From 8555fbfa0f95f7f9020473fd8acfe5e9b1afb6bf Mon Sep 17 00:00:00 2001
From: Tanner Collin <git@tannercollin.com>
Date: Mon, 17 Feb 2020 00:19:44 +0000
Subject: [PATCH] Improve scroll handling and cache fetch results

---
 webclient/src/Admin.js        | 24 +++++++++----------
 webclient/src/App.js          |  3 +++
 webclient/src/Classes.js      |  5 +++-
 webclient/src/Courses.js      |  5 +++-
 webclient/src/ManageScroll.js | 44 +++++++++++++++++++++++++++++++++++
 webclient/src/Members.js      | 14 +++++++----
 6 files changed, 76 insertions(+), 19 deletions(-)
 create mode 100644 webclient/src/ManageScroll.js

diff --git a/webclient/src/Admin.js b/webclient/src/Admin.js
index c1903bd..631f0b4 100644
--- a/webclient/src/Admin.js
+++ b/webclient/src/Admin.js
@@ -38,19 +38,17 @@ export function Admin(props) {
 						</a>
 					</p>
 
-					<p>
-						Automate with wget (keep secret, that's <b>your</b> login token):
-						{reveal ?
-							<pre>
-								wget \
-								<br />  --content-disposition \
-								<br />  --header="Authorization: Token {token}" \
-								<br />  {apiUrl}/backup/
-							</pre>
-						:
-							<div><Button onClick={() => setReveal(true)}>Show Secret</Button></div>
-						}
-					</p>
+					Automate with wget (keep secret, that's <b>your</b> login token): <br />
+					{reveal ?
+						<pre>
+							wget \
+							<br />  --content-disposition \
+							<br />  --header="Authorization: Token {token}" \
+							<br />  {apiUrl}/backup/
+						</pre>
+					:
+						<Button onClick={() => setReveal(true)}>Show Secret</Button>
+					}
 				</div>
 			:
 				<p>Loading...</p>
diff --git a/webclient/src/App.js b/webclient/src/App.js
index b6a380d..70743da 100644
--- a/webclient/src/App.js
+++ b/webclient/src/App.js
@@ -4,6 +4,7 @@ import './semantic-ui/semantic.min.css';
 import './light.css';
 import { Container, Divider, Dropdown, Form, Grid, Header, Icon, Image, Menu, Message, Segment, Table } from 'semantic-ui-react';
 import { isAdmin, requester } from './utils.js';
+import { ManageScroll } from './ManageScroll.js';
 import { Home } from './Home.js';
 import { Account } from './Account.js';
 import { Transactions, TransactionDetail } from './Transactions.js';
@@ -71,6 +72,8 @@ function App() {
 
 	return (
 		<div>
+			<ManageScroll />
+
 			<div className='content-wrap'>
 			<div className='content-wrap-inside'>
 
diff --git a/webclient/src/Classes.js b/webclient/src/Classes.js
index f5a3143..541dde9 100644
--- a/webclient/src/Classes.js
+++ b/webclient/src/Classes.js
@@ -48,14 +48,17 @@ function ClassTable(props) {
 	);
 };
 
+let classesCache = false;
+
 export function Classes(props) {
-	const [classes, setClasses] = useState(false);
+	const [classes, setClasses] = useState(classesCache);
 	const { token } = props;
 
 	useEffect(() => {
 		requester('/sessions/', 'GET', token)
 		.then(res => {
 			setClasses(res.results);
+			classesCache = res.results;
 		})
 		.catch(err => {
 			console.log(err);
diff --git a/webclient/src/Courses.js b/webclient/src/Courses.js
index b09648c..8609533 100644
--- a/webclient/src/Courses.js
+++ b/webclient/src/Courses.js
@@ -8,14 +8,17 @@ import { NotFound, PleaseLogin } from './Misc.js';
 import { InstructorCourseList, InstructorCourseDetail } from './InstructorCourses.js';
 import { InstructorClassList } from './InstructorClasses.js';
 
+let courseCache = false;
+
 export function Courses(props) {
-	const [courses, setCourses] = useState(false);
+	const [courses, setCourses] = useState(courseCache);
 	const { token, user } = props;
 
 	useEffect(() => {
 		requester('/courses/', 'GET', token)
 		.then(res => {
 			setCourses(res.results);
+			courseCache = res.results;
 		})
 		.catch(err => {
 			console.log(err);
diff --git a/webclient/src/ManageScroll.js b/webclient/src/ManageScroll.js
new file mode 100644
index 0000000..ded7bec
--- /dev/null
+++ b/webclient/src/ManageScroll.js
@@ -0,0 +1,44 @@
+import React, { useState, useEffect, useReducer, useContext } from 'react';
+import { BrowserRouter as Router, Switch, Route, Link, useParams, useHistory } from 'react-router-dom';
+
+let scrollPositions = {};
+let timeout = null;
+
+export function ManageScroll() {
+	const history = useHistory();
+
+	const scrollListener = () => {
+		if (timeout) {
+			window.cancelAnimationFrame(timeout);
+		}
+
+		timeout = window.requestAnimationFrame(() => {
+			const key = history.location.key;
+			if (key in scrollPositions) {
+				scrollPositions[key] = window.scrollY;
+			}
+		});
+	};
+
+	useEffect(() => {
+		window.addEventListener('scroll', scrollListener);
+		return () => {
+			window.removeEventListener('scroll', scrollListener);
+		}
+	}, []);
+
+	useEffect(() => {
+		const key = history.location.key;
+
+		if (key in scrollPositions) {
+			window.scrollTo(0, scrollPositions[key]);
+		} else {
+			window.scrollTo(0, 0);
+			scrollPositions[key] = 0;
+		}
+	}, [history.location]);
+
+	return (
+		null
+	);
+};
diff --git a/webclient/src/Members.js b/webclient/src/Members.js
index b057992..3ab28a9 100644
--- a/webclient/src/Members.js
+++ b/webclient/src/Members.js
@@ -49,13 +49,16 @@ export function MembersDropdown(props) {
 	);
 };
 
+let searchCache = '';
+
 export function Members(props) {
 	const [response, setResponse] = useState(false);
-	const searchDefault = {seq: 0, q: ''};
+	const searchDefault = {seq: 0, q: searchCache};
 	const [search, setSearch] = useState(searchDefault);
 	const { token } = props;
 
 	useEffect(() => {
+		searchCache = search.q;
 		requester('/search/', 'POST', token, search)
 		.then(res => {
 			if (!search.seq || res.seq > response.seq) {
@@ -82,7 +85,7 @@ export function Members(props) {
 			{search.q.length ?
 				<Button
 					content='Clear'
-					onClick={() => setSearch(searchDefault)}
+					onClick={() => setSearch({seq: 0, q: ''})}
 				/> : ''
 			}
 
@@ -118,17 +121,20 @@ export function Members(props) {
 	);
 };
 
+let resultCache = {};
+
 export function MemberDetail(props) {
-	const [result, setResult] = useState(false);
+	const { id } = useParams();
+	const [result, setResult] = useState(resultCache[id] || false);
 	const [refreshCount, refreshResult] = useReducer(x => x + 1, 0);
 	const [error, setError] = useState(false);
 	const { token, user } = props;
-	const { id } = useParams();
 
 	useEffect(() => {
 		requester('/search/'+id+'/', 'GET', token)
 		.then(res => {
 			setResult(res);
+			resultCache[id] = res;
 		})
 		.catch(err => {
 			console.log(err);