globalThis.Wegwichtel ??= {};
(function (ns) {
  'use strict';

  class WegwichtelI18n {
    static #languages = new Map(ns.TextCatalogs);
    static #fallbackLanguage = this.#languages.keys().next().value;
    static #language = this.#fallbackLanguage;

    static get language() { return this.#language; }

    static detectLanguage(preferences = globalThis.navigator?.languages ?? [globalThis.navigator?.language]) {
      for (const language of preferences) {
        const requested = String(language ?? '').toLowerCase();
        if (this.#languages.has(requested)) return requested;
        const base = requested.split('-')[0];
        if (this.#languages.has(base)) return base;
      }
      return this.#fallbackLanguage;
    }

    static register(language, messages) {
      this.#languages.set(language.toLowerCase(), Object.freeze({ ...messages }));
    }

    static setLanguage(language, root = globalThis.document) {
      const requested = String(language).toLowerCase();
      const base = requested.split('-')[0];
      this.#language = this.#fallbackLanguage;
      if (this.#languages.has(base)) this.#language = base;
      if (this.#languages.has(requested)) this.#language = requested;
      this.apply(root);
      return this.#language;
    }

    static t(key, variables = {}) {
      let value = this.#lookup(this.#languages.get(this.#language), key)
        ?? this.#lookup(this.#languages.get(this.#fallbackLanguage), key);
      if (value == null) throw new RangeError(`Missing translation: ${key}`);
      if (typeof value === 'object') {
        const plural = new Intl.PluralRules(this.#language).select(Number(variables.count));
        value = value[plural] ?? value.other;
      }
      return value.replaceAll(/\{(\w+)\}/g, (placeholder, name) => {
        if (!Object.hasOwn(variables, name)) return placeholder;
        return String(variables[name] ?? '');
      });
    }

    static #lookup(catalog, key) {
      if (Object.hasOwn(catalog, key)) return catalog[key];
      let value = catalog;
      for (const part of key.split('.')) {
        if (!value || !Object.hasOwn(value, part)) return undefined;
        value = value[part];
      }
      return value;
    }

    static apply(root = globalThis.document) {
      if (!root?.querySelectorAll) return;
      if (root.documentElement) root.documentElement.lang = this.#language;
      for (const element of root.querySelectorAll('[data-i18n]')) {
        if (element.dataset?.i18n) element.textContent = this.t(element.dataset.i18n);
      }
      for (const [attribute, key] of [['title', 'i18nTitle'], ['aria-label', 'i18nAriaLabel'], ['placeholder', 'i18nPlaceholder'], ['alt', 'i18nAlt']]) {
        for (const element of root.querySelectorAll(`[data-i18n-${attribute}]`)) {
          if (element.dataset?.[key] && typeof element.setAttribute === 'function') element.setAttribute(attribute, this.t(element.dataset[key]));
        }
      }
    }
  }

  ns.I18n = WegwichtelI18n;
  WegwichtelI18n.setLanguage(WegwichtelI18n.detectLanguage());
}(globalThis.Wegwichtel));