React drawer

'use client';

import { cloneElement, createContext, isValidElement, useCallback, useContext, useEffect, useId, useLayoutEffect, useRef, useState } from 'react';
import { createPortal } from 'react-dom';
import { cn, formatPercent, prefersReducedMotion, useLocale, useTexts } from '@/lib/kit';
import { Icon } from '@/components/ui/icon';

const useIsoLayoutEffect = typeof window === 'undefined' ? useEffect : useLayoutEffect;

const TEXTS = {
  en: { close: 'Close', handle: 'Resize the drawer', handleHint: 'Arrow up and down change the height, Escape closes.', height: 'Drawer at {p}', edge: 'Drag to close' },
  de: { close: 'Schließen', handle: 'Höhe ändern', handleHint: 'Pfeil hoch und runter ändern die Höhe, Escape schließt.', height: 'Schublade bei {p}', edge: 'Zum Schließen ziehen' },
};

export type DrawerSide = 'left' | 'right' | 'top' | 'bottom';

export interface DrawerProps {
  /** The button that opens it */
  trigger?: React.ReactElement | null;
  open?: boolean;
  defaultOpen?: boolean;
  onOpenChange?: (open: boolean) => void;
  side?: DrawerSide;
  /** The side on phones below 640 px, e.g. bottom for a side drawer */
  mobileSide?: DrawerSide;
  /** Modal: focus stays inside, the page is inert and dimmed. Off: the page stays usable next to the drawer. */
  modal?: boolean;
  /** Lives inside its positioned parent instead of the window (a phone frame, a panel, a map) */
  contained?: boolean;
  /** Heights for a top or bottom drawer as parts of the available height, e.g. [0.25, 0.55, 0.92] */
  snapPoints?: number[];
  /** Index of the snap point it opens at */
  defaultSnap?: number;
  onSnapChange?: (index: number) => void;
  /** Swipe toward the edge, Escape and the scrim close it */
  dismissible?: boolean;
  /** Width of a side drawer */
  size?: 'sm' | 'md' | 'lg';
  /** Inset from the edges with all corners rounded */
  floating?: boolean;
  title: React.ReactNode;
  description?: React.ReactNode;
  /** Something next to the title, e.g. a count */
  meta?: React.ReactNode;
  footer?: React.ReactNode | ((close: () => void) => React.ReactNode);
  hideClose?: boolean;
  labels?: Partial<(typeof TEXTS)['en']>;
  className?: string;
  children?: React.ReactNode;
}

/* A drawer opened from inside another one pushes its parent back a little */
const ParentContext = createContext<((open: boolean) => void) | null>(null);

let locks = 0;
function lockScroll() {
  const html = document.documentElement;
  if (locks++ === 0) {
    const gutter = window.innerWidth - html.clientWidth;
    html.dataset.drawerOverflow = html.style.overflow;
    html.style.overflow = 'hidden';
    if (gutter) html.style.paddingRight = `${gutter}px`;
  }
  return () => {
    if (--locks === 0) {
      html.style.overflow = html.dataset.drawerOverflow ?? '';
      html.style.paddingRight = '';
      delete html.dataset.drawerOverflow;
    }
  };
}

const WIDTH = { sm: 'w-[min(20rem,calc(100%-2.5rem))]', md: 'w-[min(26rem,calc(100%-2.5rem))]', lg: 'w-[min(36rem,calc(100%-2.5rem))]' };
const FOCUSABLE = 'a[href],button:not([disabled]),input:not([disabled]),select:not([disabled]),textarea:not([disabled]),[tabindex]:not([tabindex="-1"])';
const EASE = 'cubic-bezier(0.2, 0.8, 0.2, 1)';

/**
 * A drawer from any edge you can drag. Bottom and top drawers rest on snap points and follow a
 * swipe, side drawers close with a swipe toward their edge. Modal on the native dialog (focus
 * trap, inert page, Escape, scrim, scroll lock, focus back), or non-modal next to a usable page,
 * or contained in a frame. Drawers nest, the parent steps back.
 *   <Drawer side="bottom" snapPoints={[0.3, 0.6, 0.92]} trigger={<Button>Filters</Button>} title="Filters">…</Drawer>
 */
export function Drawer({
  trigger,
  open: openProp,
  defaultOpen,
  onOpenChange,
  side: sideProp = 'right',
  mobileSide,
  modal = true,
  contained,
  snapPoints,
  defaultSnap,
  onSnapChange,
  dismissible = true,
  size = 'md',
  floating,
  title,
  description,
  meta,
  footer,
  hideClose,
  labels,
  className,
  children,
}: DrawerProps) {
  const t = useTexts(TEXTS, labels);
  const locale = useLocale();
  const id = useId();
  const [inner, setInner] = useState(Boolean(defaultOpen));
  const open = openProp ?? inner;
  const setOpen = useCallback(
    (v: boolean) => {
      setInner(v);
      onOpenChange?.(v);
    },
    [onOpenChange],
  );
  const close = useCallback(() => setOpen(false), [setOpen]);

