"use client";
import { useInView, useMotionValue, useSpring } from "motion/react";
import { useCallback, useEffect, useRef } from "react";

type CountUpProps = {
  to: number;
  from?: number;
  direction?: "up" | "down";
  delay?: number;
  duration?: number;
  className?: string;
  startWhen?: boolean;
  separator?: string;
  onStart?: () => void;
  onEnd?: () => void;
};

const CountUp = ({
  to,
  from = 0,
  direction = "up",
  delay = 0,
  duration = 2,
  className = "",
  startWhen = true,
  separator = "",
  onStart,
  onEnd,
}: CountUpProps) => {
  const ref = useRef<HTMLSpanElement>(null);

  const motionValue = useMotionValue(direction === "down" ? to : from);

  const springValue = useSpring(motionValue, {
    mass: 0.2,
    stiffness: 500,
    damping: 120,
  });

  const isInView = useInView(ref, { once: true, margin: "0px" });

  const getDecimalPlaces = (num: number): number => {
    const str = num.toString();
    if (str.includes(".")) {
      const decimals = str.split(".")[1];
      if (parseInt(decimals) !== 0) {
        return decimals.length;
      }
    }
    return 0;
  };

  const maxDecimals = Math.max(getDecimalPlaces(from), getDecimalPlaces(to));

  const formatValue = useCallback(
    (latest: number) => {
      const hasDecimals = maxDecimals > 0;

      const options: Intl.NumberFormatOptions = {
        useGrouping: !!separator,
        minimumFractionDigits: hasDecimals ? maxDecimals : 0,
        maximumFractionDigits: hasDecimals ? maxDecimals : 0,
      };

      const formatted = Intl.NumberFormat("en-US", options).format(latest);
      return separator ? formatted.replace(/,/g, separator) : formatted;
    },
    [maxDecimals, separator]
  );

  useEffect(() => {
    if (ref.current) {
      ref.current.textContent = formatValue(direction === "down" ? to : from);
    }
  }, [from, to, direction, formatValue]);

  useEffect(() => {
    if (isInView && startWhen) {
      onStart?.();

      const timeoutId = setTimeout(() => {
        motionValue.set(direction === "down" ? from : to);
      }, delay * 1000);

      return () => clearTimeout(timeoutId);
    }
  }, [isInView, startWhen, motionValue, direction, from, to, delay, onStart]);

  useEffect(() => {
    let ended = false;

    const unsubscribe = springValue.on("change", (latest: number) => {
      if (ref.current) {
        ref.current.textContent = formatValue(latest);
      }

      if (!ended && Math.abs(latest - to) < 0.1) {
        ended = true;
        onEnd?.();
      }
    });

    return () => unsubscribe();
  }, [springValue, formatValue, to, onEnd]);

  return <span className={className} ref={ref} />;
};

export default CountUp;