Zoom beim Scrollen

'use client';

import { useCallback, useEffect, useRef, useState } from 'react';
import { cn, round, useTexts } from '@/lib/kit';
import { Eyebrow } from '@/components/ui/section';
import { Button } from '@/components/ui/button';
import { Icon, type IconName } from '@/components/ui/icon';
import { Reveal } from '@/components/ui/reveal';
import { PhoneFrame } from '@/components/ui/frame';
import { lerp, scrollToProgress, smooth, span, useLive, useSceneProgress } from '@/components/ui/scroll-scene';

/*
 * A picture or a product that zooms from small to the full screen while the page scrolls. The
 * section stands still for about two screens, the heading steps back, the picture grows, and at the
 * end its own text arrives on it. Only transform and opacity move, written straight onto the moving
 * elements, so drawn or photographed pictures are never repainted while scrolling.
 *
 * Without JavaScript and with reduced motion there is no zoom: the section shows its finished
 * state, heading, picture and text, in a calm normal layout.
 *
 *   image     a photo grows from a card to the whole window, a place and an offer arrive on it
 *   product   a product screen grows from small to wide, notes appear on it
 *   video     a film grows to the window, the play button lands in the middle
 *   grid      nine pictures, the middle one fills the window while the others drift away
 *   app-icon  an app icon grows into the phone with the app, its features arrive around it
 */

export type ZoomRevealVariant = 'image' | 'product' | 'video' | 'grid' | 'app-icon';

export interface ZoomNote {
  label: string;
  icon?: IconName;
}

export interface ZoomRevealProps extends Omit<React.HTMLAttributes<HTMLElement>, 'title'> {
  variant?: ZoomRevealVariant;
  eyebrow?: string;
  title: React.ReactNode;
  description?: string;
  /** The picture that zooms: a photo, a screenshot in a BrowserFrame, a video poster, the phone screen */
  media?: React.ReactNode;
  /** grid: nine pictures, the fifth one zooms */
  images?: React.ReactNode[];
  /** app-icon: the icon the phone grows out of */
  icon?: React.ReactNode;
  /** Text that arrives on the picture at the end (image, video, grid) */
  overlay?: { eyebrow?: string; title: string; text?: string };
  /** product, app-icon: short notes that appear around the screen */
  notes?: ZoomNote[];
  action?: { label: string; href: string };
  /** video: length shown on the player */
  duration?: string;
  labels?: Partial<(typeof TEXTS)['en']>;
}

const TEXTS = {
  en: { play: 'Play film', pause: 'Pause film' },
  de: { play: 'Film abspielen', pause: 'Film anhalten' },
};

type Els = Record<string, HTMLElement | null>;
interface Box {
  w: number;
  h: number;
  /** grid: size of the middle tile, measured with the stage */
  tw: number;
  th: number;
}

const tf = (el: HTMLElement | null, t: string) => {
  if (el) el.style.transform = t;
};
const op = (el: HTMLElement | null, o: number) => {
  if (el) el.style.opacity = String(round(o, 3));
};
/** Like op, and a piece that has faded out completely also leaves the page, so nothing hidden lies over the picture */
const opv = (el: HTMLElement | null, o: number) => {
  op(el, o);
  if (el) el.style.visibility = round(o, 3) <= 0 ? 'hidden' : '';
};

/* ------------------------------------------------------------------ */
/* What every variant does with the progress                           */
/* ------------------------------------------------------------------ */

const NOTE_AT = [0.62, 0.7, 0.78, 0.86];

function applyHead(e: Els, p: number, a = 0.18, b = 0.42) {
  const x = smooth(span(p, a, b));
  op(e.head, 1 - x);
  tf(e.head, `translate3d(0, ${round(-48 * x, 1)}px, 0)`);
}

function applyOverlay(e: Els, p: number) {
  const x = smooth(span(p, 0.7, 0.9));
  op(e.shade, span(p, 0.55, 0.85));
  op(e.over, x);
  tf(e.over, `translate3d(0, ${round(28 * (1 - x), 1)}px, 0)`);
}

