Video-Section mit Kapiteln

'use client';

import { useCallback, useEffect, useId, useRef, useState } from 'react';
import { cn, prefersReducedMotion, round, useTexts } from '@/lib/kit';
import { Icon } from '@/components/ui/icon';
import { Eyebrow, Section } from '@/components/ui/section';
import { Reveal } from '@/components/ui/reveal';
import { Stagger } from '@/components/ui/motion';
import { Button } from '@/components/ui/button';

/*
 * A section around one video: poster, play, chapters and the transcript.
 * With `src` it plays the file. Without it the section runs as a preview,
 * the poster stays and time moves on, so chapters and transcript can be
 * tried on any page.
 *
 *   chapters    the player beside a chapter list that follows the time
 *   transcript  the player above a transcript that unfolds, the line
 *               being spoken lights up, every line jumps to its time
 *   feature     a large centered player with facts and an action below
 *   split       text and points beside the player, chapters as marks
 */

export type VideoSectionVariant = 'chapters' | 'transcript' | 'feature' | 'split';

export interface VideoChapter {
  /** Start in seconds */
  time: number;
  title: string;
  text?: string;
}

export interface TranscriptLine {
  time: number;
  text: string;
  speaker?: string;
}

const TEXTS = {
  en: {
    play: 'Play video',
    pause: 'Pause',
    resume: 'Play',
    position: 'Position',
    chapters: 'Chapters',
    transcript: 'Transcript',
    showTranscript: 'Show transcript',
    hideTranscript: 'Hide transcript',
    jump: 'Jump to {time}',
    minutes: '{n} min',
    of: 'of',
    now: 'Now playing',
  },
  de: {
    play: 'Video abspielen',
    pause: 'Pausieren',
    resume: 'Abspielen',
    position: 'Position',
    chapters: 'Kapitel',
    transcript: 'Transkript',
    showTranscript: 'Transkript zeigen',
    hideTranscript: 'Transkript ausblenden',
    jump: 'Zu {time} springen',
    minutes: '{n} Min.',
    of: 'von',
    now: 'Läuft gerade',
  },
};
type Texts = (typeof TEXTS)['en'];

export interface VideoSectionProps {
  variant?: VideoSectionVariant;
  eyebrow?: React.ReactNode;
  title?: React.ReactNode;
  description?: React.ReactNode;
  /** The poster, e.g. a drawn scene or an <img> */
  poster?: React.ReactNode;
  /** Video file. Without it the section runs as a preview. */
  src?: string;
  /** Length in seconds */
  duration?: number;
  /** Name of the video, for the player's label */
  videoTitle?: string;
  chapters?: VideoChapter[];
  transcript?: TranscriptLine[];
  /** split: points beside the player */
  points?: string[];
  /** feature: facts under the player */
  facts?: { value: string; label: string }[];
  action?: { label: string; href: string };
  /** transcript: open from the start */
  defaultOpen?: boolean;
  labels?: Partial<Texts>;
  className?: string;
}

const focus = 'outline-none focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-solid focus-visible:outline-ring';

/** 65 -> 1:05 */
export const clock = (s: number) => {
  const v = Math.max(0, Math.floor(s));
  const h = Math.floor(v / 3600);
  const m = Math.floor((v % 3600) / 60);
  const ss = String(v % 60).padStart(2, '0');
  return h ? `${h}:${String(m).padStart(2, '0')}:${ss}` : `${m}:${ss}`;
};

/* ------------------------------------------------------------------ */
/* Playback                                                            */
/* ------------------------------------------------------------------ */

function usePlayback(duration: number, src?: string) {
  const video = useRef<HTMLVideoElement>(null);
  const [time, setTime] = useState(0);
  const [playing, setPlaying] = useState(false);
  const [started, setStarted] = useState(false);
  const [length, setLength] = useState(duration);

  // preview: time moves on by itself while playing
  useEffect(() => {
    if (src || !playing) return;
    let last = performance.now();
    let frame = requestAnimationFrame(function tick(now) {
      const dt = (now - last) / 1000;
      last = now;
      setTime((t) => Math.min(length, t + dt));
      frame = requestAnimationFrame(tick);
    });
    return () => cancelAnimationFrame(frame);
  }, [playing, src, length]);

  useEffect(() => {
    if (!src && playing && time >= length) setPlaying(false);
  }, [time, playing, src, length]);

