2 files changed, 80 insertions, 1 deletions
diff --git a/src/SMAPI/Framework/StateTracking/ChestTracker.cs b/src/SMAPI/Framework/StateTracking/ChestTracker.cs
new file mode 100644
index 00000000..4440bf4b
--- /dev/null
+++ b/src/SMAPI/Framework/StateTracking/ChestTracker.cs
@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using StardewModdingAPI.Enums;
+using StardewModdingAPI.Events;
+using StardewModdingAPI.Framework.StateTracking.FieldWatchers;
+using StardewValley;
+using ChangeType = StardewModdingAPI.Events.ChangeType;
+using Chest = StardewValley.Objects.Chest;
+
+namespace StardewModdingAPI.Framework.StateTracking
+{
+    internal class ChestTracker
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>The chest's inventory as of the last reset.</summary>
+        private IDictionary<Item, int> PreviousInventory;
+
+        /// <summary>The chest's inventory change as of the last update.</summary>
+        private IDictionary<Item, int> CurrentInventory;
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The chest being tracked</summary>
+        public Chest Chest { get; }
+
+        /*********
+        ** Public methods
+        *********/
+        public ChestTracker(Chest chest)
+        {
+            this.Chest = chest;
+            this.PreviousInventory = this.GetInventory();
+        }
+
+        public void Update()
+        {
+            this.CurrentInventory = this.GetInventory();
+        }
+
+
+        public void Reset()
+        {
+            this.PreviousInventory = this.CurrentInventory;
+        }
+
+        public IEnumerable<ItemStackChange> GetInventoryChanges()
+        {
+            IDictionary<Item, int> previous = this.PreviousInventory;
+            Console.WriteLine(previous.Count);
+            IDictionary<Item, int> current = this.GetInventory();
+            Console.WriteLine(current.Count);
+            foreach (Item item in previous.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 };
+            }
+        }
+
+        /*********
+        ** Private methods
+        *********/
+
+        private IDictionary<Item, int> GetInventory()
+        {
+            return this.Chest.items
+                .Where(n => n != null)
+                .Distinct()
+                .ToDictionary(n => n, n => n.Stack);
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/StateTracking/Snapshots/WorldLocationsSnapshot.cs b/src/SMAPI/Framework/StateTracking/Snapshots/WorldLocationsSnapshot.cs
index 73ed2d8f..ed8001d6 100644
--- a/src/SMAPI/Framework/StateTracking/Snapshots/WorldLocationsSnapshot.cs
+++ b/src/SMAPI/Framework/StateTracking/Snapshots/WorldLocationsSnapshot.cs
@@ -43,7 +43,7 @@ namespace StardewModdingAPI.Framework.StateTracking.Snapshots
             foreach (LocationTracker locationWatcher in watcher.Locations)
             {
                 if (!this.LocationsDict.TryGetValue(locationWatcher.Location, out LocationSnapshot snapshot))
-                    this.LocationsDict[locationWatcher.Location] = snapshot = new LocationSnapshot(locationWatcher.Location);
+                    this.LocationsDict[locationWatcher.Location] = snapshot = new LocationSnapshot(locationWatcher);
 
                 snapshot.Update(locationWatcher);
             }