const APPLY: Record<ZoomRevealVariant, (p: number, e: Els, b: Box) => void> = {
  image(p, e, b) {
    const z = smooth(span(p, 0.06, 0.68));
    const s0 = b.w < 640 ? 0.6 : 0.36;
    tf(e.media, `translate3d(0, ${round(lerp(b.h * (b.w < 640 ? 0.2 : 0.17), 0, z), 1)}px, 0) scale(${round(lerp(s0, 1, z), 4)})`);
    tf(e.img, `scale(${round(lerp(1.3, 1, z), 4)})`);
    applyHead(e, p);
    applyOverlay(e, p);
  },
  video(p, e, b) {
    APPLY.image(p, e, b);
    const x = smooth(span(p, 0.66, 0.84));
    op(e.play, x);
    tf(e.play, `scale(${round(lerp(0.6, 1, x), 3)})`);
  },
  product(p, e, b) {
    const z = smooth(span(p, 0.06, 0.66));
    tf(e.media, `translate3d(0, ${round(lerp(b.h * (b.w < 640 ? 0.26 : 0.2), 0, z), 1)}px, 0) scale(${round(lerp(b.w < 640 ? 0.78 : 0.6, 1, z), 4)})`);
    applyHead(e, p, 0.2, 0.46);
    NOTE_AT.forEach((at, i) => {
      const x = smooth(span(p, at, at + 0.1));
      for (const k of [`note${i}`, `mnote${i}`]) {
        opv(e[k], x);
        tf(e[k], `translate3d(0, ${round(12 * (1 - x), 1)}px, 0) scale(${round(lerp(0.92, 1, x), 3)})`);
      }
    });
  },
  grid(p, e, b) {
    const z = smooth(span(p, 0.1, 0.7));
    // The middle tile grows until it covers the window, the others move out by the same rate
    const tw = b.tw || 1;
    const th = b.th || 1;
    const full = Math.max(b.w / tw, b.h / th) * 1.02;
    const s = lerp(1, full, z);
    tf(e.t4, `scale(${round(s, 4)})`);
    for (let i = 0; i < 9; i++) {
      if (i === 4) continue;
      const col = (i % 3) - 1;
      const row = Math.floor(i / 3) - 1;
      // Each neighbour stays next to the growing tile, so they move out as one picture plane
      const dx = col * (tw * (s - 1) * 0.5);
      const dy = row * (th * (s - 1) * 0.5);
      tf(e[`t${i}`], `translate3d(${round(dx, 1)}px, ${round(dy, 1)}px, 0)`);
      opv(e[`t${i}`], 1 - span(p, 0.3, 0.62));
    }
    applyHead(e, p, 0.08, 0.3);
    applyOverlay(e, p);
  },
  'app-icon'(p, e, b) {
    const z = smooth(span(p, 0.12, 0.6));
    const end = b.w < 640 ? Math.min(0.78, (b.h * 0.6) / 540) : Math.min(1, (b.h * 0.78) / 540);
    tf(e.media, `translate3d(0, ${round(lerp(b.h * 0.08, 0, z), 1)}px, 0) scale(${round(lerp(0.3, end, z), 4)})`);
    // The icon gives way to the phone halfway through the growth
    const x = smooth(span(p, 0.22, 0.42));
    opv(e.icon, 1 - x);
    opv(e.phone, x);
    applyHead(e, p, 0.1, 0.32);
    NOTE_AT.forEach((at, i) => {
      const y = smooth(span(p, at, at + 0.1));
      opv(e[`note${i}`], y);
      tf(e[`note${i}`], `translate3d(${round((i % 2 ? 16 : -16) * (1 - y), 1)}px, 0, 0)`);
      opv(e[`mnote${i}`], y);
      tf(e[`mnote${i}`], `translate3d(0, ${round(12 * (1 - y), 1)}px, 0)`);
    });
  },
};

