Belege und Quellen

'use client';

import { Fragment, useEffect, useId, useRef, useState } from 'react';
import { cn, prefersReducedMotion, useTexts } from '@/lib/kit';
import { Icon, type IconName } from '@/components/ui/icon';
import { Reveal } from '@/components/ui/reveal';
import { Stagger, useScrollFade } from '@/components/ui/motion';

export type CitationsVariant = 'source-cards' | 'footnotes' | 'hover-preview' | 'side-panel' | 'claim-check';

export interface CitationSource {
  id: number;
  title: string;
  /** Domain or place, e.g. "kanzlei-berger.de" or "Contracts folder" */
  site: string;
  href?: string;
  /** e.g. "Mar 2026" */
  date?: string;
  kind?: 'web' | 'doc' | 'internal' | 'paper';
  /** The quoted passage. ==Marked words== are the part the answer relies on. */
  excerpt?: string;
}

export interface CitationClaim {
  id: string;
  claim: string;
  /** Source id */
  source?: number;
  /** The words in the source that back the claim */
  quote?: string;
  status: 'supported' | 'partial' | 'missing';
  note?: string;
}

export interface CitationsProps {
  variant?: CitationsVariant;
  title?: string;
  /** The question that was asked */
  question?: string;
  /** Paragraphs of the answer. [1] or [1, 3] cite sources, **bold** works. */
  answer?: string[];
  sources?: CitationSource[];
  /** claim-check */
  claims?: CitationClaim[];
  labels?: Partial<(typeof TEXTS)['en']>;
  className?: string;
}

const TEXTS = {
  en: {
    sources: 'Sources',
    answer: 'Answer',
    usedIn: 'Cited {n} times',
    usedOnce: 'Cited once',
    all: 'All',
    web: 'Web',
    doc: 'Documents',
    internal: 'Internal',
    paper: 'Studies',
    open: 'Open source',
    footnotes: 'Notes',
    back: 'Back to the text',
    note: 'Note {n}',
    preview: 'Preview of source {n}',
    quoted: 'Quoted passage',
    verify: 'Check against the source',
    supported: 'Backed by the source',
    partial: 'Partly backed',
    missing: 'No source found',
    
    evidence: 'In the source',
    noEvidence: 'None of the sources says this. Treat it as unconfirmed.',
    summary: '{ok} of {total} claims backed by a source',
    honest: 'Sources can be outdated or wrong. Open them before you rely on an answer.',
    selectHint: 'Select a sentence to see its source',
    sentence: 'Sentence with source {n}',
  },
  de: {
    sources: 'Quellen',
    answer: 'Antwort',
    usedIn: '{n}-mal zitiert',
    usedOnce: 'Einmal zitiert',
    all: 'Alle',
    web: 'Web',
    doc: 'Dokumente',
    internal: 'Intern',
    paper: 'Studien',
    open: 'Quelle öffnen',
    footnotes: 'Anmerkungen',
    back: 'Zurück zum Text',
    note: 'Anmerkung {n}',
    preview: 'Vorschau auf Quelle {n}',
    quoted: 'Zitierte Stelle',
    verify: 'Mit der Quelle abgleichen',
    supported: 'Von der Quelle gedeckt',
    partial: 'Teilweise gedeckt',
    missing: 'Keine Quelle gefunden',
    
    evidence: 'In der Quelle',
    noEvidence: 'Keine der Quellen sagt das. Behandle es als unbestätigt.',
    summary: '{ok} von {total} Aussagen durch eine Quelle gedeckt',
    honest: 'Quellen können veraltet oder falsch sein. Öffne sie, bevor du dich auf eine Antwort verlässt.',
    selectHint: 'Wähl einen Satz, um seine Quelle zu sehen',
    sentence: 'Satz mit Quelle {n}',
  },
};

type Texts = (typeof TEXTS)['en'];
type P = CitationsProps & { t: Texts };
const fill = (s: string, v: Record<string, string | number>) => s.replace(/\{(\w+)\}/g, (_, k) => String(v[k] ?? ''));

const CSS =
  '@keyframes cit-up{from{opacity:0;transform:translateY(8px)}}@keyframes cit-pop{from{opacity:0;transform:translateY(4px) scale(.97)}}@keyframes cit-flash{from{background-color:color-mix(in oklab,var(--primary) 30%,transparent)}}' +
  '@media (prefers-reduced-motion:no-preference){.cit-up{animation:cit-up .45s var(--ease-kit) var(--cit-d,0ms) both}.cit-pop{animation:cit-pop .22s var(--ease-kit) both}.cit-flash{animation:cit-flash 1.4s ease-out both}}';

function Style() {
  return (
    <style href="kit-citations" precedence="default">
      {CSS}
    </style>
  );
}

