unify item diff logic for players & chests

9 files changed, 135 insertions, 93 deletions

diff --git a/src/SMAPI/Events/ChestInventoryChangedEventArgs.cs b/src/SMAPI/Events/ChestInventoryChangedEventArgs.cs
index 7771cd7c..4b4c4210 100644
--- a/src/SMAPI/Events/ChestInventoryChangedEventArgs.cs
+++ b/src/SMAPI/Events/ChestInventoryChangedEventArgs.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using StardewValley;
 using StardewValley.Objects;
 
@@ -16,8 +17,14 @@ namespace StardewModdingAPI.Events
         /// <summary>The location containing the chest.</summary>
         public GameLocation Location { get; }
 
-        /// <summary>The inventory changes in the chest.</summary>
-        public ItemStackChange[] Changes { get; }
+        /// <summary>The added item stacks.</summary>
+        public IEnumerable<Item> Added { get; }
+
+        /// <summary>The removed item stacks.</summary>
+        public IEnumerable<Item> Removed { get; }
+
+        /// <summary>The item stacks whose size changed.</summary>
+        public IEnumerable<ItemStackSizeChange> QuantityChanged { get; }
 
 
         /*********
@@ -26,12 +33,16 @@ namespace StardewModdingAPI.Events
         /// <summary>Construct an instance.</summary>
         /// <param name="chest">The chest whose inventory changed.</param>
         /// <param name="location">The location containing the chest.</param>
-        /// <param name="changes">The inventory changes in the chest.</param>
-        internal ChestInventoryChangedEventArgs(Chest chest, GameLocation location, ItemStackChange[] changes)
+        /// <param name="added">The added item stacks.</param>
+        /// <param name="removed">The removed item stacks.</param>
+        /// <param name="quantityChanged">The item stacks whose size changed.</param>
+        internal ChestInventoryChangedEventArgs(Chest chest, GameLocation location, Item[] added, Item[] removed, ItemStackSizeChange[] quantityChanged)
         {
             this.Location = location;
             this.Chest = chest;
-            this.Changes = changes;
+            this.Added = added;
+            this.Removed = removed;
+            this.QuantityChanged = quantityChanged;
         }
     }
 }
diff --git a/src/SMAPI/Events/InventoryChangedEventArgs.cs b/src/SMAPI/Events/InventoryChangedEventArgs.cs
index 874c2e48..40cd4128 100644
--- a/src/SMAPI/Events/InventoryChangedEventArgs.cs
+++ b/src/SMAPI/Events/InventoryChangedEventArgs.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using StardewValley;
 
 namespace StardewModdingAPI.Events
@@ -14,13 +13,13 @@ namespace StardewModdingAPI.Events
         /// <summary>The player whose inventory changed.</summary>
         public Farmer Player { get; }
 
-        /// <summary>The added items.</summary>
+        /// <summary>The added item stacks.</summary>
         public IEnumerable<Item> Added { get; }
 
-        /// <summary>The removed items.</summary>
+        /// <summary>The removed item stacks.</summary>
         public IEnumerable<Item> Removed { get; }
 
-        /// <summary>The items whose stack sizes changed, with the relative change.</summary>
+        /// <summary>The item stacks whose size changed.</summary>
         public IEnumerable<ItemStackSizeChange> QuantityChanged { get; }
 
