{-# LANGUAGE DataKinds            #-}
{-# LANGUAGE ExplicitNamespaces   #-}
{-# LANGUAGE FlexibleContexts     #-}
{-# LANGUAGE FlexibleInstances    #-}
{-# LANGUAGE NoImplicitPrelude    #-}
{-# LANGUAGE OverloadedStrings    #-}
{-# LANGUAGE Rank2Types           #-}
{-# LANGUAGE ScopedTypeVariables  #-}
{-# LANGUAGE TypeOperators        #-}
{-# LANGUAGE TypeSynonymInstances #-}

module RFC.Servant.Server
  ( ApiCtx
  , apiCtxToHandler
  , ResourceDefinition(..)
  , ServerAPI
  , ServerImpl
  , module Servant
  , module Servant.Docs
  , module Servant.HTML.Blaze
  , module Text.Blaze.Html
  , module RFC.Data.IdAnd
  , module RFC.Servant.API
  ) where

import           Control.Monad.Trans.AWS
import           Control.Natural         ( type (~>) )
import           Data.Aeson              as JSON
import           Network.AWS             as AWS
import           Network.Wreq.Session    as Wreq
import           RFC.Data.IdAnd
import           RFC.HTTP.Client
import           RFC.Prelude             hiding ( Handler )
import qualified RFC.Psql                as Psql
import qualified RFC.Redis               as Redis
import           RFC.Servant.API
import           Servant
import           Servant.Docs            hiding ( API )
import           Servant.HTML.Blaze      ( HTML )
import           Servant.Server          ( Handler, runHandler )
import           Text.Blaze.Html

type ApiCtx =
  AWST
    ( ReaderT Wreq.Session
      ( ReaderT Psql.ConnectionPool
        ( ReaderT Redis.ConnectionPool
          Handler
        )
      )
    )

instance MonadUnliftIO Handler where
  withRunInIO iobFactory = liftIO $ iobFactory converter
    where
      converter h = do
        eitherT <- runHandler h
        case eitherT of
          Left err -> throwIO err
          Right a  -> return a
  {-# INLINE withRunInIO #-}

instance HasAPIClient ApiCtx where
  getAPIClient = lift ask
  {-# INLINE getAPIClient #-}

instance (Monad m) => HasAPIClient (ReaderT Wreq.Session m) where
  getAPIClient = ask
  {-# INLINE getAPIClient #-}

instance Redis.HasRedis ApiCtx where
  getRedisPool = lift . lift $ lift ask
  {-# INLINE getRedisPool #-}

apiCtxToHandler :: Wreq.Session -> Redis.ConnectionPool -> Psql.ConnectionPool -> AWS.Env -> ApiCtx ~> Handler
apiCtxToHandler apiClient redisPool psqlPool awsEnv = toHandler
  where
    toHandler :: ApiCtx ~> Handler
    toHandler = withRedis . withPsql . withAPIClient . withAws
      where
        withAPIClient m = runReaderT m apiClient
        withRedis m = runReaderT m redisPool
        withPsql m = runReaderT m psqlPool
        withAws = runAWST awsEnv
{-# INLINE apiCtxToHandler #-}

type FetchAllImpl a = ApiCtx (RefMap a)
type FetchAllAPI a = JGet (RefMap a)
type FetchImpl a = UUID -> ApiCtx (IdAnd a)
type FetchAPI a = Capture "id" UUID :> JGet (IdAnd a)
type CreateImpl a = a -> ApiCtx (IdAnd a)
type CreateAPI a = JReqBody a :> JPost (IdAnd a)
--type PatchImpl a = UUID -> JSON.Patch -> ApiCtx (IdAnd a)
--type PatchAPI a = Capture "id" UUID :> ReqBody '[JSON] JSON.Patch :> Patch '[JSON] (IdAnd a)
type ReplaceImpl a = UUID -> a -> ApiCtx (IdAnd a)
type ReplaceAPI a = Capture "id" UUID :> JReqBody a :> JPost (IdAnd a)
type DeleteImpl = UUID -> ApiCtx ()
type DeleteAPI a = Capture "id" UUID :> JDelete ()

type ServerImpl a =
  (FetchAllImpl a)
  :<|> (FetchImpl a)
  :<|> (CreateImpl a)
  -- :<|> (PatchImpl a)
  :<|> (ReplaceImpl a)
  :<|> DeleteImpl
type ServerAPI a =
  (FetchAllAPI a)
  :<|> (FetchAPI a)
  :<|> (CreateAPI a)
  -- :<|> (PatchAPI a)
  :<|> (ReplaceAPI a)
  :<|> (DeleteAPI a)


class (FromJSON a, ToJSON a, Show a) => ResourceDefinition a where


  -- | Provide all UUID of all the children of this resource.
  --   The graph of all resources to children should form a directed acyclic graph.
  resourceChildIds :: IdAnd (Proxy a) -> ApiCtx [UUID]

  -- | Update the child id for the parent at the first 'UUID' argument from the second 'UUID' argument to the third 'UUID' argument.
  resourceUpdateChildId :: IdAnd (Proxy a) -> UUID -> UUID -> ApiCtx ()

  restFetchAll :: FetchAllImpl a
  restFetchAll = idAndsToMap <$> fetchAllResources
  {-# INLINE restFetchAll #-}

  restFetch :: FetchImpl a
  restFetch uuid = do
    maybeResource <- fetchResource uuid
    case maybeResource of
      Nothing -> throwError $ err404
        { errReasonPhrase = "No resource found for id"
        , errBody = toUTF8 $ "Could not find a resource with UUID: " <> show uuid
        }
      Just value -> return $ tupleToIdAnd (uuid, value)
  {-# INLINE restFetch #-}

  restCreate :: CreateImpl a
  restCreate a = do
      maybeId <- createResource a
      case maybeId of
        (Just id) -> restFetch id
        Nothing -> throwIO $ err400
          { errReasonPhrase = "Could not create resource"
          , errBody = toUTF8 $ show a
          }
  {-# INLINE restCreate #-}

{-
  restPatch :: PatchImpl a
  restPatch id patch = do
    (IdAnd (_,original::a)) <- restFetch id
    case JSON.patch patch $ toJSON original of
      Error str -> throwError $ err400
        { errReasonPhrase = "Error applying patch"
        , errBody = toUTF8 str
        }
      Success jsonValue ->
        case JSON.eitherDecode' $ JSON.encode jsonValue of
          Left err -> throwError $ err400
            { errReasonPhrase = "Error rebuilding object after patch"
            , errBody = toUTF8 err
            }
          Right value -> restReplace id value
  {-# INLINE restPatch #-}
-}

  restReplace :: ReplaceImpl a
  restReplace id value = do
      replaceResource newValue
      restFetch id
    where
      newValue = tupleToIdAnd (id,value)
  {-# INLINE restReplace #-}

  restDelete :: Proxy a -> DeleteImpl
  restDelete = deleteResource

  restServer :: ServerImpl a
  restServer =
    restFetchAll
    :<|> restFetch
    :<|> restCreate
    -- :<|> restPatch
    :<|> restReplace
    :<|> (restDelete (Proxy::Proxy a))

  fetchResource :: UUID -> ApiCtx (Maybe a)
  fetchAllResources :: ApiCtx [IdAnd a]
  createResource :: a -> ApiCtx (Maybe UUID)
  replaceResource :: (IdAnd a) -> ApiCtx ()
  deleteResource :: Proxy a -> UUID -> ApiCtx ()