  // pause when the tab hides
  useEffect(() => {
    const onHide = () => document.hidden && setPlaying(false);
    document.addEventListener('visibilitychange', onHide);
    return () => document.removeEventListener('visibilitychange', onHide);
  }, []);

  useEffect(() => {
    const v = video.current;
    if (!v) return;
    if (playing) v.play().catch(() => setPlaying(false));
    else v.pause();
  }, [playing]);

  const toggle = useCallback(() => {
    setStarted(true);
    setPlaying((p) => {
      if (!p) setTime((t) => (t >= length - 0.05 ? 0 : t));
      return !p;
    });
  }, [length]);

  const seek = useCallback(
    (t: number, play = true) => {
      const n = Math.min(Math.max(0, t), length);
      setTime(n);
      if (video.current) video.current.currentTime = n;
      setStarted(true);
      if (play) setPlaying(true);
    },
    [length],
  );

  const videoProps = src
    ? {
        ref: video,
        src,
        playsInline: true,
        preload: 'metadata' as const,
        onTimeUpdate: (e: React.SyntheticEvent<HTMLVideoElement>) => setTime(e.currentTarget.currentTime),
        onLoadedMetadata: (e: React.SyntheticEvent<HTMLVideoElement>) => Number.isFinite(e.currentTarget.duration) && setLength(e.currentTarget.duration),
        onEnded: () => setPlaying(false),
      }
    : null;

  return { time, playing, started, length, toggle, seek, videoProps };
}

type Playback = ReturnType<typeof usePlayback>;

const currentIndex = (list: { time: number }[] | undefined, time: number) => {
  if (!list?.length) return -1;
  let i = 0;
  list.forEach((c, j) => {
    if (c.time <= time + 0.01) i = j;
  });
  return i;
};

/* ------------------------------------------------------------------ */
/* Player                                                              */
/* ------------------------------------------------------------------ */

function Player({ p, pb, t, className, glow = false }: { p: VideoSectionProps; pb: Playback; t: Texts; className?: string; glow?: boolean }) {
  const ci = currentIndex(p.chapters, pb.time);
  const chapter = ci >= 0 ? p.chapters?.[ci] : undefined;
  const pct = pb.length ? pb.time / pb.length : 0;
  const reduce = typeof window !== 'undefined' && prefersReducedMotion();
  // the big play button leaves with the first play, its focus moves on to the pause button
  const control = useRef<HTMLButtonElement>(null);
  const fromBig = useRef(false);
  useEffect(() => {
    if (pb.started && fromBig.current) {
      fromBig.current = false;
      control.current?.focus();
    }
  }, [pb.started]);
  return (
    <div className={cn('relative', className)}>
      {glow && <div aria-hidden className="absolute -inset-x-4 -inset-y-6 -z-10 xl:-inset-x-10 xl:-inset-y-8 rounded-[3rem] bg-[radial-gradient(closest-side,var(--glow),transparent)] blur-2xl" />}
      <div role="group" aria-label={p.videoTitle ?? t.play} className="group/player relative aspect-video overflow-hidden rounded-2xl border border-border bg-bezel shadow-[var(--shadow-lg)]">
        {/* poster, it drifts very slowly while a preview plays */}
        <div data-clip-ok className={cn('absolute inset-0 transition-[transform,filter] ease-linear [&>*]:size-full', pb.playing && !reduce ? 'scale-[1.06] duration-[20s]' : 'scale-100 duration-700', pb.videoProps && pb.started && 'opacity-0')}>
          {p.poster}
        </div>
        {pb.videoProps && <video {...pb.videoProps} className={cn('absolute inset-0 size-full object-cover', !pb.started && 'opacity-0')} aria-label={p.videoTitle} />}
        <div aria-hidden className={cn('absolute inset-0 transition-opacity duration-500', pb.started ? 'bg-[linear-gradient(to_top,rgb(0_0_0/0.55),transparent_45%)]' : 'bg-[linear-gradient(to_top,rgb(0_0_0/0.45),rgb(0_0_0/0.08)_55%,transparent)]')} />

