{-# LANGUAGE DeriveGeneric #-}

{-# LANGUAGE OverloadedStrings #-}

module PGIP.GraphQL (isGraphQL, processGraphQL) where

import PGIP.GraphQL.Resolver

import PGIP.Shared

import Driver.Options

import Data.Aeson as Aeson

import qualified Data.ByteString.Lazy as LBS

import qualified Data.Text.Lazy.Encoding as LEncoding

import Data.Maybe

import Data.Map (Map)

import qualified Data.Map as Map

import qualified Data.Text.Lazy as LText

import Data.Text as Text

import Network.Wai

import GHC.Generics

isGraphQL :: String -> [String] -> Bool

isGraphQL httpVerb pathComponents =

httpVerb == "POST" && pathComponents == ["graphql"]

processGraphQL :: HetcatsOpts -> Cache -> Request -> IO String

processGraphQL opts sessionReference request = do

body <- receivedRequestBody request

let bodyQueryE = Aeson.eitherDecode $ LBS.fromStrict body :: Either String QueryBodyAux

queryBody <- case bodyQueryE of

Left message -> fail ("bad request body: " ++ message)

Right b -> return $ toGraphQLQueryBody b

resolve opts sessionReference (graphQLQuery queryBody) (graphQLVariables queryBody)

-- This structure contains the data that is passed to the GraphQL API

data QueryBody = QueryBody { graphQLQuery :: Text

, graphQLVariables :: Map Text Text

} deriving (Show, Generic)

-- This is an auxiliary strucutre that helps to parse the request body.

-- It is then converted to QueryBody.

data QueryBodyAux = QueryBodyAux { query :: Text

, variables :: Maybe (Map Text Aeson.Value)

} deriving (Show, Generic)

instance FromJSON QueryBodyAux

-- For an unknown reason, GraphQL-API requires the query to be enclosed in {}

toGraphQLQueryBody :: QueryBodyAux -> QueryBody

toGraphQLQueryBody QueryBodyAux { query = q, variables = aesonVariables } =

QueryBody { graphQLQuery = q

, graphQLVariables = Map.map convert $

fromMaybe Map.empty aesonVariables

}

where

convert = LText.toStrict . LEncoding.decodeUtf8 . Aeson.encode