import type { ReactNode } from 'react';
import { Ban, CloudUpload, ListChecks, Receipt, ShoppingCart, TrendingDown, TrendingUp } from 'lucide-react';
import { count, money } from '@/features/store-admin/format';
import type { ConsoleTotals } from '../consoleModel';
import type { DaySeries, Trend } from '../useConsoleSeries';

/**
 * The five figures the board opens with.
 *
 * Each card carries the number, the shape of how it got there, and whether that
 * is better or worse than the period before. The sparkline is not decoration:
 * ₹12,480 taken evenly across a week and ₹12,480 taken in one afternoon are the
 * same number and completely different news, and the line is the only part of
 * the card that can tell them apart.
 *
 * Trend arrows are drawn only where a real comparison exists. `Trend.isNew`
 * marks the case where the previous period was zero — "↑ ∞%" is not a fact, so
 * it reads "new" instead.
 */
export interface KpiStripProps {
  totals: ConsoleTotals;
  days: readonly DaySeries[];
  trends: {
    online: Trend;
    counter: Trend;
    orders: Trend;
    cancelled: Trend;
  };
  comparisonLabel: string;
  isLoading: boolean;
}

export function KpiStrip({ totals, days, trends, comparisonLabel, isLoading }: KpiStripProps) {
  if (isLoading) {
    return (
      <div className="kpi-strip" aria-busy="true">
        {[0, 1, 2, 3, 4].map((i) => (
          <div key={i} className="sk-card" />
        ))}
      </div>
    );
  }

  return (
    <div className="kpi-strip">
      <Kpi
        icon={<ShoppingCart size={17} />}
        label="Online Sales"
        value={money(totals.onlineRevenue)}
        trend={trends.online}
        comparisonLabel={comparisonLabel}
        series={days.map((d) => d.online)}
      />
      <Kpi
        icon={<Receipt size={17} />}
        label="Counter Sales"
        value={money(totals.counterRevenue)}
        trend={trends.counter}
        comparisonLabel={comparisonLabel}
        series={days.map((d) => d.counter)}
      />
      <Kpi
        icon={<ListChecks size={17} />}
        label="Total Orders"
        value={count(totals.totalOrders)}
        trend={trends.orders}
        comparisonLabel={comparisonLabel}
        series={days.map((d) => d.onlineOrders + d.counterBills)}
      />
      <Kpi
        icon={<Ban size={17} />}
        label="Cancelled Orders"
        value={count(totals.cancelled)}
        trend={trends.cancelled}
        comparisonLabel={comparisonLabel}
        series={days.map(() => 0)}
        // The only card where a rise is bad news, so the colours invert.
        isInverted
      />
      <Kpi
        icon={<CloudUpload size={17} />}
        label="Unsynced Bills"
        value={count(totals.pendingBills)}
        // A live queue depth, not a period figure: there is nothing last week
        // to compare it against, so it states what it is instead.
        note={totals.pendingBills === 0 ? 'all bills are in the books' : 'waiting on a till'}
        series={days.map(() => 0)}
        isInverted
      />
    </div>
  );
}

function Kpi({
  icon, label, value, trend, comparisonLabel, series, note, isInverted,
}: {
  icon: ReactNode;
  label: string;
  value: string;
  trend?: Trend;
  comparisonLabel?: string;
  series: readonly number[];
  note?: string;
  isInverted?: boolean;
}) {
  // Up is green unless a rise is the bad outcome — cancellations, unsent bills.
  const isGood = trend ? (isInverted ? trend.direction === 'down' : trend.direction === 'up') : true;
  // A flat line on an empty period is not bad news, so it is not drawn in red.
  const hasShape = series.some((value) => value > 0);

  return (
    <article className="kpi">
      {/* Icon and figure only. The sparkline sits on the row below rather than
          beside the label: at the widths this strip actually gets — five cards
          sharing the page with Nearle Buddy — a 52px chart alongside truncates
          "Cancelled Orders" to "Cance…", and a label that has stopped naming
          its number is worse than no chart. */}
      <div className="kpi-top">
        <span className="kpi-icon" aria-hidden>{icon}</span>
        <div className="kpi-head">
          <span className="kpi-label">{label}</span>
          <span className="kpi-value">{value}</span>
        </div>
      </div>

      <div className="kpi-foot">
        {trend && !trend.isNew && trend.percent !== undefined ? (
          <div className="kpi-trend" data-good={isGood ? 'yes' : 'no'}>
            {trend.direction === 'down' ? <TrendingDown size={13} /> : <TrendingUp size={13} />}
            <strong>{trend.percent}%</strong>
            <span className="kpi-vs">vs. {comparisonLabel}</span>
          </div>
        ) : (
          <div className="kpi-trend" data-good="neutral">
            <span className="kpi-vs">{note ?? (trend?.isNew ? 'new this period' : `vs. ${comparisonLabel}`)}</span>
          </div>
        )}
        <Sparkline values={series} tone={!hasShape ? 'none' : isGood ? 'good' : 'bad'} />
      </div>
    </article>
  );
}

/**
 * The shape of the period, in about forty pixels.
 *
 * A polyline over a normalised series. Flat or empty data draws a flat line
 * rather than nothing, because an absent sparkline reads as a broken card while
 * a flat one correctly says "nothing moved".
 */
function Sparkline({ values, tone }: { values: readonly number[]; tone: 'good' | 'bad' | 'none' }) {
  const points = values.length >= 2 ? values : [0, 0];
  const peak = Math.max(...points);
  const floor = Math.min(...points);
  const span = peak - floor || 1;

  const path = points
    .map((value, i) => {
      const x = (i / (points.length - 1)) * 60;
      const y = 20 - ((value - floor) / span) * 18;
      return `${i === 0 ? 'M' : 'L'}${x.toFixed(1)},${y.toFixed(1)}`;
    })
    .join(' ');

  return (
    <svg className="spark" viewBox="0 0 60 22" aria-hidden focusable="false">
      <path d={path} fill="none" strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round"
        stroke={tone === 'none' ? 'var(--color-line)' : tone === 'bad' ? '#b3261e' : 'var(--color-brand)'} />
    </svg>
  );
}