  // The side follows the screen: a side drawer can become a bottom drawer on phones
  const [phone, setPhone] = useState(false);
  useEffect(() => {
    if (!mobileSide) return;
    const mq = window.matchMedia('(max-width: 639px)');
    const on = () => setPhone(mq.matches);
    on();
    mq.addEventListener('change', on);
    return () => mq.removeEventListener('change', on);
  }, [mobileSide]);
  const side = phone && mobileSide ? mobileSide : sideProp;
  const vertical = side === 'top' || side === 'bottom';
  const snaps = vertical && snapPoints?.length ? [...snapPoints].sort((a, b) => a - b) : null;
  const [snap, setSnapState] = useState(Math.min(defaultSnap ?? (snaps ? snaps.length - 1 : 0), (snaps?.length ?? 1) - 1));
  const setSnap = (i: number) => {
    setSnapState(i);
    onSnapChange?.(i);
  };

  /* ---------- presence and motion ---------- */
  // present: in the DOM. shown: at rest on screen (false while it slides in or out).
  const [present, setPresent] = useState(open);
  const [shown, setShown] = useState(open);
  const [mounted, setMounted] = useState(false);
  useEffect(() => setMounted(true), []);
  useEffect(() => {
    if (open) {
      setPresent(true);
      return;
    }
    setShown(false);
    if (prefersReducedMotion()) {
      setPresent(false);
      return;
    }
    const timer = window.setTimeout(() => setPresent(false), 340);
    return () => window.clearTimeout(timer);
  }, [open]);

  const dialogRef = useRef<HTMLDialogElement>(null);
  const panelRef = useRef<HTMLDivElement>(null);
  const returnTo = useRef<HTMLElement | null>(null);
  const native = modal && !contained;

  useIsoLayoutEffect(() => {
    if (!present || !open) return;
    if (!returnTo.current) returnTo.current = document.activeElement as HTMLElement;
    const d = dialogRef.current;
    let unlock: (() => void) | undefined;
    if (native && d && !d.open) {
      d.showModal();
      unlock = lockScroll();
    }
    // Slide in on the next frame, so the start position paints first
    const raf = requestAnimationFrame(() => requestAnimationFrame(() => setShown(true)));
    if (!native && !defaultOpen) {
      // A non-modal drawer takes focus once it opens, the page around stays usable
      window.setTimeout(() => (panelRef.current?.querySelector<HTMLElement>('[data-drawer-title]') ?? panelRef.current)?.focus({ preventScroll: true }), 40);
    }
    return () => {
      cancelAnimationFrame(raf);
      unlock?.();
    };
  }, [present, open, native]);

  useEffect(() => {
    if (present) return;
    if (dialogRef.current?.open) dialogRef.current.close();
    const back = returnTo.current;
    returnTo.current = null;
    if (back && document.contains(back) && (!document.activeElement || document.activeElement === document.body)) back.focus({ preventScroll: true });
  }, [present]);

  // Tell the parent drawer that a child is open
  const parent = useContext(ParentContext);
  useEffect(() => {
    if (!parent) return;
    parent(open);
    return () => parent(false);
  }, [open, parent]);
  const [childOpen, setChildOpen] = useState(false);

