refactor(dashboards): extract shared Sparkline primitive from number tile

packages/app/src/components/NumberTileBackgroundChart.tsx

@@ -1,12 +1,5 @@
 import { useMemo } from 'react';
 import { ErrorBoundary } from 'react-error-boundary';
-import {
-  Area,
-  AreaChart,
-  Line,
-  LineChart,
-  ResponsiveContainer,
-} from 'recharts';
 import { isBuilderChartConfig } from '@hyperdx/common-utils/dist/guards';
 import {
   BackgroundChart,
@@ -26,23 +19,12 @@ import { useQueriedChartConfig } from '@/hooks/useChartConfig';
 import { useSource } from '@/source';
 import { getColorFromCSSToken } from '@/utils';
 
+import { Sparkline, type SparklinePoint } from './Sparkline';
+
 // Trend hue used when neither the background override nor the tile's static
 // `color` is set, so a sparkline is always visible once enabled.
 const DEFAULT_BACKGROUND_TOKEN: ChartPaletteToken = 'chart-blue';
 
-// The sparkline sits behind the value, so it is intentionally low-contrast:
-// a translucent stroke with a fainter area fill.
-const STROKE_OPACITY = 0.5;
-const STROKE_WIDTH = 2;
-const AREA_FILL_OPACITY = 0.15;
-
-// `y` is the plotted value; `x` (bucket timestamp, seconds) is retained for
-// ordering and future axis use. With no `<XAxis>`, recharts spaces points by
-// array order, which is already sorted by bucket.
-const VALUE_KEY = 'y';
-
-type SparklinePoint = { x: number; y: number };
-
 /**
  * Flatten the time-chart formatter's `graphResults` into sparkline points.
  * Number tiles are single-series, so a single value series is read by key.
@@ -163,8 +145,6 @@ function NumberTileBackgroundChartInner({
       DEFAULT_BACKGROUND_TOKEN,
   );
 
-  const margin = { top: 4, right: 0, bottom: 0, left: 0 };
-
   return (
     <div
       aria-hidden
@@ -176,35 +156,7 @@ function NumberTileBackgroundChartInner({
         zIndex: 0,
       }}
     >
-      <ResponsiveContainer width="100%" height="100%">
-        {backgroundChart.type === 'area' ? (
-          <AreaChart data={points} margin={margin}>
-            <Area
-              type="monotone"
-              dataKey={VALUE_KEY}
-              stroke={color}
-              strokeOpacity={STROKE_OPACITY}
-              strokeWidth={STROKE_WIDTH}
-              fill={color}
-              fillOpacity={AREA_FILL_OPACITY}
-              isAnimationActive={false}
-              dot={false}
-            />
-          </AreaChart>
-        ) : (
-          <LineChart data={points} margin={margin}>
-            <Line
-              type="monotone"
-              dataKey={VALUE_KEY}
-              stroke={color}
-              strokeOpacity={STROKE_OPACITY}
-              strokeWidth={STROKE_WIDTH}
-              isAnimationActive={false}
-              dot={false}
-            />
-          </LineChart>
-        )}
-      </ResponsiveContainer>
+      <Sparkline points={points} type={backgroundChart.type} color={color} />
     </div>
   );
 }

