Number input

'use client';

import { useEffect, useId, useRef, useState } from 'react';
import { cn, prefersReducedMotion, round, useLocale, useTexts } from '@/lib/kit';
import { Icon, type IconName } from '@/components/ui/icon';
import { CONTROL_HEIGHT, controlBox, useControl, useShake, withField, type ControlSize, type FieldOwnProps } from '@/components/ui/input';

/*
 * A number field after the spin button pattern (WAI-ARIA APG): the field
 * holds the value, arrows step, Page Up and Page Down take big steps, Home
 * and End jump to the limits. Typed text is read in the format of the
 * language (1.280,5 or 1,280.5) and snapped to the step on Enter or blur.
 * Four looks: buttons stacked at the end, buttons on both sides, a compact
 * cart quantity, and a design tool field you drag sideways.
 */

const TEXTS = {
  en: { increase: 'Increase', decrease: 'Decrease', remove: 'Remove', scrub: 'Drag sideways to change' },
  de: { increase: 'Erhöhen', decrease: 'Verringern', remove: 'Entfernen', scrub: 'Seitlich ziehen zum Ändern' },
};

export type NumberInputVariant = 'stepper' | 'split' | 'quantity' | 'scrub';

export interface NumberInputProps extends FieldOwnProps {
  variant?: NumberInputVariant;
  value?: number;
  defaultValue?: number;
  onValueChange?: (value: number) => void;
  min?: number;
  max?: number;
  step?: number;
  /** Step for Page Up, Page Down and Shift with an arrow. Default 10 steps. */
  bigStep?: number;
  /** Digits after the decimal mark. Default from the step. */
  decimals?: number;
  /** Quiet text before the value, e.g. "$" */
  prefix?: string;
  /** Quiet text after the value, e.g. "px", "€" or "kg" */
  unit?: string;
  /** Group thousands (1,280). Default true. */
  grouping?: boolean;
  /** scrub: a short letter at the start that you drag, e.g. "W". Without handle and handleIcon the label is the handle, inside the box. */
  handle?: string;
  /** scrub: an icon at the start that you drag, instead of the letter */
  handleIcon?: IconName;
  /** quantity: at the minimum the minus turns into a remove button */
  onRemove?: () => void;
  size?: ControlSize;
  name?: string;
  id?: string;
  disabled?: boolean;
  required?: boolean;
  invalid?: boolean;
  /** Accessible name when there is no visible label */
  'aria-label'?: string;
  labels?: Partial<(typeof TEXTS)['en']>;
  className?: string;
}

const decimalsOf = (n: number) => {
  const s = String(n);
  return s.includes('.') ? s.split('.')[1].length : 0;
};

/** Reads typed text in the format of the language. Returns null when it is not a number. */
export function parseNumber(text: string, locale: 'en' | 'de'): number | null {
  let s = text.replace(/[\s  ]/g, '').replace(/[^\d.,+-]/g, '');
  if (!s || s === '-' || s === '+') return null;
  if (locale === 'de') {
    if (s.includes(',')) s = s.replace(/\./g, '').replace(',', '.');
    else if (/\.\d{3}(\.|$)/.test(s)) s = s.replace(/\./g, '');
  } else s = s.replace(/,/g, '');
  const n = Number(s);
  return Number.isFinite(n) ? n : null;
}

/** Repeats an action while a button is held: once at once, then faster and faster */
function useHold(action: () => void) {
  const timer = useRef<number | undefined>(undefined);
  const latest = useRef(action);
  latest.current = action;
  const stop = () => window.clearTimeout(timer.current);
  useEffect(() => stop, []);
  const start = (e: React.PointerEvent) => {
    if (e.button !== 0) return;
    e.preventDefault();
    latest.current();
    let delay = 380;
    const tick = () => {
      latest.current();
      delay = Math.max(40, delay * 0.82);
      timer.current = window.setTimeout(tick, delay);
    };
    timer.current = window.setTimeout(tick, delay);
  };
  return { onPointerDown: start, onPointerUp: stop, onPointerLeave: stop, onPointerCancel: stop, onContextMenu: (e: React.MouseEvent) => e.preventDefault() };
}