  /* ---------- Escape and focus for drawers without a native dialog ---------- */
  useEffect(() => {
    if (native || !open || !present) return;
    const onKey = (e: KeyboardEvent) => {
      if (e.key !== 'Escape' || childOpen || !dismissible) return;
      // Non-modal: only while focus is inside, so Escape elsewhere on the page is left alone
      if (!modal && !panelRef.current?.contains(document.activeElement)) return;
      e.preventDefault();
      close();
    };
    document.addEventListener('keydown', onKey);
    return () => document.removeEventListener('keydown', onKey);
  }, [native, open, present, modal, childOpen, dismissible, close]);

  const trapTab = (e: React.KeyboardEvent) => {
    if (e.key !== 'Tab' || !modal || native) return;
    const list = Array.from(panelRef.current?.querySelectorAll<HTMLElement>(FOCUSABLE) ?? []).filter((el) => el.offsetParent !== null);
    if (!list.length) return;
    const first = list[0];
    const last = list[list.length - 1];
    if (e.shiftKey && document.activeElement === first) (e.preventDefault(), last.focus());
    else if (!e.shiftKey && document.activeElement === last) (e.preventDefault(), first.focus());
  };

  /* ---------- dragging ---------- */
  const [drag, setDrag] = useState(0);
  const dragging = useRef<{ start: number; last: number; time: number; v: number; size: number } | null>(null);
  const axis = (e: React.PointerEvent) => (vertical ? e.clientY : e.clientX);
  // Positive drag moves toward the edge the drawer belongs to
  const sign = side === 'bottom' || side === 'right' ? 1 : -1;
  const onPointerDown = (e: React.PointerEvent<HTMLElement>) => {
    if (e.button !== 0 || (e.target as HTMLElement).closest('button:not([data-drawer-handle]),a,input,select,textarea')) return;
    const box = panelRef.current?.getBoundingClientRect();
    dragging.current = { start: axis(e), last: axis(e), time: performance.now(), v: 0, size: vertical ? box?.height ?? 1 : box?.width ?? 1 };
    e.currentTarget.setPointerCapture(e.pointerId);
  };
  const onPointerMove = (e: React.PointerEvent) => {
    const d = dragging.current;
    if (!d) return;
    const now = performance.now();
    const pos = axis(e);
    d.v = ((pos - d.last) / Math.max(1, now - d.time)) * sign;
    d.last = pos;
    d.time = now;
    let delta = (pos - d.start) * sign;
    // Past the top snap the drawer resists, it does not fly off
    if (delta < 0) delta = snaps && snap < snaps.length - 1 ? delta : -Math.sqrt(-delta) * 2.2;
    setDrag(delta);
  };
  const onPointerUp = () => {
    const d = dragging.current;
    if (!d) return;
    dragging.current = null;
    const delta = drag;
    setDrag(0);
    if (snaps) {
      const H = availableHeight();
      const current = snaps[snap] * H - delta;
      // Throw: the speed carries it a little further
      const projected = current - d.v * 180;
      if (dismissible && projected < snaps[0] * H * 0.55) return close();
      let best = 0;
      snaps.forEach((s, i) => Math.abs(s * H - projected) < Math.abs(snaps[best] * H - projected) && (best = i));
      setSnap(best);
      return;
    }
    if (dismissible && (delta > d.size * 0.35 || (d.v > 0.6 && delta > 24))) close();
  };
  const dragProps = { onPointerDown, onPointerMove, onPointerUp, onPointerCancel: onPointerUp };

  const containerRef = useRef<HTMLDivElement>(null);
  const availableHeight = () => (contained ? containerRef.current?.clientHeight ?? 600 : window.innerHeight);

  /* ---------- handle keys ---------- */
  const onHandleKey = (e: React.KeyboardEvent) => {
    if (!snaps) return;
    const up = side === 'bottom' ? 'ArrowUp' : 'ArrowDown';
    const down = side === 'bottom' ? 'ArrowDown' : 'ArrowUp';
    if (e.key === up) (e.preventDefault(), setSnap(Math.min(snaps.length - 1, snap + 1)));
    else if (e.key === down) {
      e.preventDefault();
      if (snap === 0 && dismissible) close();
      else setSnap(Math.max(0, snap - 1));
    } else if (e.key === 'Home') (e.preventDefault(), setSnap(snaps.length - 1));
    else if (e.key === 'End') (e.preventDefault(), setSnap(0));
  };

