Split screen layout

'use client';

import { useEffect, useId, useRef, useState } from 'react';
import { cn, 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 screen in two halves.
 *
 *   halves    one half holds a picture that stays while the other half
 *             scrolls through its panels, the picture changes with them
 *   switch    two offers side by side, the chosen one opens wide; on
 *             phones a switch on top shows one at a time
 *   contrast  a light and a dark half edge to edge, each with its action
 *   either-or two choices as cards with a round "or" between them
 *
 * Every half is a `panel`: eyebrow, title, text, points, action and media.
 */

export type SplitScreenVariant = 'halves' | 'switch' | 'contrast' | 'either-or';

export interface SplitPanel {
  /** Short name, used on the switch */
  label?: string;
  eyebrow?: string;
  title: string;
  text?: string;
  points?: string[];
  action?: { label: string; href: string };
  media?: React.ReactNode;
}

const TEXTS = {
  en: { or: 'or', choose: 'Choose a side', more: 'Show details for {name}' },
  de: { or: 'oder', choose: 'Seite wählen', more: 'Details zu {name} zeigen' },
};
type Texts = (typeof TEXTS)['en'];

export interface SplitScreenProps {
  variant?: SplitScreenVariant;
  eyebrow?: React.ReactNode;
  title?: React.ReactNode;
  description?: React.ReactNode;
  panels: SplitPanel[];
  /** halves: the picture half on the right */
  reverse?: 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';

function Points({ points, className }: { points?: string[]; className?: string }) {
  if (!points?.length) return null;
  return (
    <Stagger as="ul" step={70} className={cn('space-y-2.5', className)}>
      {points.map((pt) => (
        <li key={pt} className="flex gap-3 text-[15px] 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>
  );
}

function Head({ p, center = false, className }: { p: SplitScreenProps; center?: boolean; className?: string }) {
  if (!p.title && !p.eyebrow) return null;
  return (
    <div className={cn('mb-12 max-w-[44rem] sm:mb-14', 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>
  );
}

const fillImg = '[&>*]:size-full';

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

function Halves({ p }: { p: SplitScreenProps }) {
  const [active, setActive] = useState(0);
  const uid = useId();
  const refs = useRef<(HTMLElement | null)[]>([]);
  useEffect(() => {
    let frame = 0;
    const update = () => {
      frame = 0;
      const line = window.innerHeight * 0.5;
      let i = 0;
      refs.current.forEach((el, j) => {
        if (el && el.getBoundingClientRect().top <= line) i = j;
      });
      setActive(i);
    };
    const onScroll = () => {
      if (!frame) frame = requestAnimationFrame(update);
    };
    update();
    window.addEventListener('scroll', onScroll, { passive: true });
    return () => {
      cancelAnimationFrame(frame);
      window.removeEventListener('scroll', onScroll);
    };
  }, []);
  return (
    <div className={cn('grid grid-cols-[minmax(0,1fr)] lg:grid-cols-2', p.reverse && 'lg:[&>*:first-child]:order-2')}>
      {/* the picture half: sticky on desktop, the pictures cross over */}
      <div className="relative hidden lg:block">
        <div className="sticky top-0 h-dvh max-h-[56rem] overflow-hidden bg-muted">
          {p.panels.map((pn, i) => (
            <div key={i} aria-hidden={i !== active} data-clip-ok className={cn('absolute inset-0 transition-[opacity,transform] duration-700 ease-[var(--ease-kit)] motion-reduce:transition-none', fillImg, i === active ? 'scale-100 opacity-100' : 'invisible scale-[1.04] opacity-0')}>
              {pn.media}
            </div>
          ))}
          <div aria-hidden className="absolute bottom-6 left-6 flex gap-1.5">
            {p.panels.map((_, i) => (
              <span key={i} className={cn('h-1 rounded-full bg-white/90 shadow-[0_1px_4px_rgb(0_0_0/0.3)] transition-[width,opacity] duration-500', i === active ? 'w-8' : 'w-3 opacity-50')} />
            ))}
          </div>
        </div>
      </div>
      <div className="kit-container lg:max-w-none lg:px-16 xl:px-24">
        {(p.title || p.eyebrow) && (
          <div className="pt-20 sm:pt-24 lg:pt-32">
            <Head p={p} className="mb-0 sm:mb-0" />
          </div>
        )}
        {p.panels.map((pn, i) => (
          <section key={i} ref={(el) => void (refs.current[i] = el)} aria-labelledby={`${uid}-h${i}`} className="flex flex-col justify-center py-14 lg:min-h-[80dvh] lg:py-24">
            <div data-clip-ok className={cn('relative mb-8 aspect-[4/3] overflow-hidden rounded-2xl border border-border bg-muted lg:hidden', fillImg)}>{pn.media}</div>
            <Reveal className="max-w-[32rem]">
              <p className="mb-4 text-[13px] font-medium tabular-nums text-subtle-foreground">
                {String(i + 1).padStart(2, '0')} / {String(p.panels.length).padStart(2, '0')}
                {pn.eyebrow && <span className="ml-3 text-[color-mix(in_oklab,var(--primary)_75%,var(--muted-foreground))]">{pn.eyebrow}</span>}
              </p>
              <h3 id={`${uid}-h${i}`} className="text-balance text-[clamp(1.625rem,1.3rem+1.2vw,2.375rem)] font-semibold leading-[1.1] tracking-[-0.03em] text-foreground">
                {pn.title}
              </h3>
              {pn.text && <p className="mt-5 text-pretty text-[17px] leading-relaxed text-muted-foreground">{pn.text}</p>}
              <Points points={pn.points} className="mt-7" />
              {pn.action && (
                <div className="mt-8">
                  <Button href={pn.action.href} variant={i === p.panels.length - 1 ? 'primary' : 'outline'} icon="arrow-right" className="max-sm:w-full">
                    {pn.action.label}
                  </Button>
                </div>
              )}
            </Reveal>
          </section>
        ))}
      </div>
    </div>
  );
}

