Merge branch 'develop' into stable

1 files changed, 443 insertions, 175 deletions

diff --git a/src/SMAPI/Framework/SContentManager.cs b/src/SMAPI/Framework/SContentManager.cs
index db202567..a755a6df 100644
--- a/src/SMAPI/Framework/SContentManager.cs
+++ b/src/SMAPI/Framework/SContentManager.cs
@@ -1,13 +1,17 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Contracts;
 using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Threading;
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Content;
+using Microsoft.Xna.Framework.Graphics;
 using StardewModdingAPI.Framework.Content;
-using StardewModdingAPI.Framework.ModLoading;
+using StardewModdingAPI.Framework.Exceptions;
 using StardewModdingAPI.Framework.Reflection;
 using StardewModdingAPI.Framework.Utilities;
 using StardewModdingAPI.Metadata;
@@ -15,7 +19,17 @@ using StardewValley;
 
 namespace StardewModdingAPI.Framework
 {
-    /// <summary>SMAPI's implementation of the game's content manager which lets it raise content events.</summary>
+    /// <summary>A thread-safe content manager which intercepts assets being loaded to let SMAPI mods inject or edit them.</summary>
+    /// <remarks>
+    /// This is the centralised content manager which manages all game assets. The game and mods don't use this class
+    /// directly; instead they use one of several <see cref="ContentManagerShim"/> instances, which proxy requests to
+    /// this class. That ensures that when the game disposes one content manager, the others can continue unaffected.
+    /// That notably requires this class to be thread-safe, since the content managers can be disposed asynchronously.
+    /// 
+    /// Note that assets in the cache have two identifiers: the asset name (like "bundles") and key (like "bundles.pt-BR").
+    /// For English and non-translatable assets, these have the same value. The underlying cache only knows about asset
+    /// keys, and the game and mods only know about asset names. The content manager handles resolving them.
+    /// </remarks>
     internal class SContentManager : LocalizedContentManager
     {
         /*********
@@ -27,11 +41,8 @@ namespace StardewModdingAPI.Framework
         /// <summary>Encapsulates monitoring and logging.</summary>
         private readonly IMonitor Monitor;
 
-        /// <summary>The underlying content manager's asset cache.</summary>
-        private readonly IDictionary<string, object> Cache;
-
-        /// <summary>Applies platform-specific asset key normalisation so it's consistent with the underlying cache.</summary>
-        private readonly Func<string, string> NormaliseAssetNameForPlatform;
+        /// <summary>The underlying asset cache.</summary>
+        private readonly ContentCache Cache;
 
         /// <summary>The private <see cref="LocalizedContentManager"/> method which generates the locale portion of an asset name.</summary>
         private readonly IPrivateMethod GetKeyLocale;
@@ -46,10 +57,13 @@ namespace StardewModdingAPI.Framework
         private readonly ContextHash<string> AssetsBeingLoaded = new ContextHash<string>();
 
         /// <summary>A lookup of the content managers which loaded each asset.</summary>
-        private readonly IDictionary<string, HashSet<ContentManager>> AssetLoaders = new Dictionary<string, HashSet<ContentManager>>();
+        private readonly IDictionary<string, HashSet<ContentManager>> ContentManagersByAssetKey = new Dictionary<string, HashSet<ContentManager>>();
+
+        /// <summary>The path prefix for assets in mod folders.</summary>
+        private readonly string ModContentPrefix;
 
-        /// <summary>An object locked to prevent concurrent changes to the underlying assets.</summary>
-        private readonly object Lock = new object();
+        /// <summary>A lock used to prevents concurrent changes to the cache while data is being read.</summary>
+        private readonly ReaderWriterLockSlim Lock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);
 
