import { ReactNode, useState } from 'react';
import {
  Area, AreaChart, Bar, BarChart, CartesianGrid, Legend, Line, LineChart,
  ResponsiveContainer, Tooltip, XAxis, YAxis,
} from 'recharts';
import './Chart.css';

export interface Series {
  key: string;
  label: string;
  /** 1-based slot in the categorical palette. Assigned in order, never cycled. */
  slot: 1 | 2 | 3 | 4 | 5 | 6;
  unit?: string;
  /** Round displayed values to this many decimals. */
  decimals?: number;
}

interface ChartProps {
  title: string;
  subtitle?: string;
  data: Array<Record<string, any>>;
  series: Series[];
  type: 'line' | 'bar' | 'stacked-bar' | 'area';
  xKey?: string;
  height?: number;
  /** Y-axis label; a chart has exactly one axis — never two scales. */
  unit?: string;
  footer?: ReactNode;
}

const fmt = (value: any, decimals = 0) =>
  value == null
    ? '—'
    : typeof value === 'number'
    ? value.toLocaleString(undefined, {
        minimumFractionDigits: decimals,
        maximumFractionDigits: decimals,
      })
    : String(value);

function TooltipBox({ active, payload, label, series }: any) {
  if (!active || !payload?.length) return null;
  return (
    <div className="viz-tooltip">
      <div className="viz-tooltip-label">{label}</div>
      {payload.map((entry: any) => {
        const s = series.find((x: Series) => x.key === entry.dataKey);
        return (
          <div key={entry.dataKey} className="viz-tooltip-row">
            <span
              className="viz-swatch"
              style={{ background: entry.color }}
              aria-hidden="true"
            />
            <span className="viz-tooltip-name">{s?.label ?? entry.dataKey}</span>
            <span className="viz-tooltip-value">
              {fmt(entry.value, s?.decimals)}
              {s?.unit ? ` ${s.unit}` : ''}
            </span>
          </div>
        );
      })}
    </div>
  );
}

function Chart({
  title, subtitle, data, series, type, xKey = 'date', height = 240, unit, footer,
}: ChartProps) {
  // A table view is the relief for series whose colour falls below 3:1 on the
  // light surface, and doubles as the non-visual reading of any chart.
  const [showTable, setShowTable] = useState(false);

  const present = series.filter((s) => data.some((row) => row[s.key] != null));
  if (present.length === 0) {
    return (
      <figure className="viz">
        <figcaption className="viz-head">
          <h4>{title}</h4>
        </figcaption>
        <div className="viz-empty">暂无数据</div>
      </figure>
    );
  }

  const color = (s: Series) => `var(--series-${s.slot})`;
  const axis = {
    stroke: 'var(--border-strong)',
    tick: { fill: 'var(--text-muted)', fontSize: 11 },
    tickLine: false,
  };
  const margin = { top: 8, right: 8, bottom: 0, left: -8 };

  // A legend is mandatory from two series up; a single series is named by the
  // title, so a legend box would only repeat it.
  const legend =
    present.length > 1 ? (
      <Legend
        verticalAlign="top"
        align="left"
        height={28}
        iconType="circle"
        iconSize={8}
        formatter={(value: string) => {
          const s = present.find((x) => x.key === value);
          return <span className="viz-legend-item">{s?.label ?? value}</span>;
        }}
      />
    ) : null;

  const grid = <CartesianGrid stroke="var(--grid)" vertical={false} />;
  const tip = (
    <Tooltip
      content={<TooltipBox series={present} />}
      cursor={{ stroke: 'var(--border-strong)', strokeWidth: 1 }}
    />
  );