/* ------------------------------------------------------------------ */
/* Pieces                                                              */
/* ------------------------------------------------------------------ */

function Head({ eyebrow, title, description, center = true, className }: { eyebrow?: string; title: React.ReactNode; description?: string; center?: boolean; className?: string }) {
  return (
    <div className={cn('max-w-[46rem]', center && 'mx-auto text-center', className)}>
      {eyebrow && <Eyebrow>{eyebrow}</Eyebrow>}
      <h2 className="text-balance text-h1 font-semibold text-foreground">{title}</h2>
      {description && <p className={cn('mt-5 max-w-[36rem] text-pretty text-lead text-muted-foreground', center && 'mx-auto')}>{description}</p>}
    </div>
  );
}

function OverlayText({ overlay, action }: Pick<ZoomRevealProps, 'overlay' | 'action'>) {
  if (!overlay) return null;
  return (
    <div className="flex flex-col gap-6 sm:flex-row sm:items-end sm:justify-between">
      <div className="max-w-[34rem]">
        {overlay.eyebrow && <p className="text-[13.5px] font-medium text-[color-mix(in_oklab,var(--primary)_35%,var(--foreground))]">{overlay.eyebrow}</p>}
        <h3 className="mt-2 text-balance text-h2 font-semibold text-foreground">{overlay.title}</h3>
        {overlay.text && <p className="mt-3 max-w-[30rem] text-pretty text-[15.5px] leading-relaxed text-muted-foreground">{overlay.text}</p>}
      </div>
      {action && (
        <div className="max-sm:w-full max-sm:[&>span]:w-full sm:shrink-0">
          <Button href={action.href} icon="arrow-right" magnetic className="max-sm:w-full">
            {action.label}
          </Button>
        </div>
      )}
    </div>
  );
}

/** A dark veil from the bottom so the overlay text reads on any picture */
const SHADE = 'dark pointer-events-none absolute inset-0 bg-[linear-gradient(to_top,color-mix(in_oklab,var(--background)_92%,transparent)_0%,color-mix(in_oklab,var(--background)_55%,transparent)_38%,transparent_70%)]';

function PlayButton({ playing, onToggle, t, duration }: { playing: boolean; onToggle: () => void; t: (typeof TEXTS)['en']; duration?: string }) {
  return (
    <button
      type="button"
      onClick={onToggle}
      aria-pressed={playing}
      aria-label={playing ? t.pause : t.play}
      className="group flex items-center gap-3 rounded-full bg-[color-mix(in_oklab,var(--foreground)_14%,transparent)] py-2 pl-2 pr-5 text-[14px] font-medium text-foreground shadow-[var(--shadow-lg)] backdrop-blur-md transition-transform duration-300 ease-[var(--ease-kit)] hover:scale-[1.04] focus-visible:outline-2 focus-visible:outline-solid focus-visible:outline-offset-4 focus-visible:outline-primary motion-reduce:transition-none"
    >
      <span className="flex size-12 items-center justify-center rounded-full bg-primary text-primary-foreground">
        <Icon name={playing ? 'pause' : 'play'} size={20} />
      </span>
      <span>{playing ? t.pause : t.play}</span>
      {duration && <span className="tabular-nums text-muted-foreground">{duration}</span>}
    </button>
  );
}

function Progress({ playing }: { playing: boolean }) {
  return (
    <span aria-hidden className="absolute inset-x-0 bottom-0 h-1 bg-[color-mix(in_oklab,var(--foreground)_18%,transparent)]">
      <span className={cn('absolute inset-0 origin-left bg-primary', playing ? 'animate-kit-progress' : 'scale-x-[0.18]')} style={{ '--kit-duration': '30s' } as React.CSSProperties} />
    </span>
  );
}

