refactor: LineChart component (#6072)

Initial version of a reusable trend chart, with a tooltip and vertical highlight

frontend/src/component/executiveDashboard/ExecutiveDashboard.tsx

@@ -77,7 +77,7 @@ export const ExecutiveDashboard: VFC = () => {
             <Box sx={(theme) => ({ paddingBottom: theme.spacing(4) })}>
                 <PageHeader
                     titleElement={
-                        <Typography variant='h1' component='h2'>
+                        <Typography variant='h1' component='span'>
                             Dashboard
                         </Typography>
                     }

frontend/src/component/executiveDashboard/LineChart/LineChart.tsx

@@ -0,0 +1,3 @@
+import { lazy } from 'react';
+
+export const LineChart = lazy(() => import('./LineChartComponent'));

frontend/src/component/executiveDashboard/LineChart/LineChartComponent.tsx

@@ -1,15 +1,15 @@
 import { useMemo, useState, type VFC } from 'react';
 import {
-    Chart as ChartJS,
     CategoryScale,
     LinearScale,
     PointElement,
     LineElement,
-    Title,
     Tooltip,
     Legend,
     TimeScale,
     Chart,
+    type ChartData,
+    type ScatterDataPoint,
 } from 'chart.js';
 import { Line } from 'react-chartjs-2';
 import 'chartjs-adapter-date-fns';
@@ -18,7 +18,6 @@ import {
     useLocationSettings,
     type ILocationSettings,
 } from 'hooks/useLocationSettings';
-import { ExecutiveSummarySchema } from 'openapi';
 import { ChartTooltip, TooltipState } from './ChartTooltip/ChartTooltip';
 
 const createOptions = (
@@ -34,7 +33,6 @@ const createOptions = (
                 labels: {
                     boxWidth: 12,
                     padding: 30,
-                    // usePointStyle: true,
                     generateLabels: (chart: Chart) => {
                         const datasets = chart.data.datasets;
                         const {
@@ -122,8 +120,8 @@ const createOptions = (
                     unit: 'month',
                 },
                 grid: {
-                    color: theme.palette.divider,
-                    borderColor: theme.palette.divider,
+                    color: 'transparent',
+                    borderColor: 'transparent',
                 },
                 ticks: {
                     color: theme.palette.text.secondary,
@@ -132,47 +130,41 @@ const createOptions = (
         },
     }) as const;
 
-interface IUsersChartComponentProps {
-    userTrends: ExecutiveSummarySchema['userTrends'];
-}
+// Vertical line on the hovered chart, filled with gradient. Highlights a section of a chart when you hover over datapoints
+const customHighlightPlugin = {
+    id: 'customLine',
+    afterDraw: (chart: Chart) => {
+        const width = 26;
+        if (chart.tooltip?.opacity && chart.tooltip.x) {
+            const x = chart.tooltip.caretX;
+            const yAxis = chart.scales.y;
+            const ctx = chart.ctx;
+            ctx.save();
+            const gradient = ctx.createLinearGradient(
+                x,
+                yAxis.top,
+                x,
+                yAxis.bottom,
+            );
+            gradient.addColorStop(0, 'rgba(129, 122, 254, 0)');
+            gradient.addColorStop(1, 'rgba(129, 122, 254, 0.12)');
+            ctx.fillStyle = gradient;
+            ctx.fillRect(
+                x - width / 2,
+                yAxis.top,
+                width,
+                yAxis.bottom - yAxis.top,
+            );
+            ctx.restore();
+        }
+    },
+};
 
-const createData = (
-    theme: Theme,
-    userTrends: ExecutiveSummarySchema['userTrends'],
-) => ({
-    labels: userTrends.map((item) => item.date),
-    datasets: [
-        {
-            label: 'Total users',
-            data: userTrends.map((item) => item.total),
-            borderColor: theme.palette.primary.light,
-            backgroundColor: theme.palette.primary.light,
-            fill: true,
-        },
-        {
-            label: 'Active users',
-            data: userTrends.map((item) => item.active),
-            borderColor: theme.palette.success.border,
-            backgroundColor: theme.palette.success.border,
-        },
-        {
-            label: 'Inactive users',
-            data: userTrends.map((item) => item.inactive),
-            borderColor: theme.palette.warning.border,
-            backgroundColor: theme.palette.warning.border,
-        },
-    ],
-});
-
-const UsersChartComponent: VFC<IUsersChartComponentProps> = ({
-    userTrends,
-}) => {
+const LineChartComponent: VFC<{
+    data: ChartData<'line', (number | ScatterDataPoint | null)[], unknown>;
+}> = ({ data }) => {
     const theme = useTheme();
     const { locationSettings } = useLocationSettings();
-    const data = useMemo(
-        () => createData(theme, userTrends),
-        [theme, userTrends],
-    );
 
