import { useState, useRef, useEffect } from 'react';

// Frame-rate-independent easing of a scalar toward a moving target (alpha from
// dt + a time constant). The rAF loop runs continuously so the value keeps
// gliding between the bridge's discrete value updates — turning a stuttery
// ~10–20 Hz stream into a smooth 60 fps motion. To avoid needless React work it
// only re-renders the consumer while the value is actually moving: once settled,
// the functional setState returns the same number and React bails (Object.is).
export function useEased(target, tau = 0.08) {
  const [, force] = useState(0);
  const cur = useRef(target), tg = useRef(target);
  tg.current = target;
  useEffect(() => {
    let raf, last = 0;
    const loop = (now) => {
      const dt = last ? Math.min(0.05, (now - last) / 1000) : 0.016; last = now;
      const k = 1 - Math.exp(-dt / tau);
      const next = cur.current + (tg.current - cur.current) * k;
      const settled = Math.abs(tg.current - next) < 0.02;
      const val = settled ? tg.current : next;
      if (val !== cur.current) { cur.current = val; force((n) => (n + 1) & 0xffff); }
      raf = requestAnimationFrame(loop);
    };
    raf = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(raf);
  }, [tau]);
  return cur.current;
}

// As above but eases along the shortest arc across the 0↔360 wrap (headings).
export function useEasedAngle(target, tau = 0.08) {
  const [, force] = useState(0);
  const cur = useRef(target), tg = useRef(target);
  tg.current = target;
  useEffect(() => {
    let raf, last = 0;
    const loop = (now) => {
      const dt = last ? Math.min(0.05, (now - last) / 1000) : 0.016; last = now;
      const k = 1 - Math.exp(-dt / tau);
      const d = ((tg.current - cur.current + 540) % 360) - 180; // shortest signed arc
      const next = Math.abs(d) < 0.05 ? tg.current : cur.current + d * k;
      const val = ((next % 360) + 360) % 360;
      if (val !== cur.current) { cur.current = val; force((n) => (n + 1) & 0xffff); }
      raf = requestAnimationFrame(loop);
    };
    raf = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(raf);
  }, [tau]);
  return cur.current;
}