Flächendiagramm

'use client';

import { useId } from 'react';
import { CartesianFrame, GlideDot, linePath, seriesColor, seriesOpacity, type ChartA11y, type ChartSeries, type Datum } from '@/components/ui/chart';

export interface AreaChartProps extends ChartA11y {
  /** Rows, one per x value, e.g. { day: '2026-09-14', visits: 412 } */
  data: Datum[];
  /** Key of the x value. "2026-03" and "2026-03-14" are read as dates and formatted per language. */
  xKey: string;
  /** One area per series, in slot order (accent, grey, two accent tones) */
  series: ChartSeries[];
  /** Value format, e.g. { style: 'currency', currency: 'EUR', maximumFractionDigits: 0 } */
  format?: Intl.NumberFormatOptions;
  xFormat?: Intl.DateTimeFormatOptions;
  tooltipXFormat?: Intl.DateTimeFormatOptions;
  /** Stack the series to a total. Each band gets a tint and a top line in its series color. */
  stacked?: boolean;
  /** wash: an even, quiet tint. gradient: the tint fades towards the baseline. */
  fill?: 'wash' | 'gradient';
  curve?: 'smooth' | 'linear';
  /** Plot height in px, axis labels included */
  height?: number;
  /** Legend above the plot. Default: for two series and more. */
  legend?: boolean;
  /** Header of the first table column */
  xLabel?: string;
  className?: string;
}

/**
 * Areas over time: a single tinted area, a gradient, or stacked bands.
 *   <AreaChart data={rows} xKey="day" series={[{ key: 'visits', label: 'Visits' }]} fill="gradient" />
 */
export function AreaChart({ data, xKey, series, format, xFormat, tooltipXFormat, stacked = false, fill = 'wash', curve = 'smooth', height = 260, legend, xLabel, label, summary, labels, animate, className }: AreaChartProps) {
  const uid = useId().replace(/[^a-zA-Z0-9]/g, '');
  const num = (d: Datum, k: string) => (typeof d[k] === 'number' ? (d[k] as number) : null);
  // Cumulative tops per series when stacked
  const tops = series.map((_, si) => data.map((d) => series.slice(0, si + 1).reduce((a, s) => a + Math.max(0, num(d, s.key) ?? 0), 0)));
  const all = stacked ? tops[tops.length - 1] ?? [] : data.flatMap((d) => series.map((s) => num(d, s.key))).filter((v): v is number => v !== null);
  const extent: [number, number] = [Math.min(0, ...all), Math.max(0, ...all)];
  const smooth = curve === 'smooth';

  return (
    <CartesianFrame
      data={data}
      xKey={xKey}
      series={series}
      format={format}
      xFormat={xFormat}
      tooltipXFormat={tooltipXFormat}
      height={height}
      scale="point"
      extent={extent}
      legend={legend}
      legendShape={stacked ? 'rect' : 'line'}
      crosshair
      total={stacked}
      xLabel={xLabel}
      label={label}
      summary={summary}
      labels={labels}
      animate={animate}
      className={className}
      marks={({ cat, val, animated, focus }) => (
        <>
          <defs>
            {series.map((s, si) => (
              <linearGradient key={s.key} id={`${uid}-g${si}`} x1="0" x2="0" y1="0" y2="1">
                <stop offset="0" stopColor={seriesColor(si, s.color)} stopOpacity={stacked ? 0.55 : 0.3} />
                <stop offset="1" stopColor={seriesColor(si, s.color)} stopOpacity={stacked ? 0.22 : 0} />
              </linearGradient>
            ))}
          </defs>
          {/* Draw from the last series down, so the first sits in front when not stacked */}
          {[...series.keys()].reverse().map((si) => {
            const s = series[si];
            const color = seriesColor(si, s.color);
            const style = animated ? ({ '--kitch-d': `${si * 120}ms` } as React.CSSProperties) : undefined;
            const op = seriesOpacity(si, focus);
            if (stacked) {
              const upper: [number, number][] = data.map((_, i) => [cat(i), val(tops[si][i])]);
              const lower: [number, number][] = data.map((_, i) => [cat(i), val(si ? tops[si - 1][i] : 0)]).reverse() as [number, number][];
              const top = linePath(upper, smooth);
              const bottom = linePath(lower, smooth).replace(/^M/, 'L');
              return (
                <g key={s.key} className="kitch-series" opacity={op}>
                  <path d={`${top} ${bottom} Z`} fill={fill === 'gradient' ? `url(#${uid}-g${si})` : color} fillOpacity={fill === 'gradient' ? 1 : 0.4} className={animated ? 'kitch-clip' : undefined} style={style} />
                  {/* Each band ends in a crisp line of its own color */}
                  <path d={top} fill="none" stroke={color} strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" pathLength={1} className={animated ? 'kitch-draw' : undefined} style={style} />
                </g>
              );
            }
            const segments: [number, number][][] = [[]];
            data.forEach((d, i) => {
              const v = num(d, s.key);
              if (v !== null) segments[segments.length - 1].push([cat(i), val(v)]);
              else if (segments[segments.length - 1].length) segments.push([]);
            });
            return (
              <g key={s.key} className="kitch-series" opacity={op}>
                {segments
                  .filter((seg) => seg.length > 1)
                  .map((seg, k) => {
                    const top = linePath(seg, smooth);
                    const base = val(Math.max(extent[0], 0));
                    return (
                      <g key={k}>
                        <path
                          d={`${top} L${seg[seg.length - 1][0]} ${base} L${seg[0][0]} ${base} Z`}
                          fill={fill === 'gradient' ? `url(#${uid}-g${si})` : color}
                          fillOpacity={fill === 'gradient' ? 1 : si === 0 ? 0.12 : 0.1}
                          className={animated ? 'kitch-clip' : undefined}
                          style={style}
                        />
                        <path d={top} fill="none" stroke={color} strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" strokeDasharray={s.dashed ? '4 5' : undefined} pathLength={s.dashed ? undefined : 1} className={animated ? (s.dashed ? 'kitch-clip' : 'kitch-draw') : undefined} style={style} />
                      </g>
                    );
                  })}
              </g>
            );
          })}
        </>
      )}
      overlay={({ cat, val, shown, open, jump, focus }) =>
        shown !== null &&
        series.map((s, si) => {
          const v = stacked ? tops[si][shown] : num(data[shown], s.key);
          return v !== null && v !== undefined ? <GlideDot key={s.key} x={cat(shown)} y={val(v)} open={open} jump={jump} color={seriesColor(si, s.color)} opacity={seriesOpacity(si, focus)} /> : null;
        })
      }
    />
  );
}