 
         /*********
@@ -71,121 +85,176 @@ namespace StardewModdingAPI.Framework
         /*********
         ** Public methods
         *********/
+        /****
+        ** Constructor
+        ****/
         /// <summary>Construct an instance.</summary>
         /// <param name="serviceProvider">The service provider to use to locate services.</param>
         /// <param name="rootDirectory">The root directory to search for content.</param>
         /// <param name="currentCulture">The current culture for which to localise content.</param>
         /// <param name="languageCodeOverride">The current language code for which to localise content.</param>
         /// <param name="monitor">Encapsulates monitoring and logging.</param>
-        public SContentManager(IServiceProvider serviceProvider, string rootDirectory, CultureInfo currentCulture, string languageCodeOverride, IMonitor monitor)
+        /// <param name="reflection">Simplifies access to private code.</param>
+        public SContentManager(IServiceProvider serviceProvider, string rootDirectory, CultureInfo currentCulture, string languageCodeOverride, IMonitor monitor, Reflector reflection)
             : base(serviceProvider, rootDirectory, currentCulture, languageCodeOverride)
         {
-            // validate
-            if (monitor == null)
-                throw new ArgumentNullException(nameof(monitor));
-
-            // initialise
-            var reflection = new Reflector();
-            this.Monitor = monitor;
-
-            // get underlying fields for interception
-            this.Cache = reflection.GetPrivateField<Dictionary<string, object>>(this, "loadedAssets").GetValue();
+            // init
+            this.Monitor = monitor ?? throw new ArgumentNullException(nameof(monitor));
+            this.Cache = new ContentCache(this, reflection, SContentManager.PossiblePathSeparators, SContentManager.PreferredPathSeparator);
             this.GetKeyLocale = reflection.GetPrivateMethod(this, "languageCode");
-
-            // get asset key normalisation logic
-            if (Constants.TargetPlatform == Platform.Windows)
-            {
-                IPrivateMethod method = reflection.GetPrivateMethod(typeof(TitleContainer), "GetCleanPath");
-                this.NormaliseAssetNameForPlatform = path => method.Invoke<string>(path);
-            }
-            else
-                this.NormaliseAssetNameForPlatform = key => key.Replace('\\', '/'); // based on MonoGame's ContentManager.Load<T> logic
+            this.ModContentPrefix = this.GetRelativePath(Constants.ModPath);
 
             // get asset data
             this.CoreAssets = new CoreAssets(this.NormaliseAssetName);
             this.KeyLocales = this.GetKeyLocales(reflection);
         }
 
+        /****
+        ** Asset key/name handling
+        ****/
         /// <summary>Normalise path separators in a file path. For asset keys, see <see cref="NormaliseAssetName"/> instead.</summary>
         /// <param name="path">The file path to normalise.</param>
+        [Pure]
         public string NormalisePathSeparators(string path)
         {
-            string[] parts = path.Split(SContentManager.PossiblePathSeparators, StringSplitOptions.RemoveEmptyEntries);
-            string normalised = string.Join(SContentManager.PreferredPathSeparator, parts);
-            if (path.StartsWith(SContentManager.PreferredPathSeparator))
-                normalised = SContentManager.PreferredPathSeparator + normalised; // keep root slash
-            return normalised;
+            return this.Cache.NormalisePathSeparators(path);
         }
 
         /// <summary>Normalise an asset name so it's consistent with the underlying cache.</summary>
         /// <param name="assetName">The asset key.</param>
+        [Pure]
         public string NormaliseAssetName(string assetName)
         {
-            assetName = this.NormalisePathSeparators(assetName);
-            if (assetName.EndsWith(".xnb", StringComparison.InvariantCultureIgnoreCase))
-                return assetName.Substring(0, assetName.Length - 4);
-            return this.NormaliseAssetNameForPlatform(assetName);
+            return this.Cache.NormaliseKey(assetName);
+        }
+
+        /// <summary>Assert that the given key has a valid format.</summary>
+        /// <param name="key">The asset key to check.</param>
+        /// <exception cref="ArgumentException">The asset key is empty or contains invalid characters.</exception>
+        [SuppressMessage("ReSharper", "ParameterOnlyUsedForPreconditionCheck.Local", Justification = "Parameter is only used for assertion checks by design.")]
+        public void AssertValidAssetKeyFormat(string key)
+        {
+            if (string.IsNullOrWhiteSpace(key))
+                throw new ArgumentException("The asset key or local path is empty.");
+            if (key.Intersect(Path.GetInvalidPathChars()).Any())
+                throw new ArgumentException("The asset key or local path contains invalid characters.");
+        }
+
+        /// <summary>Get a directory path relative to the content root.</summary>
+        /// <param name="targetPath">The target file path.</param>
+        public string GetRelativePath(string targetPath)
+        {
+            // convert to URIs
+            Uri from = new Uri(this.FullRootDirectory + "/");
+            Uri to = new Uri(targetPath + "/");
+            if (from.Scheme != to.Scheme)
+                throw new InvalidOperationException($"Can't get path for '{targetPath}' relative to '{this.FullRootDirectory}'.");
+
+            // get relative path
+            return Uri.UnescapeDataString(from.MakeRelativeUri(to).ToString())
+                .Replace(Path.DirectorySeparatorChar == '/' ? '\\' : '/', Path.DirectorySeparatorChar); // use correct separator for platform
+        }
+
+        /****
+        ** Content loading
+        ****/
+        /// <summary>Get the current content locale.</summary>
+        public string GetLocale()
+        {
+            return this.GetKeyLocale.Invoke<string>();
         }
 
