Morpheus GraphQL Client

Morpheus GraphQL Client with Template haskell QuasiQuotes

defineByDocumentFile
    "./schema.gql"
  [gql|
    query GetHero ($character: Character)
      {
        deity (fatherOf:$character) {
          name
          power
          worships {
            deity2Name: name
          }
        }
      }
  |]

with schema:

input Character {
  name: String!
}

type Deity {
  name: String!
  worships: Deity
  power: Power!
}

enum Power {
  Lightning
  Teleportation
  Omniscience
}

will validate query and Generate:

• namespaced response and variable types
• instance for Fetch typeClass

data GetHero = GetHero {
  deity: DeityDeity
}

-- from: {user
data DeityDeity = DeityDeity {
  name: Text,
  worships: Maybe DeityWorshipsDeity
  power: Power
}

-- from: {deity{worships
data DeityWorshipsDeity = DeityWorshipsDeity {
  name: Text,
}

data Power =
    PowerLightning
  | PowerTeleportation
  | PowerOmniscience

data GetHeroArgs = GetHeroArgs {
  character: Character
}

data Character = Character {
  name: Person
}

as you see, response type field name collision can be handled with GraphQL alias.

with fetch you can fetch well typed response GetHero.

  fetchHero :: Args GetHero -> m (Either String GetHero)
  fetchHero = fetch jsonRes args
      where
        args = GetHeroArgs {character = Person {name = "Zeus"}}
        jsonRes :: ByteString -> m ByteString
        jsonRes = <GraphQL APi>

in this case, jsonRes resolves a request into a response in some monad m.

A fetch resolver implementation against a real API may look like the following:

{-# LANGUAGE OverloadedStrings #-}

import Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString.Char8 as C8
import Network.HTTP.Req

resolver :: String -> ByteString -> IO ByteString
resolver tok b = runReq defaultHttpConfig $ do
    let headers = header "Content-Type" "application/json"
    responseBody <$> req POST (https "swapi.graph.cool") (ReqBodyLbs b) lbsResponse headers

this is demonstrated in examples/src/Client/StarWarsClient.hs

types can be generated from introspection too:

defineByIntrospectionFile "./introspection.json"