream.App;

/// <summary>
/// Opens the read-only DAT collection owned for the lifetime of an App process.
/// </summary>
/// <remarks>
/// DatReaderWriter's default <see cref="FileCachingStrategy.OnDemand"/> retains
/// every unpacked file entry for the lifetime of the collection. The runtime has
/// bounded decoded-content caches of its own, so retaining that second,
/// unbounded copy makes memory depend on every landblock visited. Keep the small
/// B-tree lookup cache, but read file payloads on demand and let the owning
/// runtime caches decide their residency.
/// </remarks>
internal static class RuntimeDatCollectionFactory
{
    internal static IDatReaderWriter OpenReadOnly(string datDirectory) =>
        new RuntimeDatCollection(new DatCollection(CreateReadOnlyOptions(datDirectory)));

    internal static DatCollectionOptions CreateReadOnlyOptions(string datDirectory)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(datDirectory);

        return new DatCollectionOptions
        {
            DatDirectory = datDirectory,
            AccessType = DatAccessType.Read,
            IndexCachingStrategy = IndexCachingStrategy.OnDemand,
            FileCachingStrategy = FileCachingStrategy.Never,
        };
    }
}

/// <summary>
/// Owns the runtime's one raw DAT handle set and its one shared bounded typed
/// object facade. Disposing this owner closes both layers exactly once.
/// </summary>
internal sealed class RuntimeDatCollection : IDatReaderWriter
{
    private readonly DatCollection _raw;
    private readonly DatCollectionAdapter _bounded;
    private bool _disposed;

    internal RuntimeDatCollection(DatCollection raw)
    {
        ArgumentNullException.ThrowIfNull(raw);
        _raw = raw;
        _bounded = new DatCollectionAdapter(raw);
    }

    public string SourceDirectory => _bounded.SourceDirectory;
    public IDatDatabase Portal => _bounded.Portal;
    public IDatDatabase Cell => _bounded.Cell;
    public ReadOnlyDictionary<uint, IDatDatabase> CellRegions => _bounded.CellRegions;
    public IDatDatabase HighRes => _bounded.HighRes;
    public IDatDatabase Language => _bounded.Language;
    public IDatDatabase Local => _bounded.Local;
    public ReadOnlyDictionary<uint, uint> RegionFileMap => _bounded.RegionFileMap;
    public int PortalIteration => _bounded.PortalIteration;
    public int CellIteration => _bounded.CellIteration;
    public int HighResIteration => _bounded.HighResIteration;
    public int LanguageIteration => _bounded.LanguageIteration;

    [return: MaybeNull]
    public T Get<T>(uint fileId) where T : IDBObj => _bounded.Get<T>(fileId);

    public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value)
        where T : IDBObj =>
        _bounded.TryGet(fileId, out value);

    public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj =>
        _bounded.GetAllIdsOfType<T>();

    public bool TryGetFileBytes(uint regionId, uint fileId, ref byte[] bytes, out int bytesRead) =>
        _bounded.TryGetFileBytes(regionId, fileId, ref bytes, out bytesRead);

    public IEnumerable<IDatReaderWriter.IdResolution> ResolveId(uint id) =>
        _bounded.ResolveId(id);

    public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
        _bounded.TrySave(obj, iteration);

    public bool TrySave<T>(uint regionId, T obj, int iteration = 0) where T : IDBObj =>
        _bounded.TrySave(regionId, obj, iteration);

    public void Dispose()
    {
        if (_disposed)
            return;

        _disposed = true;
        _bounded.Dispose();
        _raw.Dispose();
    }
}