import pl from "../locales/pl.js";
import en from "../locales/en.js";
import de from "../locales/de.js";

const STORAGE_KEY = "karczma_lang";
const catalogs = { pl, en, de };
const LANG_BUSY_MIN_MS = 280;

let currentLang = "pl";
let langBusy = false;
/** @type {Set<(lang: string) => void | Promise<void>>} */
const listeners = new Set();
/** @type {Set<(busy: boolean) => void>} */
const busyListeners = new Set();

/** @type {Set<{ el: HTMLElement, close: () => void }>} */
const openPickerClosers = new Set();
let documentClickBound = false;

function interpolate(template, vars = {}) {
  return String(template).replace(/\{(\w+)\}/g, (_, key) => {
    return vars[key] != null ? String(vars[key]) : `{${key}}`;
  });
}

function ensureDocumentClickHandler() {
  if (documentClickBound) return;
  documentClickBound = true;
  document.addEventListener("click", (e) => {
    openPickerClosers.forEach((picker) => {
      if (!picker.el.contains(e.target)) {
        picker.close();
      }
    });
  });
}

function setLangBusy(busy) {
  langBusy = !!busy;
  document.documentElement.classList.toggle("is-lang-loading", langBusy);
  busyListeners.forEach((cb) => {
    try {
      cb(langBusy);
    } catch (err) {
      console.warn("[i18n] busy listener failed", err);
    }
  });
}

export function getAvailableLanguages() {
  const fromConfig = window.APP_CONFIG?.languages;
  if (Array.isArray(fromConfig) && fromConfig.length) {
    return fromConfig;
  }
  return [
    { code: "pl", label: "Polski", flag: "🇵🇱" },
    { code: "en", label: "English", flag: "🇬🇧" },
    { code: "de", label: "Deutsch", flag: "🇩🇪" },
  ];
}

export function getLang() {
  return currentLang;
}

export function isLangBusy() {
  return langBusy;
}

export function t(key, vars = {}) {
  const catalog = catalogs[currentLang] || catalogs.pl;
  const fallback = catalogs.pl;
  const value = catalog[key] ?? fallback[key] ?? key;
  return interpolate(value, vars);
}

export function applyTranslations(root = document) {
  root.querySelectorAll("[data-i18n]").forEach((el) => {
    const key = el.getAttribute("data-i18n");
    if (!key) return;
    const html = el.hasAttribute("data-i18n-html");
    const text = t(key);
    if (html) {
      el.innerHTML = text;
    } else {
      el.textContent = text;
    }
  });

  root.querySelectorAll("[data-i18n-placeholder]").forEach((el) => {
    const key = el.getAttribute("data-i18n-placeholder");
    if (!key) return;
    el.setAttribute("placeholder", t(key));
  });

  root.querySelectorAll("[data-i18n-aria]").forEach((el) => {
    const key = el.getAttribute("data-i18n-aria");
    if (!key) return;
    el.setAttribute("aria-label", t(key));
  });

  document.documentElement.lang = t("html.lang");
  document.title = t("doc.title");
}

export function onLangChange(callback) {
  listeners.add(callback);
  return () => listeners.delete(callback);
}

export function onLangBusyChange(callback) {
  busyListeners.add(callback);
  return () => busyListeners.delete(callback);
}

export async function setLang(lang, { persist = true, notify = true } = {}) {
  const next = catalogs[lang] ? lang : "pl";
  const changed = next !== currentLang;
  currentLang = next;

  if (persist) {
    try {
      localStorage.setItem(STORAGE_KEY, currentLang);
    } catch {
      // ignore
    }
  }

  applyTranslations();

  if (!(notify && changed)) {
    return currentLang;
  }

  if (langBusy) {
    return currentLang;
  }

  const startedAt = Date.now();
  setLangBusy(true);

  try {
    const tasks = [];
    listeners.forEach((cb) => {
      try {
        const result = cb(currentLang);
        if (result != null && typeof result.then === "function") {
          tasks.push(result);
        }
      } catch (err) {
        console.warn("[i18n] listener failed", err);
      }
    });
    if (tasks.length) {
      await Promise.allSettled(tasks);
    }
  } finally {
    const wait = Math.max(0, LANG_BUSY_MIN_MS - (Date.now() - startedAt));
    if (wait > 0) {
      await new Promise((resolve) => setTimeout(resolve, wait));
    }
    setLangBusy(false);
  }