         /// <summary>Whether the affected player is the local one.</summary>
@@ -32,28 +31,15 @@ namespace StardewModdingAPI.Events
         *********/
         /// <summary>Construct an instance.</summary>
         /// <param name="player">The player whose inventory changed.</param>
-        /// <param name="changedItems">The inventory changes.</param>
-        internal InventoryChangedEventArgs(Farmer player, ItemStackChange[] changedItems)
+        /// <param name="added">The added item stacks.</param>
+        /// <param name="removed">The removed item stacks.</param>
+        /// <param name="quantityChanged">The item stacks whose size changed.</param>
+        internal InventoryChangedEventArgs(Farmer player, Item[] added, Item[] removed, ItemStackSizeChange[] quantityChanged)
         {
             this.Player = player;
-            this.Added = changedItems
-                .Where(n => n.ChangeType == ChangeType.Added)
-                .Select(p => p.Item)
-                .ToArray();
-
-            this.Removed = changedItems
-                .Where(n => n.ChangeType == ChangeType.Removed)
-                .Select(p => p.Item)
-                .ToArray();
-
-            this.QuantityChanged = changedItems
-                .Where(n => n.ChangeType == ChangeType.StackChange)
-                .Select(change => new ItemStackSizeChange(
-                    item: change.Item,
-                    oldSize: change.Item.Stack - change.StackChange,
-                    newSize: change.Item.Stack
-                ))
-                .ToArray();
+            this.Added = added;
+            this.Removed = removed;
+            this.QuantityChanged = quantityChanged;
         }
     }
 }
diff --git a/src/SMAPI/Events/ItemStackChange.cs b/src/SMAPI/Events/ItemStackChange.cs
deleted file mode 100644
index cb5d2b88..00000000
--- a/src/SMAPI/Events/ItemStackChange.cs
+++ /dev/null
@@ -1,20 +0,0 @@
-using StardewValley;
-
-namespace StardewModdingAPI.Events
-{
-    /// <summary>Represents an inventory slot that changed.</summary>
-    public class ItemStackChange
-    {
-        /*********
-        ** Accessors
-        *********/
-        /// <summary>The item in the slot.</summary>
-        public Item Item { get; set; }
-
-        /// <summary>The amount by which the item's stack size changed.</summary>
-        public int StackChange { get; set; }
-
-        /// <summary>How the inventory slot changed.</summary>
-        public ChangeType ChangeType { get; set; }
-    }
-}
diff --git a/src/SMAPI/Framework/SGame.cs b/src/SMAPI/Framework/SGame.cs
index eccb6387..e2b22ba7 100644
--- a/src/SMAPI/Framework/SGame.cs
+++ b/src/SMAPI/Framework/SGame.cs
@@ -706,7 +706,10 @@ namespace StardewModdingAPI.Framework
                                 if (events.ChestInventoryChanged.HasListeners())
                                 {
                                     foreach (var pair in locState.ChestItems)
-                                        events.ChestInventoryChanged.Raise(new ChestInventoryChangedEventArgs(pair.Key, location, pair.Value));
+                                    {
+                                        SnapshotItemListDiff diff = pair.Value;
+                                        events.ChestInventoryChanged.Raise(new ChestInventoryChangedEventArgs(pair.Key, location, added: diff.Added, removed: diff.Removed, quantityChanged: diff.QuantityChanged));
+                                    }
                                 }
 
                                 // terrain features changed
@@ -747,12 +750,13 @@ namespace StardewModdingAPI.Framework
                             }
 
                             // raise player inventory changed
-                            ItemStackChange[] changedItems = playerState.InventoryChanges.ToArray();
-                            if (changedItems.Any())
+                            if (playerState.Inventory.IsChanged)
                             {
+                                var inventory = playerState.Inventory;
+
                                 if (this.Monitor.IsVerbose)
                                     this.Monitor.Log("Events: player inventory changed.", LogLevel.Trace);
-                                events.InventoryChanged.Raise(new InventoryChangedEventArgs(player, changedItems));
+                                events.InventoryChanged.Raise(new InventoryChangedEventArgs(player, added: inventory.Added, removed: inventory.Removed, quantityChanged: inventory.QuantityChanged));
                             }
                         }
                     }
diff --git a/src/SMAPI/Framework/SnapshotItemListDiff.cs b/src/SMAPI/Framework/SnapshotItemListDiff.cs
new file mode 100644
index 00000000..e8ab1b1e
--- /dev/null
+++ b/src/SMAPI/Framework/SnapshotItemListDiff.cs
@@ -0,0 +1,66 @@
+using System.Collections.Generic;
+using System.Linq;
+using StardewModdingAPI.Events;
+using StardewValley;
+
+namespace StardewModdingAPI.Framework
+{
+    /// <summary>A snapshot of a tracked item list.</summary>
+    internal class SnapshotItemListDiff
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>Whether the item list changed.</summary>
+        public bool IsChanged { get; }
+
+        /// <summary>The removed values.</summary>
+        public Item[] Removed { get; }
+
+        /// <summary>The added values.</summary>
+        public Item[] Added { get; }
+
+        /// <summary>The items whose stack sizes changed.</summary>
+        public ItemStackSizeChange[] QuantityChanged { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Update the snapshot.</summary>
+        /// <param name="added">The added values.</param>
+        /// <param name="removed">The removed values.</param>
+        /// <param name="sizesChanged">The items whose stack sizes changed.</param>
+        public SnapshotItemListDiff(Item[] added, Item[] removed, ItemStackSizeChange[] sizesChanged)
+        {
+            this.Removed = removed;
+            this.Added = added;
+            this.QuantityChanged = sizesChanged;
+
+            this.IsChanged = removed.Length > 0 || added.Length > 0 || sizesChanged.Length > 0;
+        }
+
+        /// <summary>Get a snapshot diff if anything changed in the given data.</summary>
+        /// <param name="added">The added item stacks.</param>
+        /// <param name="removed">The removed item stacks.</param>
+        /// <param name="stackSizes">The items with their previous stack sizes.</param>
+        /// <param name="changes">The inventory changes, or <c>null</c> if nothing changed.</param>
+        /// <returns>Returns whether anything changed.</returns>
+        public static bool TryGetChanges(ISet<Item> added, ISet<Item> removed, IDictionary<Item, int> stackSizes, out SnapshotItemListDiff changes)
+        {
+            KeyValuePair<Item, int>[] sizesChanged = stackSizes.Where(p => p.Key.Stack != p.Value).ToArray();
+            if (sizesChanged.Any() || added.Any() || removed.Any())
+            {
+                changes = new SnapshotItemListDiff(
+                    added: added.ToArray(),
+                    removed: removed.ToArray(),
+                    sizesChanged: sizesChanged.Select(p => new ItemStackSizeChange(p.Key, p.Value, p.Key.Stack)).ToArray()
+                );
+                return true;
+            }
+
+            changes = null;
+            return false;
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/StateTracking/ChestTracker.cs b/src/SMAPI/Framework/StateTracking/ChestTracker.cs
index 3ce70c17..65f58ee7 100644
--- a/src/SMAPI/Framework/StateTracking/ChestTracker.cs
+++ b/src/SMAPI/Framework/StateTracking/ChestTracker.cs
@@ -1,12 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using StardewModdingAPI.Events;
 using StardewModdingAPI.Framework.StateTracking.Comparers;
 using StardewModdingAPI.Framework.StateTracking.FieldWatchers;
 using StardewValley;
 using StardewValley.Objects;
-using ChangeType = StardewModdingAPI.Events.ChangeType;
 