        {/* chapter name while playing */}
        {chapter && pb.started && (
          <span key={chapter.title} className="dark absolute left-3 top-3 max-w-[calc(100%-1.5rem)] truncate rounded-md bg-black/55 px-2.5 py-1 text-[12px] font-medium text-white backdrop-blur-md motion-safe:animate-[kit-rise_0.4s_var(--ease-kit)] sm:left-4 sm:top-4">
            {chapter.title}
          </span>
        )}

        {/* the big play button before the first play */}
        {!pb.started && (
          <button type="button" onClick={() => { fromBig.current = true; pb.toggle(); }} aria-label={p.videoTitle ? `${t.play}: ${p.videoTitle}` : t.play} className={cn('absolute inset-0 flex cursor-pointer items-center justify-center', focus, 'focus-visible:-outline-offset-4')}>
            <span className="relative flex size-16 items-center justify-center rounded-full bg-white text-black shadow-[0_10px_40px_rgb(0_0_0/0.35)] transition-transform duration-300 ease-[var(--ease-kit)] group-hover/player:scale-110 sm:size-20">
              <span aria-hidden className="absolute -inset-2 rounded-full border border-white/60 motion-safe:animate-kit-pulse" />
              <Icon name="play" size={26} className="translate-x-0.5" />
            </span>
            <span className="absolute bottom-4 left-4 right-4 flex items-center justify-between gap-3 text-left text-white sm:bottom-5 sm:left-5 sm:right-5">
              <span className="truncate text-[14px] font-medium">{p.videoTitle}</span>
              <span className="shrink-0 rounded-md bg-black/55 px-2 py-0.5 text-[12px] font-medium tabular-nums backdrop-blur-md">{clock(pb.length)}</span>
            </span>
          </button>
        )}

        {/* controls */}
        {pb.started && (
          <div className="dark absolute inset-x-0 bottom-0 flex items-center gap-2 px-2 pb-2 pt-6 text-white sm:gap-3 sm:px-4 sm:pb-3">
            <button ref={control} type="button" onClick={pb.toggle} aria-label={pb.playing ? t.pause : t.resume} className={cn('flex size-11 shrink-0 cursor-pointer items-center justify-center rounded-full transition-colors hover:bg-white/15', focus)}>
              <Icon name={pb.playing ? 'pause' : 'play'} size={18} />
            </button>
            <div className="relative flex h-11 min-w-0 flex-1 items-center">
              <div aria-hidden className="pointer-events-none absolute inset-x-0 h-1 overflow-hidden rounded-full bg-white/25">
                <div className="h-full origin-left bg-white" style={{ transform: `scaleX(${round(pct, 4)})` }} />
              </div>
              {p.chapters?.slice(1).map((c) => (
                <span key={c.time} aria-hidden className="pointer-events-none absolute h-1 w-0.5 bg-black/50" style={{ left: `${round((c.time / pb.length) * 100, 3)}%` }} />
              ))}
              <input
                type="range"
                min={0}
                max={round(pb.length)}
                step={1}
                value={round(pb.time)}
                aria-label={t.position}
                aria-valuetext={`${clock(pb.time)} ${t.of} ${clock(pb.length)}`}
                onChange={(e) => pb.seek(Number(e.target.value), pb.playing)}
                className="relative h-11 w-full cursor-pointer appearance-none bg-transparent outline-none [&::-moz-range-thumb]:size-3.5 [&::-moz-range-thumb]:rounded-full [&::-moz-range-thumb]:border-0 [&::-moz-range-thumb]:bg-white [&::-webkit-slider-thumb]:size-3.5 [&::-webkit-slider-thumb]:appearance-none [&::-webkit-slider-thumb]:rounded-full [&::-webkit-slider-thumb]:bg-white [&::-webkit-slider-thumb]:shadow-[0_0_0_4px_rgb(255_255_255/0.2)] focus-visible:[&::-webkit-slider-thumb]:shadow-[0_0_0_4px_var(--ring)]"
              />
            </div>
            <span className="shrink-0 text-[12px] font-medium tabular-nums text-white/90 sm:text-[13px]">
              {clock(pb.time)} <span className="text-white/60">/ {clock(pb.length)}</span>
            </span>
          </div>
        )}
      </div>
    </div>
  );
}

