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xterminal/source/base/reactivity.ts

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+import { isFunction } from "../helpers";
+import type { IDisposable } from "../types";
+
+/**
+ * Reactivity
+ * => https://github.com/henryhale/reactivity
+ */
+
+/**
+ * Effect - callback triggered when a reactive value changes
+ */
+export type IEffect = () => void;
+
+/**
+ * Reactive value -> all effects are disposable
+ */
+export interface IReactive<T> extends IDisposable {
+    value: T;
+}
+
+/**
+ * Global observer
+ */
+let observer: IEffect | null;
+
+/**
+ * Function that creates a disposable reactive object from a primitive value
+ * @param value The primitive value (initial)
+ * @returns Reactive object
+ */
+export function ref<T>(value: T): IReactive<T> {
+    const observers = new Set<IEffect>();
+    let disposed = false;
+    return {
+        get value() {
+            // allow subscriptons only when the object is not disposed
+            if (!disposed && isFunction(observer)) {
+                observers.add(observer);
+            }
+            return value;
+        },
+        set value(newValue) {
+            value = newValue;
+            // alert subscribers only when the object is not disposed
+            if (!disposed) {
+                observers.forEach((o) => o.call(undefined));
+            }
+        },
+        dispose() {
+            if (disposed) return;
+            disposed = true;
+            // remove all subscriptions
+            observers.clear();
+        }
+    };
+}
+
+/**
+ * Function that opens a subscription to reactive values
+ * @param fn The subscription (function) to be made
+ */
+export function createEffect(fn: IEffect): void {
+    if (!isFunction(fn)) return;
+    observer = fn;
+    try {
+        fn.call(undefined);
+    } finally {
+        observer = null;
+    }
+}