 namespace StardewModdingAPI.Framework.StateTracking
 {
@@ -83,26 +81,12 @@ namespace StardewModdingAPI.Framework.StateTracking
             this.Removed.Clear();
         }
 
-        /// <summary>Get the inventory changes since the last update.</summary>
-        public IEnumerable<ItemStackChange> GetInventoryChanges()
+        /// <summary>Get the inventory changes since the last update, if anything changed.</summary>
+        /// <param name="changes">The inventory changes, or <c>null</c> if nothing changed.</param>
+        /// <returns>Returns whether anything changed.</returns>
+        public bool TryGetInventoryChanges(out SnapshotItemListDiff changes)
         {
-            // removed
-            foreach (Item item in this.Removed)
-                yield return new ItemStackChange { Item = item, StackChange = -item.Stack, ChangeType = ChangeType.Removed };
-
-            // added
-            foreach (Item item in this.Added)
-                yield return new ItemStackChange { Item = item, StackChange = item.Stack, ChangeType = ChangeType.Added };
-
-            // stack size changed
-            foreach (var entry in this.StackSizes)
-            {
-                Item item = entry.Key;
-                int prevStack = entry.Value;
-
-                if (item.Stack != prevStack)
-                    yield return new ItemStackChange { Item = item, StackChange = item.Stack - prevStack, ChangeType = ChangeType.StackChange };
-            }
+            return SnapshotItemListDiff.TryGetChanges(added: this.Added, removed: this.Removed, stackSizes: this.StackSizes, out changes);
         }
 
         /// <summary>Release watchers and resources.</summary>
diff --git a/src/SMAPI/Framework/StateTracking/PlayerTracker.cs b/src/SMAPI/Framework/StateTracking/PlayerTracker.cs
index d25f3345..cf49a7c1 100644
--- a/src/SMAPI/Framework/StateTracking/PlayerTracker.cs
+++ b/src/SMAPI/Framework/StateTracking/PlayerTracker.cs
@@ -2,10 +2,9 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using StardewModdingAPI.Enums;
-using StardewModdingAPI.Events;
+using StardewModdingAPI.Framework.StateTracking.Comparers;
 using StardewModdingAPI.Framework.StateTracking.FieldWatchers;
 using StardewValley;
-using ChangeType = StardewModdingAPI.Events.ChangeType;
 
 namespace StardewModdingAPI.Framework.StateTracking
 {
@@ -99,20 +98,24 @@ namespace StardewModdingAPI.Framework.StateTracking
             return this.Player.currentLocation ?? this.LastValidLocation;
         }
 
