1 files changed, 83 insertions, 0 deletions
diff --git a/src/SMAPI/Framework/StateTracking/FieldWatchers/NetValueWatcher.cs b/src/SMAPI/Framework/StateTracking/FieldWatchers/NetValueWatcher.cs
new file mode 100644
index 00000000..188ed9f3
--- /dev/null
+++ b/src/SMAPI/Framework/StateTracking/FieldWatchers/NetValueWatcher.cs
@@ -0,0 +1,83 @@
+using Netcode;
+
+namespace StardewModdingAPI.Framework.StateTracking.FieldWatchers
+{
+    /// <summary>A watcher which detects changes to a net value field.</summary>
+    internal class NetValueWatcher<T, TSelf> : BaseDisposableWatcher, IValueWatcher<T> where TSelf : NetFieldBase<T, TSelf>
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The field being watched.</summary>
+        private readonly NetFieldBase<T, TSelf> Field;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>Whether the value changed since the last reset.</summary>
+        public bool IsChanged { get; private set; }
+
+        /// <summary>The field value at the last reset.</summary>
+        public T PreviousValue { get; private set; }
+
+        /// <summary>The latest value.</summary>
+        public T CurrentValue { get; private set; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="field">The field to watch.</param>
+        public NetValueWatcher(NetFieldBase<T, TSelf> field)
+        {
+            this.Field = field;
+            this.PreviousValue = field.Value;
+            this.CurrentValue = field.Value;
+
+            field.fieldChangeVisibleEvent += this.OnValueChanged;
+            field.fieldChangeEvent += this.OnValueChanged;
+        }
+
+        /// <summary>Update the current value if needed.</summary>
+        public void Update()
+        {
+            this.AssertNotDisposed();
+        }
+
+        /// <summary>Set the current value as the baseline.</summary>
+        public void Reset()
+        {
+            this.AssertNotDisposed();
+
+            this.PreviousValue = this.CurrentValue;
+            this.IsChanged = false;
+        }
+
+        /// <summary>Stop watching the field and release all references.</summary>
+        public override void Dispose()
+        {
+            if (!this.IsDisposed)
+            {
+                this.Field.fieldChangeEvent -= this.OnValueChanged;
+                this.Field.fieldChangeVisibleEvent -= this.OnValueChanged;
+            }
+            base.Dispose();
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>A callback invoked when the field's value changes.</summary>
+        /// <param name="field">The field being watched.</param>
+        /// <param name="oldValue">The old field value.</param>
+        /// <param name="newValue">The new field value.</param>
+        private void OnValueChanged(TSelf field, T oldValue, T newValue)
+        {
+            this.CurrentValue = newValue;
+            this.IsChanged = true;
+        }
+    }
+}