{-# LANGUAGE NamedFieldPuns, OverloadedStrings #-}

{-|
Module      : AWS.Lambda.Context
Description : AWS Lambda Context classes and related methods.
Copyright   : (c) Nike, Inc., 2018
License     : BSD3
Maintainer  : nathan.fairhurst@nike.com, fernando.freire@nike.com
Stability   : stable
-}

module AWS.Lambda.Context (
  ClientApplication(..),
  ClientContext(..),
  CognitoIdentity(..),
  LambdaContext(..),
  HasLambdaContext(..),
  defConfig,
  getRemainingTime,
  runReaderTLambdaContext
) where

import           Control.Monad.IO.Class (MonadIO, liftIO)
import           Control.Monad.Reader   (ReaderT, runReaderT)
import           Data.Aeson             (FromJSON, ToJSON)
import           Data.Map               (Map)
import           Data.Text              (Text)
import           Data.Time.Clock        (DiffTime, UTCTime,
                                         diffUTCTime, getCurrentTime)
import           Data.Time.Clock.POSIX  (posixSecondsToUTCTime)
import           GHC.Generics           (Generic)
import           System.Envy            (DefConfig (..))

data ClientApplication = ClientApplication
  { appTitle       :: Text,
    appVersionName :: Text,
    appVersionCode :: Text,
    appPackageName :: Text
  } deriving (Show, Generic)

instance ToJSON ClientApplication
instance FromJSON ClientApplication

data ClientContext = ClientContext
  { client      :: ClientApplication,
    custom      :: Map Text Text,
    environment :: Map Text Text
  } deriving (Show, Generic)

instance ToJSON ClientContext
instance FromJSON ClientContext

data CognitoIdentity = CognitoIdentity
  { identityId     :: Text
  , identityPoolId :: Text
  } deriving (Show, Generic)

instance ToJSON CognitoIdentity
instance FromJSON CognitoIdentity

getRemainingTime :: MonadIO m => LambdaContext -> m DiffTime
getRemainingTime LambdaContext { deadline } =
  liftIO $ fmap (realToFrac . diffUTCTime deadline) getCurrentTime

data LambdaContext = LambdaContext
  { functionName       :: Text,
    functionVersion    :: Text,
    functionMemorySize :: Int,
    logGroupName       :: Text,
    logStreamName      :: Text,
    -- The following context values come from headers rather than env vars.
    awsRequestId       :: Text,
    invokedFunctionArn :: Text,
    xRayTraceId        :: Text,
    deadline           :: UTCTime,
    clientContext      :: Maybe ClientContext,
    identity           :: Maybe CognitoIdentity
  } deriving (Show, Generic)

class HasLambdaContext r where
  withContext :: (LambdaContext -> r -> r)

instance HasLambdaContext LambdaContext where
  withContext = const

instance DefConfig LambdaContext where
  defConfig = LambdaContext "" "" 0 "" "" "" "" "" (posixSecondsToUTCTime 0) Nothing Nothing

-- | Helper for using arbitrary monads with only the LambdaContext in its Reader
runReaderTLambdaContext :: ReaderT LambdaContext m a -> m a
runReaderTLambdaContext = flip runReaderT defConfig