function Switch({ p, t }: { p: SplitScreenProps; t: Texts }) {
  const [on, setOn] = useState(0);
  const id = useId();
  const tabs = useRef<(HTMLButtonElement | null)[]>([]);
  const key = (e: React.KeyboardEvent, i: number) => {
    const n = p.panels.length;
    const next = e.key === 'ArrowRight' ? (i + 1) % n : e.key === 'ArrowLeft' ? (i - 1 + n) % n : e.key === 'Home' ? 0 : e.key === 'End' ? n - 1 : -1;
    if (next < 0) return;
    e.preventDefault();
    setOn(next);
    tabs.current[next]?.focus();
  };
  return (
    <>
      <Head p={p} center />
      {/* phones and tablets: a switch, desktop: the halves are the switch */}
      <div role="tablist" aria-label={t.choose} className="mx-auto mb-6 grid max-w-[24rem] grid-cols-2 gap-1 rounded-xl border border-border bg-surface p-1 lg:hidden">
        {p.panels.map((pn, i) => (
          <button
            key={i}
            ref={(el) => void (tabs.current[i] = el)}
            role="tab"
            id={`${id}-tab-${i}`}
            aria-selected={on === i}
            aria-controls={`${id}-panel-${i}`}
            tabIndex={on === i ? 0 : -1}
            onClick={() => setOn(i)}
            onKeyDown={(e) => key(e, i)}
            className={cn('min-h-11 cursor-pointer rounded-lg text-[14px] font-medium transition-[background-color,color,box-shadow] duration-300', on === i ? 'bg-background text-foreground shadow-[var(--shadow-sm)]' : 'text-muted-foreground hover:text-foreground', focus)}
          >
            {pn.label ?? pn.title}
          </button>
        ))}
      </div>
      <div className="flex flex-col gap-4 lg:min-h-[34rem] lg:flex-row">
        {p.panels.map((pn, i) => {
          const open = on === i;
          return (
            <div
              key={i}
              id={`${id}-panel-${i}`}
              role="tabpanel"
              aria-labelledby={`${id}-tab-${i}`}
              onMouseEnter={() => setOn(i)}
              onFocus={() => setOn(i)}
              className={cn(
                'group relative overflow-hidden rounded-2xl border bg-card shadow-[var(--highlight),var(--shadow-sm)] transition-[flex-grow,border-color] duration-700 ease-[var(--ease-kit)] motion-reduce:transition-none lg:flex lg:basis-0',
                open ? 'border-border-strong lg:grow-[1.7]' : 'border-border max-lg:hidden lg:grow',
              )}
            >
              <div data-clip-ok className={cn('relative aspect-[16/10] overflow-hidden bg-muted transition-opacity duration-700 lg:absolute lg:inset-0 lg:aspect-auto', fillImg, open ? 'lg:opacity-100' : 'lg:opacity-60')}>
                {pn.media}
              </div>
              <div aria-hidden className="pointer-events-none absolute inset-0 hidden bg-[linear-gradient(to_top,rgb(0_0_0/0.92),rgb(0_0_0/0.72)_50%,rgb(0_0_0/0.3))] lg:block" />
              <div className="relative flex flex-col justify-end p-6 sm:p-8 lg:w-full lg:text-white">
                {pn.eyebrow && <p className="text-[13px] font-medium text-[color-mix(in_oklab,var(--primary)_75%,var(--muted-foreground))] lg:text-white/80">{pn.eyebrow}</p>}
                <h3 className="mt-2 text-balance text-[clamp(1.5rem,1.25rem+1vw,2.125rem)] font-semibold leading-tight tracking-[-0.03em]">{pn.title}</h3>
                <div className={cn('grid transition-[grid-template-rows,opacity] duration-700 ease-[var(--ease-kit)] motion-reduce:transition-none', open ? 'grid-rows-[1fr] opacity-100' : 'grid-rows-[0fr] opacity-0')}>
                  <div className={cn('min-h-0 overflow-hidden', !open && 'invisible')}>
                    {pn.text && <p className="mt-4 max-w-[30rem] text-pretty text-[16px] leading-relaxed text-muted-foreground lg:text-white/85">{pn.text}</p>}
                    <Points points={pn.points} className="mt-5 lg:[&_li]:text-white lg:[&_li>span]:bg-white/15 lg:[&_li>span]:text-white" />
                    {pn.action && (
                      <div className="mt-7">
                        <Button href={pn.action.href} icon="arrow-right" className="max-sm:w-full lg:bg-white lg:text-black lg:hover:bg-white/90">
                          {pn.action.label}
                        </Button>
                      </div>
                    )}
                  </div>
                </div>
                {!open && (
                  <button type="button" onClick={() => setOn(i)} className={cn('mt-4 hidden min-h-11 w-fit cursor-pointer items-center gap-2 rounded-lg border border-white/30 bg-white/10 px-4 text-[13px] font-medium text-white backdrop-blur-md transition-colors hover:bg-white/20 lg:inline-flex', focus)}>
                    {t.more.replace('{name}', pn.label ?? pn.title)}
                    <Icon name="arrow-right" size={14} />
                  </button>
                )}
              </div>
            </div>
          );
        })}
      </div>
    </>
  );
}

