Kennzahl

'use client';

import { useId, useRef } from 'react';
import { cn, round, useInView, useLocale, useTexts } from '@/lib/kit';
import { Icon, type IconName } from '@/components/ui/icon';
import { NumberTicker } from '@/components/ui/number-ticker';

export type StatTrend = 'up' | 'down' | 'flat';

/** Entrance only for elements that were below the fold, so nothing above it blinks on load */
function useEntrance<T extends Element>() {
  const [ref, inView] = useInView<T>();
  const waited = useRef(false);
  if (!inView) waited.current = true;
  return [ref, inView, inView && waited.current] as const;
}

/**
 * A formatted value like "$48,210", "48.210 €" or "3,8 %" with exactly one number in it
 * counts up with the number ticker, the text around it stays. Anything else shows as it is.
 */
function CountedValue({ value }: { value: React.ReactNode }) {
  const locale = useLocale();
  if (typeof value !== 'string') return <>{value}</>;
  const runs = value.match(/\d[\d.,]*\d|\d/g);
  if (!runs || runs.length !== 1) return <>{value}</>;
  const run = runs[0];
  const de = locale === 'de';
  const plain = de ? run.replace(/\./g, '').replace(',', '.') : run.replace(/,/g, '');
  const n = Number(plain);
  const decimals = plain.includes('.') ? plain.length - plain.indexOf('.') - 1 : 0;
  const fmt = new Intl.NumberFormat(de ? 'de-DE' : 'en-US', { minimumFractionDigits: decimals, maximumFractionDigits: decimals });
  // Only when the ticker writes the number exactly as given
  if (!Number.isFinite(n) || fmt.format(n) !== run) return <>{value}</>;
  const at = value.indexOf(run);
  return (
    <>
      {value.slice(0, at)}
      <NumberTicker value={n} format={{ minimumFractionDigits: decimals, maximumFractionDigits: decimals }} duration={1600} />
      {value.slice(at + run.length)}
    </>
  );
}
export type StatCardVariant = 'default' | 'plain' | 'accent';

export interface StatDelta {
  /** Formatted change, e.g. "+12.4%" or "−3" */
  value: string;
  trend: StatTrend;
  /** Is this change good news? Defaults to up = good, down = bad. Pass false for e.g. rising costs. */
  positive?: boolean;
  /** Small text after the delta, e.g. "vs last month" */
  note?: string;
}

export interface StatCardProps {
  label: React.ReactNode;
  /** The formatted number, e.g. "$48,210" or "48.210 €" */
  value: React.ReactNode;
  delta?: StatDelta;
  icon?: IconName;
  description?: React.ReactNode;
  /** Values for a small chart under the number */
  sparkline?: number[];
  /** Progress towards a goal */
  goal?: { value: number; max: number; label: React.ReactNode };
  /** Makes the whole card a link */
  href?: string;
  /** default: card. plain: no frame, for StatGrid. accent: filled with the accent color. */
  variant?: StatCardVariant;
  /** Count the number up when the card scrolls into view. Default true, works for values with one number. */
  count?: boolean;
  size?: 'md' | 'lg';
  labels?: Partial<(typeof TEXTS)['en']>;
  className?: string;
}

const TEXTS = {
  en: { up: 'up', down: 'down', flat: 'unchanged', goal: 'of goal' },
  de: { up: 'gestiegen', down: 'gesunken', flat: 'unverändert', goal: 'vom Ziel' },
};

