From 06de42884868d8f5353c420e17d6503669f5066b Mon Sep 17 00:00:00 2001
From: Jon Koops <jonkoops@gmail.com>
Date: Wed, 23 Feb 2022 11:29:50 +0100
Subject: [PATCH] Add 'useSetTimeout' hook to manage timers (#2134)

---
 src/components/alert/Alerts.tsx |  2 ++
 src/utils/useSetTimeout.test.ts | 61 +++++++++++++++++++++++++++++++++
 src/utils/useSetTimeout.ts      | 34 ++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 src/utils/useSetTimeout.test.ts
 create mode 100644 src/utils/useSetTimeout.ts

diff --git a/src/components/alert/Alerts.tsx b/src/components/alert/Alerts.tsx
index ec34386090..0ada79f079 100644
--- a/src/components/alert/Alerts.tsx
+++ b/src/components/alert/Alerts.tsx
@@ -4,6 +4,7 @@ import { AlertVariant } from "@patternfly/react-core";
 import type { AxiosError } from "axios";
 
 import useRequiredContext from "../../utils/useRequiredContext";
+import useSetTimeout from "../../utils/useSetTimeout";
 import { AlertPanel, AlertType } from "./AlertPanel";
 
 type AlertProps = {
@@ -23,6 +24,7 @@ export const useAlerts = () => useRequiredContext(AlertContext);
 export const AlertProvider: FunctionComponent = ({ children }) => {
   const { t } = useTranslation();
   const [alerts, setAlerts] = useState<AlertType[]>([]);
+  const setTimeout = useSetTimeout();
 
   const createId = () => new Date().getTime();
 
diff --git a/src/utils/useSetTimeout.test.ts b/src/utils/useSetTimeout.test.ts
new file mode 100644
index 0000000000..879da96c7c
--- /dev/null
+++ b/src/utils/useSetTimeout.test.ts
@@ -0,0 +1,61 @@
+/**
+ * @jest-environment jsdom
+ */
+import { renderHook } from "@testing-library/react-hooks";
+import useSetTimeout from "./useSetTimeout";
+
+jest.useFakeTimers();
+
+describe("useSetTimeout", () => {
+  it("schedules timeouts and triggers the callbacks", () => {
+    const { result } = renderHook(() => useSetTimeout());
+    const setTimeoutSpy = jest.spyOn(global, "setTimeout");
+
+    // Schedule some timeouts...
+    const callback1 = jest.fn();
+    const callback2 = jest.fn();
+    result.current(callback1, 1000);
+    result.current(callback2, 500);
+
+    // Ensure that setTimeout was actually called with the correct arguments.
+    expect(setTimeoutSpy).toHaveBeenCalledTimes(2);
+    expect(setTimeoutSpy).toBeCalledWith(expect.any(Function), 1000);
+    expect(setTimeoutSpy).toBeCalledWith(expect.any(Function), 500);
+
+    // Ensure callbacks are called after timers run.
+    expect(callback2).not.toBeCalled();
+    jest.advanceTimersByTime(500);
+    expect(callback1).not.toBeCalled();
+    expect(callback2).toBeCalled();
+    jest.advanceTimersByTime(500);
+    expect(callback1).toBeCalled();
+
+    setTimeoutSpy.mockRestore();
+  });
+
+  it("throws if a timeout is scheduled after the component has unmounted", () => {
+    const { result, unmount } = renderHook(() => useSetTimeout());
+
+    unmount();
+
+    expect(() => result.current(jest.fn(), 1000)).toThrowError(
+      "Can't schedule a timeout on an unmounted component."
+    );
+  });
+
+  it("clears a timeout if the component unmounts", () => {
+    const { result, unmount } = renderHook(() => useSetTimeout());
+    const timerId = 42;
+    const setTimeoutSpy = jest
+      .spyOn(global, "setTimeout")
+      .mockReturnValueOnce(timerId as unknown as NodeJS.Timeout);
+    const clearTimeoutSpy = jest.spyOn(global, "clearTimeout");
+
+    result.current(jest.fn(), 1000);
+    unmount();
+
+    expect(clearTimeoutSpy).toBeCalledWith(timerId);
+
+    setTimeoutSpy.mockRestore();
+  });
+});
diff --git a/src/utils/useSetTimeout.ts b/src/utils/useSetTimeout.ts
new file mode 100644
index 0000000000..c00441fe6e
--- /dev/null
+++ b/src/utils/useSetTimeout.ts
@@ -0,0 +1,34 @@
+import { useEffect, useRef } from "react";
+
+export default function useSetTimeout() {
+  const didUnmountRef = useRef(false);
+  const { current: scheduledTimers } = useRef(new Set<number>());
+
+  useEffect(
+    () => () => {
+      didUnmountRef.current = true;
+      clearAll();
+    },
+    []
+  );
+
+  function clearAll() {
+    scheduledTimers.forEach((timer) => clearTimeout(timer));
+    scheduledTimers.clear();
+  }
+
+  return function scheduleTimeout(callback: () => void, delay: number) {
+    if (didUnmountRef.current) {
+      throw new Error("Can't schedule a timeout on an unmounted component.");
+    }
+
+    const timer = Number(setTimeout(handleCallback, delay));
+
+    scheduledTimers.add(timer);
+
+    function handleCallback() {
+      scheduledTimers.delete(timer);
+      callback();
+    }
+  };
+}