whyrating/.cursor/rules/wisdom-chart-patterns.mdc

---
description: ---
---

---
title: "Chart Component Patterns"
purpose: "Creating or modifying chart components in LiquidRender"
answers:
  - "How do I use Recharts in LiquidRender?"
  - "What color palette should charts use?"
  - "How do I configure axes in chart components?"
  - "How do I handle SSR for charts?"
  - "How do I add legends and tooltips consistently?"
  - "How do I transform data for Recharts?"
  - "How do I handle empty chart states?"

read_when: "You're creating, modifying, or debugging chart components"
skip_when: "You're working on non-chart components like tables or forms"

depends_on:
  files:
    - "packages/liquid-render/src/renderer/components/utils.ts"
    - "packages/liquid-render/src/renderer/components/line-chart.tsx"
    - "packages/liquid-render/src/renderer/components/bar-chart.tsx"
    - "packages/liquid-render/src/renderer/components/pie-chart.tsx"
    - "packages/liquid-render/src/renderer/components/area-chart.tsx"
  entities:
    - "chartColors"
    - "tokens"
    - "isBrowser"
    - "fieldToLabel"
    - "ResponsiveContainer"
  concepts:
    - "Recharts library"
    - "SSR hydration"
    - "Design tokens"

confidence: 0.85
verified_at: "2025-12-27"
---

# Chart Component Patterns

> **Read when:** You're creating, modifying, or debugging chart components
>
> **Skip when:** You're working on non-chart components like tables or forms

## Sections

| Section | Summary |
|---------|---------|
| [Recharts Setup](#recharts-setup) | ResponsiveContainer and SSR handling |
| [Color Palette](#color-palette) | chartColors array from utils.ts |
| [Axis Configuration](#axis-configuration) | XAxis and YAxis consistent styling |
| [Legend & Tooltip](#legend--tooltip) | Tooltip and Legend styling patterns |
| [Data Transformation](#data-transformation) | Auto-detecting x/y fields from data |
| [Empty State Handling](#empty-state-handling) | Placeholder UI for no-data scenarios |

---

## Recharts Setup

> **TL;DR:** Wrap all charts in `ResponsiveContainer` and check `isBrowser` before rendering Recharts components.

Charts must be responsive and handle server-side rendering gracefully. The `ResponsiveContainer` makes charts fluid, while `isBrowser` prevents hydration mismatches.

### Basic Structure

```tsx
import {
  LineChart as RechartsLineChart,
  Line,
  XAxis,
  YAxis,
  CartesianGrid,
  Tooltip,
  Legend,
  ResponsiveContainer,
} from 'recharts';
import { isBrowser } from './utils';

// SSR fallback - always check before rendering Recharts
if (!isBrowser) {
  return (
    <div data-liquid-type="line" style={styles.wrapper}>
      {label && <div style={styles.header}>{label}</div>}
      <div style={styles.placeholder}>
        [Line chart - {chartData.length} points]
      </div>
    </div>
  );
}

// Client-side render with ResponsiveContainer
return (
  <ResponsiveContainer width="100%" height={220}>
    <RechartsLineChart data={chartData} margin={{ top: 5, right: 20, bottom: 5, left: 0 }}>
      {/* Chart components */}
    </RechartsLineChart>
  </ResponsiveContainer>
);
```

### Key Points

- **Always** use `ResponsiveContainer` with `width="100%"` and explicit `height`
- Default chart height is `220px` across all chart types
- Use `margin={{ top: 5, right: 20, bottom: 5, left: 0 }}` for consistent spacing
- The SSR placeholder shows chart type and data summary in brackets

---

## Color Palette

> **TL;DR:** Import `chartColors` from utils.ts and cycle through with modulo for multi-series charts.

The color palette is defined in `utils.ts` and provides 8 harmonious colors for data visualization:

```tsx
import { chartColors } from './utils';

// chartColors = [
//   '#3b82f6', // blue
//   '#22c55e', // green
//   '#f59e0b', // amber
//   '#ef4444', // red
//   '#8b5cf6', // violet
//   '#ec4899', // pink
//   '#06b6d4', // cyan
//   '#84cc16', // lime
// ]

// Single series - use first color
<Line stroke={chartColors[0]} />

// Multiple series - cycle with modulo
{numericFields.map((field, i) => (
  <Line
    key={field}
    stroke={chartColors[i % chartColors.length]}
    fill={chartColors[i % chartColors.length]}
  />
))}
```

### Color Usage by Chart Type

| Chart Type | Color Property | Example |
|------------|----------------|---------|
| Line | `stroke`, `dot.fill` | `stroke={chartColors[0]}` |
| Bar | `fill` | `fill={chartColors[i % chartColors.length]}` |
| Area | `stroke`, `fill` (often gradient) | `stroke={chartColors[0]}` |
| Pie | `Cell` fill | `<Cell fill={chartColors[index % chartColors.length]} />` |

---

## Axis Configuration

> **TL;DR:** Use `tokens.colors.mutedForeground` for tick text and `tokens.colors.border` for axis lines.