/* ------------------------------------------------------------------ */
/* Shared parts                                                        */
/* ------------------------------------------------------------------ */

const TONES = ['--primary', '--info', '--success', '--warning', '--destructive'];
const KIND_ICON: Record<NonNullable<CitationSource['kind']>, IconName> = { web: 'globe', doc: 'file', internal: 'folder', paper: 'book-open' };

function SiteTile({ source, size = 28 }: { source: CitationSource; size?: number }) {
  const tone = TONES[(source.id - 1) % TONES.length];
  return (
    <span aria-hidden className="grid shrink-0 place-items-center rounded-lg text-[12px] font-semibold uppercase" style={{ width: size, height: size, background: `color-mix(in oklab, var(${tone}) 16%, var(--card))`, color: `color-mix(in oklab, var(${tone}) 72%, var(--foreground))`, fontSize: Math.round(size * 0.42) }}>
      {source.kind && source.kind !== 'web' ? <Icon name={KIND_ICON[source.kind]} size={Math.round(size * 0.5)} /> : source.site.replace(/^www\./, '').charAt(0)}
    </span>
  );
}

/** Excerpt with ==marked== words */
function Excerpt({ text, className }: { text: string; className?: string }) {
  return (
    <span className={className}>
      {text.split(/(==[^=]+==)/g).map((part, i) =>
        part.startsWith('==') ? (
          <mark key={i} className="rounded-[3px] bg-[color-mix(in_oklab,var(--warning)_30%,transparent)] px-0.5 text-foreground">
            {part.slice(2, -2)}
          </mark>
        ) : (
          <Fragment key={i}>{part}</Fragment>
        ),
      )}
    </span>
  );
}

function bold(text: string) {
  return text.split(/(\*\*[^*]+\*\*)/g).map((part, i) => (part.startsWith('**') ? <strong key={i} className="font-semibold text-foreground">{part.slice(2, -2)}</strong> : <Fragment key={i}>{part}</Fragment>));
}

/** Splits a paragraph into text and [n, m] markers */
function parts(text: string) {
  const out: ({ text: string } | { ids: number[] })[] = [];
  let last = 0;
  for (const m of text.matchAll(/\s?\[(\d+(?:\s*,\s*\d+)*)\]/g)) {
    if (m.index! > last) out.push({ text: text.slice(last, m.index) });
    out.push({ ids: m[1].split(',').map((x) => Number(x.trim())) });
    last = m.index! + m[0].length;
  }
  if (last < text.length) out.push({ text: text.slice(last) });
  return out;
}

type Glued = { text: string } | { lead: string; ids: number[] };
/** Like parts, but each marker carries the word before it and the punctuation after it */
function glue(text: string): Glued[] {
  const ps = parts(text) as ({ text: string } | { ids: number[]; lead?: string })[];
  for (let i = 0; i < ps.length; i++) {
    const x = ps[i];
    if (!('ids' in x)) continue;
    const prev = ps[i - 1];
    const next = ps[i + 1];
    let lead = '';
    if (prev && 'text' in prev) {
      const m = /(\S+)$/.exec(prev.text);
      if (m) {
        lead = m[1];
        prev.text = prev.text.slice(0, m.index);
      }
    }
    if (next && 'text' in next) {
      const m = /^[.,;:!?)]+/.exec(next.text);
      if (m) {
        lead += m[0];
        next.text = next.text.slice(m[0].length);
      }
    }
    x.lead = lead;
  }
  return ps.map((x) => ('ids' in x ? { lead: x.lead ?? '', ids: x.ids } : x));
}

/** Sentences of a paragraph, each with the ids it cites */
function sentences(text: string) {
  return text.split(/(?<=[.!?])\s+(?=[A-ZÄÖÜ„“"(])/).map((s) => ({ text: s.replace(/\s?\[[\d,\s]+\]/g, '').trim(), ids: Array.from(s.matchAll(/\[(\d+(?:\s*,\s*\d+)*)\]/g)).flatMap((m) => m[1].split(',').map((x) => Number(x.trim()))) }));
}

function Stage({ title, question, children, className, wide }: { title?: string; question?: string; children: React.ReactNode; className?: string; wide?: boolean }) {
  return (
    <section className={cn('kit-glow relative overflow-clip bg-surface py-12 sm:py-16 lg:py-20', className)}>
      <div className="kit-container">
        <div className={cn('mx-auto w-full', wide ? 'max-w-[68rem]' : 'max-w-[46rem]')}>
          {(title || question) && (
            <Reveal className="mb-6 sm:mb-8">
              {title && <p className="mb-2 flex items-center gap-1.5 text-[13px] font-medium text-[color-mix(in_oklab,var(--primary)_75%,var(--muted-foreground))]"><Icon name="quote" size={14} />{title}</p>}
              {question && <h2 className="text-balance text-[22px] font-semibold leading-tight tracking-[-0.02em] text-foreground sm:text-[28px]">{question}</h2>}
            </Reveal>
          )}
          {children}
        </div>
      </div>
    </section>
  );
}

function Honest({ t }: { t: Texts }) {
  return (
    <p className="mt-5 flex items-start gap-2 text-[12.5px] leading-snug text-muted-foreground">
      <Icon name="info" size={14} className="mt-px shrink-0" />
      {t.honest}
    </p>
  );
}

const markCls = 'inline-flex h-[1.35em] min-w-[1.35em] items-center justify-center rounded-[5px] px-1 align-[0.12em] text-[11px] font-semibold tabular-nums leading-none transition-colors duration-200';

