module Yesod.Session.Persist.Yesod
  ( -- * Concretely
    makeSessionBackend
  , SessionConfiguration (..)

    -- * More general
  , makeSessionBackend'
  , SessionConfiguration' (..)

    -- * Extra general
  , makeSessionBackend''

    -- * Reëxport
  , SessionBackend
  ) where

import Internal.Prelude

import Data.Text.Encoding (encodeUtf8)
import Session.Key
import Yesod.Core.Types (SessionBackend (..))
import Yesod.Session.Cookie.Logic
import Yesod.Session.Cookie.Reading
import Yesod.Session.Manager
import Yesod.Session.Manager.Load
import Yesod.Session.Manager.Save
import Yesod.Session.Options
import Yesod.Session.Persist.Storage
import Yesod.Session.Storage.Operation

data SessionConfiguration persistentBackend persistentRecord = SessionConfiguration
  { persistence :: SessionPersistence persistentBackend persistentRecord IO
  -- ^ Mapping between 'Yesod.Session.Persist.Session' and your Persistent entity
  , options :: Options (ReaderT persistentBackend IO) IO
  -- ^ Various options that have defaults; see 'defaultOptions'
  }

-- | Use this to implement 'Yesod.Core.makeSessionBackend'.
--
-- The @session@ type parameter represents the Persistent entity
-- you're using to store sessions
-- (see the 'SessionPersistence' field of the configuration).
makeSessionBackend
  :: forall persistentBackend persistentRecord
   . SessionConfiguration persistentBackend persistentRecord
  -> IO SessionBackend
makeSessionBackend configuration =
  let SessionConfiguration {persistence, options} = configuration
  in  case persistence of
        SessionPersistence {runTransaction} ->
          makeSessionBackend'
            SessionConfiguration'
              { storage = persistentStorage persistence
              , options = options
              , runTransaction
              }

data SessionConfiguration' session = forall tx.
  Monad tx =>
  SessionConfiguration'
  { storage :: forall a. StorageOperation a -> tx a
  , options :: Options tx IO
  , runTransaction :: forall a. tx a -> IO a
  }

makeSessionBackend' :: SessionConfiguration' session -> IO SessionBackend
makeSessionBackend' SessionConfiguration' {options = options :: Options tx m, ..} = do
  keyManager :: SessionKeyManager tx <-
    makeSessionKeyManager <$> options.randomization
  let sessionManager = SessionManager {keyManager, storage, options, runTransaction}
  pure $ makeSessionBackend'' sessionManager

makeSessionBackend'' :: Monad tx => SessionManager tx IO -> SessionBackend
makeSessionBackend'' sessionManager@SessionManager {options} =
  SessionBackend
    { sbLoadSession = \req -> do
        let
          cookie = findSessionKey (encodeUtf8 options.cookieName) req
          sessionKeyMaybe = cookie >>= checkedSessionKeyFromCookieValue sessionManager

        load <- loadSessionMaybe sessionManager sessionKeyMaybe

        pure
          ( loadedData load
          , \newData -> do
              save <- saveSession sessionManager load newData
              pure $ setCookie options CookieContext {cookie, load = load.got, save}
          )
    }