encapsulate & cache asset operation groups (#766)

This is needed for the upcoming Stardew Valley 1.6 to avoid duplicate checks between DoesAssetExist and Load calls, and to make sure the answer doesn't change between them.

4 files changed, 179 insertions, 49 deletions

diff --git a/src/SMAPI/Framework/Content/AssetOperationGroup.cs b/src/SMAPI/Framework/Content/AssetOperationGroup.cs
new file mode 100644
index 00000000..a2fcb722
--- /dev/null
+++ b/src/SMAPI/Framework/Content/AssetOperationGroup.cs
@@ -0,0 +1,33 @@
+namespace StardewModdingAPI.Framework.Content
+{
+    /// <summary>A set of operations to apply to an asset for a given <see cref="IAssetEditor"/> or <see cref="IAssetLoader"/> implementation.</summary>
+    internal class AssetOperationGroup
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The mod applying the changes.</summary>
+        public IModMetadata Mod { get; }
+
+        /// <summary>The load operations to apply.</summary>
+        public AssetLoadOperation[] LoadOperations { get; }
+
+        /// <summary>The edit operations to apply.</summary>
+        public AssetEditOperation[] EditOperations { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="mod">The mod applying the changes.</param>
+        /// <param name="loadOperations">The load operations to apply.</param>
+        /// <param name="editOperations">The edit operations to apply.</param>
+        public AssetOperationGroup(IModMetadata mod, AssetLoadOperation[] loadOperations, AssetEditOperation[] editOperations)
+        {
+            this.Mod = mod;
+            this.LoadOperations = loadOperations;
+            this.EditOperations = editOperations;
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/ContentCoordinator.cs b/src/SMAPI/Framework/ContentCoordinator.cs
index fbbbe2d2..bf944e23 100644
--- a/src/SMAPI/Framework/ContentCoordinator.cs
+++ b/src/SMAPI/Framework/ContentCoordinator.cs
@@ -10,6 +10,8 @@ using Microsoft.Xna.Framework.Content;
 using StardewModdingAPI.Framework.Content;
 using StardewModdingAPI.Framework.ContentManagers;
 using StardewModdingAPI.Framework.Reflection;
+using StardewModdingAPI.Framework.Utilities;
+using StardewModdingAPI.Internal;
 using StardewModdingAPI.Metadata;
 using StardewModdingAPI.Toolkit.Serialization;
 using StardewModdingAPI.Toolkit.Utilities;
@@ -68,6 +70,9 @@ namespace StardewModdingAPI.Framework
         /// <summary>The language enum values indexed by locale code.</summary>
         private Lazy<Dictionary<string, LocalizedContentManager.LanguageCode>> LocaleCodes;
 
+        /// <summary>The cached asset load/edit operations to apply, indexed by asset name.</summary>
+        private readonly TickCacheDictionary<IAssetName, AssetOperationGroup[]> AssetOperationsByKey = new();
+
 
         /*********
         ** Accessors
@@ -351,17 +356,17 @@ namespace StardewModdingAPI.Framework
         public IEnumerable<IAssetName> InvalidateCache(Func<IContentManager, string, Type, bool> predicate, bool dispose = false)
         {
             // invalidate cache & track removed assets
-            IDictionary<IAssetName, Type> removedAssets = new Dictionary<IAssetName, Type>();
+            IDictionary<IAssetName, Type> invalidatedAssets = new Dictionary<IAssetName, Type>();
             this.ContentManagerLock.InReadLock(() =>
             {
                 // cached assets
                 foreach (IContentManager contentManager in this.ContentManagers)
                 {
-                    foreach (var entry in contentManager.InvalidateCache((key, type) => predicate(contentManager, key, type), dispose))
+                    foreach ((string key, object asset) in contentManager.InvalidateCache((key, type) => predicate(contentManager, key, type), dispose))
                     {
-                        AssetName assetName = this.ParseAssetName(entry.Key);
-                        if (!removedAssets.ContainsKey(assetName))
-                            removedAssets[assetName] = entry.Value.GetType();
+                        AssetName assetName = this.ParseAssetName(key);
+                        if (!invalidatedAssets.ContainsKey(assetName))
+                            invalidatedAssets[assetName] = asset.GetType();
                     }
                 }
 
@@ -376,18 +381,22 @@ namespace StardewModdingAPI.Framework
 
                         // get map path
                         AssetName mapPath = this.ParseAssetName(this.MainContentManager.AssertAndNormalizeAssetName(location.mapPath.Value));
-                        if (!removedAssets.ContainsKey(mapPath) && predicate(this.MainContentManager, mapPath.Name, typeof(Map)))
-                            removedAssets[mapPath] = typeof(Map);
+                        if (!invalidatedAssets.ContainsKey(mapPath) && predicate(this.MainContentManager, mapPath.Name, typeof(Map)))
+                            invalidatedAssets[mapPath] = typeof(Map);
                     }
                 }
             });
 
