Aetheria/Assets/Scripts/ServerShared/AetheriaStores.cs

using System;
using System.Linq;
using GameCult.Caching;
using GameCult.Caching.MessagePack;

// Aetheria's stores: one home store per type, composed here and nowhere else.
public static class AetheriaStores
{
    public static readonly Type[] CatalogTypes = { typeof(ItemData), typeof(Faction), typeof(FactionProductData), typeof(PersonalityAttribute), typeof(NameFile), typeof(InputLayout), typeof(Loadout) };
    public static readonly Type[] RunTypes = { typeof(OrbitData), typeof(BodyData), typeof(SavedZone), typeof(SavedGame), typeof(ProvenanceLedger) };
    public static readonly Type[] PlayerTypes = { typeof(PlayerSettings) };

    // Attaches (hydrates) the catalog read-only unless catalogWritable, then the run and player stores when given.
    // Throws when a [CultGlobal] type routed to the catalog has no record. The one exemption is a writable catalog with
    // no records at all, a seed store being authored from nothing; a populated catalog is held to it however it opens.
    public static CultCache Open(string catalogPath, string runPath = null, string playerPath = null, bool catalogWritable = false)
    {
        var cache = new CultCache();
        try
        {
            cache.AddBackingStore(new SingleFileMessagePackBackingStore(catalogPath, !catalogWritable), CatalogTypes);
            if (runPath != null) cache.AddBackingStore(new SingleFileMessagePackBackingStore(runPath), RunTypes);
            if (playerPath != null) cache.AddBackingStore(new SingleFileMessagePackBackingStore(playerPath), PlayerTypes);
            var seeding = catalogWritable && !cache.AllStoredDocuments.Any(stored =>
                CatalogTypes.Any(home => home.IsAssignableFrom(stored.Descriptor.DocumentType)));
            var missing = seeding ? null : cache.Registry.AllDescriptors.FirstOrDefault(descriptor =>
                descriptor.IsGlobal &&
                CatalogTypes.Any(home => home.IsAssignableFrom(descriptor.DocumentType)) &&
                cache.AllStoredDocuments.All(stored => stored.Descriptor != descriptor));
            if (missing != null)
                throw new InvalidOperationException($"Catalog {catalogPath} has no {missing.SchemaName} record; catalog globals are authored, never invented.");
            return cache;
        }
        catch
        {
            cache.Dispose();
            throw;
        }
    }
}

public static class CultRecordRefs
{
    public static bool IsSet(this CultRecordKey key) => !string.IsNullOrEmpty(key.Value);
    public static bool IsSet<T>(this CultRecordRef<T> reference) => reference.Key.IsSet();

    // The document a reference names, or null when it is unset or names nothing this cache holds.
    public static T Get<T>(this CultCache cache, CultRecordRef<T> reference) where T : class =>
        reference.IsSet() ? cache.Get<T>(reference.Key) : null;

    // A reference to a document this cache holds. The key comes from the cache, never from the document.
    public static CultRecordRef<T> RefOf<T>(this CultCache cache, T document) where T : class =>
        new CultRecordRef<T>(cache.TryGetHandle(document)?.Key ??
                             throw new InvalidOperationException($"This cache holds no such {document.GetType().Name}."));

    // Writes a document to its home store; the cache mints its key the first time.
    public static CultRecordRef<T> Upsert<T>(this CultCache cache, T document) where T : class =>
        new CultRecordRef<T>(cache.UpsertAsync(document).Result.Key);
}