function Head({ p, center = false, className }: { p: VideoSectionProps; center?: boolean; className?: string }) {
  if (!p.title && !p.eyebrow) return null;
  return (
    <div className={cn('max-w-[44rem]', center && 'mx-auto text-center', className)}>
      {p.eyebrow && <Eyebrow>{p.eyebrow}</Eyebrow>}
      {p.title && <h2 className="text-balance text-h2 font-semibold text-foreground">{p.title}</h2>}
      {p.description && <p className={cn('mt-5 text-pretty text-lead text-muted-foreground', center && 'mx-auto max-w-[36rem]')}>{p.description}</p>}
    </div>
  );
}

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

function Chapters({ p, t }: { p: VideoSectionProps; t: Texts }) {
  const pb = usePlayback(p.duration ?? 240, p.src);
  const chapters = p.chapters ?? [];
  const ci = currentIndex(chapters, pb.time);
  return (
    <>
      <Head p={p} className="mb-10 sm:mb-12" />
      <div className="grid grid-cols-[minmax(0,1fr)] gap-6 lg:grid-cols-[minmax(0,1fr)_22rem] lg:gap-8">
        <Reveal effect="scale">
          <Player p={p} pb={pb} t={t} />
        </Reveal>
        <nav aria-label={t.chapters} className="lg:relative">
          <div className="flex h-full flex-col overflow-hidden rounded-2xl border border-border bg-card shadow-[var(--highlight),var(--shadow-sm)] lg:absolute lg:inset-0">
            <p className="flex items-center justify-between border-b border-border px-5 py-3.5 text-[14px] font-semibold text-foreground">
              {t.chapters}
              <span className="text-[13px] font-normal tabular-nums text-muted-foreground">{chapters.length}</span>
            </p>
            <ol className="kit-scrollbar relative min-h-0 flex-1 overflow-y-auto p-2">
              {chapters.map((c, i) => {
                const on = pb.started && i === ci;
                const end = chapters[i + 1]?.time ?? pb.length;
                const local = on ? Math.min(1, Math.max(0, (pb.time - c.time) / Math.max(1, end - c.time))) : 0;
                return (
                  <li key={c.time}>
                    <button
                      type="button"
                      onClick={() => pb.seek(c.time)}
                      aria-current={on ? 'step' : undefined}
                      aria-label={`${c.title}, ${t.jump.replace('{time}', clock(c.time))}`}
                      className={cn('relative grid w-full cursor-pointer grid-cols-[3rem_minmax(0,1fr)] gap-3 overflow-hidden rounded-lg px-3 py-3 text-left transition-colors', on ? 'bg-accent' : 'hover:bg-accent/60', focus)}
                    >
                      <span className={cn('pt-px text-[12.5px] font-medium tabular-nums', on ? 'text-primary' : 'text-muted-foreground')}>{clock(c.time)}</span>
                      <span className="min-w-0">
                        <span className={cn('block text-[14.5px] font-medium leading-snug', on ? 'text-foreground' : 'text-foreground/90')}>{c.title}</span>
                        {c.text && <span className="mt-1 block text-pretty text-[13px] leading-relaxed text-muted-foreground">{c.text}</span>}
                      </span>
                      {on && (
                        <span aria-hidden className="absolute inset-x-3 bottom-0 h-0.5 overflow-hidden rounded-full bg-track">
                          <span className="block h-full origin-left bg-primary" style={{ transform: `scaleX(${round(local, 3)})` }} />
                        </span>
                      )}
                    </button>
                  </li>
                );
              })}
            </ol>
          </div>
        </nav>
      </div>
    </>
  );
}

function Transcript({ p, t }: { p: VideoSectionProps; t: Texts }) {
  const pb = usePlayback(p.duration ?? 240, p.src);
  const lines = p.transcript ?? [];
  const li = currentIndex(lines, pb.time);
  const [open, setOpen] = useState(!!p.defaultOpen);
  const id = useId();
  const box = useRef<HTMLOListElement>(null);