// product: the notes sit on the top and bottom edge of the screen, half outside it. There they only
// touch the window bar and the bottom margin of the screenshot, never its text or figures.
const NOTE_POS = ['left-[12%] top-0 -translate-y-1/2', 'right-[6%] top-0 -translate-y-1/2', 'left-[8%] bottom-0 translate-y-1/2', 'right-[10%] bottom-0 translate-y-1/2'];

function Note({ note, className, setRef }: { note: ZoomNote; className?: string; setRef?: (n: HTMLElement | null) => void }) {
  return (
    <span ref={setRef} className={cn('inline-flex items-center gap-2 rounded-full border border-border bg-card px-3.5 py-2 text-[13px] font-medium text-foreground shadow-[var(--highlight),var(--shadow-md)]', className)}>
      <span className="flex size-6 items-center justify-center rounded-full bg-[color-mix(in_oklab,var(--primary)_14%,var(--card))] text-primary">
        <Icon name={note.icon ?? 'check'} size={13} />
      </span>
      {note.label}
    </span>
  );
}

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

/** A picture or product that zooms to the full window while the page scrolls. */
export function ZoomReveal({ variant = 'image', eyebrow, title, description, media, images, icon, overlay, notes, action, duration, labels, className, onFocus, ...rest }: ZoomRevealProps) {
  const t = useTexts(TEXTS, labels);
  const live = useLive();
  const els = useRef<Els>({});
  const box = useRef<Box>({ w: 0, h: 0, tw: 0, th: 0 });
  const last = useRef(0);
  const [playing, setPlaying] = useState(false);
  const set = (k: string) => (n: HTMLElement | null) => {
    els.current[k] = n;
  };
  const apply = useCallback(
    (p: number) => {
      last.current = p;
      APPLY[variant](p, els.current, box.current);
    },
    [variant],
  );
  const track = useSceneProgress<HTMLDivElement>(live, { self: false, onProgress: apply });

  // The stage size, measured when the scene goes live and on resize, never while scrolling
  useEffect(() => {
    if (!live) return;
    const stage = els.current.stage;
    if (!stage) return;
    const measure = () => {
      const tile = els.current.t4;
      box.current = { w: stage.clientWidth, h: stage.clientHeight, tw: tile?.offsetWidth ?? 0, th: tile?.offsetHeight ?? 0 };
      apply(last.current);
    };
    measure();
    const ro = new ResizeObserver(measure);
    ro.observe(stage);
    return () => ro.disconnect();
  }, [live, apply]);

  const list = notes ?? [];
  const screens = variant === 'grid' ? 3 : 2.8;

