"use client";

import { useEffect, useRef, useState } from "react";
import { motion, useInView, useReducedMotion } from "motion/react";

type TypeNovaProps = {
  text: string;
  className?: string;
  /** Milliseconds per letter. */
  speed?: number;
  /** Colour of the flash each new letter lands with. */
  glow?: string;
  /** Type only the first time it scrolls into view. */
  once?: boolean;
};

/* TypeNova: types the text one letter at a time; each new letter lands as a bright flash that cools down. */
export function TypeNova({ text, className = "", speed = 55, glow = "#a78bfa", once = true }: TypeNovaProps) {
  const reduce = useReducedMotion();
  const ref = useRef<HTMLSpanElement>(null);
  const inView = useInView(ref, { once, amount: 0.6 });
  const [count, setCount] = useState(0);

  useEffect(() => {
    if (!inView || reduce) return;
    let n = 0;
    let timer = 0;
    const tick = () => {
      setCount(n);
      if (n++ < text.length) timer = window.setTimeout(tick, speed);
    };
    timer = window.setTimeout(tick, 0);
    return () => window.clearTimeout(timer);
  }, [inView, reduce, text, speed]);

  const shown = reduce ? text.length : count;
  const letters = [...text];

  return (
    <span ref={ref} className={className}>
      <span className="sr-only">{text}</span>
      <span aria-hidden>
        {letters.slice(0, shown).map((ch, i) => (
          // Plain inline letters (no transform), so long lines still wrap between words only.
          <motion.span
            key={i}
            initial={reduce ? false : { filter: "brightness(2.2)", textShadow: `0 0 18px ${glow}` }}
            animate={{ filter: "brightness(1)", textShadow: `0 0 0px ${glow}` }}
            transition={{ duration: 0.6, ease: [0.22, 1, 0.36, 1] }}
          >
            {ch}
          </motion.span>
        ))}
        {!reduce && shown < letters.length && (
          // Zero-width holder, so the caret never pushes the text around.
          <span className="relative inline-block w-0">
            <motion.span
              className="absolute bottom-[-0.1em] left-px h-[0.9em] w-[2px]"
              style={{ background: glow, boxShadow: `0 0 8px ${glow}` }}
              animate={{ opacity: [1, 0.2, 1] }}
              transition={{ duration: 0.8, repeat: Infinity }}
            />
          </span>
        )}
        {/* Untyped letters hold their space, so the line never shifts while typing. */}
        <span className="invisible whitespace-pre">{letters.slice(shown).join("")}</span>
      </span>
    </span>
  );
}