function Contrast({ p }: { p: SplitScreenProps }) {
  return (
    <div className="grid grid-cols-[minmax(0,1fr)] md:grid-cols-2">
      {p.panels.slice(0, 2).map((pn, i) => (
        <div key={i} className={cn('group relative isolate overflow-hidden', i === 1 ? 'dark bg-background text-foreground' : 'bg-surface text-foreground')}>
          <div className="flex h-full flex-col gap-12 px-6 py-16 sm:px-10 sm:py-20 lg:px-16 lg:py-24 xl:px-20">
            <Reveal delay={i * 120} className="max-w-[28rem]">
              {pn.eyebrow && <p className="text-[13px] font-medium text-[color-mix(in_oklab,var(--primary)_75%,var(--muted-foreground))]">{pn.eyebrow}</p>}
              <h3 className="mt-3 text-balance text-[clamp(1.75rem,1.35rem+1.5vw,2.75rem)] font-semibold leading-[1.08] tracking-[-0.035em]">{pn.title}</h3>
              {pn.text && <p className="mt-5 text-pretty text-[16.5px] leading-relaxed text-muted-foreground">{pn.text}</p>}
              <Points points={pn.points} className="mt-7" />
              {pn.action && (
                <div className="mt-9">
                  <Button href={pn.action.href} variant={i === 1 ? 'primary' : 'outline'} icon="arrow-right" magnetic={i === 1} className="max-sm:w-full">
                    {pn.action.label}
                  </Button>
                </div>
              )}
            </Reveal>
            {pn.media && (
              <div data-clip-ok className={cn('relative aspect-[16/10] overflow-hidden rounded-xl border border-border shadow-[var(--shadow-lg)] md:mt-auto', fillImg)}>
                <div className={cn('absolute inset-0 transition-transform duration-700 ease-[var(--ease-kit)] group-hover:scale-[1.04] motion-reduce:transition-none', fillImg)}>{pn.media}</div>
              </div>
            )}
          </div>
        </div>
      ))}
    </div>
  );
}

