-- | Headers for mail messages and HTTP requests/responses
module MessageHeaders(module MessageHeaders,module HeaderName) where
import Data.Char(isSpace)
import Utils2(apFst)
import HeaderName

type Headers = [Header]
type Header  = (HeaderName,String)

header name value = (name,value)::Header

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--lookupHeader headers = getheader headers . headerName

getheader headers h =
  dropWhile isSpace (maybe  "" id $ lookup h (headers::Headers))

renameHdr from to' = map (apFst (\h -> if h==from then to' else h))
             -- to is a keyword

-- | Replace existing header or add a new one.
updateHdr (h,r) [] = [(h,r)]
updateHdr (h,r) ((h',r'):hdrs) =
	if h==h'
	then (h',r):hdrs
	else (h',r'):updateHdr (h,r) hdrs

-- | Modify all existing headers with the given 'HeaderName'.
modHdr h f =
  let modhdr (h',r) = (h',if h'==(h::HeaderName) then f r else r)
  in map modhdr
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