         /// <summary>Get whether the content manager has already loaded and cached the given asset.</summary>
         /// <param name="assetName">The asset path relative to the loader root directory, not including the <c>.xnb</c> extension.</param>
         public bool IsLoaded(string assetName)
         {
-            lock (this.Lock)
-            {
-                assetName = this.NormaliseAssetName(assetName);
-                return this.IsNormalisedKeyLoaded(assetName);
-            }
+            assetName = this.Cache.NormaliseKey(assetName);
+            return this.WithReadLock(() => this.IsNormalisedKeyLoaded(assetName));
         }
 
-        /// <summary>Load an asset that has been processed by the content pipeline.</summary>
-        /// <typeparam name="T">The type of asset to load.</typeparam>
-        /// <param name="assetName">The asset path relative to the loader root directory, not including the <c>.xnb</c> extension.</param>
+        /// <summary>Get the cached asset keys.</summary>
+        public IEnumerable<string> GetAssetKeys()
+        {
+            return this.WithReadLock(() =>
+                this.Cache.Keys
+                    .Select(this.GetAssetName)
+                    .Distinct()
+            );
+        }
+
+        /// <summary>Load an asset through the content pipeline. When loading a <c>.png</c> file, this must be called outside the game's draw loop.</summary>
+        /// <typeparam name="T">The expected asset type.</typeparam>
+        /// <param name="assetName">The asset path relative to the content directory.</param>
         public override T Load<T>(string assetName)
         {
             return this.LoadFor<T>(assetName, this);
         }
 
-        /// <summary>Load an asset that has been processed by the content pipeline.</summary>
-        /// <typeparam name="T">The type of asset to load.</typeparam>
-        /// <param name="assetName">The asset path relative to the loader root directory, not including the <c>.xnb</c> extension.</param>
+        /// <summary>Load an asset through the content pipeline. When loading a <c>.png</c> file, this must be called outside the game's draw loop.</summary>
+        /// <typeparam name="T">The expected asset type.</typeparam>
+        /// <param name="assetName">The asset path relative to the content directory.</param>
         /// <param name="instance">The content manager instance for which to load the asset.</param>
+        /// <exception cref="ArgumentException">The <paramref name="assetName"/> is empty or contains invalid characters.</exception>
+        /// <exception cref="ContentLoadException">The content asset couldn't be loaded (e.g. because it doesn't exist).</exception>
         public T LoadFor<T>(string assetName, ContentManager instance)
         {
-            lock (this.Lock)
-            {
-                assetName = this.NormaliseAssetName(assetName);
+            // normalise asset key
+            this.AssertValidAssetKeyFormat(assetName);
+            assetName = this.NormaliseAssetName(assetName);
 
-                // skip if already loaded
-                if (this.IsNormalisedKeyLoaded(assetName))
-                {
-                    this.TrackAssetLoader(assetName, instance);
-                    return base.Load<T>(assetName);
-                }
+            // load game content
+            if (!assetName.StartsWith(this.ModContentPrefix))
+                return this.LoadImpl<T>(assetName, instance);
 
-                // load asset
-                T data;
-                if (this.AssetsBeingLoaded.Contains(assetName))
-                {
-                    this.Monitor.Log($"Broke loop while loading asset '{assetName}'.", LogLevel.Warn);
-                    this.Monitor.Log($"Bypassing mod loaders for this asset. Stack trace:\n{Environment.StackTrace}", LogLevel.Trace);
-                    data = base.Load<T>(assetName);
-                }
-                else
+            // load mod content
+            SContentLoadException GetContentError(string reasonPhrase) => new SContentLoadException($"Failed loading content asset '{assetName}': {reasonPhrase}.");
+            try
+            {
+                return this.WithWriteLock(() =>
                 {
-                    data = this.AssetsBeingLoaded.Track(assetName, () =>
-                    {
-                        IAssetInfo info = new AssetInfo(this.GetLocale(), assetName, typeof(T), this.NormaliseAssetName);
-                        IAssetData asset = this.ApplyLoader<T>(info) ?? new AssetDataForObject(info, base.Load<T>(assetName), this.NormaliseAssetName);
-                        asset = this.ApplyEditors<T>(info, asset);
-                        return (T)asset.Data;
-                    });
-                }
+                    // try cache
+                    if (this.IsLoaded(assetName))
+                        return this.LoadImpl<T>(assetName, instance);
 
