add timing/interval/expiry hooks

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/hooks/useTimeout.ts

@@ -0,0 +1,67 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {useEffect, useRef, useState} from "react";
+
+type Handler = () => void;
+
+// Hook to simplify timeouts in functional components
+export const useTimeout = (handler: Handler, timeoutMs: number) => {
+    // Create a ref that stores handler
+    const savedHandler = useRef<Handler>();
+
+    // Update ref.current value if handler changes.
+    useEffect(() => {
+        savedHandler.current = handler;
+    }, [handler]);
+
+    // Set up timer
+    useEffect(() => {
+        const timeoutID = setTimeout(() => {
+            savedHandler.current();
+        }, timeoutMs);
+        return () => clearTimeout(timeoutID);
+    }, [timeoutMs]);
+};
+
+// Hook to simplify intervals in functional components
+export const useInterval = (handler: Handler, intervalMs: number) => {
+    // Create a ref that stores handler
+    const savedHandler = useRef<Handler>();
+
+    // Update ref.current value if handler changes.
+    useEffect(() => {
+        savedHandler.current = handler;
+    }, [handler]);
+
+    // Set up timer
+    useEffect(() => {
+        const intervalID = setInterval(() => {
+            savedHandler.current();
+        }, intervalMs);
+        return () => clearInterval(intervalID);
+    }, [intervalMs]);
+};
+
+// Hook to simplify a variable counting down to 0, handler called when it reached 0
+export const useExpiringCounter = (handler: Handler, intervalMs: number, initialCount: number) => {
+    const [count, setCount] = useState(initialCount);
+    useInterval(() => setCount(c => c - 1), intervalMs);
+    if (count === 0) {
+        handler();
+    }
+    return count;
+};