  /* ---------- Finished, static layout: no JavaScript, reduced motion, server ---------- */
  if (!live) {
    return (
      <section {...rest} onFocus={onFocus} className={cn('relative overflow-x-clip py-20 sm:py-24 lg:py-32', className)}>
        <div className="kit-container">
          <Reveal>
            <Head eyebrow={eyebrow} title={title} description={description} />
          </Reveal>
          <div className="mt-12 sm:mt-16">
            {(variant === 'image' || variant === 'video') && (
              <div className="relative isolate aspect-[4/5] overflow-hidden rounded-2xl bg-surface sm:aspect-[16/9] [&>.m>*]:size-full">
                <div className="m absolute inset-0 -z-10">{media}</div>
                <span className={cn(SHADE, '-z-10')} />
                {variant === 'video' && (
                  // On a phone the text below is taller, so the button sits higher, clear of it
                  <div className="absolute inset-0 flex items-center justify-center pb-[38%] sm:pb-0">
                    <PlayButton playing={playing} onToggle={() => setPlaying((v) => !v)} t={t} duration={duration} />
                  </div>
                )}
                <div className="dark absolute inset-x-0 bottom-0 p-6 sm:p-10">
                  <OverlayText overlay={overlay} action={action} />
                </div>
                {variant === 'video' && <Progress playing={playing} />}
              </div>
            )}
            {variant === 'product' && (
              <div className="relative">
                <div className="mx-auto max-w-[68rem]">{media}</div>
                {list.length > 0 && (
                  <ul className="mt-8 flex flex-wrap justify-center gap-3">
                    {list.map((n, i) => (
                      <li key={i}>
                        <Note note={n} />
                      </li>
                    ))}
                  </ul>
                )}
              </div>
            )}
            {variant === 'grid' && (
              <div>
                <div className="grid grid-cols-3 gap-2 sm:gap-3">
                  {Array.from({ length: 9 }, (_, i) => (
                    <div key={i} className={cn('relative aspect-[4/3] overflow-hidden rounded-xl bg-surface [&>*]:size-full', i === 4 && 'ring-2 ring-primary ring-offset-2 ring-offset-background')}>
                      {images?.[i % (images.length || 1)]}
                    </div>
                  ))}
                </div>
                <div className="mt-10">
                  <OverlayText overlay={overlay} action={action} />
                </div>
              </div>
            )}
            {variant === 'app-icon' && (
              <div className="grid grid-cols-1 items-center gap-3 md:grid-cols-[1fr_auto_1fr] md:gap-10">
                <ul className="order-2 grid grid-cols-1 gap-3 sm:grid-cols-2 md:order-1 md:grid-cols-1 md:justify-items-end">
                  {list.filter((_, i) => i % 2 === 0).map((n, i) => (
                    <li key={i}>
                      <Note note={n} />
                    </li>
                  ))}
                </ul>
                <div className="order-1 mx-auto mb-7 md:order-2 md:mb-0">
                  <PhoneFrame className="w-[min(260px,70vw)]">{media}</PhoneFrame>
                </div>
                <ul className="order-3 grid grid-cols-1 gap-3 sm:grid-cols-2 md:grid-cols-1 md:justify-items-start">
                  {list.filter((_, i) => i % 2 === 1).map((n, i) => (
                    <li key={i}>
                      <Note note={n} />
                    </li>
                  ))}
                </ul>
              </div>
            )}
          </div>
        </div>
      </section>
    );
  }

  /* ---------- Live scene ---------- */
  // The play button and the closing action wait for the end of the scene; tabbing to them goes there
  const onSceneFocus = (e: React.FocusEvent<HTMLElement>) => {
    onFocus?.(e);
    const target = e.target as Node;
    if (els.current.over?.contains(target) || els.current.play?.contains(target)) scrollToProgress(track.current, 0.97);
  };
  const head = (
    <div ref={set('head')} className="relative z-20 px-6 pt-[clamp(2.5rem,9svh,6rem)] will-change-transform">
      <Head eyebrow={eyebrow} title={title} description={description} />
    </div>
  );

  return (
    <section {...rest} onFocus={onSceneFocus} className={cn('relative overflow-x-clip', className)}>
      <div ref={track} className="relative" style={{ height: `${screens * 100}svh` }}>
        <div ref={set('stage')} className="sticky top-0 h-svh overflow-clip">
          {(variant === 'image' || variant === 'video') && (
            <>
              {head}
              <div ref={set('media')} className="absolute inset-2 isolate overflow-hidden rounded-2xl bg-surface will-change-transform sm:inset-3">
                <div ref={set('img')} data-clip-ok className="absolute inset-0 will-change-transform [&>*]:size-full">
                  {media}
                </div>
                <span ref={set('shade')} className={SHADE} style={{ opacity: 0 }} />
              </div>
              {variant === 'video' && (
                <div ref={set('play')} className="absolute inset-0 z-20 flex items-center justify-center" style={{ opacity: 0 }}>
                  <PlayButton playing={playing} onToggle={() => setPlaying((v) => !v)} t={t} duration={duration} />
                </div>
              )}
              <div ref={set('over')} className="dark absolute inset-x-2 bottom-2 z-20 sm:inset-x-3 sm:bottom-3" style={{ opacity: 0 }}>
                <div className="kit-container pb-8 sm:pb-12">
                  <OverlayText overlay={overlay} action={action} />
                </div>
                {variant === 'video' && <Progress playing={playing} />}
              </div>
            </>
          )}