-                // update cache & return data
-                this.Cache[assetName] = data;
-                this.TrackAssetLoader(assetName, instance);
-                return data;
+                    // get file
+                    FileInfo file = this.GetModFile(assetName);
+                    if (!file.Exists)
+                        throw GetContentError("the specified path doesn't exist.");
+
+                    // load content
+                    switch (file.Extension.ToLower())
+                    {
+                        // XNB file
+                        case ".xnb":
+                            return this.LoadImpl<T>(assetName, instance);
+
+                        // unpacked map
+                        case ".tbin":
+                            throw GetContentError($"can't read unpacked map file '{assetName}' directly from the underlying content manager. It must be loaded through the mod's {typeof(IModHelper)}.{nameof(IModHelper.Content)} helper.");
+
+                        // unpacked image
+                        case ".png":
+                            // validate
+                            if (typeof(T) != typeof(Texture2D))
+                                throw GetContentError($"can't read file with extension '{file.Extension}' as type '{typeof(T)}'; must be type '{typeof(Texture2D)}'.");
+
+                            // fetch & cache
+                            using (FileStream stream = File.OpenRead(file.FullName))
+                            {
+                                Texture2D texture = Texture2D.FromStream(Game1.graphics.GraphicsDevice, stream);
+                                texture = this.PremultiplyTransparency(texture);
+                                this.InjectWithoutLock(assetName, texture, instance);
+                                return (T)(object)texture;
+                            }
+
+                        default:
+                            throw GetContentError($"unknown file extension '{file.Extension}'; must be one of '.png', '.tbin', or '.xnb'.");
+                    }
+                });
+            }
+            catch (Exception ex) when (!(ex is SContentLoadException))
+            {
+                throw new SContentLoadException($"The content manager failed loading content asset '{assetName}'.", ex);
             }
         }
 
@@ -193,40 +262,15 @@ namespace StardewModdingAPI.Framework
         /// <typeparam name="T">The type of asset to inject.</typeparam>
         /// <param name="assetName">The asset path relative to the loader root directory, not including the <c>.xnb</c> extension.</param>
         /// <param name="value">The asset value.</param>
-        public void Inject<T>(string assetName, T value)
-        {
-            lock (this.Lock)
-            {
-                assetName = this.NormaliseAssetName(assetName);
-                this.Cache[assetName] = value;
-                this.TrackAssetLoader(assetName, this);
-            }
-        }
-
-        /// <summary>Get the current content locale.</summary>
-        public string GetLocale()
-        {
-            return this.GetKeyLocale.Invoke<string>();
-        }
-
-        /// <summary>Get the cached asset keys.</summary>
-        public IEnumerable<string> GetAssetKeys()
+        /// <param name="instance">The content manager instance for which to load the asset.</param>
+        public void Inject<T>(string assetName, T value, ContentManager instance)
         {
-            lock (this.Lock)
-            {
-                IEnumerable<string> GetAllAssetKeys()
-                {
-                    foreach (string cacheKey in this.Cache.Keys)
-                    {
-                        this.ParseCacheKey(cacheKey, out string assetKey, out string _);
-                        yield return assetKey;
-                    }
-                }
-
-                return GetAllAssetKeys().Distinct();
-            }
+            this.WithWriteLock(() => this.InjectWithoutLock(assetName, value, instance));
         }
 
+        /****
+        ** Cache invalidation
+        ****/
         /// <summary>Purge assets from the cache that match one of the interceptors.</summary>
         /// <param name="editors">The asset editors for which to purge matching assets.</param>
         /// <param name="loaders">The asset loaders for which to purge matching assets.</param>
@@ -239,21 +283,34 @@ namespace StardewModdingAPI.Framework
             // get CanEdit/Load methods
             MethodInfo canEdit = typeof(IAssetEditor).GetMethod(nameof(IAssetEditor.CanEdit));
             MethodInfo canLoad = typeof(IAssetLoader).GetMethod(nameof(IAssetLoader.CanLoad));
+            if (canEdit == null || canLoad == null)
+                throw new InvalidOperationException("SMAPI could not access the interceptor methods."); // should never happen
 
             // invalidate matching keys
-            return this.InvalidateCache((assetName, assetType) =>
+            return this.InvalidateCache(asset =>
             {
-                // get asset metadata
-                IAssetInfo info = new AssetInfo(this.GetLocale(), assetName, assetType, this.NormaliseAssetName);
-
                 // check loaders
-                MethodInfo canLoadGeneric = canLoad.MakeGenericMethod(assetType);
-                if (loaders.Any(loader => (bool)canLoadGeneric.Invoke(loader, new object[] { info })))
+                MethodInfo canLoadGeneric = canLoad.MakeGenericMethod(asset.DataType);
+                if (loaders.Any(loader => (bool)canLoadGeneric.Invoke(loader, new object[] { asset })))
                     return true;
 