  /* ---------- geometry ---------- */
  const maxSnap = snaps ? snaps[snaps.length - 1] : 1;
  const restOffset = snaps ? `${((maxSnap - snaps[snap]) / maxSnap) * 100}%` : '0%';
  // Out of sight: the full size, plus the inset and the shadow of a floating drawer
  const hidden = floating ? 'calc(100% + 32px)' : 'calc(100% + 16px)';
  const offset = shown ? restOffset : hidden;
  const move = vertical ? 'translateY' : 'translateX';
  const s = side === 'bottom' || side === 'right' ? 1 : -1;
  const transform = `${move}(calc(${s} * (${offset} + ${Math.round(drag)}px)))`;
  const transition = dragging.current ? 'none' : `transform ${shown ? 480 : 300}ms ${shown ? EASE : 'cubic-bezier(0.4,0,0.9,0.6)'}`;

  const inset = floating ? 'm-2' : '';
  const place: Record<DrawerSide, string> = {
    right: cn('inset-y-0 end-0 h-full', WIDTH[size]),
    left: cn('inset-y-0 start-0 h-full', WIDTH[size]),
    bottom: cn('inset-x-0 bottom-0 mx-auto w-full max-w-[48rem]', !snaps && 'max-h-[88%]'),
    top: cn('inset-x-0 top-0 mx-auto w-full max-w-[48rem]', !snaps && 'max-h-[88%]'),
  };
  const round: Record<DrawerSide, string> = {
    right: floating ? 'rounded-2xl' : 'rounded-s-2xl',
    left: floating ? 'rounded-2xl' : 'rounded-e-2xl',
    bottom: floating ? 'rounded-2xl' : 'rounded-t-2xl',
    top: floating ? 'rounded-2xl' : 'rounded-b-2xl',
  };
  const border: Record<DrawerSide, string> = { right: 'border-s', left: 'border-e', bottom: 'border-t', top: 'border-b' };

  const percent = snaps ? formatPercent(Math.round(snaps[snap] * 100), locale) : '';
  const handle = vertical && (
    <button
      type="button"
      data-drawer-handle=""
      aria-label={t.handle}
      aria-describedby={`${id}-hh`}
      onKeyDown={onHandleKey}
      onClick={(e) => {
        if (e.detail === 0 || !snaps) return;
        setSnap(snap === snaps.length - 1 ? 0 : snap + 1);
      }}
      className={cn(
        'group/handle relative mx-auto grid h-6 w-full shrink-0 cursor-grab touch-none place-items-center outline-none active:cursor-grabbing',
        'after:absolute after:inset-x-0 after:-inset-y-2.5',
        side === 'top' && 'order-last',
      )}
    >
      <span className="h-1 w-10 rounded-full bg-border-strong transition-[width,background-color] duration-200 group-hover/handle:w-12 group-hover/handle:bg-[color-mix(in_oklab,var(--foreground)_40%,transparent)] group-focus-visible/handle:w-12 group-focus-visible/handle:bg-primary group-focus-visible/handle:outline-2 group-focus-visible/handle:outline-offset-4 group-focus-visible/handle:outline-solid group-focus-visible/handle:outline-ring" />
      <span id={`${id}-hh`} className="sr-only">
        {t.handleHint}
      </span>
    </button>
  );
  const edgeGrip = !vertical && dismissible && (
    <span
      aria-hidden
      {...dragProps}
      title={t.edge}
      className={cn('absolute inset-y-0 z-10 grid w-5 cursor-grab touch-none place-items-center active:cursor-grabbing', side === 'right' ? '-start-2.5' : '-end-2.5')}
    >
      <span className="h-10 w-1 rounded-full bg-border-strong transition-[height] duration-200 hover:h-14" />
    </span>
  );