/** The line draws itself from the start when it scrolls into view, the area fades in under it, the end point pops */
function Spark({ values, accent, tall }: { values: number[]; accent: boolean; tall?: boolean }) {
  const id = useId().replace(/:/g, '');
  const [ref, inView, entering] = useEntrance<SVGSVGElement>();
  const w = 240;
  const h = 56;
  const min = Math.min(...values);
  const max = Math.max(...values);
  const span = max - min || 1;
  const pts = values.map((v, i) => [round((i / (values.length - 1)) * w), round(h - 4 - ((v - min) / span) * (h - 10))] as const);
  // Smooth curve through the points (monotone enough for small series)
  const d = pts.reduce((acc, [x, y], i) => {
    if (i === 0) return `M${x} ${y}`;
    const [px, py] = pts[i - 1];
    const cx = round((px + x) / 2);
    return `${acc} C${cx} ${py} ${cx} ${y} ${x} ${y}`;
  }, '');
  const stroke = accent ? 'var(--primary-foreground)' : 'var(--primary)';
  const [lx, ly] = pts[pts.length - 1];
  return (
    <div className={cn('relative w-full', tall ? 'h-24 sm:h-32' : 'h-14')} aria-hidden>
    <svg ref={ref} viewBox={`0 0 ${w} ${h}`} preserveAspectRatio="none" className="absolute inset-0 size-full overflow-visible">
      <defs>
        <linearGradient id={`sc-${id}`} x1="0" x2="0" y1="0" y2="1">
          <stop offset="0" stopColor={stroke} stopOpacity={accent ? 0.28 : 0.2} />
          <stop offset="1" stopColor={stroke} stopOpacity="0" />
        </linearGradient>
      </defs>
      <path d={`${d} L${w} ${h} L0 ${h} Z`} fill={`url(#sc-${id})`} className="transition-[opacity,clip-path] duration-[1400ms] ease-[var(--ease-kit)] motion-reduce:transition-none" style={{ opacity: inView ? 1 : 0, clipPath: `inset(0 ${inView ? 0 : 100}% 0 0)` }} />
      <path
        d={d}
        fill="none"
        stroke={stroke}
        strokeWidth="2"
        strokeLinecap="round"
        vectorEffect="non-scaling-stroke"
        pathLength={1}
        strokeDasharray="1 1"
        strokeDashoffset={inView ? 0 : 1}
        className="transition-[stroke-dashoffset] duration-[1400ms] ease-[var(--ease-kit)] motion-reduce:transition-none"
      />
    </svg>
      <span
        className={cn('absolute size-2 -translate-x-1/2 -translate-y-1/2 rounded-full ring-4 transition-[opacity,scale] duration-500 ease-[cubic-bezier(0.34,1.56,0.64,1)] motion-reduce:transition-none', entering && 'delay-[1200ms]', accent ? 'bg-primary-foreground ring-[color-mix(in_oklab,var(--primary-foreground)_22%,transparent)]' : 'bg-primary ring-[color-mix(in_oklab,var(--primary)_16%,transparent)]', inView ? 'scale-100 opacity-100' : 'scale-0 opacity-0')}
        style={{ left: `${round((lx / w) * 100)}%`, top: `${round((ly / h) * 100)}%` }}
      />
    </div>
  );
}

function Delta({ delta, accent, t }: { delta: StatDelta; accent: boolean; t: (typeof TEXTS)['en'] }) {
  const good = delta.positive ?? delta.trend === 'up';
  const tone = delta.trend === 'flat' ? 'neutral' : good ? 'good' : 'bad';
  return (
    <span className="inline-flex flex-wrap items-center gap-x-1.5 gap-y-0.5 text-[13px]">
      <span
        className={cn(
          'inline-flex h-6 items-center gap-0.5 rounded-md px-1.5 font-medium tabular-nums',
          accent
            ? 'bg-[color-mix(in_oklab,var(--primary-foreground)_16%,transparent)] text-primary-foreground'
            : tone === 'good'
              ? 'bg-[color-mix(in_oklab,var(--success)_13%,transparent)] text-success-foreground'
              : tone === 'bad'
                ? 'bg-[color-mix(in_oklab,var(--destructive)_12%,transparent)] text-[color-mix(in_oklab,var(--destructive)_85%,var(--foreground))]'
                : 'bg-muted text-muted-foreground',
        )}
      >
        <Icon name={delta.trend === 'up' ? 'arrow-up-right' : delta.trend === 'down' ? 'arrow-down-right' : 'arrow-right'} size={13} strokeWidth={2} />
        {delta.value}
        <span className="sr-only">, {t[delta.trend]}</span>
      </span>
      {delta.note && <span className={accent ? 'text-[color-mix(in_oklab,var(--primary-foreground)_72%,transparent)]' : 'text-muted-foreground'}>{delta.note}</span>}
    </span>
  );
}

