Makes CollectionStorage thread safe for parallel initialization of collections by one or multiple IPC consumers without requring framework thread synchronization.

Penumbra/Collections/Manager/CollectionStorage.cs

@@ -31,69 +31,102 @@ public class CollectionStorage : IReadOnlyList<ModCollection>, IDisposable, ISer
 
     public ModCollection Create(string name, int index, ModCollection? duplicate)
     {
-        var newCollection = duplicate?.Duplicate(name, CurrentCollectionId, index)
-         ?? ModCollection.CreateEmpty(name, CurrentCollectionId, index, _modStorage.Count);
-        _collectionsByLocal[CurrentCollectionId] =  newCollection;
-        CurrentCollectionId                      += 1;
+        var localId       = AllocateNextId();
+        var newCollection = duplicate?.Duplicate(name, localId, index)
+         ?? ModCollection.CreateEmpty(name, localId, index, _modStorage.Count);
+        AddAtLocalId(newCollection, localId);
         return newCollection;
     }
 
     public ModCollection CreateFromData(Guid id, string name, int version, Dictionary<string, ModSettings.SavedSettings> allSettings,
         IReadOnlyList<string> inheritances)
     {
+        var localId       = AllocateNextId();
         var newCollection = ModCollection.CreateFromData(_saveService, _modStorage,
-            new ModCollectionIdentity(id, CurrentCollectionId, name, Count), version, allSettings, inheritances);
-        _collectionsByLocal[CurrentCollectionId] =  newCollection;
-        CurrentCollectionId                      += 1;
+            new ModCollectionIdentity(id, localId, name, Count), version, allSettings, inheritances);
+        AddAtLocalId(newCollection, localId);
         return newCollection;
     }
 
     public ModCollection CreateTemporary(string name, int index, int globalChangeCounter)
     {
-        var newCollection = ModCollection.CreateTemporary(name, CurrentCollectionId, index, globalChangeCounter);
-        _collectionsByLocal[CurrentCollectionId] =  newCollection;
-        CurrentCollectionId                      += 1;
+        var localId       = AllocateNextId();
+        var newCollection = ModCollection.CreateTemporary(name, localId, index, globalChangeCounter);
+        AddAtLocalId(newCollection, localId);
         return newCollection;
     }
 
+    /// <remarks> Atomically add to _collectionLocal at the id given. </remarks>
+    private void AddAtLocalId(ModCollection newCollection, LocalCollectionId id)
+    {
+        _collectionsByLocal.AddOrUpdate(id,
+            static (_, newColl) => newColl,
+            static (_, _, newColl) => newColl,
+            newCollection);
+    }
+
     public void Delete(ModCollection collection)
-        => _collectionsByLocal.Remove(collection.Identity.LocalId);
+        => _collectionsByLocal.TryRemove(collection.Identity.LocalId, out _);
 
     /// <remarks> The empty collection is always available at Index 0. </remarks>
     private readonly List<ModCollection> _collections =
     [
         ModCollection.Empty,
     ];
+
+    private readonly Lock _collectionsLock = new();
 
     /// <remarks> A list of all collections ever created still existing by their local id. </remarks>
-    private readonly Dictionary<LocalCollectionId, ModCollection>
+    private readonly ConcurrentDictionary<LocalCollectionId, ModCollection>
         _collectionsByLocal = new() { [LocalCollectionId.Zero] = ModCollection.Empty };
 
 
     public readonly ModCollection DefaultNamed;
 
-    /// <remarks> Incremented by 1 because the empty collection gets Zero. </remarks>
-    public LocalCollectionId CurrentCollectionId { get; private set; } = LocalCollectionId.Zero + 1;
+    /// <remarks> Starts at 1 because the empty collection gets Zero. </remarks>
+    private int _currentCollectionIdValue = 1;
+
+    /// <remarks> Starts at 1 because the empty collection gets Zero. </remarks>
+    public LocalCollectionId CurrentCollectionId => new(_currentCollectionIdValue);
+
+    private LocalCollectionId AllocateNextId()
+    {
+        var newLocalId = new LocalCollectionId(_currentCollectionIdValue);
+        Interlocked.Increment(ref _currentCollectionIdValue);
+        return newLocalId;
+    }
 