/* ------------------------------------------------------------------ */
/* source-cards                                                        */
/* ------------------------------------------------------------------ */

function SourceCards({ t, title, question, answer = [], sources = [], className }: P) {
  const [focus, setFocus] = useState<number | null>(null);
  const [kind, setKind] = useState<string>('all');
  const [row, fade] = useScrollFade<HTMLDivElement>();
  // A number in the text lights up its card and brings it into view, also when a filter hid it
  const pick = (id: number) => {
    const next = focus === id ? null : id;
    setFocus(next);
    if (next == null) return;
    const k = sources.find((s) => s.id === id)?.kind ?? 'web';
    if (kind !== 'all' && kind !== k) setKind('all');
    requestAnimationFrame(() => row.current?.querySelector(`[data-card="${id}"]`)?.scrollIntoView({ behavior: prefersReducedMotion() ? 'auto' : 'smooth', block: 'nearest', inline: 'nearest' }));
  };
  const uses = (id: number) => answer.reduce((n, p) => n + parts(p).filter((x) => 'ids' in x && x.ids.includes(id)).length, 0);
  const kinds = Array.from(new Set(sources.map((s) => s.kind ?? 'web')));
  const shown = sources.filter((s) => kind === 'all' || (s.kind ?? 'web') === kind);

  return (
    <Stage title={title} question={question} className={className} wide>
      <div className="mb-3 flex flex-wrap items-center justify-between gap-3">
        <p className="text-[13px] font-medium text-foreground">
          {t.sources} <span className="tabular-nums text-muted-foreground">{sources.length}</span>
        </p>
        {kinds.length > 1 && (
          <div role="group" aria-label={t.sources} className="flex gap-1 rounded-lg bg-[color-mix(in_oklab,var(--foreground)_5%,transparent)] p-1">
            {['all', ...kinds].map((k) => (
              <button key={k} type="button" aria-pressed={kind === k} onClick={() => setKind(k)} className={cn('h-9 rounded-md px-2.5 text-[12.5px] font-medium transition-colors max-sm:h-11 max-sm:min-w-11', kind === k ? 'bg-card text-foreground shadow-[var(--highlight),var(--shadow-sm)]' : 'text-muted-foreground hover:text-foreground')}>
                {t[k as 'all' | 'web']}
              </button>
            ))}
          </div>
        )}
      </div>
      <div ref={row} tabIndex={0} aria-label={t.sources} className={cn('kit-no-scrollbar -mx-6 overflow-x-auto px-6 pb-1 sm:mx-0 sm:px-0 lg:overflow-visible', fade, 'lg:[mask-image:none]')}>
        <Stagger as="ul" step={70} className="flex w-max gap-3 lg:grid lg:w-auto lg:grid-cols-4">
          {shown.map((s) => {
            const n = uses(s.id);
            const on = focus === s.id;
            return (
              <li key={s.id} data-card={s.id} className="w-[15.5rem] lg:w-auto">
                <button
                  type="button"
                  aria-pressed={on}
                  onClick={() => setFocus(on ? null : s.id)}
                  className={cn(
                    'group flex h-full w-full flex-col rounded-xl border bg-card p-3.5 text-left shadow-[var(--highlight),var(--shadow-sm)] transition-[border-color,transform,box-shadow] duration-300 ease-[var(--ease-kit)] hover:-translate-y-0.5 hover:shadow-[var(--highlight),var(--shadow-md)] motion-reduce:hover:translate-y-0',
                    on ? 'border-[color-mix(in_oklab,var(--primary)_60%,var(--border))]' : 'border-border hover:border-border-strong',
                  )}
                >
                  <span className="flex items-center gap-2">
                    <SiteTile source={s} size={24} />
                    <span className="min-w-0 flex-1 truncate text-[12px] text-muted-foreground">{s.site}</span>
                    <span className={cn(markCls, on ? 'bg-primary text-primary-foreground' : 'bg-[color-mix(in_oklab,var(--foreground)_8%,transparent)] text-muted-foreground')}>{s.id}</span>
                  </span>
                  <span className="mt-2.5 line-clamp-2 text-[13.5px] font-medium leading-snug text-foreground">{s.title}</span>
                  <span className="mt-auto flex items-center justify-between gap-2 pt-3 text-[11.5px] text-subtle-foreground">
                    <span>{s.date}</span>
                    <span className="tabular-nums">{n === 1 ? t.usedOnce : fill(t.usedIn, { n })}</span>
                  </span>
                </button>
              </li>
            );
          })}
        </Stagger>
      </div>
      <Reveal delay={120}>
        <div className="mt-6 rounded-2xl border border-border bg-card p-5 shadow-[var(--highlight),var(--shadow-sm)] sm:p-6">
          <p className="mb-3 flex items-center gap-1.5 text-[12.5px] font-medium text-muted-foreground">
            <Icon name="sparkle" size={14} className="text-primary" />
            {t.answer}
          </p>
          <div className="space-y-3.5 text-pretty text-[15px] leading-relaxed text-muted-foreground">
            {answer.map((p, i) => (
              <p key={i}>
                {glue(p).map((x, j) =>
                  'text' in x ? (
                    <Fragment key={j}>{bold(x.text)}</Fragment>
                  ) : (
                    <span key={j} className="whitespace-nowrap">
                      {bold(x.lead)}
                      <span className="ml-1 inline-flex gap-0.5">
                      {x.ids.map((id) => (
                        <button key={id} type="button" aria-label={fill(t.note, { n: id })} aria-pressed={focus === id} onClick={() => pick(id)} className={cn(markCls, "relative after:absolute after:-inset-x-0.5 after:-inset-y-4 after:content-['']", focus === id ? 'bg-primary text-primary-foreground' : 'bg-[color-mix(in_oklab,var(--primary)_14%,var(--card))] text-[color-mix(in_oklab,var(--primary)_75%,var(--foreground))] hover:bg-[color-mix(in_oklab,var(--primary)_24%,var(--card))]')}>
                          {id}
                        </button>
                      ))}
                      </span>
                    </span>
                  ),
                )}
              </p>
            ))}
          </div>
        </div>
      </Reveal>
      <Honest t={t} />
    </Stage>
  );
}

