Calendar.hs

{-# LANGUAGE MultiParamTypeClasses  #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE FlexibleInstances #-}
module Grocery.Database.Calendar where

import Grocery.DatabaseSchema
import Grocery.Types.Meal
import Database.Persist
import Database.Persist.Sqlite
import qualified Database.Esqueleto      as E
import           Database.Esqueleto      ((^.))
import Data.Time
import Control.Monad.Trans -- for MonadIO
import Data.List

getMeals :: (MonadIO m) => DbUserId -> SqlPersistT m [Meal]
getMeals user = do
  results <- E.select $
        E.from $ \(m `E.InnerJoin` u `E.LeftOuterJoin` r) -> do
          E.on     (m ^. DbMealUserId   E.==. u ^. DbUserId)
          E.on     (r ^. DbRecipeMealId E.==. m ^. DbMealId)
          E.where_ (m ^. DbMealUserId   E.==. E.val user )
          return (m,r)
  let r2 = groupBy (\a b -> entityKey (fst a) == entityKey (fst b)) results
  let r3 = map (\list -> ( (fst . head) list
                         ,  map snd list
                         )) r2

  return (map deserializeDb r3)

class DeserializeDb a r | a -> r where
  deserializeDb :: a -> r

instance DeserializeDb (Entity DbMeal, [Entity DbRecipe]) Meal where
  deserializeDb ((Entity _ val), recipes) =
    let d = dbMealDay val
        n = dbMealName val
    in  Meal Nothing (utctDay d) n []