-        /// <summary>Get the inventory changes since the last update.</summary>
-        public IEnumerable<ItemStackChange> GetInventoryChanges()
+        /// <summary>Get the inventory changes since the last update, if anything changed.</summary>
+        /// <param name="changes">The inventory changes, or <c>null</c> if nothing changed.</param>
+        /// <returns>Returns whether anything changed.</returns>
+        public bool TryGetInventoryChanges(out SnapshotItemListDiff changes)
         {
-            IDictionary<Item, int> previous = this.PreviousInventory;
             IDictionary<Item, int> current = this.GetInventory();
-            foreach (Item item in previous.Keys.Union(current.Keys))
+
+            ISet<Item> added = new HashSet<Item>(new ObjectReferenceComparer<Item>());
+            ISet<Item> removed = new HashSet<Item>(new ObjectReferenceComparer<Item>());
+            foreach (Item item in this.PreviousInventory.Keys.Union(current.Keys))
             {
-                if (!previous.TryGetValue(item, out int prevStack))
-                    yield return new ItemStackChange { Item = item, StackChange = item.Stack, ChangeType = ChangeType.Added };
-                else if (!current.TryGetValue(item, out int newStack))
-                    yield return new ItemStackChange { Item = item, StackChange = -item.Stack, ChangeType = ChangeType.Removed };
-                else if (prevStack != newStack)
-                    yield return new ItemStackChange { Item = item, StackChange = newStack - prevStack, ChangeType = ChangeType.StackChange };
+                if (!this.PreviousInventory.ContainsKey(item))
+                    added.Add(item);
+                else if (!current.ContainsKey(item))
+                    removed.Add(item);
             }
+
+            return SnapshotItemListDiff.TryGetChanges(added: added, removed: removed, stackSizes: this.PreviousInventory, out changes);
         }
 
         /// <summary>Release watchers and resources.</summary>
diff --git a/src/SMAPI/Framework/StateTracking/Snapshots/LocationSnapshot.cs b/src/SMAPI/Framework/StateTracking/Snapshots/LocationSnapshot.cs
index edfba736..6ae52fd0 100644
--- a/src/SMAPI/Framework/StateTracking/Snapshots/LocationSnapshot.cs
+++ b/src/SMAPI/Framework/StateTracking/Snapshots/LocationSnapshot.cs
@@ -1,7 +1,5 @@
 using System.Collections.Generic;
-using System.Linq;
 using Microsoft.Xna.Framework;
-using StardewModdingAPI.Events;
 using StardewValley;
 using StardewValley.Buildings;
 using StardewValley.Objects;
@@ -37,7 +35,7 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
         public SnapshotListDiff<KeyValuePair<Vector2, TerrainFeature>> TerrainFeatures { get; } = new SnapshotListDiff<KeyValuePair<Vector2, TerrainFeature>>();
 
         /// <summary>Tracks changed chest inventories.</summary>
-        public IDictionary<Chest, ItemStackChange[]> ChestItems { get; } = new Dictionary<Chest, ItemStackChange[]>();
+        public IDictionary<Chest, SnapshotItemListDiff> ChestItems { get; } = new Dictionary<Chest, SnapshotItemListDiff>();
 
 
         /*********
@@ -66,8 +64,7 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
             this.ChestItems.Clear();
             foreach (ChestTracker tracker in watcher.ChestWatchers.Values)
             {
-                ItemStackChange[] changes = tracker.GetInventoryChanges().ToArray();
-                if (changes.Length > 0)
+                if (tracker.TryGetInventoryChanges(out SnapshotItemListDiff changes))
                     this.ChestItems[tracker.Chest] = changes;
             }
         }
diff --git a/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs b/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs
index 7bcd9f82..f0fb9485 100644
--- a/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs
+++ b/src/SMAPI/Framework/StateTracking/Snapshots/PlayerSnapshot.cs
@@ -11,6 +11,13 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
     internal class PlayerSnapshot
     {
         /*********
+        ** Fields
+        *********/
+        /// <summary>An empty item list diff.</summary>
+        private readonly SnapshotItemListDiff EmptyItemListDiff = new SnapshotItemListDiff(new Item[0], new Item[0], new ItemStackSizeChange[0]);
+
+
+        /*********
         ** Accessors
         *********/
         /// <summary>The player being tracked.</summary>
@@ -27,7 +34,7 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
                 .ToDictionary(skill => skill, skill => new SnapshotDiff<int>());
 
         /// <summary>Get a list of inventory changes.</summary>
-        public IEnumerable<ItemStackChange> InventoryChanges { get; private set; }
+        public SnapshotItemListDiff Inventory { get; private set; }
 
 
         /*********
@@ -47,7 +54,11 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
             this.Location.Update(watcher.LocationWatcher);
             foreach (var pair in this.Skills)
                 pair.Value.Update(watcher.SkillWatchers[pair.Key]);
-            this.InventoryChanges = watcher.GetInventoryChanges().ToArray();
+
+            this.Inventory = watcher.TryGetInventoryChanges(out SnapshotItemListDiff itemChanges)
+                ? itemChanges
+                : this.EmptyItemListDiff;
+
         }
     }
 }