feature/31 create graphical error notifications

client/src/App.tsx

@@ -3,7 +3,8 @@ import styled, { ThemeProvider } from 'styled-components';
 import { DndProvider } from 'react-dnd';
 import HTML5Backend from 'react-dnd-html5-backend';
 
-import { MuiThemeProvider, Box } from '@material-ui/core';
+import { MuiThemeProvider, Box, Snackbar } from '@material-ui/core';
+import { Alert } from '@material-ui/lab';
 import Link from '@material-ui/core/Link';
 import Grid from '@material-ui/core/Grid';
 import { CourseData, ClassData, filterOutClasses } from '@notangles/common';
@@ -18,6 +19,7 @@ import useColorMapper from './hooks/useColorMapper';
 import storage from './utils/storage';
 
 import { darkTheme, lightTheme } from './constants/theme';
+import NetworkError from './interfaces/NetworkError';
 
 const StyledApp = styled(Box)`
   height: 100%;
@@ -68,6 +70,8 @@ const App: FunctionComponent = () => {
   const [selectedClasses, setSelectedClasses] = useState<ClassData[]>([]);
   const [is12HourMode, setIs12HourMode] = useState<boolean>(storage.get('is12HourMode'));
   const [isDarkMode, setIsDarkMode] = useState<boolean>(storage.get('isDarkMode'));
+  const [errorMsg, setErrorMsg] = useState<String>('');
+  const [errorVisibility, setErrorVisibility] = useState<boolean>(false);
 
   const assignedColors = useColorMapper(
     selectedCourses.map((course) => course.code),
@@ -102,11 +106,16 @@ const App: FunctionComponent = () => {
   };
 
   const handleSelectCourse = async (courseCode: string) => {
-    const selectedCourseClasses = await getCourseInfo('2020', 'T3', courseCode);
-    if (selectedCourseClasses) {
+    try {
+      const selectedCourseClasses = await getCourseInfo('2020', 'T3', courseCode);
       const newSelectedCourses = [...selectedCourses, selectedCourseClasses];
       populateTimetable(selectedCourseClasses); // TODO: temp until auto-timetabling is done
       setSelectedCourses(newSelectedCourses);
+    } catch (e) {
+      if (e instanceof NetworkError) {
+        setErrorMsg(e.message);
+        setErrorVisibility(true);
+      }
     }
   };
 
@@ -120,6 +129,10 @@ const App: FunctionComponent = () => {
     ));
   };
 
+  const handleErrorClose = () => {
+    setErrorVisibility(false);
+  };
+
   return (
     <MuiThemeProvider theme={isDarkMode ? darkTheme : lightTheme}>
       <ThemeProvider theme={isDarkMode ? darkTheme : lightTheme}>
@@ -138,6 +151,8 @@ const App: FunctionComponent = () => {
                       assignedColors={assignedColors}
                       handleSelect={handleSelectCourse}
                       handleRemove={handleRemoveCourse}
+                      setErrorMsg={setErrorMsg}
+                      setErrorVisibility={setErrorVisibility}
                     />
                   </SelectWrapper>
                 </Grid>
@@ -171,6 +186,11 @@ const App: FunctionComponent = () => {
                   GitHub
                 </Link>
               </Footer>
+              <Snackbar open={errorVisibility} autoHideDuration={6000} onClose={handleErrorClose}>
+                <Alert severity="error" onClose={handleErrorClose} variant="filled">
+                  {errorMsg}
+                </Alert>
+              </Snackbar>
             </Content>
           </ContentWrapper>
         </StyledApp>

client/src/api/getCourseInfo.ts

@@ -1,6 +1,9 @@
 import { CourseData } from '@notangles/common';
 import { DbCourse, dbCourseToCourseData } from '../interfaces/DbCourse';
 import { API_URL } from './config';
+import NetworkError from '../interfaces/NetworkError';
+import timeoutPromise from '../utils/timeoutPromise';
+import TimeoutError from '../interfaces/TimeoutError';
 
 /**
  * Fetches the information of a specified course
@@ -18,19 +21,24 @@ const getCourseInfo = async (
   year: string,
   term: string,
   courseCode: string,
-): Promise<CourseData | null> => {
+): Promise<CourseData> => {
   const baseURL = `${API_URL}/terms/${year}-${term}`;
   try {
-    const data = await fetch(`${baseURL}/courses/${courseCode}/`);
+    const data = await timeoutPromise(1000, fetch(`${baseURL}/courses/${courseCode}/`));
+    if (data.status === 400) {
+      throw new NetworkError('Internal server error');
+    }
     const json: DbCourse = await data.json();
     if (!json) {
-      throw Error('Fetch did not get results');
+      throw new NetworkError('Internal server error');
     }
-
     return dbCourseToCourseData(json);
   } catch (error) {
-    console.error(error);
-    return null;
+    if (error instanceof TimeoutError) {
+      throw new NetworkError('Could not connect to server');
+    } else {
+      throw error;
+    }
   }
 };
 

