feat: add change to localStorage plugin

Author: WitoDelnat

src/core/keat.ts

@@ -13,11 +13,15 @@ import { mutable } from "./utils";
 
 export type ExtractFeatures<K> = K extends KeatApi<infer K> ? keyof K : never;
 
+export type Listener = () => void;
+export type Unsubscribe = () => void;
+
 export function keatCore<TFeatures extends AnyFeatures>({
   features,
   display = "swap",
   plugins = [],
 }: KeatInit<TFeatures>): KeatApi<TFeatures> {
+  let listeners: Listener[] = [];
   let defaultDisplay = display;
   let defaultUser: User | undefined = undefined;
   let configId = 0;
@@ -33,6 +37,9 @@ export function keatCore<TFeatures extends AnyFeatures>({
               configId += 1;
               config = newConfig;
             },
+            onChange: () => {
+              listeners.forEach((l) => l());
+            },
           }
         )
       )
@@ -98,6 +105,12 @@ export function keatCore<TFeatures extends AnyFeatures>({
       const useLatest = loader.useLatest(display);
       return evaluate(feature as string, user, useLatest ? configId : 0);
     },
+    onChange: (listener: Listener): Unsubscribe => {
+      listeners.push(listener);
+      return () => {
+        listeners = listeners.filter((l) => l === listener);
+      };
+    },
   };
 }
 

src/core/plugin.ts

@@ -25,6 +25,7 @@ export type OnPluginInitCtx = {
 
 export type OnPluginInitApi = {
   setConfig: (newConfig: Config) => void;
+  onChange: () => void;
 };
 
 export type OnEvalHook = (

src/core/types.ts

@@ -1,3 +1,4 @@
+import { Listener, Unsubscribe } from "./keat";
 import type { Plugin } from "./plugin";
 
 /**
@@ -64,6 +65,7 @@ export type KeatApi<TFeatures extends AnyFeatures> = {
       ? TFeatures[TFeature]["variates"][number]
       : boolean
     : boolean;
+  onChange(listener: Listener): Unsubscribe;
 };
 
 /* * * * * * * * * * * * *

src/plugins/localStorage.ts

@@ -16,32 +16,49 @@ type Options = {
   value?: string;
 
   /**
-   * Whether the local storage item should only
-   * retried at initialisation.
+   * Whether the local storage is polled for updated.
    *
-   * @default false
+   * The default polling time every 2 seconds.
+   * You can change it by setting a number (in ms).
    */
-  once?: boolean;
+  poll?: boolean | number;
 };
 
 export const localStorage = (
   name: string,
-  { key, value, once = false }: Options = {}
+  { key, value, poll = false }: Options = {}
 ): Plugin => {
-  const item = once ?? window.localStorage.getItem(key ?? name);
+  const k = key ?? name;
+  let item = window.localStorage.getItem(k);
+
   return {
+    onPluginInit(_, { onChange }) {
+      const pollInterval =
+        poll === true ? 2000 : typeof poll === "number" && poll > 0 ? poll : 0;
+      if (hasSetInterval() && pollInterval > 0) {
+        setInterval(() => {
+          const newItem = window.localStorage.getItem(k);
+          const hasChanged = item !== newItem;
+          item = newItem;
+          if (hasChanged) onChange();
+        }, pollInterval);
+      }
+    },
     onEval({ variates, rules }, { setResult }) {
       if (typeof window === "undefined") return;
 
       const index = rules.findIndex((rule) =>
         takeStrings(rule).some((r) => {
           if (r !== name) return false;
-          const i = once ? item : window.localStorage.getItem(key ?? name);
-          return value ? i === value : Boolean(i);
+          return value ? item === value : Boolean(item);
         })
       );
 
       if (index !== -1) setResult(variates[index]);
     },
   };
 };
+
+function hasSetInterval() {
+  return typeof window !== "undefined" && window.setInterval;
+}

src/react/KeatReact.tsx

@@ -1,4 +1,4 @@
-import React, { ReactNode, useEffect } from "react";
+import React, { ReactNode, useEffect, useReducer } from "react";
 import { AnyFeatures, Display, KeatApi, keatCore, KeatInit } from "../core";
 
 type KeatReactApi<TFeatures extends AnyFeatures> = KeatApi<TFeatures> & {
@@ -48,11 +48,17 @@ export function keatReact<TFeatures extends AnyFeatures>(
       children,
     }) {
       const [loading, setLoading] = React.useState(true);
+      const [_, forceUpdate] = useReducer((x) => x + 1, 0);
 
       useEffect(() => {
         keatInstance.ready(display).then(() => setLoading(false));
       }, [setLoading]);
 
+      useEffect(() => {
+        const unsubscribe = keatInstance.onChange(forceUpdate);
+        return () => unsubscribe();
+      }, []);
+
       if (loading) {
         return <>{invisible}</>;
       }