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

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

export default function CountUp({
  to,
  from = 0,
  direction = "up",
  delay = 0,
  duration = 2,
  className = "",
  startWhen = true,
  separator = "",
  suffix = "",
  prefix = "",
  padMinLength,
  onStart,
  onEnd,
}: CountUpProps) {
  const ref = useRef<HTMLSpanElement>(null);
  const containerRef = useRef<HTMLSpanElement>(null);
  const motionValue = useMotionValue(direction === "down" ? to : from);

  const damping = 20 + 40 * (1 / duration);
  const stiffness = 100 * (1 / duration);

  const springValue = useSpring(motionValue, {
    damping,
    stiffness,
  });

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

  const getDecimalPlaces = (num: number) => {
    const str = num.toString();
    if (str.includes(".")) {
      const decimals = str.split(".")[1];
      if (decimals && parseInt(decimals, 10) !== 0) {
        return decimals.length;
      }
    }
    return 0;
  };

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

  const formatValue = useCallback(
    (latest: number) => {
      if (padMinLength != null) {
        const n = Math.round(latest);
        return n.toString().padStart(padMinLength, "0");
      }
      const hasDecimals = maxDecimals > 0;
      const options: Intl.NumberFormatOptions = {
        useGrouping: !!separator,
        minimumFractionDigits: hasDecimals ? maxDecimals : 0,
        maximumFractionDigits: hasDecimals ? maxDecimals : 0,
      };
      let formattedNumber = Intl.NumberFormat("de-DE", options).format(latest);
      if (separator) {
        formattedNumber = formattedNumber.replace(/\s/g, separator);
      }
      return formattedNumber;
    },
    [maxDecimals, separator, padMinLength]
  );

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

  useEffect(() => {
    if (isInView && startWhen) {
      if (typeof onStart === "function") onStart();

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

      const durationTimeoutId = setTimeout(
        () => {
          if (typeof onEnd === "function") onEnd();
        },
        delay * 1000 + duration * 1000
      );

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

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

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

  return (
    <span ref={containerRef} className={className}>
      {prefix && <span>{prefix}</span>}
      <span ref={ref} />
      {suffix && <span>{suffix}</span>}
    </span>
  );
}