     /// <summary> Default enumeration skips the empty collection. </summary>
     public IEnumerator<ModCollection> GetEnumerator()
-        => _collections.Skip(1).GetEnumerator();
+        => GetModSnapShot().ToList().GetEnumerator();
 
     IEnumerator IEnumerable.GetEnumerator()
         => GetEnumerator();
 
     public int Count
-        => _collections.Count;
+    {
+        get
+        {
+            lock(_collectionsLock)
+                return _collections.Count;
+        }
+    }
 
     public ModCollection this[int index]
-        => _collections[index];
+    {    
+        get
+        {
+            lock(_collectionsLock)
+                return _collections[index];
+        }
+    }
 
     /// <summary> Find a collection by its name. If the name is empty or None, the empty collection is returned. </summary>
     public bool ByName(string name, [NotNullWhen(true)] out ModCollection? collection)
     {
         if (name.Length != 0)
-            return _collections.FindFirst(c => string.Equals(c.Identity.Name, name, StringComparison.OrdinalIgnoreCase), out collection);
-
+            lock(_collectionsLock)
+                return _collections.FindFirst(c => string.Equals(c.Identity.Name, name, StringComparison.OrdinalIgnoreCase), out collection);    
         collection = ModCollection.Empty;
         return true;
     }
@@ -102,8 +135,8 @@ public bool ByName(string name, [NotNullWhen(true)] out ModCollection? collectio
     public bool ById(Guid id, [NotNullWhen(true)] out ModCollection? collection)
     {
         if (id != Guid.Empty)
-            return _collections.FindFirst(c => c.Identity.Id == id, out collection);
-
+            lock(_collectionsLock)
+                return _collections.FindFirst(c => c.Identity.Id == id, out collection);
         collection = ModCollection.Empty;
         return true;
     }
@@ -155,8 +188,12 @@ public bool AddCollection(string name, ModCollection? duplicate)
         if (name.Length == 0)
             return false;
 
-        var newCollection = Create(name, _collections.Count, duplicate);
-        _collections.Add(newCollection);
+        ModCollection newCollection;
+        lock (_collectionsLock)
+        {
+            newCollection = Create(name, _collections.Count, duplicate);
+            _collections.Add(newCollection);
+        }
         _saveService.ImmediateSave(new ModCollectionSave(_modStorage, newCollection));
         Penumbra.Messager.NotificationMessage($"Created new collection {newCollection.Identity.AnonymizedName}.", NotificationType.Success, false);
         _communicator.CollectionChange.Invoke(CollectionType.Inactive, null, newCollection, string.Empty);
@@ -168,25 +205,28 @@ public bool AddCollection(string name, ModCollection? duplicate)
     /// </summary>
     public bool RemoveCollection(ModCollection collection)
     {
-        if (collection.Identity.Index <= ModCollection.Empty.Identity.Index || collection.Identity.Index >= _collections.Count)
+        lock (_collectionsLock) 
         {
-            Penumbra.Messager.NotificationMessage("Can not remove the empty collection.", NotificationType.Error, false);
-            return false;
-        }
+            if (collection.Identity.Index <= ModCollection.Empty.Identity.Index || collection.Identity.Index >= _collections.Count)
+            {
+                Penumbra.Messager.NotificationMessage("Can not remove the empty collection.", NotificationType.Error, false);
+                return false;
+            }
 
-        if (collection.Identity.Index == DefaultNamed.Identity.Index)
-        {
-            Penumbra.Messager.NotificationMessage("Can not remove the default collection.", NotificationType.Error, false);
-            return false;
-        }
+            if (collection.Identity.Index == DefaultNamed.Identity.Index)
+            {
+                Penumbra.Messager.NotificationMessage("Can not remove the default collection.", NotificationType.Error, false);
+                return false;
+            }
+
+            Delete(collection);
+            _saveService.ImmediateDelete(new ModCollectionSave(_modStorage, collection));
 
-        Delete(collection);
-        _saveService.ImmediateDelete(new ModCollectionSave(_modStorage, collection));
-        _collections.RemoveAt(collection.Identity.Index);
-        // Update indices.
-        for (var i = collection.Identity.Index; i < Count; ++i)
-            _collections[i].Identity.Index = i;
-        _collectionsByLocal.Remove(collection.Identity.LocalId);
+            _collections.RemoveAt(collection.Identity.Index);
+            // Update indices.
+            for (var i = collection.Identity.Index; i < _collections.Count; ++i)
+                _collections[i].Identity.Index = i;
+        }
 
