symantic-http-demo/API.hs

   1 {-# LANGUAGE DataKinds #-}
   2 {-# LANGUAGE MultiParamTypeClasses #-}
   3 {-# LANGUAGE NoMonomorphismRestriction #-}
   4 {-# LANGUAGE OverloadedStrings #-}
   5 {-# LANGUAGE TypeApplications #-}
   6 {-# LANGUAGE TypeFamilies #-}
   7 {-# OPTIONS_GHC -fno-warn-orphans #-}
   8 {-# OPTIONS_GHC -Wno-missing-signatures #-}
   9 module API where
  10 import Text.Read (readMaybe)
  11 import qualified Pipes as P
  12 import qualified Data.Text.Lazy as TL
  13 import qualified Data.Text.Lazy.Encoding as TL
  14
  15 import Symantic.HTTP
  16
  17 -- | Define the API, common to the client and server.
  18 -- Either use @NoMonomorphismRestriction@ like here,
  19 -- or add an argument to 'api',
  20 -- to let the compiler infer its (complex) type.
  21 -- Read the executables of the client and of the server
  22 -- to see how to derive code from this 'api'.
  23 api =
  24  "succ" </> capture @Integer "n"
  25         <.> get @Integer @'[PlainText]
  26
  27   <!>
  28   "countdown" </> capture @Integer "n"
  29               <.> getStream @(P.Producer Integer IO ())
  30                             @'[PlainText]
  31                             @NewlineFraming
  32
  33 instance MimeEncodable Integer PlainText where
  34   mimeEncode _ = TL.encodeUtf8 . TL.pack . show
  35 instance MimeDecodable Integer PlainText where
  36   mimeDecode _mt bs =
  37     let s = TL.unpack $ TL.decodeUtf8 bs in
  38     case readMaybe s of
  39      Nothing -> Left $ "cannot parse as Integer: "<>s
  40      Just n -> Right n