  const render = () => {
    if (type === 'bar' || type === 'stacked-bar') {
      const stacked = type === 'stacked-bar';
      return (
        <BarChart data={data} margin={margin} barCategoryGap="22%">
          {grid}
          <XAxis dataKey={xKey} {...axis} />
          <YAxis {...axis} width={48} />
          {tip}
          {legend}
          {present.map((s, i) => (
            <Bar
              key={s.key}
              dataKey={s.key}
              name={s.key}
              fill={color(s)}
              stackId={stacked ? 'stack' : undefined}
              // 4px rounded data-end on the topmost segment only, so the shape
              // reads as one bar anchored to the baseline.
              radius={
                stacked
                  ? i === present.length - 1
                    ? [4, 4, 0, 0]
                    : [0, 0, 0, 0]
                  : [4, 4, 0, 0]
              }
              // A 2px gap in the surface colour separates adjacent fills.
              stroke="var(--surface-1)"
              strokeWidth={stacked ? 2 : 0}
              isAnimationActive={false}
            />
          ))}
        </BarChart>
      );
    }

    if (type === 'area') {
      return (
        <AreaChart data={data} margin={margin}>
          <defs>
            {present.map((s) => (
              <linearGradient key={s.key} id={`fill-${s.key}`} x1="0" y1="0" x2="0" y2="1">
                <stop offset="0%" stopColor={color(s)} stopOpacity={0.22} />
                <stop offset="100%" stopColor={color(s)} stopOpacity={0.02} />
              </linearGradient>
            ))}
          </defs>
          {grid}
          <XAxis dataKey={xKey} {...axis} />
          <YAxis {...axis} width={48} />
          {tip}
          {legend}
          {present.map((s) => (
            <Area
              key={s.key}
              type="monotone"
              dataKey={s.key}
              name={s.key}
              stroke={color(s)}
              strokeWidth={2}
              fill={`url(#fill-${s.key})`}
              connectNulls
              isAnimationActive={false}
            />
          ))}
        </AreaChart>
      );
    }

    return (
      <LineChart data={data} margin={margin}>
        {grid}
        <XAxis dataKey={xKey} {...axis} />
        <YAxis {...axis} width={48} domain={['auto', 'auto']} />
        {tip}
        {legend}
        {present.map((s) => (
          <Line
            key={s.key}
            type="monotone"
            dataKey={s.key}
            name={s.key}
            stroke={color(s)}
            strokeWidth={2}
            dot={false}
            // A 2px surface ring keeps overlapping markers readable.
            activeDot={{ r: 5, strokeWidth: 2, stroke: 'var(--surface-1)' }}
            // Days the device recorded nothing must not fragment the line.
            connectNulls
            isAnimationActive={false}
          />
        ))}
      </LineChart>
    );
  };

  return (
    <figure className="viz">
      <figcaption className="viz-head">
        <div>
          <h4>
            {title}
            {unit && <span className="viz-unit"> ({unit})</span>}
          </h4>
          {subtitle && <p className="viz-sub">{subtitle}</p>}
        </div>
        <button
          type="button"
          className="viz-toggle"
          onClick={() => setShowTable((v) => !v)}
          aria-pressed={showTable}
        >
          {showTable ? '看图表' : '看数据'}
        </button>
      </figcaption>

      {showTable ? (
        <div className="viz-table-wrap">
          <table className="viz-table">
            <thead>
              <tr>
                <th scope="col">日期</th>
                {present.map((s) => (
                  <th key={s.key} scope="col">
                    <span
                      className="viz-swatch"
                      style={{ background: color(s) }}
                      aria-hidden="true"
                    />
                    {s.label}
                    {s.unit ? ` (${s.unit})` : ''}
                  </th>
                ))}
              </tr>
            </thead>
            <tbody>
              {[...data].reverse().map((row, i) => (
                <tr key={`${row[xKey]}-${i}`}>
                  <th scope="row">{row[xKey]}</th>
                  {present.map((s) => (
                    <td key={s.key}>{fmt(row[s.key], s.decimals)}</td>
                  ))}
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      ) : (
        <ResponsiveContainer width="100%" height={height}>
          {render()}
        </ResponsiveContainer>
      )}

      {footer && <div className="viz-foot">{footer}</div>}
    </figure>
  );
}

export default Chart;