client/src/api/getCoursesList.ts

@@ -1,5 +1,8 @@
 import { CoursesList } from '../interfaces/CourseOverview';
 import { API_URL } from './config';
+import NetworkError from '../interfaces/NetworkError';
+import timeoutPromise from '../utils/timeoutPromise';
+import TimeoutError from '../interfaces/TimeoutError';
 
 interface FetchedCourse {
   _id: string;
@@ -29,14 +32,20 @@ const toCoursesList = (data: FetchedCourse[]): CoursesList => (
 const getCoursesList = async (
   year: string,
   term: string,
-): Promise<CoursesList | null> => {
+): Promise<CoursesList> => {
   const baseURL = `${API_URL}/terms/${year}-${term}`;
   try {
-    const res = await fetch(`${baseURL}/courses/`);
-    return toCoursesList(await res.json());
+    const data = await timeoutPromise(1000, fetch(`${baseURL}/courses/`));
+    if (data.status === 400) {
+      throw new NetworkError('Internal server error');
+    }
+    return toCoursesList(await data.json());
   } catch (error) {
-    console.error(error);
-    return null;
+    if (error instanceof TimeoutError) {
+      throw new NetworkError('Could not connect to server');
+    } else {
+      throw error;
+    }
   }
 };
 

client/src/components/CourseSelect.tsx

@@ -18,6 +18,7 @@ import styled, { css } from 'styled-components';
 import { CourseData } from '@notangles/common';
 import { CoursesList, CourseOverview } from '../interfaces/CourseOverview';
 import getCoursesList from '../api/getCoursesList';
+import NetworkError from '../interfaces/NetworkError';
 
 const SEARCH_DELAY = 300;
 
@@ -54,7 +55,7 @@ const StyledSelect = styled(Box)`
   left: -1px;
 `;
 
-const StyledTextField = styled(TextField)<{
+const StyledTextField = styled(TextField) <{
   theme: Theme
 }>`
   .MuiOutlinedInput-root {
@@ -83,7 +84,7 @@ const StyledInputAdornment = styled(InputAdornment)`
 
 const StyledChip = styled(Chip).withConfig({
   shouldForwardProp: (prop) => !['backgroundColor'].includes(prop),
-})<{
+}) <{
   backgroundColor: string
 }>`
   transition: none !important;
@@ -123,13 +124,17 @@ interface CourseSelectProps {
   assignedColors: Record<string, string>
   handleSelect(courseCode: string): void
   handleRemove(courseCode: string): void
+  setErrorMsg(errorMsg: string): void
+  setErrorVisibility(visibility: boolean): void
 }
 
 const CourseSelect: React.FC<CourseSelectProps> = ({
   selectedCourses,
   assignedColors,
   handleSelect,
   handleRemove,
+  setErrorMsg,
+  setErrorVisibility,
 }) => {
   const [coursesList, setCoursesList] = useState<CoursesList>([]);
   const [options, setOptions] = useState<CoursesList>([]);
@@ -253,10 +258,15 @@ const CourseSelect: React.FC<CourseSelectProps> = ({
   };
 
   const fetchCoursesList = async () => {
-    const fetchedCoursesList = await getCoursesList('2020', 'T3');
-    if (fetchedCoursesList) {
+    try {
+      const fetchedCoursesList = await getCoursesList('2020', 'T3');
       setCoursesList(fetchedCoursesList);
       fuzzy = new Fuse(fetchedCoursesList, searchOptions);
+    } catch (e) {
+      if (e instanceof NetworkError) {
+        setErrorMsg(e.message);
+        setErrorVisibility(true);
+      }
     }
   };
 

client/src/interfaces/NetworkError.tsx

@@ -0,0 +1,5 @@
+export default class NetworkError extends Error {
+  constructor(message = '') {
+    super(message);
+  }
+}

client/src/utils/timeoutPromise.ts

@@ -0,0 +1,19 @@
+import TimeoutError from '../interfaces/TimeoutError';
+
+export default function timeoutPromise(ms: number, promise: Promise<Response>): Promise<Response> {
+  return new Promise((resolve, reject) => {
+    const timeoutId = setTimeout(() => {
+      reject(new TimeoutError('timeout'));
+    }, ms);
+    promise.then(
+      (res) => {
+        clearTimeout(timeoutId);
+        resolve(res);
+      },
+      (err) => {
+        clearTimeout(timeoutId);
+        reject(err);
+      },
+    );
+  });
+}