     const [tooltip, setTooltip] = useState<null | TooltipState>(null);
     const options = useMemo(
@@ -182,21 +174,25 @@ const UsersChartComponent: VFC<IUsersChartComponentProps> = ({
 
     return (
         <>
-            <Line options={options} data={data} />
+            <Line
+                options={options}
+                data={data}
+                plugins={[customHighlightPlugin]}
+            />
             <ChartTooltip tooltip={tooltip} />
         </>
     );
 };
 
-ChartJS.register(
+Chart.register(
     CategoryScale,
     LinearScale,
     PointElement,
     LineElement,
     TimeScale,
-    Title,
     Tooltip,
     Legend,
 );
 
-export default UsersChartComponent;
+// for lazy-loading
+export default LineChartComponent;

frontend/src/component/executiveDashboard/UsersChart/UsersChart.tsx

@@ -1,3 +1,42 @@
-import { lazy } from 'react';
+import { useMemo, type VFC } from 'react';
+import 'chartjs-adapter-date-fns';
+import { useTheme } from '@mui/material';
+import { ExecutiveSummarySchema } from 'openapi';
+import { LineChart } from '../LineChart/LineChart';
 
-export const UsersChart = lazy(() => import('./UsersChartComponent'));
+interface IUsersChartProps {
+    userTrends: ExecutiveSummarySchema['userTrends'];
+}
+
+export const UsersChart: VFC<IUsersChartProps> = ({ userTrends }) => {
+    const theme = useTheme();
+    const data = useMemo(
+        () => ({
+            labels: userTrends.map((item) => item.date),
+            datasets: [
+                {
+                    label: 'Total users',
+                    data: userTrends.map((item) => item.total),
+                    borderColor: theme.palette.primary.light,
+                    backgroundColor: theme.palette.primary.light,
+                    fill: true,
+                },
+                {
+                    label: 'Active users',
+                    data: userTrends.map((item) => item.active),
+                    borderColor: theme.palette.success.border,
+                    backgroundColor: theme.palette.success.border,
+                },
+                {
+                    label: 'Inactive users',
+                    data: userTrends.map((item) => item.inactive),
+                    borderColor: theme.palette.warning.border,
+                    backgroundColor: theme.palette.warning.border,
+                },
+            ],
+        }),
+        [theme, userTrends],
+    );
+
+    return <LineChart data={data} />;
+};

frontend/src/component/executiveDashboard/Widget/Widget.tsx

@@ -1,23 +1,27 @@
 import { FC, ReactNode } from 'react';
-import { Paper, Typography } from '@mui/material';
+import { Paper, Typography, styled } from '@mui/material';
 import { HelpIcon } from 'component/common/HelpIcon/HelpIcon';
 import { ConditionallyRender } from 'component/common/ConditionallyRender/ConditionallyRender';
 
+const StyledPaper = styled(Paper)(({ theme }) => ({
+    padding: theme.spacing(3),
+    borderRadius: `${theme.shape.borderRadiusLarge}px`,
+    minWidth: 0, // bugfix, see: https://github.com/chartjs/Chart.js/issues/4156#issuecomment-295180128
+    position: 'relative',
+}));
+
 export const Widget: FC<{
     title: ReactNode;
     order?: number;
     span?: number;
     tooltip?: ReactNode;
 }> = ({ title, order, children, span = 1, tooltip }) => (
-    <Paper
+    <StyledPaper
         elevation={0}
-        sx={(theme) => ({
-            padding: 3,
-            borderRadius: `${theme.shape.borderRadiusLarge}px`,
+        sx={{
             order,
             gridColumn: `span ${span}`,
-            minWidth: 0, // bugfix, see: https://github.com/chartjs/Chart.js/issues/4156#issuecomment-295180128
-        })}
+        }}
     >
         <Typography
             variant='h3'
@@ -35,5 +39,5 @@ export const Widget: FC<{
             />
         </Typography>
         {children}
-    </Paper>
+    </StyledPaper>
 );