/** The value slides in from the side it came from: up when it grows, down when it shrinks */
function nudge(el: HTMLElement | null, dir: number) {
  if (!el || !dir || prefersReducedMotion() || typeof el.animate !== 'function') return;
  el.animate([{ transform: `translateY(${dir > 0 ? 7 : -7}px)`, opacity: 0.25 }, { transform: 'translateY(0)', opacity: 1 }], { duration: 260, easing: 'cubic-bezier(0.2,0.7,0.2,1)' });
}

/** A short sideways bump when a limit is reached */
function bump(el: HTMLElement | null) {
  if (!el || prefersReducedMotion() || typeof el.animate !== 'function') return;
  el.animate([{ transform: 'translateX(0)' }, { transform: 'translateX(3px)' }, { transform: 'translateX(-2px)' }, { transform: 'translateX(0)' }], { duration: 240, easing: 'ease-out' });
}

const STEP_BTN =
  'relative grid shrink-0 place-items-center text-muted-foreground outline-none transition-[background-color,color,scale] duration-200 ease-[var(--ease-kit)] hover:bg-accent hover:text-foreground active:scale-90 focus-visible:z-10 focus-visible:bg-accent focus-visible:text-foreground focus-visible:shadow-[inset_0_0_0_2px_color-mix(in_oklab,var(--primary)_55%,transparent)] disabled:pointer-events-none disabled:opacity-35 motion-reduce:transition-none';

function NumberBox(props: Omit<NumberInputProps, keyof FieldOwnProps> & { inlineLabel?: React.ReactNode }) {
  const {
    variant = 'stepper', value: valueProp, defaultValue, onValueChange, min = -Infinity, max = Infinity, step = 1, bigStep, decimals, prefix, unit,
    grouping = true, handle, handleIcon, onRemove, size = 'md', name, id, disabled, required, invalid, labels, className, inlineLabel,
  } = props;
  const t = useTexts(TEXTS, labels);
  const locale = useLocale();
  const c = useControl({ id, invalid, disabled, required });
  const digits = decimals ?? decimalsOf(step);
  const big = bigStep ?? step * 10;
  const [inner, setInner] = useState(() => defaultValue ?? (Number.isFinite(min) ? min : 0));
  const value = valueProp ?? inner;
  const [draft, setDraft] = useState<string | null>(null);
  const boxRef = useRef<HTMLDivElement>(null);
  const inputRef = useRef<HTMLInputElement>(null);
  const valueRef = useRef<HTMLSpanElement>(null);
  const hintId = useId();
  useShake(boxRef, c.invalid);

  const fmt = (n: number, group = grouping) => n.toLocaleString(locale === 'de' ? 'de-DE' : 'en-US', { minimumFractionDigits: digits, maximumFractionDigits: digits, useGrouping: group });
  const snap = (n: number) => {
    const base = Number.isFinite(min) ? min : 0;
    const snapped = round(base + Math.round((n - base) / step) * step, digits);
    return Math.min(max, Math.max(min, snapped));
  };

  const commit = (next: number, from: 'step' | 'type' = 'step') => {
    // Steps land on the grid of the step, typed values are kept as typed (only limits and digits apply)
    const v = from === 'type' ? Math.min(max, Math.max(min, round(next, digits))) : snap(next);
    if (v === value) {
      if (from === 'step' && next !== value) bump(boxRef.current);
      return;
    }
    if (from === 'step') nudge(variant === 'stepper' || variant === 'scrub' ? inputRef.current : valueRef.current ?? inputRef.current, v - value);
    setInner(v);
    onValueChange?.(v);
  };
  const by = (delta: number) => commit(value + delta);

  const plus = useHold(() => by(step));
  const minus = useHold(() => (onRemove && value <= min ? onRemove() : by(-step)));
  const atMin = value <= min;
  const atMax = value >= max;
  const removeMode = variant === 'quantity' && Boolean(onRemove) && atMin;

  const onKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
    const k = e.key;
    const map: Record<string, () => void> = {
      ArrowUp: () => by(e.shiftKey ? big : step),
      ArrowDown: () => by(-(e.shiftKey ? big : step)),
      PageUp: () => by(big),
      PageDown: () => by(-big),
      Home: () => Number.isFinite(min) && commit(min),
      End: () => Number.isFinite(max) && commit(max),
    };
    if (map[k]) {
      e.preventDefault();
      if (draft !== null) {
        const typed = parseNumber(draft, locale);
        setDraft(null);
        if (typed !== null && snap(typed) !== value) return commit(typed, 'type');
      }
      map[k]();
    } else if (k === 'Enter') {
      finish();
    } else if (k === 'Escape' && draft !== null) {
      e.preventDefault();
      setDraft(null);
    }
  };
  const finish = () => {
    if (draft === null) return;
    const typed = parseNumber(draft, locale);
    setDraft(null);
    if (typed !== null) commit(typed, 'type');
  };

