'use client';

import { useCallback, useRef, useState } from 'react';
import { HONEYPOT_FIELD, ELAPSED_MS_FIELD, type HumanitySignals } from '../utils/humanity-signals';

/**
 * useHumanitySignals — client primitive backing the invisible bot-protection
 * layer. Owns the honeypot <input> ref + a mount timestamp, and exposes the
 * props to render the field plus a getter that produces the wire object to
 * merge into a form's POST body. Reused by every public form (contact,
 * waitlist, ticket, review) so the signal shape lives in exactly one place.
 *
 * Usage:
 *   const { honeypotInputProps, getSignals, resetSignals } = useHumanitySignals()
 *   // render: <HoneypotField {...honeypotInputProps} />
 *   // submit: fetch(url, { body: JSON.stringify({ ...formData, ...getSignals() }) })
 *   // after a successful submit: resetSignals()
 *
 * The two signals are origin-independent (they ride in the body), so they keep
 * working when the form is embedded behind a reverse-proxy / prefixed URL.
 */
export function useHumanitySignals() {
  const ref = useRef<HTMLInputElement>(null);
  // performance.now() is monotonic (immune to wall-clock skew). SSR-guarded
  // even though the hook only executes on the client.
  //
  // Sampled in a lazy `useState` initialiser, then copied into a ref. Not
  // `useRef(performance.now())`: that argument is re-evaluated on EVERY render
  // even though only the first call uses it, so the component would read the
  // clock during render forever. And not state alone: `resetSignals` restarts
  // the window after a successful submit, which through state would re-render
  // the whole form for a value nothing renders.
  const [mountedAt] = useState(() => (typeof performance !== 'undefined' ? performance.now() : 0));
  const startedAtRef = useRef<number>(mountedAt);

  const getSignals = useCallback(
    (): HumanitySignals => ({
      [HONEYPOT_FIELD]: ref.current?.value ?? '',
      [ELAPSED_MS_FIELD]: typeof performance !== 'undefined' ? Math.round(performance.now() - startedAtRef.current) : 0,
    }),
    [],
  );

  const resetSignals = useCallback(() => {
    if (ref.current) ref.current.value = '';
    if (typeof performance !== 'undefined') startedAtRef.current = performance.now();
  }, []);

  return { honeypotInputProps: { ref, name: HONEYPOT_FIELD }, getSignals, resetSignals } as const;
}