export type AppLocale = 'ru' | 'en'
export type AppCurrency = 'USD' | 'RUB' | 'CNY' | 'EUR' | 'AED'

export type CurrencyRatesResponse = {
  baseCurrency: 'USD'
  rates: Record<AppCurrency, number>
  updatedAt: string
  nextUpdateAt: string
  provider: string
  documentation: string
  termsOfUse: string
  attributionUrl: string
}

export type LocaleOption = {
  code: AppLocale
  label: string
  nativeLabel: string
}

export type CurrencyOption = {
  code: AppCurrency
  label: string
  symbol: string
}

type TranslationKey =
  | 'settings.language'
  | 'settings.currency'
  | 'settings.open'
  | 'settings.apply'
  | 'settings.ratesProvider'
  | 'settings.ratesBy'

const LOCALE_MAP: Record<AppLocale, string> = {
  ru: 'ru-RU',
  en: 'en-US',
}

const CURRENCY_SYMBOLS: Record<AppCurrency, string> = {
  USD: '$',
  RUB: '₽',
  CNY: '¥',
  EUR: '€',
  AED: 'د.إ',
}

const LOCALES: AppLocale[] = ['ru', 'en']
const CURRENCIES: AppCurrency[] = ['USD', 'RUB', 'CNY', 'EUR', 'AED']

const localeCodes = new Set<AppLocale>(LOCALES)
const currencyCodes = new Set<AppCurrency>(CURRENCIES)

function normalizeLocale(value: unknown): AppLocale {
  return localeCodes.has(value as AppLocale) ? value as AppLocale : 'ru'
}

function assertCurrency(value: unknown): AppCurrency {
  const normalized = String(value || '').trim().toUpperCase()

  if (!currencyCodes.has(normalized as AppCurrency)) {
    throw createError({
      statusCode: 500,
      statusMessage: `Unsupported currency: ${normalized || 'empty'}`,
    })
  }

  return normalized as AppCurrency
}

function normalizeCurrency(value: unknown): AppCurrency {
  const normalized = String(value || '').trim().toUpperCase()
  return currencyCodes.has(normalized as AppCurrency) ? normalized as AppCurrency : 'USD'
}

export function useLocaleCurrency() {
  const { locale: i18nLocale, setLocale: setI18nLocale, t: i18nT } = useI18n()
  const currencyCookie = useCookie<AppCurrency>('ex_currency', {
    default: () => 'USD',
    sameSite: 'lax',
    path: '/',
  })
  const currencyRates = useState<CurrencyRatesResponse | null>('currency-rates', () => null)

  const locale = computed<AppLocale>({
    get: () => normalizeLocale(i18nLocale.value),
    set: (value) => {
      i18nLocale.value = normalizeLocale(value)
    },
  })

  const currency = computed<AppCurrency>({
    get: () => normalizeCurrency(currencyCookie.value),
    set: (value) => {
      currencyCookie.value = normalizeCurrency(value)
    },
  })

  const intlLocale = computed(() => LOCALE_MAP[locale.value])
  const localeOptions = computed<LocaleOption[]>(() => LOCALES.map(code => ({
    code,
    label: i18nT(`settings.locales.${code}.label`),
    nativeLabel: i18nT(`settings.locales.${code}.nativeLabel`),
  })))
  const currencyOptions = computed<CurrencyOption[]>(() => CURRENCIES.map(code => ({
    code,
    label: i18nT(`settings.currencies.${code}`),
    symbol: CURRENCY_SYMBOLS[code],
  })))
  const languageCode = computed(() => locale.value.toUpperCase())
  const currencyCode = computed(() => currency.value)
  const ratesProviderUrl = computed(() => currencyRates.value?.attributionUrl || 'https://www.exchangerate-api.com')

  async function setLocale(value: AppLocale) {
    const normalizedLocale = normalizeLocale(value)
    locale.value = normalizedLocale
    await setI18nLocale(normalizedLocale)
  }

  function setCurrency(value: AppCurrency) {
    currency.value = value
  }

  function t(key: TranslationKey) {
    return i18nT(key)
  }

  function getRates() {
    if (!currencyRates.value) {
      throw createError({
        statusCode: 500,
        statusMessage: 'Currency rates are not loaded',
      })
    }

    return currencyRates.value.rates
  }

  function convertMoney(value: number, sourceCurrency: AppCurrency = 'USD', targetCurrency: AppCurrency = currency.value) {
    const rates = getRates()
    const amountInUsd = value / rates[sourceCurrency]
    return amountInUsd * rates[targetCurrency]
  }

  function formatMoney(value: number, sourceCurrency: string = 'USD') {
    const normalizedSourceCurrency = assertCurrency(sourceCurrency)
    const convertedValue = convertMoney(value, normalizedSourceCurrency, currency.value)

    return new Intl.NumberFormat(intlLocale.value, {
      style: 'currency',
      currency: currency.value,
      maximumFractionDigits: currency.value === 'RUB' ? 0 : 0,
    }).format(convertedValue)
  }

  function formatDate(value: Date | string, options: Intl.DateTimeFormatOptions = {}) {
    const date = value instanceof Date ? value : new Date(value)
    return new Intl.DateTimeFormat(intlLocale.value, options).format(date)
  }

  function formatDateTime(value: Date | string) {
    return formatDate(value, {
      day: '2-digit',
      month: 'short',
      hour: '2-digit',
      minute: '2-digit',
    })
  }

  return {
    locale,
    currency,
    intlLocale,
    localeOptions,
    currencyOptions,
    languageCode,
    currencyCode,
    setLocale,
    setCurrency,
    convertMoney,
    formatMoney,
    formatDate,
    formatDateTime,
    currencyRates,
    ratesProviderUrl,
    t,
  }
}