refactor a bit

src/components/Panel.tsx

@@ -14,69 +14,96 @@ import { PanelData, TimeRange, PanelProps } from '@grafana/data';
 import { VizLegend } from '@grafana/ui';
 import { LegendDisplayMode } from '@grafana/schema';
 
-import React, { useCallback, useRef } from 'react';
+import React, { useRef, useEffect, useMemo } from 'react';
 import { css } from 'emotion';
 import * as _ from 'lodash';
 
 interface Props extends PanelProps<PanelOptions> {}
 
 export function Panel({ options, data, width, height, timeRange, onChangeTimeRange, replaceVariables }: Props) {
-  const grafanaSeriesList = getGrafanaSeriesList(data, timeRange);
-  let chartContainer = useRef(null);
+  const grafanaSeriesList = useMemo(() => getGrafanaSeriesList(data, timeRange), [data, timeRange]);
+  const podContainerRef = useRef<HTMLDivElement>(null);
 
-  // we request animation frame here because we need an existing DOM-element at the moment we render the pod
-  window.requestAnimationFrame(() => {
+  const podContainer = useMemo(() => {
+    const chartHeight = height - 20;
+
+    const chartClickHandler = (event: React.MouseEvent<HTMLDivElement>) => {
+      event.preventDefault();
+      if (options.gauge.link === undefined || options.gauge.link === '') {
+        return;
+      }
+      const link = replaceVariables(options.gauge.link);
+      window.open(link, '_self');
+    };
+
+    const isLinkActive = options.gauge.link !== undefined && options.gauge.link !== '';
+
+    return (
+      <div
+        ref={podContainerRef}
+        className={css`
+          width: ${width}px;
+          height: ${chartHeight}px;
+          cursor: ${isLinkActive ? 'pointer' : 'default'};
+        `}
+        onClick={chartClickHandler}
+      ></div>
+    );
+  }, [width, height, options.gauge.link, replaceVariables]);
+
+  useEffect(() => {
     let pod;
+    if (podContainerRef.current === null) {
+      return;
+    }
     switch (options.visualizationType) {
       case Pod.GAUGE:
         const series = new Series(grafanaSeriesList, options.gauge.value).getChartwerkSeries();
         const chartwerkGaugeOptions = new GaugeOptions(grafanaSeriesList, options).getChartwerkOptions();
-        pod = new ChartwerkGaugePod((chartContainer as any).current, series, chartwerkGaugeOptions);
+        pod = new ChartwerkGaugePod(podContainerRef.current, series, chartwerkGaugeOptions);
         break;
       case Pod.BAR:
         const barSeries = new BarSeries(grafanaSeriesList).getChartwerkSeries();
         const chartwerkBarOptions = new BarOptions(grafanaSeriesList, onChangeTimeRange).getChartwerkOptions();
-        pod = new ChartwerkBarPod((chartContainer as any).current, barSeries, chartwerkBarOptions);
+        pod = new ChartwerkBarPod(podContainerRef.current, barSeries, chartwerkBarOptions);
         break;
       default:
         throw new Error(`Unknown visualization type: ${options.visualizationType}`);
     }
     pod.render();
-  });
+  }, [podContainer, grafanaSeriesList, onChangeTimeRange, options]);
 
-  const isLinkActive = !_.isEmpty(options.gauge.link);
-  const chartClickHandler = useCallback((event: React.MouseEvent<HTMLDivElement>) => {
-    event.preventDefault();
-    if (!isLinkActive) {
-      return;
-    }
-    const link = replaceVariables(options.gauge.link as string);
-    window.open(link, '_self');
-  }, [options.gauge.link]);
-  const legendItems = _.map(grafanaSeriesList, (serie) => {
+  const legendItems = useMemo(
+    () =>
+      _.map(grafanaSeriesList, (serie) => {
         return {
           label: serie.alias,
           color: serie.color,
           yAxis: 1,
         };
-  });
-  const chartHeight = options.visualizationType !== Pod.GAUGE ? height - 20 : height;
+      }),
+    [grafanaSeriesList]
+  );
+
+  switch (options.visualizationType) {
+    case Pod.LINE:
+    case Pod.BAR:
       return (
         <div>
-      <div
-        ref={chartContainer}
-        className={css`
-          width: ${width}px;
-          height: ${chartHeight}px;
-          cursor: ${isLinkActive ? 'pointer' : 'default'};
-        `}
-        onClick={chartClickHandler}
-      ></div>
-      {options.visualizationType !== Pod.GAUGE && (
+          {podContainer}
+
           <VizLegend placement={'bottom'} items={legendItems} displayMode={LegendDisplayMode.List} />
-      )}
         </div>
       );
+    case Pod.GAUGE:
+      return (
+        <div>
+          {podContainer}
+        </div>
+      );
+    default:
+      throw new Error(`Unknown visualization type: ${options.visualizationType}`);
+  }
 }
 
 function getGrafanaSeriesList(grafanaData: PanelData, timeRange: TimeRange): any[] {