  return currentLang;
}

export function initI18n() {
  let stored = "";
  try {
    stored = localStorage.getItem(STORAGE_KEY) || "";
  } catch {
    stored = "";
  }
  const initial = catalogs[stored] ? stored : "pl";
  return setLang(initial, { persist: true, notify: false });
}

function flagImgHtml(code) {
  const safe = String(code || "pl").toLowerCase().replace(/[^a-z]/g, "") || "pl";
  return `<img class="lang-flag-img" src="assets/img/flags/${safe}.svg" alt="" width="28" height="20" decoding="async">`;
}

function spinnerHtml() {
  return `<span class="lang-picker-spinner" aria-hidden="true"></span>`;
}

export function createLanguagePicker({ idPrefix = "lang" } = {}) {
  ensureDocumentClickHandler();

  const wrap = document.createElement("div");
  wrap.className = "lang-picker";
  wrap.dataset.langPicker = "1";

  const btn = document.createElement("button");
  btn.type = "button";
  btn.className = "lang-picker-btn";
  btn.id = `${idPrefix}Btn`;
  btn.setAttribute("aria-haspopup", "listbox");
  btn.setAttribute("aria-expanded", "false");

  const menu = document.createElement("div");
  menu.className = "lang-picker-menu hidden";
  menu.id = `${idPrefix}Menu`;
  menu.setAttribute("role", "listbox");

  const pickerApi = {
    el: wrap,
    close: () => {
      menu.classList.add("hidden");
      btn.setAttribute("aria-expanded", "false");
      wrap.classList.remove("is-open");
      openPickerClosers.delete(pickerApi);
    },
  };

  function paintButton() {
    const langs = getAvailableLanguages();
    const current = langs.find((l) => l.code === getLang()) || langs[0];
    const code = current?.code || "pl";

    if (langBusy) {
      btn.innerHTML = spinnerHtml();
      btn.disabled = true;
      btn.setAttribute("aria-busy", "true");
      btn.setAttribute("aria-label", t("lang.loading"));
      wrap.classList.add("is-loading");
      return;
    }

    btn.disabled = false;
    btn.setAttribute("aria-busy", "false");
    btn.innerHTML = flagImgHtml(code);
    btn.setAttribute("aria-label", `${t("lang.aria")}: ${current?.label || code}`);
    wrap.classList.remove("is-loading");
  }

  function refresh() {
    paintButton();

    const langs = getAvailableLanguages();
    menu.innerHTML = "";
    langs.forEach((lang) => {
      const option = document.createElement("button");
      option.type = "button";
      option.className = "lang-picker-option" + (lang.code === getLang() ? " is-active" : "");
      option.setAttribute("role", "option");
      option.setAttribute("aria-selected", lang.code === getLang() ? "true" : "false");
      option.disabled = langBusy;
      option.innerHTML = `${flagImgHtml(lang.code)}<span>${lang.label}</span>`;
      option.addEventListener("click", (e) => {
        e.stopPropagation();
        if (langBusy) return;
        pickerApi.close();
        if (lang.code !== getLang()) {
          void setLang(lang.code);
        }
      });
      menu.appendChild(option);
    });
  }

  function open() {
    if (langBusy) return;
    openPickerClosers.forEach((p) => {
      if (p !== pickerApi) p.close();
    });
    menu.classList.remove("hidden");
    btn.setAttribute("aria-expanded", "true");
    wrap.classList.add("is-open");
    openPickerClosers.add(pickerApi);
  }

  btn.addEventListener("click", (e) => {
    e.stopPropagation();
    if (langBusy) return;
    if (menu.classList.contains("hidden")) open();
    else pickerApi.close();
  });

  wrap.appendChild(btn);
  wrap.appendChild(menu);
  refresh();

  onLangChange(() => refresh());
  onLangBusyChange(() => {
    if (langBusy) pickerApi.close();
    paintButton();
  });

  return { el: wrap, refresh, close: pickerApi.close };
}