Header.hs

module Freckle.App.Http.Header
  ( HasHeaders (..)
  , getHeaderCsv
  , lookupHeader

    -- * Utilities
  , splitHeader
  ) where

import Prelude

import Data.ByteString (ByteString)
import Data.ByteString.Char8 qualified as BS8
import Data.Char (isSpace)
import Data.Maybe (listToMaybe)
import Network.HTTP.Client (Request, Response, requestHeaders, responseHeaders)
import Network.HTTP.Simple (getRequestHeader, getResponseHeader)
import Network.HTTP.Types.Header (Header, HeaderName)

class HasHeaders a where
  getHeaders :: a -> [Header]

  getHeader :: HeaderName -> a -> [ByteString]
  getHeader h = map snd . filter ((== h) . fst) . getHeaders

instance HasHeaders [Header] where
  getHeaders = id

instance HasHeaders Request where
  getHeaders = requestHeaders
  getHeader = getRequestHeader

instance HasHeaders (Response body) where
  getHeaders = responseHeaders
  getHeader = getResponseHeader

getHeaderCsv :: HasHeaders a => HeaderName -> a -> [ByteString]
getHeaderCsv hn = concatMap splitHeader . getHeader hn

splitHeader :: ByteString -> [ByteString]
splitHeader = map trimSpace . BS8.split ','

trimSpace :: ByteString -> ByteString
trimSpace = BS8.dropWhile isSpace . BS8.dropWhileEnd isSpace

lookupHeader :: HasHeaders a => HeaderName -> a -> Maybe ByteString
lookupHeader h = listToMaybe . getHeader h