          {variant === 'product' && (
            <>
              {head}
              <div className="absolute inset-0 flex items-center justify-center px-4 sm:px-8">
                <div ref={set('media')} className="relative w-[min(68rem,100%,125svh)] will-change-transform">
                  {media}
                  {list.slice(0, 4).map((n, i) => (
                    <Note key={i} note={n} setRef={set(`note${i}`)} className={cn('absolute z-10 hidden sm:inline-flex', NOTE_POS[i])} />
                  ))}
                </div>
              </div>
              <ul className="absolute inset-x-4 bottom-4 z-20 grid grid-cols-2 gap-2 sm:hidden">
                {list.slice(0, 4).map((n, i) => (
                  <li key={i} ref={set(`mnote${i}`)} style={{ opacity: 0 }}>
                    <Note note={n} className="w-full text-[12.5px]" />
                  </li>
                ))}
              </ul>
            </>
          )}

          {variant === 'grid' && (
            <>
              <div className="absolute inset-0 grid grid-cols-3 grid-rows-3 gap-2 p-2 sm:gap-3 sm:p-3">
                {Array.from({ length: 9 }, (_, i) => (
                  <div key={i} ref={set(`t${i}`)} className={cn('relative overflow-hidden rounded-xl bg-surface will-change-transform [&>*]:size-full', i === 4 && 'z-10')}>
                    {images?.[i % (images.length || 1)]}
                  </div>
                ))}
              </div>
              <div className="pointer-events-none absolute inset-0 z-10 flex items-center justify-center">
                <div ref={set('head')} className="pointer-events-auto mx-6 max-w-[40rem] rounded-2xl border border-border bg-[color-mix(in_oklab,var(--background)_82%,transparent)] p-6 text-center shadow-[var(--shadow-lg)] backdrop-blur-md will-change-transform sm:p-8">
                  {eyebrow && <Eyebrow>{eyebrow}</Eyebrow>}
                  <h2 className="text-balance text-h2 font-semibold text-foreground">{title}</h2>
                  {description && <p className="mx-auto mt-4 max-w-[30rem] text-pretty text-[15.5px] leading-relaxed text-muted-foreground">{description}</p>}
                </div>
              </div>
              <span ref={set('shade')} className={cn(SHADE, 'z-10')} style={{ opacity: 0 }} />
              <div ref={set('over')} className="dark absolute inset-x-0 bottom-0 z-20" style={{ opacity: 0 }}>
                <div className="kit-container pb-8 sm:pb-12">
                  <OverlayText overlay={overlay} action={action} />
                </div>
              </div>
            </>
          )}

          {variant === 'app-icon' && (
            <>
              {head}
              <div className="absolute inset-0 flex items-center justify-center pt-[6svh]">
                <div ref={set('media')} className="relative will-change-transform">
                  <div ref={set('phone')} style={{ opacity: 0 }}>
                    <PhoneFrame className="w-[260px]">{media}</PhoneFrame>
                  </div>
                  <div ref={set('icon')} className="absolute inset-x-0 top-1/2 flex aspect-square -translate-y-1/2 items-center justify-center overflow-hidden rounded-[58px] shadow-[var(--shadow-lg)] [&>*]:size-full">
                    {icon}
                  </div>
                  {list.slice(0, 4).map((n, i) => (
                    <Note
                      key={i}
                      note={n}
                      setRef={set(`note${i}`)}
                      className={cn('absolute z-10 hidden whitespace-nowrap md:inline-flex', i % 2 ? 'left-[calc(100%+2.5rem)]' : 'right-[calc(100%+2.5rem)]', ['top-[18%]', 'top-[34%]', 'top-[58%]', 'top-[74%]'][i])}
                    />
                  ))}
                </div>
              </div>
              <ul className="absolute inset-x-4 bottom-4 z-20 grid grid-cols-2 gap-2 md:hidden">
                {list.slice(0, 4).map((n, i) => (
                  <li key={i} ref={set(`mnote${i}`)} style={{ opacity: 0 }}>
                    <Note note={n} className="w-full text-[12.5px]" />
                  </li>
                ))}
              </ul>
            </>
          )}
        </div>
      </div>
    </section>
  );
}