                 // check editors
-                MethodInfo canEditGeneric = canEdit.MakeGenericMethod(assetType);
-                return editors.Any(editor => (bool)canEditGeneric.Invoke(editor, new object[] { info }));
+                MethodInfo canEditGeneric = canEdit.MakeGenericMethod(asset.DataType);
+                return editors.Any(editor => (bool)canEditGeneric.Invoke(editor, new object[] { asset }));
+            });
+        }
+
+        /// <summary>Purge matched assets from the cache.</summary>
+        /// <param name="predicate">Matches the asset keys to invalidate.</param>
+        /// <param name="dispose">Whether to dispose invalidated assets. This should only be <c>true</c> when they're being invalidated as part of a dispose, to avoid crashing the game.</param>
+        /// <returns>Returns whether any cache entries were invalidated.</returns>
+        public bool InvalidateCache(Func<IAssetInfo, bool> predicate, bool dispose = false)
+        {
+            string locale = this.GetLocale();
+            return this.InvalidateCache((assetName, type) =>
+            {
+                IAssetInfo info = new AssetInfo(locale, assetName, type, this.NormaliseAssetName);
+                return predicate(info);
             });
         }
 
@@ -263,83 +320,81 @@ namespace StardewModdingAPI.Framework
         /// <returns>Returns whether any cache entries were invalidated.</returns>
         public bool InvalidateCache(Func<string, Type, bool> predicate, bool dispose = false)
         {
-            lock (this.Lock)
+            return this.WithWriteLock(() =>
             {
-                // find matching asset keys
-                HashSet<string> purgeCacheKeys = new HashSet<string>(StringComparer.InvariantCultureIgnoreCase);
-                HashSet<string> purgeAssetKeys = new HashSet<string>(StringComparer.InvariantCultureIgnoreCase);
-                foreach (string cacheKey in this.Cache.Keys)
+                // invalidate matching keys
+                HashSet<string> removeKeys = new HashSet<string>(StringComparer.InvariantCultureIgnoreCase);
+                HashSet<string> removeAssetNames = new HashSet<string>(StringComparer.InvariantCultureIgnoreCase);
+                this.Cache.Remove((key, type) =>
                 {
-                    this.ParseCacheKey(cacheKey, out string assetKey, out _);
-                    Type type = this.Cache[cacheKey].GetType();
-                    if (predicate(assetKey, type))
+                    this.ParseCacheKey(key, out string assetName, out _);
+                    if (removeAssetNames.Contains(assetName) || predicate(assetName, type))
                     {
-                        purgeAssetKeys.Add(assetKey);
-                        purgeCacheKeys.Add(cacheKey);
+                        removeAssetNames.Add(assetName);
+                        removeKeys.Add(key);
+                        return true;
                     }
-                }
+                    return false;
+                });
 
-                // purge assets
-                foreach (string key in purgeCacheKeys)
-                {
-                    if (dispose && this.Cache[key] is IDisposable disposable)
-                        disposable.Dispose();
-                    this.Cache.Remove(key);
-                    this.AssetLoaders.Remove(key);
-                }
+                // update reference tracking
+                foreach (string key in removeKeys)
+                    this.ContentManagersByAssetKey.Remove(key);
 
                 // reload core game assets
                 int reloaded = 0;
-                foreach (string key in purgeAssetKeys)
+                foreach (string key in removeAssetNames)
                 {
                     if (this.CoreAssets.ReloadForKey(this, key))
                         reloaded++;
                 }
 
                 // report result
-                if (purgeCacheKeys.Any())
+                if (removeKeys.Any())
                 {
-                    this.Monitor.Log($"Invalidated {purgeCacheKeys.Count} cache entries for {purgeAssetKeys.Count} asset keys: {string.Join(", ", purgeCacheKeys.OrderBy(p => p, StringComparer.InvariantCultureIgnoreCase))}. Reloaded {reloaded} core assets.", LogLevel.Trace);
+                    this.Monitor.Log($"Invalidated {removeAssetNames.Count} asset names: {string.Join(", ", removeKeys.OrderBy(p => p, StringComparer.InvariantCultureIgnoreCase))}. Reloaded {reloaded} core assets.", LogLevel.Trace);
                     return true;
                 }
                 this.Monitor.Log("Invalidated 0 cache entries.", LogLevel.Trace);
                 return false;
-            }
+            });
         }
 
+        /****
+        ** Disposal
+        ****/
         /// <summary>Dispose assets for the given content manager shim.</summary>
         /// <param name="shim">The content manager whose assets to dispose.</param>
         internal void DisposeFor(ContentManagerShim shim)
         {
             this.Monitor.Log($"Content manager '{shim.Name}' disposed, disposing assets that aren't needed by any other asset loader.", LogLevel.Trace);
 