/* ------------------------------------------------------------------ */
/* footnotes                                                           */
/* ------------------------------------------------------------------ */

function Footnotes({ t, title, question, answer = [], sources = [], className }: P) {
  const uid = useId().replace(/:/g, '');
  const [flash, setFlash] = useState<string | null>(null);
  const go = (id: string) => {
    const el = document.getElementById(id);
    if (!el) return;
    el.scrollIntoView({ behavior: prefersReducedMotion() ? 'auto' : 'smooth', block: 'center' });
    el.focus({ preventScroll: true });
    setFlash(id);
  };
  useEffect(() => {
    if (!flash) return;
    const id = window.setTimeout(() => setFlash(null), 1500);
    return () => window.clearTimeout(id);
  }, [flash]);
  const used = sources.filter((s) => answer.some((p) => parts(p).some((x) => 'ids' in x && x.ids.includes(s.id))));

  return (
    <Stage title={title} question={question} className={className}>
      <Reveal delay={80}>
        <article className="rounded-2xl border border-border bg-card px-5 py-6 shadow-[var(--highlight),var(--shadow-sm)] sm:px-8 sm:py-8">
          <div className="space-y-4 text-pretty text-[15.5px] leading-[1.75] text-muted-foreground">
            {answer.map((p, i) => (
              <p key={i}>
                {glue(p).map((x, j) =>
                  'text' in x ? (
                    <Fragment key={j}>{bold(x.text)}</Fragment>
                  ) : (
                    <span key={j} className="whitespace-nowrap">
                    {bold(x.lead)}
                    {x.ids.map((id, k) => (
                      <sup key={`${j}-${id}`} className={k ? undefined : "ml-0.5"}>
                        {k > 0 && <span className="text-[11.5px] text-muted-foreground">,</span>}
                        <a
                          id={`${uid}-ref-${i}-${j}-${k}`}
                          href={`#${uid}-fn-${id}`}
                          aria-label={fill(t.note, { n: id })}
                          onClick={(e) => (e.preventDefault(), go(`${uid}-fn-${id}`))}
                          className={cn('rounded-[4px] px-0.5 text-[11.5px] font-semibold text-[color-mix(in_oklab,var(--primary)_80%,var(--foreground))] underline decoration-[color-mix(in_oklab,var(--primary)_40%,transparent)] underline-offset-2 hover:decoration-primary', flash === `${uid}-ref-${i}-${j}-${k}` && 'cit-flash')}
                        >
                          {id}
                        </a>
                      </sup>
                    ))}
                    </span>
                  ),
                )}
              </p>
            ))}
          </div>
          <hr className="my-7 w-16 border-border-strong" />
          <h3 className="mb-3 text-[13px] font-medium text-foreground">{t.footnotes}</h3>
          <Stagger as="ol" step={60} className="space-y-1">
            {used.map((s) => {
              const firstRef = (() => {
                for (let i = 0; i < answer.length; i++) {
                  const ps = parts(answer[i]);
                  for (let j = 0; j < ps.length; j++) {
                    const x = ps[j];
                    if ('ids' in x && x.ids.includes(s.id)) return `${uid}-ref-${i}-${j}-${x.ids.indexOf(s.id)}`;
                  }
                }
                return '';
              })();
              const id = `${uid}-fn-${s.id}`;
              return (
                <li key={s.id} id={id} tabIndex={-1} className={cn('grid grid-cols-[1.5rem_minmax(0,1fr)] gap-2 rounded-lg px-2 py-2 text-[13.5px] leading-relaxed outline-none focus-visible:ring-2 focus-visible:ring-primary', flash === id && 'cit-flash')}>
                  <span className="pt-px text-right font-semibold tabular-nums text-muted-foreground">{s.id}.</span>
                  <span className="min-w-0">
                    <span className="text-foreground">{s.title}</span>
                    <span className="text-muted-foreground">
                      {' '}
                      · {s.site}
                      {s.date && `, ${s.date}`}
                    </span>
                    {s.excerpt && <Excerpt text={s.excerpt} className="mt-1.5 block border-l-2 border-border-strong pl-2.5 text-[13px] italic text-muted-foreground" />}
                    <span className="mt-1 flex flex-wrap gap-x-4 gap-y-1">
                      {s.href && (
                        <a href={s.href} className="inline-flex min-h-8 items-center gap-1 text-[12.5px] font-medium text-foreground underline-offset-4 hover:underline max-sm:min-h-11">
                          {t.open}
                          <Icon name="arrow-up-right" size={13} />
                        </a>
                      )}
                      <a href={`#${firstRef}`} onClick={(e) => (e.preventDefault(), go(firstRef))} className="inline-flex min-h-8 items-center gap-1 text-[12.5px] text-muted-foreground underline-offset-4 hover:text-foreground hover:underline max-sm:min-h-11">
                        <Icon name="corner-down-left" size={13} className="rotate-90" />
                        {t.back}
                      </a>
                    </span>
                  </span>
                </li>
              );
            })}
          </Stagger>
        </article>
      </Reveal>
      <Honest t={t} />
    </Stage>
  );
}