  // keep the spoken line in view inside the panel, never move the page
  useEffect(() => {
    const el = box.current;
    const on = el?.querySelector<HTMLElement>('[aria-current="true"]');
    if (!el || !on || !open || !pb.started) return;
    const top = on.offsetTop - el.clientHeight / 2 + on.clientHeight / 2;
    el.scrollTo({ top, behavior: prefersReducedMotion() ? 'auto' : 'smooth' });
  }, [li, open, pb.started]);

  return (
    <div className="mx-auto max-w-[56rem]">
      <Head p={p} className="mb-10 sm:mb-12" />
      <Reveal effect="scale">
        <Player p={p} pb={pb} t={t} />
      </Reveal>
      <div className="mt-4 overflow-hidden rounded-2xl border border-border bg-card shadow-[var(--highlight),var(--shadow-sm)]">
        <button type="button" aria-expanded={open} aria-controls={id} onClick={() => setOpen((o) => !o)} className={cn('flex min-h-14 w-full cursor-pointer items-center gap-3 px-5 text-left transition-colors hover:bg-surface', focus, 'focus-visible:-outline-offset-2')}>
          <Icon name="captions" size={18} className="text-muted-foreground" />
          <span className="flex-1 text-[14.5px] font-medium text-foreground">{open ? t.hideTranscript : t.showTranscript}</span>
          {pb.started && li >= 0 && !open && <span className="hidden max-w-[50%] truncate text-[13px] text-muted-foreground sm:block">{lines[li]?.text}</span>}
          <Icon name="chevron-down" size={18} className={cn('shrink-0 text-muted-foreground transition-transform duration-300', open && 'rotate-180')} />
        </button>
        <div id={id} className={cn('grid transition-[grid-template-rows] duration-500 ease-[var(--ease-kit)] motion-reduce:transition-none', open ? 'grid-rows-[1fr]' : 'grid-rows-[0fr]')}>
          <div className={cn('min-h-0 overflow-hidden', !open && 'invisible')}>
            <ol ref={box} aria-label={t.transcript} className="kit-scrollbar relative max-h-80 overflow-y-auto border-t border-border p-2">
              {lines.map((l, i) => {
                const on = pb.started && i === li;
                return (
                  <li key={l.time} aria-current={on ? 'true' : undefined}>
                    <button
                      type="button"
                      onClick={() => pb.seek(l.time)}
                      className={cn('grid w-full cursor-pointer grid-cols-[3.25rem_minmax(0,1fr)] gap-3 rounded-lg px-3 py-2.5 text-left transition-colors', on ? 'bg-[color-mix(in_oklab,var(--primary)_10%,var(--card))]' : 'hover:bg-accent/60', focus, 'focus-visible:-outline-offset-2')}
                    >
                      <span className={cn('pt-0.5 text-[12.5px] font-medium tabular-nums', on ? 'text-primary' : 'text-subtle-foreground')}>{clock(l.time)}</span>
                      <span className={cn('max-w-[40rem] text-pretty text-[15px] leading-relaxed', on ? 'text-foreground' : 'text-muted-foreground')}>
                        {l.speaker && <span className="font-semibold text-foreground">{l.speaker} </span>}
                        {l.text}
                      </span>
                    </button>
                  </li>
                );
              })}
            </ol>
          </div>
        </div>
      </div>
    </div>
  );
}

