"use client";

import { useEffect, useRef, type ElementType, type ReactNode, type HTMLAttributes } from "react";

type Variant = "up" | "left" | "right" | "scale";

/**
 * Scroll-triggered reveal. Uses a single IntersectionObserver (no deps).
 * Pairs with the `.reveal` / `.is-visible` rules in globals.css.
 *
 * CUSTOMIZATION HOOK — MOTION:
 *   variant → direction of entrance
 *   delay   → stagger (ms), applied as transition-delay
 */
export default function Reveal({
  children,
  variant = "up",
  delay = 0,
  as: Tag = "div",
  className = "",
  style,
  ...rest
}: HTMLAttributes<HTMLElement> & {
  children: ReactNode;
  variant?: Variant;
  delay?: number;
  as?: ElementType;
  className?: string;
}) {
  const ref = useRef<HTMLElement>(null);

  useEffect(() => {
    const el = ref.current;
    if (!el) return;

    const io = new IntersectionObserver(
      (entries) => {
        entries.forEach((entry) => {
          if (entry.isIntersecting) {
            entry.target.classList.add("is-visible");
            io.unobserve(entry.target);
          }
        });
      },
      { threshold: 0.12, rootMargin: "0px 0px -8% 0px" }
    );

    io.observe(el);
    return () => io.disconnect();
  }, []);

  const combinedStyle = delay
    ? { ...style, transitionDelay: `${delay}ms` }
    : style;

  return (
    <Tag
      ref={ref}
      data-variant={variant}
      style={combinedStyle}
      className={`reveal ${className}`}
      {...rest}
    >
      {children}
    </Tag>
  );
}