/* ------------------------------------------------------------------ */
/* hover-preview                                                       */
/* ------------------------------------------------------------------ */

function Pill({ s, t, defaultOpen }: { s: CitationSource; t: Texts; defaultOpen?: boolean }) {
  const [open, setOpen] = useState(!!defaultOpen);
  const [shift, setShift] = useState(0);
  const [up, setUp] = useState(false);
  const ref = useRef<HTMLSpanElement>(null);
  const id = useId();
  const hide = useRef<number | undefined>(undefined);
  const show = () => {
    window.clearTimeout(hide.current);
    const r = ref.current?.getBoundingClientRect();
    if (r) {
      const w = Math.min(304, window.innerWidth - 32);
      setShift(Math.round(Math.max(16 - r.left, Math.min(0, window.innerWidth - 16 - w - r.left))));
      // Near the end of the block the card opens upward, the block clips what hangs out below
      const box = ref.current?.closest('section')?.getBoundingClientRect();
      setUp(!!box && r.bottom + 280 > box.bottom && r.top - 280 > box.top);
    }
    setOpen(true);
  };
  const later = () => {
    hide.current = window.setTimeout(() => setOpen(false), 160);
  };
  useEffect(() => {
    if (defaultOpen) show();
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);
  useEffect(() => {
    if (!open) return;
    const esc = (e: KeyboardEvent) => e.key === 'Escape' && setOpen(false);
    const away = (e: PointerEvent) => !ref.current?.contains(e.target as Node) && setOpen(false);
    document.addEventListener('keydown', esc);
    document.addEventListener('pointerdown', away);
    return () => {
      document.removeEventListener('keydown', esc);
      document.removeEventListener('pointerdown', away);
    };
  }, [open]);
  return (
    <span
      ref={ref}
      className="relative inline-block align-baseline"
      onPointerEnter={(e) => e.pointerType === 'mouse' && show()}
      onPointerLeave={(e) => e.pointerType === 'mouse' && later()}
      // Tabbing from the pill to the link inside the card keeps it open
      onFocus={() => window.clearTimeout(hide.current)}
      onBlur={(e) => !ref.current?.contains(e.relatedTarget as Node) && later()}
    >
      <button
        type="button"
        aria-expanded={open}
        aria-controls={id}
        aria-label={fill(t.preview, { n: s.id })}
        onClick={() => (open ? setOpen(false) : show())}
        onFocus={show}
        className={cn("relative mx-0.5 inline-flex h-6 translate-y-[-1px] items-center gap-1 rounded-full border pl-1 pr-2 align-middle text-[11.5px] font-medium transition-colors duration-200 after:absolute after:-inset-y-2.5 after:inset-x-0 after:content-[''] max-sm:h-7", open ? 'border-[color-mix(in_oklab,var(--primary)_50%,var(--border))] bg-[color-mix(in_oklab,var(--primary)_12%,var(--card))] text-foreground' : 'border-border bg-card text-muted-foreground hover:text-foreground')}
      >
        <SiteTile source={s} size={16} />
        {s.site.replace(/^www\./, '').split('.')[0]}
      </button>
      {open && (
        <span
          id={id}
          role="dialog"
          aria-label={fill(t.preview, { n: s.id })}
          onPointerEnter={() => window.clearTimeout(hide.current)}
          onPointerLeave={later}
          style={{ left: shift }}
          className={cn('cit-pop absolute z-30 block', up ? 'bottom-[calc(100%+8px)]' : 'top-[calc(100%+8px)]', 'w-[min(19rem,calc(100vw-2rem))] rounded-xl border border-border bg-card p-3.5 text-left not-italic shadow-[var(--highlight),var(--shadow-lg)]')}
        >
          <span className="flex items-center gap-2">
            <SiteTile source={s} size={22} />
            <span className="min-w-0 flex-1 truncate text-[12px] text-muted-foreground">
              {s.site}
              {s.date && ` · ${s.date}`}
            </span>
          </span>
          <span className="mt-2 block text-[13.5px] font-semibold leading-snug text-foreground">{s.title}</span>
          {s.excerpt && (
            <span className="mt-2 block border-l-2 border-[color-mix(in_oklab,var(--warning)_60%,var(--border))] pl-2.5 text-[12.5px] leading-relaxed text-muted-foreground">
              <span className="sr-only">{t.quoted}: </span>
              <Excerpt text={s.excerpt} />
            </span>
          )}
          {s.href && (
            <a href={s.href} className="mt-2.5 inline-flex min-h-11 items-center gap-1 focus-visible:-outline-offset-2 text-[12.5px] font-medium text-foreground underline-offset-4 hover:underline sm:min-h-8">
              {t.open}
              <Icon name="arrow-up-right" size={13} />
            </a>
          )}
        </span>
      )}
    </span>
  );
}