function Feature({ p, t }: { p: VideoSectionProps; t: Texts }) {
  const pb = usePlayback(p.duration ?? 240, p.src);
  return (
    <>
      <Head p={p} center className="mb-12 sm:mb-16" />
      <Reveal effect="scale" className="mx-auto max-w-[64rem]">
        <Player p={p} pb={pb} t={t} glow />
      </Reveal>
      {(p.facts?.length || p.action) && (
        <div className="mx-auto mt-10 flex max-w-[64rem] flex-col items-center gap-8 lg:flex-row lg:justify-between">
          {p.facts?.length ? (
            <Stagger as="ul" step={90} className="grid w-full grid-cols-[minmax(0,1fr)] divide-y divide-border sm:w-auto sm:grid-flow-col sm:auto-cols-fr sm:divide-x sm:divide-y-0">
              {p.facts.map((f) => (
                <li key={f.label} className="flex items-baseline justify-between gap-4 py-3 sm:block sm:px-8 sm:py-0 sm:first:pl-0">
                  <span className="block text-[clamp(1.5rem,1.3rem+0.8vw,2rem)] font-semibold tabular-nums tracking-[-0.03em] text-foreground">{f.value}</span>
                  <span className="block text-[14px] text-muted-foreground sm:mt-1">{f.label}</span>
                </li>
              ))}
            </Stagger>
          ) : (
            <span />
          )}
          {p.action && (
            <Button href={p.action.href} icon="arrow-right" magnetic className="max-sm:w-full">
              {p.action.label}
            </Button>
          )}
        </div>
      )}
    </>
  );
}

function Split({ p, t }: { p: VideoSectionProps; t: Texts }) {
  const pb = usePlayback(p.duration ?? 240, p.src);
  const chapters = p.chapters ?? [];
  const ci = currentIndex(chapters, pb.time);
  return (
    <div className="grid grid-cols-[minmax(0,1fr)] items-center gap-12 lg:grid-cols-[minmax(0,5fr)_minmax(0,7fr)] lg:gap-16">
      <div>
        <Head p={p} />
        {p.points?.length ? (
          <Stagger as="ul" step={80} className="mt-8 space-y-3">
            {p.points.map((pt) => (
              <li key={pt} className="flex gap-3 text-[15.5px] leading-relaxed text-foreground">
                <span className="mt-1 flex size-5 shrink-0 items-center justify-center rounded-full bg-[color-mix(in_oklab,var(--primary)_14%,transparent)] text-[color-mix(in_oklab,var(--primary)_85%,var(--foreground))]">
                  <Icon name="check" size={12} strokeWidth={2.4} />
                </span>
                {pt}
              </li>
            ))}
          </Stagger>
        ) : null}
        {chapters.length > 0 && (
          <div className="mt-8 border-t border-border pt-6">
            <p className="text-[13px] font-medium text-subtle-foreground">{t.chapters}</p>
            <ol className="mt-3 flex flex-wrap gap-2">
              {chapters.map((c, i) => {
                const on = pb.started && i === ci;
                return (
                  <li key={c.time}>
                    <button
                      type="button"
                      onClick={() => pb.seek(c.time)}
                      aria-current={on ? 'step' : undefined}
                      className={cn('inline-flex min-h-11 cursor-pointer items-center gap-2 rounded-lg border px-3 text-[13px] transition-colors sm:min-h-9', on ? 'border-[color-mix(in_oklab,var(--primary)_50%,var(--border))] bg-[color-mix(in_oklab,var(--primary)_10%,var(--card))] text-foreground' : 'border-border bg-background text-muted-foreground hover:bg-accent hover:text-foreground', focus)}
                    >
                      <span className="tabular-nums text-subtle-foreground">{clock(c.time)}</span>
                      <span className="font-medium">{c.title}</span>
                    </button>
                  </li>
                );
              })}
            </ol>
          </div>
        )}
        {p.action && (
          <div className="mt-8">
            <Button href={p.action.href} variant="outline" icon="arrow-right" className="max-sm:w-full">
              {p.action.label}
            </Button>
          </div>
        )}
      </div>
      <Reveal effect="scale" className="relative">
        <Player p={p} pb={pb} t={t} glow />
      </Reveal>
    </div>
  );
}

/**
 * A section around one video with a drawn or real poster: chapters beside
 * the player, a transcript that follows, a large feature or text beside it.
 *   <VideoSection variant="chapters" poster={<img … />} duration={252} chapters={[{ time: 0, title: '…' }]} />
 */
export function VideoSection(props: VideoSectionProps) {
  const { variant = 'chapters', className, labels } = props;
  const t = useTexts(TEXTS, labels);
  return (
    <Section className={className}>
      {variant === 'transcript' ? <Transcript p={props} t={t} /> : variant === 'feature' ? <Feature p={props} t={t} /> : variant === 'split' ? <Split p={props} t={t} /> : <Chapters p={props} t={t} />}
    </Section>
  );
}