SimpleSubscription.hs

{-# LANGUAGE DeriveGeneric       #-}
{-# LANGUAGE KindSignatures      #-}
{-# LANGUAGE NamedFieldPuns      #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE RankNTypes          #-}
{-# LANGUAGE ScopedTypeVariables #-}

module Subscription.SimpleSubscription where

import           Data.Morpheus.Types       (Event (..), Resolver (..), GQLRootResolver (..))
import           Data.Text                 (Text)
import           GHC.Generics              (Generic)
import           Mythology.Character.Deity (Deity (..))
import           Mythology.Place.Places    (Realm (..))

-- TODO: importGQLDocument "examples/Subscription/api.gql"
--
data Channel
  = ChannelA
  | ChannelB

data Content
  = ContentA Int
  | ContentB Text

type MyEvent = Event Channel Content

newtype Query m = Query
  { deity :: () -> m Deity
  } deriving (Generic)

newtype Mutation m = Mutation
  { createDeity :: () -> m Deity
  } deriving (Generic)

newtype Subscription (m ::  * -> * ) = Subscription
  { newDeity :: () -> m  Deity
  } deriving (Generic)

type APIEvent = Event Channel Content

rootResolver :: GQLRootResolver IO APIEvent Query Mutation Subscription
rootResolver =
  GQLRootResolver
    { queryResolver = Query {deity = const fetchDeity}
    , mutationResolver = Mutation {createDeity}
    , subscriptionResolver = Subscription {newDeity}
    }
  where
    -- TODO: resolver $ dbDeity "" Nothing
    createDeity _args = MutResolver [Event {channels = [ChannelA], content = ContentA 1}]
        (pure Deity {
            fullName = ""
            , power  = Nothing
            , realm = Sky
        })
    newDeity _args = SubResolver [ChannelA] subResolver
      where
        subResolver (Event [ChannelA] (ContentA _value)) = fetchDeity  -- resolve New State
        subResolver (Event [ChannelA] (ContentB _value)) = fetchDeity   -- resolve New State
        subResolver _                                    = fetchDeity -- Resolve Old State
    ---------------------------------------------------------
    fetchDeity = pure Deity {
      fullName = ""
      , power  = Nothing
      , realm = Sky
    }