function HoverPreview({ t, title, question, answer = [], sources = [], className }: P) {
  const byId = (id: number) => sources.find((s) => s.id === id);
  let first = true;
  return (
    <Stage title={title} question={question} className={className}>
      <Reveal delay={80}>
        <div className="rounded-2xl border border-border bg-card px-5 py-6 shadow-[var(--highlight),var(--shadow-sm)] sm:px-8 sm:py-8">
          <div className="space-y-4 text-pretty text-[15.5px] leading-[1.85] text-muted-foreground">
            {answer.map((p, i) => (
              <p key={i}>
                {glue(p).map((x, j) =>
                  'text' in x ? (
                    <Fragment key={j}>{bold(x.text)}</Fragment>
                  ) : (
                    <Fragment key={j}>
                    {bold(x.lead)}
                    {x.ids.map((id) => {
                      const s = byId(id);
                      if (!s) return null;
                      // The first preview starts open, so the page shows what a hover does
                      const open = first;
                      first = false;
                      return <Pill key={`${j}-${id}`} s={s} t={t} defaultOpen={open && i === 0} />;
                    })}
                    </Fragment>
                  ),
                )}
              </p>
            ))}
          </div>
        </div>
      </Reveal>
      <Honest t={t} />
    </Stage>
  );
}

/* ------------------------------------------------------------------ */
/* side-panel                                                          */
/* ------------------------------------------------------------------ */

function SidePanel({ t, title, question, answer = [], sources = [], className }: P) {
  const all = answer.map((p) => sentences(p));
  const firstCited = all.flat().find((s) => s.ids.length)?.ids[0] ?? sources[0]?.id;
  const firstSel = (() => {
    for (let p = 0; p < all.length; p++) for (let i = 0; i < all[p].length; i++) if (all[p][i].ids.length) return { p, s: i };
    return null;
  })();
  const [sel, setSel] = useState<{ p: number; s: number } | null>(firstSel);
  const [src, setSrc] = useState<number | undefined>(firstCited);
  const panel = useRef<HTMLDivElement>(null);
  const chosen = useRef(false);
  useEffect(() => {
    if (src == null) return;
    const el = panel.current?.querySelector<HTMLElement>(`[data-src="${src}"]`);
    if (!el || !panel.current) return;
    const behavior = prefersReducedMotion() ? 'auto' : 'smooth';
    const top = el.offsetTop - panel.current.offsetTop - 12;
    if (window.matchMedia('(min-width: 1024px)').matches) panel.current.scrollTo({ top, behavior });
    // Phones stack the panel below, a chosen sentence brings its source into view
    else if (chosen.current) el.scrollIntoView({ behavior, block: 'nearest' });
  }, [src]);
  const choose = (p: number, s: number, id: number) => {
    chosen.current = true;
    setSel({ p, s });
    setSrc(id);
  };

