export const LOCALES = [
  "en",
  "zh",
  "zht",
  "ko",
  "de",
  "es",
  "fr",
  "it",
  "da",
  "ja",
  "pl",
  "ru",
  "ar",
  "no",
  "br",
  "th",
  "tr",
] as const

export type Locale = (typeof LOCALES)[number]

export const LOCALE_COOKIE = "oc_locale" as const
export const LOCALE_HEADER = "x-opencode-locale" as const

function fix(pathname: string) {
  if (pathname.startsWith("/")) return pathname
  return `/${pathname}`
}

const LABEL = {
  en: "English",
  zh: "简体中文",
  zht: "繁體中文",
  ko: "한국어",
  de: "Deutsch",
  es: "Español",
  fr: "Français",
  it: "Italiano",
  da: "Dansk",
  ja: "日本語",
  pl: "Polski",
  ru: "Русский",
  ar: "العربية",
  no: "Norsk",
  br: "Português (Brasil)",
  th: "ไทย",
  tr: "Türkçe",
} satisfies Record<Locale, string>

const TAG = {
  en: "en",
  zh: "zh-Hans",
  zht: "zh-Hant",
  ko: "ko",
  de: "de",
  es: "es",
  fr: "fr",
  it: "it",
  da: "da",
  ja: "ja",
  pl: "pl",
  ru: "ru",
  ar: "ar",
  no: "no",
  br: "pt-BR",
  th: "th",
  tr: "tr",
} satisfies Record<Locale, string>

export function parseLocale(value: unknown): Locale | null {
  if (typeof value !== "string") return null
  if ((LOCALES as readonly string[]).includes(value)) return value as Locale
  return null
}

export function fromPathname(pathname: string) {
  return parseLocale(fix(pathname).split("/")[1])
}

export function strip(pathname: string) {
  const locale = fromPathname(pathname)
  if (!locale) return fix(pathname)

  const next = fix(pathname).slice(locale.length + 1)
  if (!next) return "/"
  if (next.startsWith("/")) return next
  return `/${next}`
}

export function route(locale: Locale, pathname: string) {
  const next = strip(pathname)
  if (next.startsWith("/docs")) return next
  if (next.startsWith("/auth")) return next
  if (next.startsWith("/workspace")) return next
  if (locale === "en") return next
  if (next === "/") return `/${locale}`
  return `/${locale}${next}`
}

export function label(locale: Locale) {
  return LABEL[locale]
}

export function tag(locale: Locale) {
  return TAG[locale]
}

export function dir(locale: Locale) {
  if (locale === "ar") return "rtl"
  return "ltr"
}

function match(input: string): Locale | null {
  const value = input.trim().toLowerCase()
  if (!value) return null

  if (value.startsWith("zh")) {
    if (value.includes("hant") || value.includes("-tw") || value.includes("-hk") || value.includes("-mo")) return "zht"
    return "zh"
  }

  if (value.startsWith("ko")) return "ko"
  if (value.startsWith("de")) return "de"
  if (value.startsWith("es")) return "es"
  if (value.startsWith("fr")) return "fr"
  if (value.startsWith("it")) return "it"
  if (value.startsWith("da")) return "da"
  if (value.startsWith("ja")) return "ja"
  if (value.startsWith("pl")) return "pl"
  if (value.startsWith("ru")) return "ru"
  if (value.startsWith("ar")) return "ar"
  if (value.startsWith("tr")) return "tr"
  if (value.startsWith("th")) return "th"
  if (value.startsWith("pt")) return "br"
  if (value.startsWith("no") || value.startsWith("nb") || value.startsWith("nn")) return "no"
  if (value.startsWith("en")) return "en"
  return null
}

export function detectFromLanguages(languages: readonly string[]) {
  for (const language of languages) {
    const locale = match(language)
    if (locale) return locale
  }
  return "en" satisfies Locale
}

export function detectFromAcceptLanguage(header: string | null) {
  if (!header) return "en" satisfies Locale

  const items = header
    .split(",")
    .map((raw) => raw.trim())
    .filter(Boolean)
    .map((raw) => {
      const parts = raw.split(";").map((x) => x.trim())
      const lang = parts[0] ?? ""
      const q = parts
        .slice(1)
        .find((x) => x.startsWith("q="))
        ?.slice(2)
      return {
        lang,
        q: q ? Number.parseFloat(q) : 1,
      }
    })
    .sort((a, b) => b.q - a.q)

  for (const item of items) {
    if (!item.lang || item.lang === "*") continue
    const locale = match(item.lang)
    if (locale) return locale
  }

  return "en" satisfies Locale
}

export function localeFromCookieHeader(header: string | null) {
  if (!header) return null

  const raw = header
    .split(";")
    .map((x) => x.trim())
    .find((x) => x.startsWith(`${LOCALE_COOKIE}=`))
    ?.slice(`${LOCALE_COOKIE}=`.length)

  if (!raw) return null
  return parseLocale(decodeURIComponent(raw))
}

export function localeFromRequest(request: Request) {
  const fromHeader = parseLocale(request.headers.get(LOCALE_HEADER))
  if (fromHeader) return fromHeader

  const fromPath = fromPathname(new URL(request.url).pathname)
  if (fromPath) return fromPath

  return (
    localeFromCookieHeader(request.headers.get("cookie")) ??
    detectFromAcceptLanguage(request.headers.get("accept-language"))
  )
}

export function cookie(locale: Locale) {
  return `${LOCALE_COOKIE}=${encodeURIComponent(locale)}; Path=/; Max-Age=31536000; SameSite=Lax`
}

export function clearCookie() {
  return `${LOCALE_COOKIE}=; Path=/; Max-Age=0; SameSite=Lax`
}