+            // clear cached editor checks
+            foreach (IAssetName name in invalidatedAssets.Keys)
+                this.AssetOperationsByKey.Remove(name);
+
             // reload core game assets
-            if (removedAssets.Any())
+            if (invalidatedAssets.Any())
             {
                 // propagate changes to the game
                 this.CoreAssets.Propagate(
-                    assets: removedAssets.ToDictionary(p => p.Key, p => p.Value),
+                    assets: invalidatedAssets.ToDictionary(p => p.Key, p => p.Value),
                     ignoreWorld: Context.IsWorldFullyUnloaded,
                     out IDictionary<IAssetName, bool> propagated,
                     out bool updatedNpcWarps
@@ -396,7 +405,7 @@ namespace StardewModdingAPI.Framework
                 // log summary
                 StringBuilder report = new();
                 {
-                    IAssetName[] invalidatedKeys = removedAssets.Keys.ToArray();
+                    IAssetName[] invalidatedKeys = invalidatedAssets.Keys.ToArray();
                     IAssetName[] propagatedKeys = propagated.Where(p => p.Value).Select(p => p.Key).ToArray();
 
                     string FormatKeyList(IEnumerable<IAssetName> keys) => string.Join(", ", keys.Select(p => p.Name).OrderBy(p => p, StringComparer.OrdinalIgnoreCase));
@@ -414,7 +423,18 @@ namespace StardewModdingAPI.Framework
             else
                 this.Monitor.Log("Invalidated 0 cache entries.");
 
-            return removedAssets.Keys;
+            return invalidatedAssets.Keys;
+        }
+
+        /// <summary>Get the asset load and edit operations to apply to a given asset if it's (re)loaded now.</summary>
+        /// <typeparam name="T">The asset type.</typeparam>
+        /// <param name="info">The asset info to load or edit.</param>
+        public IEnumerable<AssetOperationGroup> GetAssetOperations<T>(IAssetInfo info)
+        {
+            return this.AssetOperationsByKey.GetOrSet(
+                info.Name,
+                () => this.GetAssetOperationsWithoutCache<T>(info).ToArray()
+            );
         }
 
         /// <summary>Get all loaded instances of an asset name.</summary>
@@ -534,5 +554,63 @@ namespace StardewModdingAPI.Framework
 
             return map;
         }
+
+        /// <summary>Get the asset load and edit operations to apply to a given asset if it's (re)loaded now, ignoring the <see cref="AssetOperationsByKey"/> cache.</summary>
+        /// <typeparam name="T">The asset type.</typeparam>
+        /// <param name="info">The asset info to load or edit.</param>
+        private IEnumerable<AssetOperationGroup> GetAssetOperationsWithoutCache<T>(IAssetInfo info)
+        {
+            // legacy load operations
+            foreach (ModLinked<IAssetLoader> loader in this.Loaders)
+            {
+                // check if loader applies
+                try
+                {
+                    if (!loader.Data.CanLoad<T>(info))
+                        continue;
+                }
+                catch (Exception ex)
+                {
+                    loader.Mod.LogAsMod($"Mod failed when checking whether it could load asset '{info.Name}', and will be ignored. Error details:\n{ex.GetLogSummary()}", LogLevel.Error);
+                    continue;
+                }
+
+                // add operation
+                yield return new AssetOperationGroup(
+                    mod: loader.Mod,
+                    loadOperations: new[]
+                    {
+                        new AssetLoadOperation(loader.Mod, assetInfo => loader.Data.Load<T>(assetInfo))
+                    },
+                    editOperations: Array.Empty<AssetEditOperation>()
+                );
+            }
+
+            // legacy edit operations
+            foreach (var editor in this.Editors)
+            {
+                // check if editor applies
+                try
+                {
+                    if (!editor.Data.CanEdit<T>(info))
+                        continue;
+                }
+                catch (Exception ex)
+                {
+                    editor.Mod.LogAsMod($"Mod crashed when checking whether it could edit asset '{info.Name}', and will be ignored. Error details:\n{ex.GetLogSummary()}", LogLevel.Error);
+                    continue;
+                }
+
+                // add operation
+                yield return new AssetOperationGroup(
+                    mod: editor.Mod,
+                    loadOperations: Array.Empty<AssetLoadOperation>(),
+                    editOperations: new[]
+                    {
+                        new AssetEditOperation(editor.Mod, assetData => editor.Data.Edit<T>(assetData))
+                    }
+                );
+            }
+        }
     }
 }
diff --git a/src/SMAPI/Framework/ContentManagers/GameContentManager.cs b/src/SMAPI/Framework/ContentManagers/GameContentManager.cs
index 7ed1fcda..642e526c 100644
--- a/src/SMAPI/Framework/ContentManagers/GameContentManager.cs
+++ b/src/SMAPI/Framework/ContentManagers/GameContentManager.cs
@@ -26,12 +26,6 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <summary>The assets currently being intercepted by <see cref="IAssetLoader"/> instances. This is used to prevent infinite loops when a loader loads a new asset.</summary>
         private readonly ContextHash<string> AssetsBeingLoaded = new();
 
