import { useRef, type InputHTMLAttributes, type Ref } from 'react'

export type NumericMode = 'integer' | 'decimal' | 'signed' | 'signed-decimal'

const SANITIZERS: Record<NumericMode, (raw: string) => string> = {
  // Digits only — quantities, weights, day counts.
  integer: raw => raw.replace(/[^0-9]/g, ''),
  // Digits plus a decimal separator. Both '.' and ',' pass through; callers already
  // normalize the comma (see CostsPanel.onTotalChange) so a European keypad still works.
  decimal: raw => raw.replace(/[^0-9.,]/g, ''),
  // Signed decimal — coordinates. Keeps a leading '-'.
  signed: raw => {
    const negative = raw.trimStart().startsWith('-')
    const digits = raw.replace(/[^0-9.]/g, '')
    return negative ? `-${digits}` : digits
  },
  // 'decimal' plus a leading '-' — money fields that accept a refund (#2176).
  // Distinct from 'signed' on purpose: that one strips the comma, which a
  // European keypad needs for amounts.
  'signed-decimal': raw => {
    const negative = raw.trimStart().startsWith('-')
    const digits = raw.replace(/[^0-9.,]/g, '')
    return negative ? `-${digits}` : digits
  },
}

const flipSign = (raw: string) => (raw.startsWith('-') ? raw.slice(1) : `-${raw}`)

type Props = Omit<InputHTMLAttributes<HTMLInputElement>, 'type' | 'onChange' | 'value'> & {
  value: string | number | null | undefined
  /** Receives the sanitized raw string. Callers keep their own state and commit logic. */
  onValueChange: (value: string) => void
  mode?: NumericMode
  /** Escape hatch for a field that must not steal the caret (none today). */
  selectOnFocus?: boolean
  /**
   * Accessible name for a sign toggle rendered beside the field. Set it on a signed
   * money field: iOS draws inputMode="decimal" as a pad with digits, separator and
   * backspace only, so a refund (#2176) has no minus key to type. Ignored on the
   * unsigned modes, where there is no sign to flip.
   */
  signToggleLabel?: string
  ref?: Ref<HTMLInputElement>
}

/**
 * A numeric text input that replaces its contents when you type into it.
 *
 * Two things every numeric field in the app needs, and most were getting wrong (#1513):
 *
 *  1. **Select-on-focus.** Tapping a pre-populated field puts the caret at the end, so
 *     the first digit you type is *appended*: a quantity of 1 becomes 16 instead of 6.
 *     Selecting the value on focus makes the first keystroke replace it.
 *
 *     We select twice: synchronously (works everywhere) and again on the next frame,
 *     because WebKit undoes a synchronous select() with its own post-focus caret
 *     placement — without the deferred pass, iOS silently keeps appending.
 *
 *     The deferred pass is guarded. If a keystroke lands inside that one-frame window,
 *     re-selecting would swallow what was just typed: type "4" then "8", the frame
 *     fires and selects "48", and the next character *replaces* both — "48.853" comes
 *     out as ".853". So the first input cancels the pending select and we leave the
 *     caret alone.
 *
 *  2. **type="text" + inputMode**, not type="number". They render the same keypad, but
 *     type="number" also silently mutates the value on scroll-wheel over the field and
 *     ships spinner arrows. (setSelectionRange() also throws InvalidStateError on a
 *     number input — select() happens to be allowed, but the whole class is a trap.)
 *
 * Styling and commit semantics stay with the caller: some fields save on every keystroke,
 * others on blur. This owns only the part that was uniformly broken.
 */
export function NumericInput({
  value, onValueChange, mode = 'integer', selectOnFocus = true, onFocus, inputMode, signToggleLabel, ref, ...rest
}: Props) {
  // Set while a deferred select() is queued; any input in that window cancels it.
  const selectPending = useRef(false)
  const raw = String(value ?? '')
  const signable = mode === 'signed' || mode === 'signed-decimal'

  return (
    <>
      <input
        {...rest}
        ref={ref}
        type="text"
        inputMode={inputMode ?? (mode === 'integer' ? 'numeric' : 'decimal')}
        value={value ?? ''}
        onChange={e => {
          selectPending.current = false
          onValueChange(SANITIZERS[mode](e.target.value))
        }}
        onFocus={e => {
          if (selectOnFocus) {
            const el = e.currentTarget
            el.select()
            selectPending.current = true
            requestAnimationFrame(() => {
              if (selectPending.current && document.activeElement === el) el.select()
              selectPending.current = false
            })
          }
          onFocus?.(e)
        }}
      />
      {signToggleLabel && signable && (
        <button
          type="button"
          aria-label={signToggleLabel}
          aria-pressed={raw.startsWith('-')}
          disabled={rest.disabled}
          // Keeps the caret (and on a phone the keypad) in the field, so the sign can
          // be flipped mid-entry and typing carries on where it left off.
          onMouseDown={e => e.preventDefault()}
          onClick={() => onValueChange(SANITIZERS[mode](flipSign(raw)))}
          className="text-content-faint"
          style={{ border: 0, background: 'none', padding: '0 2px', font: 'inherit', lineHeight: 1, cursor: 'pointer' }}
        >
          ±
        </button>
      )}
    </>
  )
}