import { useEffect, useRef, useState, type ReactNode } from "react";
import { cn } from "@/lib/utils";

/** Gentle fade-up scroll reveal (respects prefers-reduced-motion). */
export function Reveal({
  children,
  className,
  delayMs = 0,
}: {
  children: ReactNode;
  className?: string;
  delayMs?: number;
}) {
  const ref = useRef<HTMLDivElement>(null);
  const [inView, setInView] = useState(false);

  useEffect(() => {
    const node = ref.current;
    if (!node) return;
    if (window.matchMedia("(prefers-reduced-motion: reduce)").matches) {
      setInView(true);
      return;
    }
    const observer = new IntersectionObserver(
      (entries) => {
        for (const entry of entries) {
          if (entry.isIntersecting) {
            setInView(true);
            observer.disconnect();
          }
        }
      },
      { threshold: 0.12, rootMargin: "0px 0px -40px 0px" },
    );
    observer.observe(node);
    return () => observer.disconnect();
  }, []);

  return (
    <div
      ref={ref}
      style={delayMs ? { transitionDelay: `${delayMs}ms` } : undefined}
      className={cn("reveal", inView && "reveal-in", className)}
    >
      {children}
    </div>
  );
}