         Penumbra.Messager.NotificationMessage($"Deleted collection {collection.Identity.AnonymizedName}.", NotificationType.Success, false);
         _communicator.CollectionChange.Invoke(CollectionType.Inactive, collection, null, string.Empty);
@@ -299,49 +339,52 @@ private ModCollection SetDefaultNamedCollection()
             return collection;
 
         if (AddCollection(ModCollectionIdentity.DefaultCollectionName, null))
-            return _collections[^1];
+            return this[^1];
 
         Penumbra.Messager.NotificationMessage(
             $"Unknown problem creating a collection with the name {ModCollectionIdentity.DefaultCollectionName}, which is required to exist.",
             NotificationType.Error);
-        return Count > 1 ? _collections[1] : _collections[0];
+        return Count > 1 ? this[1] : this[0];
     }
 
     /// <summary> Move all settings in all collections to unused settings. </summary>
     private void OnModDiscoveryStarted()
     {
-        foreach (var collection in this)
+        var snapshot = GetModSnapShot();
+        foreach (var collection in snapshot)
             collection.Settings.PrepareModDiscovery(_modStorage);
     }
 
     /// <summary> Restore all settings in all collections to mods. </summary>
     private void OnModDiscoveryFinished()
     {
+        var snapshot = GetModSnapShot();
         // Re-apply all mod settings.
-        foreach (var collection in this)
+        foreach (var collection in snapshot)
             collection.Settings.ApplyModSettings(collection, _saveService, _modStorage);
     }
 
     /// <summary> Add or remove a mod from all collections, or re-save all collections where the mod has settings. </summary>
     private void OnModPathChange(ModPathChangeType type, Mod mod, DirectoryInfo? oldDirectory,
         DirectoryInfo? newDirectory)
     {
+        var snapshot = GetModSnapShot();
         switch (type)
         {
             case ModPathChangeType.Added:
-                foreach (var collection in this)
+                foreach (var collection in snapshot)
                     collection.Settings.AddMod(mod);
                 break;
             case ModPathChangeType.Deleted:
-                foreach (var collection in this)
+                foreach (var collection in snapshot)
                     collection.Settings.RemoveMod(mod);
                 break;
             case ModPathChangeType.Moved:
-                foreach (var collection in this.Where(collection => collection.GetOwnSettings(mod.Index) != null))
+                foreach (var collection in snapshot.Where(collection => collection.GetOwnSettings(mod.Index) != null))
                     _saveService.QueueSave(new ModCollectionSave(_modStorage, collection));
                 break;
             case ModPathChangeType.Reloaded:
-                foreach (var collection in this)
+                foreach (var collection in snapshot)
                 {
                     if (collection.GetOwnSettings(mod.Index)?.Settings.FixAll(mod) ?? false)
                         _saveService.QueueSave(new ModCollectionSave(_modStorage, collection));
@@ -359,8 +402,9 @@ private void OnModOptionChange(ModOptionChangeType type, Mod mod, IModGroup? gro
         type.HandlingInfo(out var requiresSaving, out _, out _);
         if (!requiresSaving)
             return;
-
-        foreach (var collection in this)
+
+        var snapshot = GetModSnapShot();
+        foreach (var collection in snapshot)
         {
             if (collection.GetOwnSettings(mod.Index)?.HandleChanges(type, mod, group, option, movedToIdx) ?? false)
                 _saveService.QueueSave(new ModCollectionSave(_modStorage, collection));
@@ -374,11 +418,22 @@ private void OnModFileChanged(Mod mod, FileRegistry file)
         if (file.CurrentUsage == 0)
             return;
 
-        foreach (var collection in this)
+        var snapshot = GetModSnapShot();
+        foreach (var collection in snapshot)
         {
             var (settings, _) = collection.GetActualSettings(mod.Index);
             if (settings is { Enabled: true })
                 collection.Counters.IncrementChange();
         }
     }
+
+    private ModCollection[] GetModSnapShot()
+    {
+        ModCollection[] snapshot;
+        lock (_collectionsLock)
+        {
+            snapshot = _collections.Skip(1).ToArray();
+        }
+        return snapshot;
+    }
 }