From 6a6ba493f66fd89e0cf5bb22f7567b4f887cd30c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julian=20T=C3=B6lle?= <julian.toelle97@gmail.com>
Date: Fri, 5 Jun 2020 01:22:04 +0200
Subject: [PATCH] refactor(frontend): create useAsync hook for handling API
 data

---
 frontend/src/components/ReportListens.tsx | 30 +++++++-----------
 frontend/src/hooks/use-async.tsx          | 38 +++++++++++++++++++++++
 2 files changed, 49 insertions(+), 19 deletions(-)
 create mode 100644 frontend/src/hooks/use-async.tsx

diff --git a/frontend/src/components/ReportListens.tsx b/frontend/src/components/ReportListens.tsx
index 8f80b93..87b0ab7 100644
--- a/frontend/src/components/ReportListens.tsx
+++ b/frontend/src/components/ReportListens.tsx
@@ -1,5 +1,5 @@
 import { format, getTime } from "date-fns";
-import React, { useEffect, useState } from "react";
+import React, { useEffect, useMemo, useState } from "react";
 import { Redirect } from "react-router-dom";
 import {
   Area,
@@ -7,13 +7,14 @@ import {
   CartesianGrid,
   ResponsiveContainer,
   Tooltip,
+  TooltipProps,
   XAxis,
   YAxis,
-  TooltipProps,
 } from "recharts";
 import { getListensReport } from "../api/api";
 import { ListenReportItem } from "../api/entities/listen-report-item";
 import { ListenReportOptions } from "../api/entities/listen-report-options";
+import { useAsync } from "../hooks/use-async";
 import { useAuth } from "../hooks/use-auth";
 
 export const ReportListens: React.FC = () => {
@@ -24,23 +25,14 @@ export const ReportListens: React.FC = () => {
     timeStart: new Date("2020-05-01"),
     timeEnd: new Date(),
   });
-  const [report, setReport] = useState<ListenReportItem[]>([]);
-  const [isLoading, setIsLoading] = useState(true);
 
-  useEffect(() => {
-    (async () => {
-      setIsLoading(true);
+  const fetchData = useMemo(() => () => getListensReport(reportOptions), [
+    reportOptions,
+  ]);
 
-      try {
-        const reportFromApi = await getListensReport(reportOptions);
-        setReport(reportFromApi);
-      } catch (err) {
-        console.error("Error while fetching recent listens:", err);
-      } finally {
-        setIsLoading(false);
-      }
-    })();
-  }, [reportOptions, setReport, setIsLoading]);
+  const { value: report, pending: isLoading } = useAsync(fetchData, []);
+
+  const reportHasItems = !isLoading && report.length !== 0;
 
   if (!user) {
     return <Redirect to="/" />;
@@ -81,12 +73,12 @@ export const ReportListens: React.FC = () => {
               <div className="loader rounded-full border-8 h-64 w-64"></div>
             </div>
           )}
-          {report.length === 0 && (
+          {!reportHasItems && (
             <div>
               <p>Report is emtpy! :(</p>
             </div>
           )}
-          {report.length > 0 && (
+          {reportHasItems && (
             <div className="w-full text-gray-700 mt-5">
               <ReportGraph options={reportOptions} data={report} />
             </div>
diff --git a/frontend/src/hooks/use-async.tsx b/frontend/src/hooks/use-async.tsx
new file mode 100644
index 0000000..8811392
--- /dev/null
+++ b/frontend/src/hooks/use-async.tsx
@@ -0,0 +1,38 @@
+import React, { useState, useEffect, useCallback } from "react";
+
+type UseAsync = <T>(
+  asyncFunction: () => Promise<T>,
+  initialValue: T
+) => { pending: boolean; value: T; error: Error | null };
+
+export const useAsync: UseAsync = <T extends any>(
+  asyncFunction: () => Promise<T>,
+  initialValue: T
+) => {
+  const [pending, setPending] = useState(false);
+  const [value, setValue] = useState<T>(initialValue);
+  const [error, setError] = useState(null);
+
+  // The execute function wraps asyncFunction and
+  // handles setting state for pending, value, and error.
+  // useCallback ensures the below useEffect is not called
+  // on every render, but only if asyncFunction changes.
+  const execute = useCallback(() => {
+    setPending(true);
+    setValue(initialValue);
+    setError(null);
+    return asyncFunction()
+      .then((response) => setValue(response))
+      .catch((err) => setError(err))
+      .finally(() => setPending(false));
+  }, [asyncFunction]);
+
+  // Call execute if we want to fire it right away.
+  // Otherwise execute can be called later, such as
+  // in an onClick handler.
+  useEffect(() => {
+    execute();
+  }, [execute]);
+
+  return { execute, pending, value, error };
+};