function EitherOr({ p, t }: { p: SplitScreenProps; t: Texts }) {
  const [a, b] = p.panels;
  const card = (pn: SplitPanel | undefined, i: number) =>
    pn && (
      <Reveal delay={i * 120} className="flex">
        <article className={cn('flex w-full flex-col rounded-2xl border bg-card p-6 shadow-[var(--highlight),var(--shadow-sm)] transition-[transform,box-shadow,border-color] duration-300 hover:-translate-y-1 hover:shadow-[var(--highlight),var(--shadow-lg)] motion-reduce:hover:translate-y-0 sm:p-8', i === 1 ? 'border-[color-mix(in_oklab,var(--primary)_40%,var(--border))]' : 'border-border')}>
          {pn.media && <div data-clip-ok className={cn('relative -mx-2 -mt-2 mb-7 aspect-[16/9] overflow-hidden rounded-xl border border-border bg-muted sm:-mx-4 sm:-mt-4', fillImg)}>{pn.media}</div>}
          {pn.eyebrow && <p className="text-[13px] font-medium text-[color-mix(in_oklab,var(--primary)_75%,var(--muted-foreground))]">{pn.eyebrow}</p>}
          <h3 className="mt-2 text-balance text-[clamp(1.375rem,1.2rem+0.7vw,1.75rem)] font-semibold leading-tight tracking-[-0.025em] text-foreground">{pn.title}</h3>
          {pn.text && <p className="mt-3 text-pretty text-[15.5px] leading-relaxed text-muted-foreground">{pn.text}</p>}
          <Points points={pn.points} className="mb-8 mt-6" />
          {pn.action && (
            <div className="mt-auto">
              <Button href={pn.action.href} variant={i === 1 ? 'primary' : 'outline'} icon="arrow-right" className="w-full">
                {pn.action.label}
              </Button>
            </div>
          )}
        </article>
      </Reveal>
    );
  return (
    <>
      <Head p={p} center />
      <div className="relative mx-auto grid max-w-[64rem] grid-cols-[minmax(0,1fr)] gap-14 md:grid-cols-2 md:gap-10 lg:gap-16">
        {card(a, 0)}
        {/* the round "or" between the two, on the gap */}
        <div aria-hidden className="pointer-events-none absolute inset-x-0 top-1/2 flex -translate-y-1/2 items-center justify-center md:inset-x-auto md:inset-y-0 md:left-1/2 md:top-0 md:-translate-x-1/2 md:translate-y-0 md:flex-col">
          <span className="hidden h-full w-px bg-[linear-gradient(transparent,var(--border-strong)_20%,var(--border-strong)_80%,transparent)] md:block" />
          <span className="absolute flex size-12 items-center justify-center rounded-full border border-border-strong bg-background text-[13px] font-semibold text-foreground shadow-[var(--shadow-md)] md:top-1/2 md:-translate-y-1/2">{t.or}</span>
        </div>
        {card(b, 1)}
      </div>
    </>
  );
}

/**
 * Two halves: a sticky picture with scrolling panels, a switch between two
 * offers, a light and a dark half, or two choices with an "or" between.
 *   <SplitScreen variant="switch" panels={[{ label: 'Private', title, text, points, action, media }, { … }]} />
 */
export function SplitScreen(props: SplitScreenProps) {
  const { variant = 'halves', className, labels } = props;
  const t = useTexts(TEXTS, labels);
  if (variant === 'halves')
    return (
      <section className={cn('relative border-y border-border', className)}>
        <Halves p={props} />
      </section>
    );
  if (variant === 'contrast')
    return (
      <section className={cn('relative', className)}>
        {(props.title || props.eyebrow) && (
          <div className="kit-container pt-20 sm:pt-24">
            <Head p={props} />
          </div>
        )}
        <Contrast p={props} />
      </section>
    );
  return <Section className={className}>{variant === 'switch' ? <Switch p={props} t={t} /> : <EitherOr p={props} t={t} />}</Section>;
}