  /* ---------- scrub: drag the handle sideways ---------- */
  const drag = useRef<{ x: number; start: number; moved: boolean } | null>(null);
  const [dragging, setDragging] = useState(false);
  const scrub = {
    onPointerDown: (e: React.PointerEvent<HTMLSpanElement>) => {
      if (c.disabled || e.button !== 0) return;
      e.preventDefault();
      e.currentTarget.setPointerCapture(e.pointerId);
      drag.current = { x: e.clientX, start: value, moved: false };
      setDragging(true);
    },
    onPointerMove: (e: React.PointerEvent<HTMLSpanElement>) => {
      const d = drag.current;
      if (!d) return;
      const dx = e.clientX - d.x;
      if (Math.abs(dx) > 2) d.moved = true;
      // One step every 4 px, Shift ten times faster, Alt ten times finer
      const factor = e.shiftKey ? 10 : e.altKey ? 0.1 : 1;
      const next = snap(d.start + Math.round(dx / 4) * step * factor);
      if (next !== value) {
        setInner(next);
        onValueChange?.(next);
      }
    },
    onPointerUp: () => {
      const d = drag.current;
      drag.current = null;
      setDragging(false);
      if (d && !d.moved) inputRef.current?.focus();
    },
  };
  useEffect(() => {
    if (!dragging) return;
    const prev = document.body.style.cursor;
    document.body.style.cursor = 'ew-resize';
    return () => void (document.body.style.cursor = prev);
  }, [dragging]);

  const shown = draft ?? fmt(value);
  // "50%" in English, "50 %" in German, degrees always close
  const tight = unit === '°' || (unit === '%' && locale === 'en');
  const valueText = `${prefix ?? ''}${fmt(value)}${unit ? `${tight ? '' : ' '}${unit}` : ''}`;
  const input = (
    <input
      ref={inputRef}
      id={c.id}
      type="text"
      inputMode={digits > 0 || min < 0 ? 'decimal' : 'numeric'}
      role="spinbutton"
      aria-valuenow={value}
      aria-valuemin={Number.isFinite(min) ? min : undefined}
      aria-valuemax={Number.isFinite(max) ? max : undefined}
      aria-valuetext={valueText}
      aria-label={props['aria-label']}
      aria-invalid={c['aria-invalid']}
      aria-describedby={cn(c['aria-describedby'], variant === 'scrub' && hintId) || undefined}
      disabled={c.disabled}
      required={c.required}
      autoComplete="off"
      spellCheck={false}
      value={shown}
      onChange={(e) => setDraft(e.target.value)}
      onFocus={(e) => {
        setDraft(fmt(value, false));
        const el = e.currentTarget;
        requestAnimationFrame(() => el.select());
      }}
      onBlur={finish}
      onKeyDown={onKeyDown}
      // In the centered looks the field is as wide as its text, so a unit sits right next to the number
      style={variant === 'split' || variant === 'quantity' ? { width: `${Math.max(shown.length, 1) + 0.6}ch` } : undefined}
      className={cn(
        'h-full min-w-0 bg-transparent tabular-nums text-inherit outline-none placeholder:text-subtle-foreground',
        // Between two buttons the box ring alone does not say which part has focus, so the number gets its own line
        variant === 'split' || variant === 'quantity' ? 'max-w-full flex-none rounded-none text-center font-medium focus-visible:shadow-[inset_0_-2px_0_var(--primary)]' : 'w-0 flex-1 text-start',
      )}
    />
  );
  const hidden = name ? <input type="hidden" name={name} value={value} /> : null;
  const affix = (text: string | undefined, side: 'start' | 'end') =>
    text ? <span aria-hidden className={cn('shrink-0 select-none text-subtle-foreground', side === 'start' ? 'pe-1' : tight ? 'ps-px' : 'ps-1')}>{text}</span> : null;