All charts follow the same axis styling pattern for visual consistency:

```tsx
import { tokens } from './utils';

<XAxis
  dataKey={xKey}
  tick={{ fontSize: 12, fill: tokens.colors.mutedForeground }}
  stroke={tokens.colors.border}
/>
<YAxis
  tick={{ fontSize: 12, fill: tokens.colors.mutedForeground }}
  stroke={tokens.colors.border}
/>
<CartesianGrid strokeDasharray="3 3" stroke={tokens.colors.border} />
```

### Axis Style Reference

| Property | Value | Purpose |
|----------|-------|---------|
| `tick.fontSize` | `12` | Readable but compact labels |
| `tick.fill` | `tokens.colors.mutedForeground` | Subdued text color |
| `stroke` | `tokens.colors.border` | Axis line color |
| `strokeDasharray` | `"3 3"` | CartesianGrid dash pattern |

---

## Legend & Tooltip

> **TL;DR:** Style tooltips with `tokens.colors.card` background and `tokens.colors.border`; use `fontSize: tokens.fontSize.sm` for legends.

Consistent tooltip and legend styling across all chart types:

```tsx
import { tokens } from './utils';

<Tooltip
  contentStyle={{
    backgroundColor: tokens.colors.card,
    border: `1px solid ${tokens.colors.border}`,
    borderRadius: tokens.radius.md,
    fontSize: tokens.fontSize.sm,
  }}
  // Bar charts also use cursor styling:
  cursor={{ fill: tokens.colors.muted }}
/>

<Legend wrapperStyle={{ fontSize: tokens.fontSize.sm }} />
```

### Tooltip Variations

```tsx
// Bar chart adds cursor highlight
<Tooltip cursor={{ fill: tokens.colors.muted }} />

// Pie chart has no cursor (circular)
<Tooltip contentStyle={{...}} />
```

---

## Data Transformation

> **TL;DR:** Use `detectXYFields()` to auto-detect category (string) and value (numeric) fields; use `fieldToLabel()` for display names.

Charts automatically detect which fields to use based on data types:

```tsx
import { fieldToLabel } from './utils';

// Helper to check numeric values
function isNumeric(value: unknown): value is number {
  return typeof value === 'number' && !isNaN(value);
}

// Auto-detect x (category) and y (numeric) fields
function detectXYFields(data: ChartDataPoint[]): { x: string; y: string } {
  if (data.length === 0) return { x: 'x', y: 'y' };

  const firstRow = data[0]!;
  const keys = Object.keys(firstRow);

  // Find first string-like field for x (category/date)
  const xField = keys.find(k => {
    const val = firstRow[k];
    return typeof val === 'string' || val instanceof Date;
  }) || keys[0] || 'x';

  // Find first numeric field for y
  const yField = keys.find(k => {
    const val = firstRow[k];
    return isNumeric(val) && k !== xField;
  }) || keys[1] || 'y';

  return { x: xField, y: yField };
}

// Detect ALL numeric fields for multi-series charts
function detectAllNumericFields(data: ChartDataPoint[], xField: string): string[] {
  if (data.length === 0) return [];
  const firstRow = data[0]!;
  return Object.keys(firstRow).filter(k =>
    k !== xField && isNumeric(firstRow[k])
  );
}

// Usage: convert field names to labels
<Line
  dataKey={field}
  name={fieldToLabel(field)}  // "total_sales" -> "Total Sales"
/>
```

### Explicit vs Auto-Detection

```tsx
// Allow explicit binding override
const { x: xKey, y: yKey } = useMemo(() => {
  const explicitX = block.binding?.x;
  const explicitY = block.binding?.y;
  if (explicitX && explicitY) {
    return { x: explicitX, y: explicitY };
  }
  return detectXYFields(chartData);  // Fallback to auto-detect
}, [block.binding, chartData]);
```

---

## Empty State Handling

> **TL;DR:** Return a styled placeholder with "No data available" message when `chartData.length === 0`.

Every chart must handle empty data gracefully:

```tsx
// Empty state with consistent styling
if (chartData.length === 0) {
  return (
    <div
      data-liquid-type="line"  // Use appropriate type
      style={styles.wrapper}
      role="img"
      aria-label={`${label ? label + ': ' : ''}Empty line chart - no data available`}
    >
      {label && <div style={styles.header}>{label}</div>}
      <div style={styles.placeholder}>No data available</div>
    </div>
  );
}

// Placeholder style definition
const styles = {
  placeholder: {
    display: 'flex',
    alignItems: 'center',
    justifyContent: 'center',
    height: '220px',
    color: tokens.colors.mutedForeground,
    fontSize: tokens.fontSize.sm,
    textAlign: 'center',
  } as React.CSSProperties,
};
```

### State Hierarchy

1. **SSR fallback** - Check `isBrowser` first, return text placeholder
2. **Empty state** - Check `chartData.length === 0`, return "No data available"
3. **Normal render** - Full chart with data

---

## See Also

- [utils.ts](/packages/liquid-render/src/renderer/components/utils.ts) - Design tokens and shared utilities
- [COMPONENT-GUIDE.md](/packages/liquid-render/docs/COMPONENT-GUIDE.md) - General component patterns
- [Recharts Documentation](https://recharts.org/en-US/) - Official Recharts API reference