/** A number that matters: label, value, change, and optionally a sparkline or a goal. */
export function StatCard({ label, value, delta, icon, description, sparkline, goal, href, variant = 'default', size = 'md', count = true, labels, className }: StatCardProps) {
  const t = useTexts(TEXTS, labels);
  const locale = useLocale();
  const accent = variant === 'accent';
  const share = goal ? Math.min(goal.value / (goal.max || 1), 1) : 0;
  const Tag = href ? 'a' : 'div';
  const [ref, inView, entering] = useEntrance<HTMLDivElement>();
  return (
    <Tag
      href={href}
      ref={ref as React.Ref<HTMLDivElement & HTMLAnchorElement>}
      className={cn(
        'group/stat relative flex min-w-0 flex-col',
        variant === 'default' && 'kit-card p-5 sm:p-6',
        variant === 'plain' && 'bg-card p-5 sm:p-6',
        accent && 'kit-shine overflow-hidden rounded-[calc(var(--radius)+4px)] bg-primary p-5 text-primary-foreground shadow-[inset_0_1px_0_rgb(255_255_255/0.16),var(--shadow-md)] sm:p-6',
        href && 'transition-[background-color,box-shadow,translate] duration-300 ease-[var(--ease-kit)] hover:-translate-y-0.5 hover:shadow-[var(--highlight),var(--shadow-lg)] motion-reduce:hover:translate-y-0',
        href && variant === 'plain' && 'hover:bg-surface',
        className,
      )}
    >
      <div className="flex items-start justify-between gap-3">
        <p className={cn('text-[13px] font-medium', accent ? 'text-[color-mix(in_oklab,var(--primary-foreground)_78%,transparent)]' : 'text-muted-foreground')}>{label}</p>
        {icon && (
          <span className={cn('grid size-8 shrink-0 place-items-center rounded-lg transition-[scale,rotate] duration-500 ease-[cubic-bezier(0.34,1.56,0.64,1)] group-hover/stat:-rotate-6 group-hover/stat:scale-110 motion-reduce:transition-none', accent ? 'bg-[color-mix(in_oklab,var(--primary-foreground)_14%,transparent)]' : 'border border-border bg-surface text-muted-foreground')}>
            <Icon name={icon} size={16} />
          </span>
        )}
        {href && !icon && <Icon name="arrow-up-right" size={16} className="text-subtle-foreground transition-transform duration-200 group-hover/stat:-translate-y-0.5 group-hover/stat:translate-x-0.5 motion-reduce:transition-none" />}
      </div>
      <p className={cn('mt-2 font-semibold tabular-nums tracking-[-0.03em]', size === 'lg' ? 'text-[2.5rem] leading-[1.1] sm:text-[3rem]' : 'text-[1.75rem] leading-tight')}>{count ? <CountedValue value={value} /> : value}</p>
      {delta && (
        <div className={cn('mt-2 transition-[opacity,translate] duration-500 ease-[var(--ease-kit)] motion-reduce:transition-none', !inView && 'translate-y-1.5 opacity-0')} style={{ transitionDelay: entering ? '700ms' : undefined }}>
          <Delta delta={delta} accent={accent} t={t} />
        </div>
      )}
      {description && <p className={cn('mt-3 text-pretty text-sm', accent ? 'text-[color-mix(in_oklab,var(--primary-foreground)_78%,transparent)]' : 'text-muted-foreground')}>{description}</p>}
      {sparkline && sparkline.length > 1 && (
        <div className="mt-auto pt-5">
          <Spark values={sparkline} accent={accent} tall={size === 'lg'} />
        </div>
      )}
      {goal && (
        <div className="mt-auto pt-5">
          <div className={cn('h-1.5 overflow-hidden rounded-full', accent ? 'bg-[color-mix(in_oklab,var(--primary-foreground)_20%,transparent)]' : 'bg-[color-mix(in_oklab,var(--foreground)_8%,transparent)]')}>
            <div
              data-clip-ok
              className={cn('h-full w-full rounded-full transition-transform duration-1000 ease-[var(--ease-kit)] motion-reduce:transition-none', accent ? 'bg-primary-foreground' : 'bg-primary')}
              style={{ transform: `translateX(${inView ? round((share - 1) * 100) : -100}%)`, transitionDelay: entering ? '300ms' : undefined }}
            />
          </div>
          <p className={cn('mt-2 flex justify-between gap-3 text-[12px]', accent ? 'text-[color-mix(in_oklab,var(--primary-foreground)_75%,transparent)]' : 'text-muted-foreground')}>
            <span>{goal.label}</span>
            <span className="tabular-nums">
              {new Intl.NumberFormat(locale === 'de' ? 'de-DE' : 'en-US', { style: 'percent' }).format(share)} {t.goal}
            </span>
          </p>
        </div>
      )}
    </Tag>
  );
}

/** Stats side by side with hairlines between them. Pass plain StatCards. */
export function StatGrid({ columns = 4, className, children }: { columns?: 2 | 3 | 4; className?: string; children: React.ReactNode }) {
  return (
    <div
      className={cn(
        'grid gap-px overflow-hidden rounded-[calc(var(--radius)+4px)] border border-border bg-border shadow-[var(--shadow-sm)]',
        columns === 2 && 'sm:grid-cols-2',
        columns === 3 && 'sm:grid-cols-3',
        columns === 4 && 'grid-cols-2 lg:grid-cols-4',
        className,
      )}
    >
      {children}
    </div>
  );
}