"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { useLocale } from "~/components/locale-provider";
import type { Locale } from "~/lib/i18n";

const OPTIONS: { value: Locale; label: string }[] = [
  { value: "zh", label: "中文" },
  { value: "en", label: "English" },
];

const UNLOCK_CLICKS = 5;
const CLICK_WINDOW_MS = 2500;
const UNLOCK_KEY = "nomadro-lang-unlock";

export function LanguageSwitcher({ className = "" }: { className?: string }) {
  const { locale, setLocale, t } = useLocale();
  const [visible, setVisible] = useState(false);
  const clicksRef = useRef(0);
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);

  useEffect(() => {
    try {
      if (window.sessionStorage.getItem(UNLOCK_KEY) === "1") {
        setVisible(true);
      }
    } catch {
      // ignore
    }
  }, []);

  const handleSecretClick = useCallback(() => {
    if (visible) return;

    clicksRef.current += 1;

    if (timerRef.current) clearTimeout(timerRef.current);
    timerRef.current = setTimeout(() => {
      clicksRef.current = 0;
    }, CLICK_WINDOW_MS);

    if (clicksRef.current >= UNLOCK_CLICKS) {
      clicksRef.current = 0;
      if (timerRef.current) clearTimeout(timerRef.current);
      setVisible(true);
      try {
        window.sessionStorage.setItem(UNLOCK_KEY, "1");
      } catch {
        // ignore
      }
    }
  }, [visible]);

  return (
    <div
      className={`absolute right-0 z-10 ${className}`}
      style={{ top: "max(0.5rem, var(--safe-top))" }}
    >
      {/* Invisible hit area — tap 5 times to reveal */}
      <button
        type="button"
        aria-hidden={!visible}
        tabIndex={-1}
        onClick={handleSecretClick}
        className="absolute right-0 top-0 h-12 w-16 cursor-default border-0 bg-transparent p-0"
        style={{ opacity: 0 }}
      />

      {visible ? (
        <label className="relative z-10 mr-4 mt-2 inline-flex items-center gap-2 text-xs text-neutral-500">
          <span className="sr-only">{t.languageLabel}</span>
          <select
            value={locale}
            onChange={(event) => setLocale(event.target.value as Locale)}
            aria-label={t.languageLabel}
            className="appearance-none rounded-lg border border-neutral-200 bg-white px-2.5 py-1.5 pr-7 text-xs font-medium text-neutral-700 shadow-sm outline-none transition hover:border-neutral-300 focus:border-neutral-400"
            style={{
              backgroundImage:
                "url(\"data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%23a3a3a3' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E\")",
              backgroundRepeat: "no-repeat",
              backgroundPosition: "right 0.55rem center",
            }}
          >
            {OPTIONS.map((option) => (
              <option key={option.value} value={option.value}>
                {option.label}
              </option>
            ))}
          </select>
        </label>
      ) : null}
    </div>
  );
}