packages/app/src/components/Sparkline.tsx

@@ -0,0 +1,88 @@
+import {
+  Area,
+  AreaChart,
+  Bar,
+  BarChart,
+  Line,
+  LineChart,
+  ResponsiveContainer,
+} from 'recharts';
+
+type SparklineType = 'line' | 'area' | 'bar';
+
+export type SparklinePoint = { x: number; y: number };
+
+// `y` is the plotted value; `x` (bucket timestamp, seconds) is retained for
+// ordering and future axis use. With no `<XAxis>`, recharts spaces points by
+// array order, which callers keep sorted by bucket.
+const VALUE_KEY = 'y';
+
+// The line / area variants are drawn behind or beside a value, so they are
+// intentionally low-contrast: a translucent stroke with a fainter area fill.
+const STROKE_OPACITY = 0.5;
+const STROKE_WIDTH = 2;
+const AREA_FILL_OPACITY = 0.15;
+
+const CHART_MARGIN = { top: 4, right: 0, bottom: 0, left: 0 };
+
+/**
+ * Chrome-less recharts trend, drawn as a line, area, or bar. No axes, grid,
+ * legend, or tooltip; dots and animation are off. Fills its parent via
+ * `ResponsiveContainer`, so the parent owns the dimensions (pass `height` to
+ * override the default 100%). Renders nothing for fewer than two points, since
+ * a single point has no trend to draw.
+ */
+export function Sparkline({
+  points,
+  type,
+  color,
+  height = '100%',
+}: {
+  points: SparklinePoint[];
+  type: SparklineType;
+  color: string;
+  height?: number | string;
+}) {
+  if (points.length < 2) return null;
+
+  return (
+    <ResponsiveContainer width="100%" height={height}>
+      {type === 'bar' ? (
+        <BarChart data={points} margin={CHART_MARGIN}>
+          <Bar
+            dataKey={VALUE_KEY}
+            fill={color}
+            maxBarSize={24}
+            isAnimationActive={false}
+          />
+        </BarChart>
+      ) : type === 'area' ? (
+        <AreaChart data={points} margin={CHART_MARGIN}>
+          <Area
+            type="monotone"
+            dataKey={VALUE_KEY}
+            stroke={color}
+            strokeOpacity={STROKE_OPACITY}
+            strokeWidth={STROKE_WIDTH}
+            fill={color}
+            fillOpacity={AREA_FILL_OPACITY}
+            isAnimationActive={false}
+            dot={false}
+          />
+        </AreaChart>
+      ) : (
+        <LineChart data={points} margin={CHART_MARGIN}>
+          <Line
+            type="monotone"
+            dataKey={VALUE_KEY}
+            stroke={color}
+            strokeOpacity={STROKE_OPACITY}
+            strokeWidth={STROKE_WIDTH}
+            isAnimationActive={false}
+            dot={false}
+          />
+        </LineChart>
+      )}
+    </ResponsiveContainer>
+  );
+}

packages/app/src/components/__tests__/Sparkline.test.tsx

@@ -0,0 +1,69 @@
+import React from 'react';
+
+import { Sparkline, type SparklinePoint } from '@/components/Sparkline';
+
+// recharts `ResponsiveContainer` sizes itself from its parent via a
+// ResizeObserver, which is a no-op in jsdom (see setupTests), so it never
+// reports a size and the chart never paints. Swap it for a fixed-size
+// pass-through so the SVG renders and the variant can be asserted.
+jest.mock('recharts', () => {
+  const actual = jest.requireActual<typeof import('recharts')>('recharts');
+  const { cloneElement } = jest.requireActual<typeof import('react')>('react');
+  return {
+    ...actual,
+    ResponsiveContainer: ({
+      children,
+    }: {
+      children: React.ReactElement<{ width?: number; height?: number }>;
+    }) => cloneElement(children, { width: 300, height: 80 }),
+  };
+});
+
+const COLOR = '#abcdef';
+
+const POINTS: SparklinePoint[] = [
+  { x: 1, y: 3 },
+  { x: 2, y: 7 },
+  { x: 3, y: 5 },
+];
+
+describe('Sparkline', () => {
+  it('renders a line trend in the given color', () => {
+    const { container } = renderWithMantine(
+      <Sparkline points={POINTS} type="line" color={COLOR} />,
+    );
+    expect(container.querySelector('.recharts-line')).toBeInTheDocument();
+    expect(container.innerHTML).toContain(COLOR);
+  });
+
+  it('renders an area trend in the given color', () => {
+    const { container } = renderWithMantine(
+      <Sparkline points={POINTS} type="area" color={COLOR} />,
+    );
+    expect(container.querySelector('.recharts-area')).toBeInTheDocument();
+    expect(container.innerHTML).toContain(COLOR);
+  });
+
+  it('renders a bar trend in the given color', () => {
+    const { container } = renderWithMantine(
+      <Sparkline points={POINTS} type="bar" color={COLOR} />,
+    );
+    expect(container.querySelector('.recharts-bar')).toBeInTheDocument();
+    expect(container.innerHTML).toContain(COLOR);
+  });
+
+  it('renders nothing for fewer than two points', () => {
+    const { container } = renderWithMantine(
+      <Sparkline points={[{ x: 1, y: 3 }]} type="line" color={COLOR} />,
+    );
+    const surface = container.querySelector('.recharts-surface');
+    expect(surface).not.toBeInTheDocument();
+  });
+
+  it('renders with an explicit numeric height (table-cell usage)', () => {
+    const { container } = renderWithMantine(
+      <Sparkline points={POINTS} type="line" color={COLOR} height={24} />,
+    );
+    expect(container.querySelector('.recharts-line')).toBeInTheDocument();
+  });
+});