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-- | Internal module for retrieving languages to localize to.
module Network.URI.Locale(rfc2616Locale) where
import System.Environment (lookupEnv)
import Control.Monad (forM)
import Data.Maybe (mapMaybe)
import Data.Char (toLower)
--- This file is based on logic in GNOME's LibSoup & GLib.
-- | Returns the languages to which responses should be localized.
-- Retrieved from Gettext configuration & reformatted for use in the
-- HTTP Accept-Language request header.
rfc2616Locale :: IO ([String], [String])
rfc2616Locale = do
locales <- forM ["LANGUAGE", "LC_ALL", "LC_MESSAGES", "LANG"] lookupEnv
let posix = split ":" $ firstJust locales "en_US"
let ietf = mapMaybe toRFC2616Lang posix
return (explode ietf, explode posix)
toRFC2616Lang "C" = Nothing
toRFC2616Lang ('C':'.':_) = Nothing
toRFC2616Lang ('C':'@':_) = Nothing
toRFC2616Lang lang = case toRFC2616Lang' lang of
"" -> Nothing
lang' -> Just lang'
toRFC2616Lang' ('_':cs) = '-' : toRFC2616Lang' cs
toRFC2616Lang' ('.':_) = []
toRFC2616Lang' ('@':_) = []
toRFC2616Lang' (c:cs) = toLower c : toRFC2616Lang' cs
toRFC2616Lang' [] = []
-- Makes sure to include the raw languages, and not just localized variants.
extractLangs (locale:locales) | (lang:_) <- split "-_.@" locale = lang : extractLangs locales
extractLangs (_:locales) = extractLangs locales
extractLangs [] = []
explode locales = locales ++ [l | l <- extractLangs locales, l `notElem` locales]
firstJust (Just a:_) _ | a /= "" = a
firstJust (_:maybes) fallback = firstJust maybes fallback
firstJust [] fallback = fallback
split b (a:as) | a `elem` b = [] : split b as
| (head':tail') <- split b as = (a:head') : tail'
| otherwise = [a:as]
split _ [] = [[]]