-            foreach (var entry in this.AssetLoaders)
-                entry.Value.Remove(shim);
-            this.InvalidateCache((key, type) => !this.AssetLoaders[key].Any(), dispose: true);
+            this.WithWriteLock(() =>
+            {
+                foreach (var entry in this.ContentManagersByAssetKey)
+                    entry.Value.Remove(shim);
+                this.InvalidateCache((key, type) => !this.ContentManagersByAssetKey[key].Any(), dispose: true);
+            });
         }
 
 
         /*********
         ** Private methods
         *********/
-        /// <summary>Get whether an asset has already been loaded.</summary>
-        /// <param name="normalisedAssetName">The normalised asset name.</param>
-        private bool IsNormalisedKeyLoaded(string normalisedAssetName)
-        {
-            return this.Cache.ContainsKey(normalisedAssetName)
-                || this.Cache.ContainsKey($"{normalisedAssetName}.{this.GetKeyLocale.Invoke<string>()}"); // translated asset
-        }
-
-        /// <summary>Track that a content manager loaded an asset.</summary>
-        /// <param name="key">The asset key that was loaded.</param>
-        /// <param name="manager">The content manager that loaded the asset.</param>
-        private void TrackAssetLoader(string key, ContentManager manager)
+        /****
+        ** Disposal
+        ****/
+        /// <summary>Dispose held resources.</summary>
+        /// <param name="disposing">Whether the content manager is disposing (rather than finalising).</param>
+        protected override void Dispose(bool disposing)
         {
-            if (!this.AssetLoaders.TryGetValue(key, out HashSet<ContentManager> hash))
-                hash = this.AssetLoaders[key] = new HashSet<ContentManager>();
-            hash.Add(manager);
+            this.Monitor.Log("Disposing SMAPI's main content manager. It will no longer be usable after this point.", LogLevel.Trace);
+            base.Dispose(disposing);
         }
 
+        /****
+        ** Asset name/key handling
+        ****/
         /// <summary>Get the locale codes (like <c>ja-JP</c>) used in asset keys.</summary>
         /// <param name="reflection">Simplifies access to private game code.</param>
         private IDictionary<string, LanguageCode> GetKeyLocales(Reflector reflection)
@@ -367,11 +422,19 @@ namespace StardewModdingAPI.Framework
             return map;
         }
 
+        /// <summary>Get the asset name from a cache key.</summary>
+        /// <param name="cacheKey">The input cache key.</param>
+        private string GetAssetName(string cacheKey)
+        {
+            this.ParseCacheKey(cacheKey, out string assetName, out string _);
+            return assetName;
+        }
+
         /// <summary>Parse a cache key into its component parts.</summary>
         /// <param name="cacheKey">The input cache key.</param>
-        /// <param name="assetKey">The original asset key.</param>
+        /// <param name="assetName">The original asset name.</param>
         /// <param name="localeCode">The asset locale code (or <c>null</c> if not localised).</param>
-        private void ParseCacheKey(string cacheKey, out string assetKey, out string localeCode)
+        private void ParseCacheKey(string cacheKey, out string assetName, out string localeCode)
         {
             // handle localised key
             if (!string.IsNullOrWhiteSpace(cacheKey))
@@ -382,7 +445,7 @@ namespace StardewModdingAPI.Framework
                     string suffix = cacheKey.Substring(lastSepIndex + 1, cacheKey.Length - lastSepIndex - 1);
                     if (this.KeyLocales.ContainsKey(suffix))
                     {
-                        assetKey = cacheKey.Substring(0, lastSepIndex);
+                        assetName = cacheKey.Substring(0, lastSepIndex);
                         localeCode = cacheKey.Substring(lastSepIndex + 1, cacheKey.Length - lastSepIndex - 1);
                         return;
                     }
@@ -390,10 +453,117 @@ namespace StardewModdingAPI.Framework
             }
 
             // handle simple key
-            assetKey = cacheKey;
+            assetName = cacheKey;
             localeCode = null;
         }
 