  const panel = (
    <ParentContext.Provider value={setChildOpen}>
      <div
        ref={panelRef}
        role={native ? undefined : 'dialog'}
        aria-modal={native ? undefined : modal}
        aria-labelledby={`${id}-t`}
        aria-describedby={description ? `${id}-d` : undefined}
        tabIndex={-1}
        onKeyDown={trapTab}
        data-nested={childOpen || undefined}
        className={cn(
          'pointer-events-auto absolute flex flex-col border-border bg-popover text-popover-foreground shadow-[var(--highlight),var(--shadow-lg)] outline-none will-change-transform motion-reduce:!transition-none',
          floating ? 'border' : border[side],
          place[side],
          round[side],
          inset,
          // A child drawer on top: this one steps back
          'data-[nested]:brightness-[0.92] data-[nested]:[scale:0.97]',
          className,
        )}
        style={{ transform, transition: `${transition}, scale 300ms ${EASE}, filter 300ms ${EASE}`, height: snaps ? `${maxSnap * 100}%` : undefined }}
      >
        {edgeGrip}
        {vertical && side === 'bottom' && <div {...dragProps}>{handle}</div>}
        <div {...(vertical ? dragProps : {})} className={cn('flex shrink-0 items-start gap-4 px-5 pb-3 sm:px-6', vertical ? (side === 'bottom' ? 'pt-1' : 'pt-5') : 'pt-5 sm:pt-6', vertical && 'cursor-grab touch-none active:cursor-grabbing')}>
          <div className="min-w-0 flex-1">
            <h2 id={`${id}-t`} data-drawer-title="" tabIndex={-1} className="flex items-center gap-2 text-[17px] font-semibold leading-snug tracking-[-0.015em] text-foreground outline-none">
              {title}
              {meta && <span className="rounded-md bg-muted px-1.5 py-0.5 text-xs font-medium tabular-nums text-muted-foreground">{meta}</span>}
            </h2>
            {description && (
              <p id={`${id}-d`} className="mt-1 text-pretty text-sm leading-relaxed text-muted-foreground">
                {description}
              </p>
            )}
          </div>
          {!hideClose && (
            <button
              type="button"
              onClick={close}
              aria-label={t.close}
              className="group/close relative -me-2 -mt-1 grid size-9 shrink-0 cursor-pointer place-items-center rounded-md text-muted-foreground transition-colors after:absolute after:-inset-1 hover:bg-accent hover:text-foreground focus-visible:outline-2 focus-visible:outline-solid focus-visible:outline-ring"
            >
              <Icon name="x" size={17} className="transition-transform duration-300 ease-[var(--ease-kit)] group-hover/close:rotate-90 motion-reduce:transition-none" />
            </button>
          )}
        </div>
        {children && <div className="kit-scrollbar relative min-h-0 flex-1 overflow-y-auto overscroll-contain px-5 pb-5 sm:px-6">{children}</div>}
        {footer && <div className="shrink-0 border-t border-border bg-surface px-5 py-4 sm:px-6 [&>*]:max-sm:w-full">{typeof footer === 'function' ? footer(close) : footer}</div>}
        {vertical && side === 'top' && <div {...dragProps}>{handle}</div>}
        {snaps && (
          <span aria-live="polite" className="sr-only">
            {shown ? t.height.replace('{p}', percent) : ''}
          </span>
        )}
      </div>
    </ParentContext.Provider>
  );

  const triggerEl =
    trigger && isValidElement<Record<string, unknown>>(trigger)
      ? cloneElement(trigger, {
          'aria-haspopup': 'dialog',
          'aria-expanded': open,
          'aria-controls': open ? id : undefined,
          onClick: (e: React.MouseEvent<HTMLElement>) => {
            (trigger.props.onClick as ((e: React.MouseEvent) => void) | undefined)?.(e);
            returnTo.current = e.currentTarget;
            setOpen(!open);
          },
        })
      : trigger;

  const scrim = modal && (
    <div
      aria-hidden
      onClick={() => dismissible && close()}
      className={cn('absolute inset-0 bg-scrim backdrop-blur-[2px] transition-opacity duration-300 ease-[var(--ease-kit)] motion-reduce:transition-none', shown ? 'opacity-100' : 'opacity-0')}
    />
  );

  let layer: React.ReactNode = null;
  if (present) {
    if (native) {
      layer = (
        <dialog
          ref={dialogRef}
          id={id}
          aria-labelledby={`${id}-t`}
          aria-describedby={description ? `${id}-d` : undefined}
          onCancel={(e) => {
            e.preventDefault();
            if (dismissible && !childOpen) close();
          }}
          className="fixed inset-0 m-0 size-full max-h-none max-w-none overflow-hidden bg-transparent p-0 text-left outline-none backdrop:bg-transparent"
        >
          {scrim}
          {panel}
        </dialog>
      );
    } else if (contained) {
      layer = (
        <div ref={containerRef} id={id} className={cn('absolute inset-0 z-30 overflow-hidden', !modal && 'pointer-events-none', 'rounded-[inherit]')}>
          {scrim}
          {panel}
        </div>
      );
    } else if (mounted) {
      layer = createPortal(
        <div id={id} className="pointer-events-none fixed inset-0 z-50 overflow-hidden">
          {panel}
        </div>,
        document.body,
      );
    }
  }

  return (
    <>
      {triggerEl}
      {layer}
    </>
  );
}