  /* ---------- split: minus | value | plus ---------- */
  if (variant === 'split' || variant === 'quantity') {
    const q = variant === 'quantity';
    const btn = q ? 'size-11 sm:size-9 rounded-[7px]' : cn('h-full aspect-square', size === 'lg' ? 'w-12' : 'w-11');
    return (
      <div
        ref={boxRef}
        data-invalid={c.invalid || undefined}
        data-disabled={c.disabled || undefined}
        className={cn(
          'group/num relative flex items-center',
          q ? 'h-11 w-[8.5rem] shrink-0 gap-0.5 rounded-lg p-0 text-base sm:h-9 sm:w-[7.25rem] sm:text-sm' : cn('w-full', CONTROL_HEIGHT[size]),
          controlBox,
          q && 'overflow-hidden',
          className,
        )}
      >
        <button
          type="button"
          aria-label={removeMode ? t.remove : t.decrease}
          aria-controls={c.id}
          disabled={c.disabled || (atMin && !removeMode)}
          {...minus}
          onKeyDown={(e) => {
            if (e.key === 'Enter' || e.key === ' ') {
              e.preventDefault();
              if (removeMode) onRemove?.();
              else by(-step);
            }
          }}
          className={cn(STEP_BTN, btn, !q && 'rounded-s-[inherit] border-e border-border', removeMode && 'hover:text-destructive')}
        >
          {/* The minus turns into a bin at the minimum, with a short turn */}
          <span key={removeMode ? 'rm' : 'minus'} className="grid place-items-center transition-[rotate,scale,opacity] duration-300 ease-[var(--ease-kit)] starting:-rotate-90 starting:scale-50 starting:opacity-0 motion-reduce:transition-none">
            <Icon name={removeMode ? 'trash' : 'minus'} size={q ? 15 : 17} />
          </span>
        </button>
        <span ref={valueRef} onClick={() => inputRef.current?.focus()} className="flex h-full min-w-0 flex-1 cursor-text items-center justify-center px-1">
          {affix(prefix, 'start')}
          {input}
          {affix(unit, 'end')}
        </span>
        <button
          type="button"
          aria-label={t.increase}
          aria-controls={c.id}
          disabled={c.disabled || atMax}
          {...plus}
          onKeyDown={(e) => {
            if (e.key === 'Enter' || e.key === ' ') {
              e.preventDefault();
              by(step);
            }
          }}
          className={cn(STEP_BTN, btn, !q && 'rounded-e-[inherit] border-s border-border')}
        >
          <Icon name="plus" size={q ? 15 : 17} />
        </button>
        {hidden}
      </div>
    );
  }

  /* ---------- scrub: a design tool field ---------- */
  if (variant === 'scrub') {
    const ranged = Number.isFinite(min) && Number.isFinite(max);
    const p = ranged ? (value - min) / (max - min) : 0;
    return (
      <div
        ref={boxRef}
        data-invalid={c.invalid || undefined}
        data-disabled={c.disabled || undefined}
        data-dragging={dragging || undefined}
        className={cn('group/num relative flex h-11 w-full items-center overflow-hidden rounded-lg text-base sm:h-9 sm:rounded-md sm:text-[13px]', controlBox, dragging && 'border-[color-mix(in_oklab,var(--primary)_60%,var(--border-strong))]', className)}
      >
        {inlineLabel ? (
          // A word as the handle: it is the label of the field too
          <label
            htmlFor={c.id}
            title={t.scrub}
            {...scrub}
            className={cn(
              'flex h-full shrink-0 cursor-ew-resize touch-none select-none items-center ps-3 pe-2 text-[13px] text-muted-foreground transition-colors duration-200 hover:text-foreground sm:ps-2.5 sm:text-[12.5px]',
              dragging && 'text-primary',
              c.disabled && 'pointer-events-none',
            )}
          >
            {inlineLabel}
          </label>
        ) : (
          <span
            aria-hidden
            title={t.scrub}
            {...scrub}
            className={cn(
              'grid h-full w-11 shrink-0 cursor-ew-resize touch-none select-none place-items-center text-[12px] font-medium text-subtle-foreground transition-colors duration-200 hover:text-foreground sm:w-8',
              dragging && 'text-primary',
              c.disabled && 'pointer-events-none',
            )}
          >
            {handleIcon ? <Icon name={handleIcon} size={15} /> : handle}
          </span>
        )}
        <span className={cn('flex h-full min-w-0 flex-1 items-center pe-2.5', inlineLabel && '[&>input]:text-end')}>
          {affix(prefix, 'start')}
          {input}
          {affix(unit, 'end')}
        </span>
        {/* Where the value sits in its range, a hairline along the bottom edge */}
        {ranged && (
          <span aria-hidden className="pointer-events-none absolute inset-x-0 bottom-0 h-[2px] overflow-hidden">
            <span
              className={cn('block h-full origin-left bg-primary transition-[scale,opacity] duration-200 ease-[var(--ease-kit)] motion-reduce:transition-none', dragging ? 'opacity-100' : 'opacity-0 group-hover/num:opacity-60 group-focus-within/num:opacity-60')}
              style={{ scale: `${round(p, 4)} 1` }}
            />
          </span>
        )}
        <span id={hintId} className="sr-only">{t.scrub}</span>
        {hidden}
      </div>
    );
  }