+        /****
+        ** Cache handling
+        ****/
+        /// <summary>Get whether an asset has already been loaded.</summary>
+        /// <param name="normalisedAssetName">The normalised asset name.</param>
+        private bool IsNormalisedKeyLoaded(string normalisedAssetName)
+        {
+            return this.Cache.ContainsKey(normalisedAssetName)
+                || this.Cache.ContainsKey($"{normalisedAssetName}.{this.GetKeyLocale.Invoke<string>()}"); // translated asset
+        }
+
+        /// <summary>Track that a content manager loaded an asset.</summary>
+        /// <param name="key">The asset key that was loaded.</param>
+        /// <param name="manager">The content manager that loaded the asset.</param>
+        private void TrackAssetLoader(string key, ContentManager manager)
+        {
+            if (!this.ContentManagersByAssetKey.TryGetValue(key, out HashSet<ContentManager> hash))
+                hash = this.ContentManagersByAssetKey[key] = new HashSet<ContentManager>();
+            hash.Add(manager);
+        }
+
+        /****
+        ** Content loading
+        ****/
+        /// <summary>Load an asset name without heuristics to support mod content.</summary>
+        /// <typeparam name="T">The type of asset to load.</typeparam>
+        /// <param name="assetName">The asset path relative to the loader root directory, not including the <c>.xnb</c> extension.</param>
+        /// <param name="instance">The content manager instance for which to load the asset.</param>
+        private T LoadImpl<T>(string assetName, ContentManager instance)
+        {
+            return this.WithWriteLock(() =>
+            {
+                // skip if already loaded
+                if (this.IsNormalisedKeyLoaded(assetName))
+                {
+                    this.TrackAssetLoader(assetName, instance);
+                    return base.Load<T>(assetName);
+                }
+
+                // load asset
+                T data;
+                if (this.AssetsBeingLoaded.Contains(assetName))
+                {
+                    this.Monitor.Log($"Broke loop while loading asset '{assetName}'.", LogLevel.Warn);
+                    this.Monitor.Log($"Bypassing mod loaders for this asset. Stack trace:\n{Environment.StackTrace}", LogLevel.Trace);
+                    data = base.Load<T>(assetName);
+                }
+                else
+                {
+                    data = this.AssetsBeingLoaded.Track(assetName, () =>
+                    {
+                        IAssetInfo info = new AssetInfo(this.GetLocale(), assetName, typeof(T), this.NormaliseAssetName);
+                        IAssetData asset = this.ApplyLoader<T>(info) ?? new AssetDataForObject(info, base.Load<T>(assetName), this.NormaliseAssetName);
+                        asset = this.ApplyEditors<T>(info, asset);
+                        return (T)asset.Data;
+                    });
+                }
+
+                // update cache & return data
+                this.InjectWithoutLock(assetName, data, instance);
+                return data;
+            });
+        }
+
+        /// <summary>Inject an asset into the cache without acquiring a write lock. This should only be called from within a write lock.</summary>
+        /// <typeparam name="T">The type of asset to inject.</typeparam>
+        /// <param name="assetName">The asset path relative to the loader root directory, not including the <c>.xnb</c> extension.</param>
+        /// <param name="value">The asset value.</param>
+        /// <param name="instance">The content manager instance for which to load the asset.</param>
+        private void InjectWithoutLock<T>(string assetName, T value, ContentManager instance)
+        {
+            assetName = this.NormaliseAssetName(assetName);
+            this.Cache[assetName] = value;
+            this.TrackAssetLoader(assetName, instance);
+        }
+
+        /// <summary>Get a file from the mod folder.</summary>
+        /// <param name="path">The asset path relative to the content folder.</param>
+        private FileInfo GetModFile(string path)
+        {
+            // try exact match
+            FileInfo file = new FileInfo(Path.Combine(this.FullRootDirectory, path));
+
+            // try with default extension
+            if (!file.Exists && file.Extension.ToLower() != ".xnb")
+            {
+                FileInfo result = new FileInfo(file.FullName + ".xnb");
+                if (result.Exists)
+                    file = result;
+            }
+
+            return file;
+        }
+
+        /// <summary>Get a file from the game's content folder.</summary>
+        /// <param name="key">The asset key.</param>
+        private FileInfo GetContentFolderFile(string key)
+        {
+            // get file path
+            string path = Path.Combine(this.FullRootDirectory, key);
+            if (!path.EndsWith(".xnb"))
+                path += ".xnb";
+
+            // get file
+            return new FileInfo(path);
+        }
+
         /// <summary>Load the initial asset from the registered <see cref="Loaders"/>.</summary>
         /// <param name="info">The basic asset metadata.</param>
         /// <returns>Returns the loaded asset metadata, or <c>null</c> if no loader matched.</returns>
@@ -510,25 +680,123 @@ namespace StardewModdingAPI.Framework
         {
             foreach (var entry in entries)
             {
-                IModMetadata metadata = entry.Key;
+                IModMetadata mod = entry.Key;
                 IList<T> interceptors = entry.Value;
 
-                // special case if mod is an interceptor
-                if (metadata.Mod is T modAsInterceptor)
-                    yield return new KeyValuePair<IModMetadata, T>(metadata, modAsInterceptor);
-
                 // registered editors
                 foreach (T interceptor in interceptors)
-                    yield return new KeyValuePair<IModMetadata, T>(metadata, interceptor);
+                    yield return new KeyValuePair<IModMetadata, T>(mod, interceptor);
             }
         }
 
