"use client";

import { useEffect, useRef, useState } from "react";

type TimeParts = {
  hours: number;
  minutes: number;
  seconds: number;
};

const LABELS = {
  hours: "ساعت",
  minutes: "دقیقه",
  seconds: "ثانیه",
} as const;

const FLIP_HALF_MS = 300;
const FLIP_TOTAL_MS = FLIP_HALF_MS * 2;

function endOfTehranDay(): number {
  const parts = new Intl.DateTimeFormat("en-CA", {
    timeZone: "Asia/Tehran",
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
  }).formatToParts(new Date());

  const year = parts.find((part) => part.type === "year")?.value;
  const month = parts.find((part) => part.type === "month")?.value;
  const day = parts.find((part) => part.type === "day")?.value;
  return new Date(`${year}-${month}-${day}T23:59:59+03:30`).getTime();
}

function getRemaining(): TimeParts {
  const total = Math.max(0, Math.floor((endOfTehranDay() - Date.now()) / 1000));
  return {
    hours: Math.floor(total / 3600),
    minutes: Math.floor((total % 3600) / 60),
    seconds: total % 60,
  };
}

function FlipDigit({ value }: { value: string }) {
  const [top, setTop] = useState(value);
  const [bottom, setBottom] = useState(value);
  const [flipFrom, setFlipFrom] = useState<string | null>(null);
  const [flipTo, setFlipTo] = useState<string | null>(null);
  const settledRef = useRef(value);

  useEffect(() => {
    if (value === settledRef.current) return;

    const from = settledRef.current;
    setFlipFrom(from);
    setFlipTo(value);
    setTop(value);

    const revealBottom = window.setTimeout(() => {
      setBottom(value);
    }, FLIP_HALF_MS);

    const clearFlip = window.setTimeout(() => {
      settledRef.current = value;
      setFlipFrom(null);
      setFlipTo(null);
    }, FLIP_TOTAL_MS);

    return () => {
      window.clearTimeout(revealBottom);
      window.clearTimeout(clearFlip);
      settledRef.current = value;
      setBottom(value);
      setFlipFrom(null);
      setFlipTo(null);
    };
  }, [value]);

  return (
    <span className={`flip-digit${flipFrom ? " is-flipping" : ""}`} aria-hidden="true">
      <span className="flip-half flip-half-top">
        <span className="flip-num">{top}</span>
      </span>
      <span className="flip-half flip-half-bottom">
        <span className="flip-num">{bottom}</span>
      </span>
      <span className="flip-digit-hinge" />
      {flipFrom != null && flipTo != null ? (
        <>
          <span className="flip-half flip-anim flip-anim-top" key={`top-${flipFrom}-${flipTo}`}>
            <span className="flip-num">{flipFrom}</span>
          </span>
          <span className="flip-half flip-anim flip-anim-bottom" key={`bot-${flipFrom}-${flipTo}`}>
            <span className="flip-num">{flipTo}</span>
          </span>
        </>
      ) : null}
    </span>
  );
}

function FlipUnit({ value, label }: { value: number; label: string }) {
  const digits = String(value).padStart(2, "0");

  return (
    <div className="flip-unit">
      <div className="flip-unit-digits">
        <FlipDigit value={digits[0]} />
        <FlipDigit value={digits[1]} />
      </div>
      <span className="flip-unit-label">{label}</span>
    </div>
  );
}

export function FlipCountdown({ className = "" }: { className?: string }) {
  const [parts, setParts] = useState<TimeParts>(() => getRemaining());

  useEffect(() => {
    const tick = () => setParts(getRemaining());
    tick();
    const timer = window.setInterval(tick, 1000);
    return () => window.clearInterval(timer);
  }, []);

  const readable = `${parts.hours} ساعت و ${parts.minutes} دقیقه`;

  return (
    <div
      className={`flip-countdown ${className}`.trim()}
      role="timer"
      aria-live="polite"
      aria-label={`زمان باقی‌مانده فروش ویژه امروز: ${readable}`}
    >
      <FlipUnit value={parts.hours} label={LABELS.hours} />
      <span className="flip-separator" aria-hidden="true">
        :
      </span>
      <FlipUnit value={parts.minutes} label={LABELS.minutes} />
      <span className="flip-separator" aria-hidden="true">
        :
      </span>
      <FlipUnit value={parts.seconds} label={LABELS.seconds} />
    </div>
  );
}