-        /// <summary>Interceptors which provide the initial versions of matching assets.</summary>
-        private IList<ModLinked<IAssetLoader>> Loaders => this.Coordinator.Loaders;
-
-        /// <summary>Interceptors which edit matching assets after they're loaded.</summary>
-        private IList<ModLinked<IAssetEditor>> Editors => this.Coordinator.Editors;
-
         /// <summary>Maps asset names to their localized form, like <c>LooseSprites\Billboard => LooseSprites\Billboard.fr-FR</c> (localized) or <c>Maps\AnimalShop => Maps\AnimalShop</c> (not localized).</summary>
         private IDictionary<string, string> LocalizedAssetNames => LocalizedContentManager.localizedAssetNames;
 
@@ -370,22 +364,9 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <param name="info">The basic asset metadata.</param>
         private IEnumerable<AssetLoadOperation> GetLoaders<T>(IAssetInfo info)
         {
-            return this.Loaders
-                .Where(loader =>
-                {
-                    try
-                    {
-                        return loader.Data.CanLoad<T>(info);
-                    }
-                    catch (Exception ex)
-                    {
-                        loader.Mod.LogAsMod($"Mod failed when checking whether it could load asset '{info.Name}', and will be ignored. Error details:\n{ex.GetLogSummary()}", LogLevel.Error);
-                        return false;
-                    }
-                })
-                .Select(
-                    loader => new AssetLoadOperation(loader.Mod, assetInfo => loader.Data.Load<T>(assetInfo))
-                );
+            return this.Coordinator
+                .GetAssetOperations<T>(info)
+                .SelectMany(p => p.LoadOperations);
         }
 
         /// <summary>Get the asset editors to apply to an asset.</summary>
@@ -393,22 +374,9 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <param name="info">The basic asset metadata.</param>
         private IEnumerable<AssetEditOperation> GetEditors<T>(IAssetInfo info)
         {
-            return this.Editors
-                .Where(editor =>
-                {
-                    try
-                    {
-                        return editor.Data.CanEdit<T>(info);
-                    }
-                    catch (Exception ex)
-                    {
-                        editor.Mod.LogAsMod($"Mod crashed when checking whether it could edit asset '{info.Name}', and will be ignored. Error details:\n{ex.GetLogSummary()}", LogLevel.Error);
-                        return false;
-                    }
-                })
-                .Select(
-                    editor => new AssetEditOperation(editor.Mod, assetData => editor.Data.Edit<T>(assetData))
-                );
+            return this.Coordinator
+                .GetAssetOperations<T>(info)
+                .SelectMany(p => p.EditOperations);
         }
 
         /// <summary>Assert that at most one loader will be applied to an asset.</summary>
diff --git a/src/SMAPI/Framework/Utilities/TickCacheDictionary.cs b/src/SMAPI/Framework/Utilities/TickCacheDictionary.cs
new file mode 100644
index 00000000..1613a480
--- /dev/null
+++ b/src/SMAPI/Framework/Utilities/TickCacheDictionary.cs
@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using StardewValley;
+
+namespace StardewModdingAPI.Framework.Utilities
+{
+    /// <summary>An in-memory dictionary cache that stores data for the duration of a game update tick.</summary>
+    /// <typeparam name="TKey">The dictionary key type.</typeparam>
+    /// <typeparam name="TValue">The dictionary value type.</typeparam>
+    internal class TickCacheDictionary<TKey, TValue>
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>The last game tick for which data was cached.</summary>
+        private int LastGameTick = -1;
+
+        /// <summary>The underlying cached data.</summary>
+        private readonly Dictionary<TKey, TValue> Cache = new();
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Get a value from the cache, fetching it first if it's not cached yet.</summary>
+        /// <param name="cacheKey">The unique key for the cached value.</param>
+        /// <param name="get">Get the latest data if it's not in the cache yet.</param>
+        public TValue GetOrSet(TKey cacheKey, Func<TValue> get)
+        {
+            // clear cache on new tick
+            if (Game1.ticks != this.LastGameTick)
+            {
+                this.Cache.Clear();
+                this.LastGameTick = Game1.ticks;
+            }
+
+            // fetch value
+            if (!this.Cache.TryGetValue(cacheKey, out TValue cached))
+                this.Cache[cacheKey] = cached = get();
+            return cached;
+        }
+
+        /// <summary>Remove an entry from the cache.</summary>
+        /// <param name="cacheKey">The unique key for the cached value.</param>
+        /// <returns>Returns whether the key was present in the dictionary.</returns>
+        public bool Remove(TKey cacheKey)
+        {
+            return this.Cache.Remove(cacheKey);
+        }
+    }
+}