// Shared hooks for scroll-driven motion
const { useState, useEffect, useRef, useLayoutEffect, useMemo, useCallback } = React;

// Intersection-based reveal: returns [ref, hasEntered]
function useInView(threshold = 0.18, once = true) {
  const ref = useRef(null);
  const [inView, setInView] = useState(false);
  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    const obs = new IntersectionObserver(
      ([e]) => {
        if (e.isIntersecting) {
          setInView(true);
          if (once) obs.unobserve(el);
        } else if (!once) {
          setInView(false);
        }
      },
      { threshold, rootMargin: '0px 0px -10% 0px' }
    );
    obs.observe(el);
    return () => obs.disconnect();
  }, [threshold, once]);
  return [ref, inView];
}

// Returns scroll progress (0..1) of an element through the viewport
// 0 = element top hits viewport bottom; 1 = element bottom hits viewport top
function useScrollProgress() {
  const ref = useRef(null);
  const [progress, setProgress] = useState(0);
  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    let ticking = false;
    const update = () => {
      const rect = el.getBoundingClientRect();
      const vh = window.innerHeight;
      const total = rect.height + vh;
      const scrolled = vh - rect.top;
      const p = Math.max(0, Math.min(1, scrolled / total));
      setProgress(p);
      ticking = false;
    };
    const onScroll = () => {
      if (!ticking) {
        window.requestAnimationFrame(update);
        ticking = true;
      }
    };
    update();
    window.addEventListener('scroll', onScroll, { passive: true });
    window.addEventListener('resize', onScroll);
    return () => {
      window.removeEventListener('scroll', onScroll);
      window.removeEventListener('resize', onScroll);
    };
  }, []);
  return [ref, progress];
}

// Maps progress 0..1 over a sticky section: 0 when the top hits viewport top,
// 1 when bottom of sticky container leaves viewport bottom.
function useStickyProgress() {
  const ref = useRef(null);
  const [progress, setProgress] = useState(0);
  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    let ticking = false;
    const update = () => {
      const rect = el.getBoundingClientRect();
      const vh = window.innerHeight;
      const total = rect.height - vh;
      const scrolled = -rect.top;
      const p = total > 0 ? Math.max(0, Math.min(1, scrolled / total)) : 0;
      setProgress(p);
      ticking = false;
    };
    const onScroll = () => {
      if (!ticking) {
        window.requestAnimationFrame(update);
        ticking = true;
      }
    };
    update();
    window.addEventListener('scroll', onScroll, { passive: true });
    window.addEventListener('resize', onScroll);
    return () => {
      window.removeEventListener('scroll', onScroll);
      window.removeEventListener('resize', onScroll);
    };
  }, []);
  return [ref, progress];
}

// Word stagger reveal helper
function StaggerWords({ text, className = '', delay = 0, step = 60 }) {
  const [ref, inView] = useInView(0.3);
  const words = text.split(' ');
  return (
    <span ref={ref} className={`word-stagger ${className} ${inView ? 'in' : ''}`}>
      {words.map((w, i) => (
        <span
          key={i}
          style={{
            transitionDelay: inView ? `${delay + i * step}ms` : '0ms',
          }}
        >
          {w}{i < words.length - 1 ? '\u00A0' : ''}
        </span>
      ))}
    </span>
  );
}

function Reveal({ children, delay = 0, className = '', as = 'div' }) {
  const [ref, inView] = useInView(0.2);
  const Tag = as;
  return (
    <Tag
      ref={ref}
      className={`reveal ${inView ? 'in' : ''} ${className}`}
      style={{ transitionDelay: inView ? `${delay}ms` : '0ms' }}
    >
      {children}
    </Tag>
  );
}

const lerp = (a, b, t) => a + (b - a) * t;
const clamp = (v, a = 0, b = 1) => Math.max(a, Math.min(b, v));
const smoothstep = (a, b, t) => {
  const x = clamp((t - a) / (b - a));
  return x * x * (3 - 2 * x);
};

Object.assign(window, {
  useInView, useScrollProgress, useStickyProgress,
  StaggerWords, Reveal,
  lerp, clamp, smoothstep,
});