{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Test.StarWars.Schema
    ( schema
    ) where

import Control.Monad.Trans.Reader (asks)
import Control.Monad.Trans.Except (throwE)
import Control.Monad.Trans.Class (lift)
import Data.Functor.Identity (Identity)
import qualified Data.HashMap.Strict as HashMap
import Data.Maybe (catMaybes)
import Data.Text (Text)
import Language.GraphQL.Type
import qualified Language.GraphQL.Type.In as In
import qualified Language.GraphQL.Type.Out as Out
import Test.StarWars.Data
import Prelude hiding (id)

-- See https://github.com/graphql/graphql-js/blob/master/src/__tests__/starWarsSchema.js

schema :: Schema Identity
schema = Schema { query = queryType, mutation = Nothing }
  where
    queryType = Out.ObjectType "Query" Nothing [] $ HashMap.fromList
        [ ("hero", heroFieldResolver)
        , ("human", humanFieldResolver)
        , ("droid", droidFieldResolver)
        ]
    heroField = Out.Field Nothing (Out.NamedObjectType heroObject)
        $ HashMap.singleton "episode"
        $ In.Argument Nothing (In.NamedEnumType episodeEnum) Nothing
    heroFieldResolver = ValueResolver heroField hero
    humanField = Out.Field Nothing (Out.NamedObjectType heroObject)
        $ HashMap.singleton "id"
        $ In.Argument Nothing (In.NonNullScalarType string) Nothing
    humanFieldResolver = ValueResolver humanField human
    droidField = Out.Field Nothing (Out.NamedObjectType droidObject) mempty
    droidFieldResolver = ValueResolver droidField droid

heroObject :: Out.ObjectType Identity
heroObject = Out.ObjectType "Human" Nothing [] $ HashMap.fromList
    [ ("id", idFieldType)
    , ("name", nameFieldType)
    , ("friends", friendsFieldType)
    , ("appearsIn", appearsInField)
    , ("homePlanet", homePlanetFieldType)
    , ("secretBackstory", secretBackstoryFieldType)
    , ("__typename", typenameFieldType)
    ]
  where
    homePlanetFieldType
      = ValueResolver (Out.Field Nothing (Out.NamedScalarType string) mempty)
      $ idField "homePlanet"

droidObject :: Out.ObjectType Identity
droidObject = Out.ObjectType "Droid" Nothing [] $ HashMap.fromList
    [ ("id", idFieldType)
    , ("name", nameFieldType)
    , ("friends", friendsFieldType)
    , ("appearsIn", appearsInField)
    , ("primaryFunction", primaryFunctionFieldType)
    , ("secretBackstory", secretBackstoryFieldType)
    , ("__typename", typenameFieldType)
    ]
  where
    primaryFunctionFieldType
        = ValueResolver (Out.Field Nothing (Out.NamedScalarType string) mempty)
        $ idField "primaryFunction"

typenameFieldType :: Resolver Identity
typenameFieldType
    = ValueResolver (Out.Field Nothing (Out.NamedScalarType string) mempty)
    $ idField "__typename"

idFieldType :: Resolver Identity
idFieldType
    = ValueResolver (Out.Field Nothing (Out.NamedScalarType id) mempty)
    $ idField "id"

nameFieldType :: Resolver  Identity
nameFieldType
    = ValueResolver (Out.Field Nothing (Out.NamedScalarType string) mempty)
    $ idField "name"

friendsFieldType :: Resolver Identity
friendsFieldType
    = ValueResolver (Out.Field Nothing fieldType mempty)
    $ idField "friends"
  where
    fieldType = Out.ListType $ Out.NamedObjectType droidObject

appearsInField :: Resolver Identity
appearsInField
    = ValueResolver (Out.Field (Just description) fieldType mempty)
    $ idField "appearsIn"
  where
    fieldType = Out.ListType $ Out.NamedEnumType episodeEnum
    description = "Which movies they appear in."

secretBackstoryFieldType :: Resolver Identity
secretBackstoryFieldType = ValueResolver field secretBackstory
  where
    field = Out.Field Nothing (Out.NamedScalarType string) mempty

idField :: Text -> Resolve Identity
idField f = do
    v <- lift $ asks values
    let (Object v') = v
    pure $ v' HashMap.! f

episodeEnum :: EnumType
episodeEnum = EnumType "Episode" (Just description)
    $ HashMap.fromList [newHope, empire, jedi]
  where
    description = "One of the films in the Star Wars Trilogy"
    newHope = ("NEW_HOPE", EnumValue $ Just "Released in 1977.")
    empire = ("EMPIRE", EnumValue $ Just "Released in 1980.")
    jedi = ("JEDI", EnumValue $ Just "Released in 1983.")

hero :: Resolve Identity
hero = do
  episode <- argument "episode"
  pure $ character $ case episode of
      Enum "NEW_HOPE" -> getHero 4
      Enum "EMPIRE" -> getHero 5
      Enum "JEDI" -> getHero 6
      _ -> artoo

human :: Resolve Identity
human = do
    id' <- argument "id"
    case id' of
        String i -> pure $ maybe Null character $ getHuman i >>= Just
        _ -> throwE "Invalid arguments."

droid :: Resolve Identity
droid = do
    id' <- argument "id"
    case id' of
        String i -> pure $ maybe Null character $ getDroid i >>= Just
        _ -> throwE "Invalid arguments."

character :: Character -> Value
character char = Object $ HashMap.fromList
    [ ("id", String $ id_ char)
    , ("name", String $ name_ char)
    , ("friends", List $ character <$> getFriends char)
    , ("appearsIn", List $ Enum <$> catMaybes (getEpisode <$> appearsIn char))
    , ("homePlanet", String $ either mempty homePlanet char)
    , ("__typename", String $ typeName char)
    ]