module HeaderName(HeaderName{-,headerName-},hn,orig,normal) where
import Utils2(strToLower,mapR)

-- | Header names for mail and HTTP, preserve original capitalization for
-- printing but use case insensitive comparisons.
data HeaderName = Name {orig  ::String, -- ^ original capitalization
                        normal::String  -- ^ normalized capitalization
                        }
-- Invariant: n::Headername ==> normal n==strToLower (orig n)

headerName orig = Name orig (strToLower orig)
hn = headerName

instance Eq HeaderName where n1==n2 = normal n1==normal n2
instance Ord HeaderName where compare n1 n2 = compare (normal n1) (normal n2)
instance Show HeaderName where showsPrec d = showsPrec d . orig
instance Read HeaderName where readsPrec d = mapR headerName . readsPrec d