  return (
    <Stage title={title} question={question} className={className} wide>
      <div className="grid grid-cols-1 gap-4 lg:grid-cols-[minmax(0,1fr)_22rem] lg:items-start lg:gap-6">
        <Reveal delay={80}>
          <div className="rounded-2xl border border-border bg-card px-5 py-6 shadow-[var(--highlight),var(--shadow-sm)] sm:px-7 sm:py-7">
            <p className="mb-4 flex items-center gap-1.5 text-[12.5px] text-muted-foreground">
              <Icon name="sparkle" size={14} className="text-primary" />
              {t.selectHint}
            </p>
            <div className="space-y-4 text-pretty text-[15.5px] leading-[1.8] text-muted-foreground">
              {all.map((ss, pi) => (
                <p key={pi}>
                  {ss.map((s, si) =>
                    s.ids.length ? (
                      <Fragment key={si}>
                        {/* A span keeps the sentence in the flow of the text, a button would wrap as a block */}
                        <span
                          role="button"
                          tabIndex={0}
                          aria-pressed={sel?.p === pi && sel.s === si}
                          onClick={() => choose(pi, si, s.ids[0])}
                          onKeyDown={(e) => {
                            if (e.key !== 'Enter' && e.key !== ' ') return;
                            e.preventDefault();
                            choose(pi, si, s.ids[0]);
                          }}
                          className={cn(
                            'cursor-pointer rounded-[4px] [box-decoration-break:clone] decoration-[color-mix(in_oklab,var(--primary)_45%,transparent)] decoration-dotted decoration-[1.5px] underline-offset-[5px] transition-colors duration-200 hover:bg-[color-mix(in_oklab,var(--primary)_8%,transparent)] hover:text-foreground',
                            sel?.p === pi && sel.s === si ? 'bg-[color-mix(in_oklab,var(--primary)_14%,transparent)] text-foreground' : 'underline',
                          )}
                        >
                          {bold(s.text)}
                          <span className="sr-only"> ({fill(t.sentence, { n: s.ids.join(', ') })})</span>
                        </span>{' '}
                      </Fragment>
                    ) : (
                      <Fragment key={si}>{bold(s.text)} </Fragment>
                    ),
                  )}
                </p>
              ))}
            </div>
          </div>
        </Reveal>
        <Reveal delay={180} className="lg:sticky lg:top-6">
          <aside aria-label={t.sources} className="overflow-hidden rounded-2xl border border-border bg-card shadow-[var(--highlight),var(--shadow-sm)]">
            <p className="border-b border-border px-4 py-3 text-[13px] font-medium text-foreground">
              {t.sources} <span className="tabular-nums text-muted-foreground">{sources.length}</span>
            </p>
            <div ref={panel} className="kit-scrollbar relative space-y-2 p-2.5 lg:max-h-[30rem] lg:overflow-y-auto">
              {sources.map((s) => {
                const on = s.id === src;
                return (
                  <button
                    key={s.id}
                    data-src={s.id}
                    type="button"
                    aria-pressed={on}
                    onClick={() => setSrc(s.id)}
                    className={cn('block w-full rounded-xl border p-3 text-left transition-[border-color,background-color] duration-300', on ? 'border-[color-mix(in_oklab,var(--primary)_50%,var(--border))] bg-[color-mix(in_oklab,var(--primary)_6%,var(--card))]' : 'border-transparent hover:bg-accent/60')}
                  >
                    <span className="flex items-center gap-2">
                      <SiteTile source={s} size={22} />
                      <span className="min-w-0 flex-1 truncate text-[12px] text-muted-foreground">{s.site}</span>
                      <span className={cn(markCls, on ? 'bg-primary text-primary-foreground' : 'bg-[color-mix(in_oklab,var(--foreground)_8%,transparent)] text-muted-foreground')}>{s.id}</span>
                    </span>
                    <span className="mt-1.5 block text-[13.5px] font-medium leading-snug text-foreground">{s.title}</span>
                    {s.excerpt && (
                      <span className={cn('grid transition-[grid-template-rows,opacity] duration-500 ease-[var(--ease-kit)]', on ? 'grid-rows-[1fr] opacity-100' : 'grid-rows-[0fr] opacity-0')}>
                        <span className="overflow-hidden">
                          <span className="mt-2 block border-l-2 border-[color-mix(in_oklab,var(--warning)_60%,var(--border))] pl-2.5 text-[12.5px] leading-relaxed text-muted-foreground">
                            <Excerpt text={s.excerpt} />
                          </span>
                        </span>
                      </span>
                    )}
                  </button>
                );
              })}
            </div>
          </aside>
        </Reveal>
      </div>
      <Honest t={t} />
    </Stage>
  );
}

/* ------------------------------------------------------------------ */
/* claim-check                                                         */
/* ------------------------------------------------------------------ */

const STATUS = {
  supported: { icon: 'check' as IconName, cls: 'bg-[color-mix(in_oklab,var(--success)_15%,var(--card))] text-success-foreground', line: 'border-[color-mix(in_oklab,var(--success)_45%,var(--border))]' },
  partial: { icon: 'minus' as IconName, cls: 'bg-[color-mix(in_oklab,var(--warning)_20%,var(--card))] text-warning-foreground', line: 'border-[color-mix(in_oklab,var(--warning)_55%,var(--border))]' },
  missing: { icon: 'help-circle' as IconName, cls: 'bg-[color-mix(in_oklab,var(--destructive)_13%,var(--card))] text-destructive', line: 'border-[color-mix(in_oklab,var(--destructive)_45%,var(--border))]' },
};