-        /// <summary>Dispose held resources.</summary>
-        /// <param name="disposing">Whether the content manager is disposing (rather than finalising).</param>
-        protected override void Dispose(bool disposing)
+        /// <summary>Premultiply a texture's alpha values to avoid transparency issues in the game. This is only possible if the game isn't currently drawing.</summary>
+        /// <param name="texture">The texture to premultiply.</param>
+        /// <returns>Returns a premultiplied texture.</returns>
+        /// <remarks>Based on <a href="https://gist.github.com/Layoric/6255384">code by Layoric</a>.</remarks>
+        private Texture2D PremultiplyTransparency(Texture2D texture)
         {
-            this.Monitor.Log("Disposing SMAPI's main content manager. It will no longer be usable after this point.", LogLevel.Trace);
-            base.Dispose(disposing);
+            // validate
+            if (Context.IsInDrawLoop)
+                throw new NotSupportedException("Can't load a PNG file while the game is drawing to the screen. Make sure you load content outside the draw loop.");
+
+            // process texture
+            SpriteBatch spriteBatch = Game1.spriteBatch;
+            GraphicsDevice gpu = Game1.graphics.GraphicsDevice;
+            using (RenderTarget2D renderTarget = new RenderTarget2D(Game1.graphics.GraphicsDevice, texture.Width, texture.Height))
+            {
+                // create blank render target to premultiply
+                gpu.SetRenderTarget(renderTarget);
+                gpu.Clear(Color.Black);
+
+                // multiply each color by the source alpha, and write just the color values into the final texture
+                spriteBatch.Begin(SpriteSortMode.Immediate, new BlendState
+                {
+                    ColorDestinationBlend = Blend.Zero,
+                    ColorWriteChannels = ColorWriteChannels.Red | ColorWriteChannels.Green | ColorWriteChannels.Blue,
+                    AlphaDestinationBlend = Blend.Zero,
+                    AlphaSourceBlend = Blend.SourceAlpha,
+                    ColorSourceBlend = Blend.SourceAlpha
+                });
+                spriteBatch.Draw(texture, texture.Bounds, Color.White);
+                spriteBatch.End();
+
+                // copy the alpha values from the source texture into the final one without multiplying them
+                spriteBatch.Begin(SpriteSortMode.Immediate, new BlendState
+                {
+                    ColorWriteChannels = ColorWriteChannels.Alpha,
+                    AlphaDestinationBlend = Blend.Zero,
+                    ColorDestinationBlend = Blend.Zero,
+                    AlphaSourceBlend = Blend.One,
+                    ColorSourceBlend = Blend.One
+                });
+                spriteBatch.Draw(texture, texture.Bounds, Color.White);
+                spriteBatch.End();
+
+                // release GPU
+                gpu.SetRenderTarget(null);
+
+                // extract premultiplied data
+                Color[] data = new Color[texture.Width * texture.Height];
+                renderTarget.GetData(data);
+
+                // unset texture from GPU to regain control
+                gpu.Textures[0] = null;
+
+                // update texture with premultiplied data
+                texture.SetData(data);
+            }
+
+            return texture;
+        }
+
+        /****
+        ** Concurrency logic
+        ****/
+        /// <summary>Acquire a read lock which prevents concurrent writes to the cache while it's open.</summary>
+        /// <typeparam name="T">The action's return value.</typeparam>
+        /// <param name="action">The action to perform.</param>
+        private T WithReadLock<T>(Func<T> action)
+        {
+            try
+            {
+                this.Lock.EnterReadLock();
+                return action();
+            }
+            finally
+            {
+                this.Lock.ExitReadLock();
+            }
+        }
+
+        /// <summary>Acquire a write lock which prevents concurrent reads or writes to the cache while it's open.</summary>
+        /// <param name="action">The action to perform.</param>
+        private void WithWriteLock(Action action)
+        {
+            try
+            {
+                this.Lock.EnterWriteLock();
+                action();
+            }
+            finally
+            {
+                this.Lock.ExitWriteLock();
+            }
+        }
+
+        /// <summary>Acquire a write lock which prevents concurrent reads or writes to the cache while it's open.</summary>
+        /// <typeparam name="T">The action's return value.</typeparam>
+        /// <param name="action">The action to perform.</param>
+        private T WithWriteLock<T>(Func<T> action)
+        {
+            try
+            {
+                this.Lock.EnterReadLock();
+                return action();
+            }
+            finally
+            {
+                this.Lock.ExitReadLock();
+            }
         }
     }
 }