Create Hysteresis utility class

Provides a simple rolling average hysteresis.

src/modules/utility/hysteresis.ts

@@ -0,0 +1,51 @@
+/**
+ * The default number of points to sample from.
+ */
+const defaultLength = 10;
+
+/**
+ * A rolling average hysteresis.
+ * @param getter A function to retrieve new values.
+ * @param length `(Optional)` The number of points to sample the rolling average from.
+ * @param threshold `(Optional)` The snapping threshold. New values with a delta greater than this threshold will cause the output to snap to said new value.
+ */
+export class Hysteresis {
+    private getter;
+    private history;
+    private length;
+    private threshold;
+
+    constructor(getter: () => number, length = defaultLength, threshold?: number) {
+        this.getter = getter;
+        this.history = new Array<number>();
+        this.length = length;
+        this.threshold = threshold;
+
+        const value = getter();
+        for (let i = 0; i < this.length; i++) {
+            this.history.push(value);
+        }
+    }
+
+    /**
+     * @returns The value from the getter with hysteresis smoothing applied.
+     */
+    public get(): number {
+        const value = this.getter();
+        this.history.shift();
+        this.history.push(value);
+        const average = this.history.reduce((a, b) => a + b) / this.length;
+        if (typeof this.threshold === "number" && Math.abs(value - this.history[this.history.length - 2]) > this.threshold) {
+            this.history = this.history.fill(value);
+            return value;
+        }
+        return average;
+    }
+
+    /**
+     * @returns The value from the getter **without** hysteresis smoothing applied.
+     */
+    public getInstant(): number {
+        return this.getter();
+    }
+}