function ClaimCheck({ t, title, question, claims = [], sources = [], className }: P) {
  const [open, setOpen] = useState<string | null>(claims.find((c) => c.status !== 'supported')?.id ?? claims[0]?.id ?? null);
  const ok = claims.filter((c) => c.status === 'supported').length;
  return (
    <Stage title={title} question={question} className={className}>
      <Reveal delay={60}>
        <div className="mb-4 rounded-2xl border border-border bg-card p-4 shadow-[var(--highlight),var(--shadow-sm)] sm:p-5">
          <div className="flex items-baseline justify-between gap-3">
            <p className="text-[14px] font-medium text-foreground">{fill(t.summary, { ok, total: claims.length })}</p>
            <p className="text-[13px] tabular-nums text-muted-foreground">
              {ok}/{claims.length}
            </p>
          </div>
          <div aria-hidden className="mt-3 flex h-2 gap-1">
            {claims.map((c, i) => (
              <span key={c.id} className={cn('cit-up h-full flex-1 rounded-full', c.status === 'supported' ? 'bg-success' : c.status === 'partial' ? 'bg-warning' : 'bg-destructive')} style={{ '--cit-d': `${200 + i * 90}ms` } as React.CSSProperties} />
            ))}
          </div>
          <div className="mt-3 flex flex-wrap gap-x-4 gap-y-1 text-[12px] text-muted-foreground">
            {(['supported', 'partial', 'missing'] as const).map((k) => (
              <span key={k} className="inline-flex items-center gap-1.5">
                <span className={cn('size-2 rounded-full', k === 'supported' ? 'bg-success' : k === 'partial' ? 'bg-warning' : 'bg-destructive')} />
                {t[k]}
              </span>
            ))}
          </div>
        </div>
      </Reveal>
      <Stagger as="ul" step={70} className="space-y-2.5">
        {claims.map((c) => {
          const s = sources.find((x) => x.id === c.source);
          const st = STATUS[c.status];
          const on = open === c.id;
          return (
            <li key={c.id} className="overflow-hidden rounded-2xl border border-border bg-card shadow-[var(--highlight),var(--shadow-sm)]">
              <button type="button" aria-expanded={on} onClick={() => setOpen(on ? null : c.id)} className="flex w-full items-start gap-3 p-4 text-left transition-colors focus-visible:-outline-offset-2 hover:bg-accent/40 sm:px-5">
                <span className={cn('mt-0.5 grid size-6 shrink-0 place-items-center rounded-full', st.cls)}>
                  <Icon name={st.icon} size={13} strokeWidth={2.2} />
                </span>
                <span className="min-w-0 flex-1">
                  <span className="block text-pretty text-[14.5px] leading-snug text-foreground">{c.claim}</span>
                  <span className={cn('mt-1 block text-[12px] font-medium', c.status === 'supported' ? 'text-success-foreground' : c.status === 'partial' ? 'text-warning-foreground' : 'text-destructive')}>{t[c.status]}</span>
                </span>
                <Icon name="chevron-down" size={16} className={cn('mt-1 shrink-0 text-muted-foreground transition-transform duration-300', on && 'rotate-180')} />
              </button>
              <div className={cn('grid transition-[grid-template-rows] duration-500 ease-[var(--ease-kit)] motion-reduce:transition-none', on ? 'grid-rows-[1fr]' : 'grid-rows-[0fr]')}>
                <div className="overflow-hidden" inert={!on || undefined}>
                  <div className="px-4 pb-4 sm:px-5 sm:pl-14">
                    {s && c.quote ? (
                      <div className={cn('rounded-xl border-l-2 bg-background/60 py-2.5 pl-3.5 pr-3', st.line)}>
                        <p className="flex items-center gap-2 text-[12px] text-muted-foreground">
                          <SiteTile source={s} size={18} />
                          <span className="truncate">
                            {t.evidence} · {s.site}
                          </span>
                        </p>
                        <Excerpt text={c.quote} className="mt-1.5 block text-[13.5px] italic leading-relaxed text-muted-foreground" />
                      </div>
                    ) : (
                      <p className="rounded-xl border border-dashed border-[color-mix(in_oklab,var(--destructive)_40%,var(--border))] px-3.5 py-2.5 text-[13px] text-muted-foreground">{t.noEvidence}</p>
                    )}
                    {c.note && <p className="mt-2 text-[12.5px] leading-relaxed text-muted-foreground">{c.note}</p>}
                    {s?.href && (
                      <a href={s.href} className="mt-2 inline-flex min-h-9 items-center gap-1 text-[12.5px] font-medium text-foreground underline-offset-4 hover:underline max-sm:min-h-11">
                        {t.verify}
                        <Icon name="arrow-up-right" size={13} />
                      </a>
                    )}
                  </div>
                </div>
              </div>
            </li>
          );
        })}
      </Stagger>
      <Honest t={t} />
    </Stage>
  );
}

/* ------------------------------------------------------------------ */

/**
 * Citations for AI answers: source cards with how often each is cited,
 * numbered footnotes with jump and back, citation pills with a preview of the
 * quoted passage, a source panel that follows the selected sentence and a
 * claim check that says which statements a source really backs.
 */
export function Citations({ variant = 'source-cards', labels, ...props }: CitationsProps) {
  const t = useTexts(TEXTS, labels);
  const p: P = { ...props, t };
  const body = (() => {
    switch (variant) {
      case 'footnotes':
        return <Footnotes {...p} />;
      case 'hover-preview':
        return <HoverPreview {...p} />;
      case 'side-panel':
        return <SidePanel {...p} />;
      case 'claim-check':
        return <ClaimCheck {...p} />;
      default:
        return <SourceCards {...p} />;
    }
  })();
  return (
    <>
      <Style />
      {body}
    </>
  );
}