  /* ---------- stepper: buttons stacked at the end ---------- */
  return (
    <div
      ref={boxRef}
      data-invalid={c.invalid || undefined}
      data-disabled={c.disabled || undefined}
      className={cn('group/num relative flex w-full items-stretch overflow-hidden', CONTROL_HEIGHT[size], controlBox, className)}
    >
      <span className={cn('flex min-w-0 flex-1 items-center', size === 'sm' ? 'px-3' : size === 'lg' ? 'px-4' : 'px-3.5')}>
        {affix(prefix, 'start')}
        {input}
        {affix(unit, 'end')}
      </span>
      {/* Phones get two wide buttons side by side, larger screens a slim column */}
      <span className="flex shrink-0 border-s border-border sm:w-8 sm:flex-col">
        <button type="button" tabIndex={-1} aria-label={t.increase} aria-controls={c.id} disabled={c.disabled || atMax} {...plus} className={cn(STEP_BTN, 'order-2 w-11 border-s border-border sm:order-1 sm:w-full sm:flex-1 sm:border-s-0 sm:border-b')}>
          <Icon name="plus" size={15} className="sm:hidden" />
          <Icon name="chevron-up" size={13} strokeWidth={2} className="max-sm:hidden" />
        </button>
        <button type="button" tabIndex={-1} aria-label={t.decrease} aria-controls={c.id} disabled={c.disabled || atMin} {...minus} className={cn(STEP_BTN, 'order-1 w-11 sm:order-2 sm:w-full sm:flex-1')}>
          <Icon name="minus" size={15} className="sm:hidden" />
          <Icon name="chevron-down" size={13} strokeWidth={2} className="max-sm:hidden" />
        </button>
      </span>
      {hidden}
    </div>
  );
}

/**
 * A number field with steps, limits and the number format of the language.
 *   <NumberInput label="Copies" min={1} max={500} defaultValue={50} unit="pcs" />
 *   <NumberInput variant="split" label="Adults" min={1} max={8} defaultValue={2} />
 *   <NumberInput variant="quantity" defaultValue={1} min={1} onRemove={() => remove(id)} aria-label="Quantity" />
 *   <NumberInput variant="scrub" handle="W" unit="px" min={0} max={1440} defaultValue={320} aria-label="Width" />
 */
export function NumberInput({ label, hint, error, optional, labelAction, className, ...rest }: NumberInputProps) {
  // scrub without a letter or icon: the label itself is the handle, inside the box
  if (rest.variant === 'scrub' && label && !rest.handle && !rest.handleIcon) {
    const box = <NumberBox {...rest} inlineLabel={label} invalid={rest.invalid ?? (error ? true : undefined)} className={hint || error ? undefined : className} />;
    return withField({ hint, error, id: rest.id, required: rest.required, disabled: rest.disabled, className }, box);
  }
  const wrapped = Boolean(label || hint || error);
  return withField({ label, hint, error, optional, labelAction, id: rest.id, required: rest.required, disabled: rest.disabled, className }, <NumberBox {...rest} invalid={rest.invalid ?? (error ? true : undefined)} className={wrapped ? undefined : className} />);
}