1 files changed, 43 insertions, 0 deletions
diff --git a/src/SMAPI/Framework/SnapshotDiff.cs b/src/SMAPI/Framework/SnapshotDiff.cs
new file mode 100644
index 00000000..5b6288ff
--- /dev/null
+++ b/src/SMAPI/Framework/SnapshotDiff.cs
@@ -0,0 +1,43 @@
+using StardewModdingAPI.Framework.StateTracking;
+
+namespace StardewModdingAPI.Framework
+{
+    /// <summary>A snapshot of a tracked value.</summary>
+    /// <typeparam name="T">The tracked value type.</typeparam>
+    internal class SnapshotDiff<T>
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>Whether the value changed since the last update.</summary>
+        public bool IsChanged { get; private set; }
+
+        /// <summary>The previous value.</summary>
+        public T Old { get; private set; }
+
+        /// <summary>The current value.</summary>
+        public T New { get; private set; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Update the snapshot.</summary>
+        /// <param name="isChanged">Whether the value changed since the last update.</param>
+        /// <param name="old">The previous value.</param>
+        /// <param name="now">The current value.</param>
+        public void Update(bool isChanged, T old, T now)
+        {
+            this.IsChanged = isChanged;
+            this.Old = old;
+            this.New = now;
+        }
+
+        /// <summary>Update the snapshot.</summary>
+        /// <param name="watcher">The value watcher to snapshot.</param>
+        public void Update(IValueWatcher<T> watcher)
+        {
+            this.Update(watcher.IsChanged, watcher.PreviousValue, watcher.CurrentValue);
+        }
+    }
+}