{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

-- |
-- Module      : Database.Relational.Monad.Trans.Restricting
-- Copyright   : 2014-2017 Kei Hibino
-- License     : BSD3
--
-- Maintainer  : ex8k.hibino@gmail.com
-- Stability   : experimental
-- Portability : unknown
--
-- This module defines monad transformer which lift to basic 'MonadQuery'.
module Database.Relational.Monad.Trans.Restricting (
  -- * Transformer into restricted context
  Restrictings, restrictings,

  -- * Result
  extractRestrict
  ) where

import Control.Monad.Trans.Class (MonadTrans (lift))
import Control.Monad.Trans.Writer (WriterT, runWriterT, tell)
import Control.Applicative (Applicative, pure, (<$>))
import Control.Arrow (second)
import Data.DList (DList, toList)

import Database.Relational.SqlSyntax (Predicate)

import Database.Relational.Monad.Class
  (MonadQualify (..), MonadRestrict(..), MonadQuery (..), MonadAggregate(..))


-- | Type to accumulate query restrictions.
--   Type 'c' is context tag of restriction building like
--   Flat (where) or Aggregated (having).
newtype Restrictings c m a =
  Restrictings (WriterT (DList (Predicate c)) m a)
  deriving (forall c (m :: * -> *) a. Monad m => m a -> Restrictings c m a
forall (m :: * -> *) a. Monad m => m a -> Restrictings c m a
forall (t :: (* -> *) -> * -> *).
(forall (m :: * -> *) a. Monad m => m a -> t m a) -> MonadTrans t
lift :: forall (m :: * -> *) a. Monad m => m a -> Restrictings c m a
$clift :: forall c (m :: * -> *) a. Monad m => m a -> Restrictings c m a
MonadTrans, forall a. a -> Restrictings c m a
forall a b.
Restrictings c m a -> Restrictings c m b -> Restrictings c m b
forall a b.
Restrictings c m a
-> (a -> Restrictings c m b) -> Restrictings c m b
forall {c} {m :: * -> *}. Monad m => Applicative (Restrictings c m)
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forall c (m :: * -> *) a b.
Monad m =>
Restrictings c m a -> Restrictings c m b -> Restrictings c m b
forall c (m :: * -> *) a b.
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Applicative m
-> (forall a b. m a -> (a -> m b) -> m b)
-> (forall a b. m a -> m b -> m b)
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-> Monad m
return :: forall a. a -> Restrictings c m a
$creturn :: forall c (m :: * -> *) a. Monad m => a -> Restrictings c m a
>> :: forall a b.
Restrictings c m a -> Restrictings c m b -> Restrictings c m b
$c>> :: forall c (m :: * -> *) a b.
Monad m =>
Restrictings c m a -> Restrictings c m b -> Restrictings c m b
>>= :: forall a b.
Restrictings c m a
-> (a -> Restrictings c m b) -> Restrictings c m b
$c>>= :: forall c (m :: * -> *) a b.
Monad m =>
Restrictings c m a
-> (a -> Restrictings c m b) -> Restrictings c m b
Monad, forall a b. a -> Restrictings c m b -> Restrictings c m a
forall a b. (a -> b) -> Restrictings c m a -> Restrictings c m b
forall c (m :: * -> *) a b.
Functor m =>
a -> Restrictings c m b -> Restrictings c m a
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forall (f :: * -> *).
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forall c (m :: * -> *) a b c.
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Functor f
-> (forall a. a -> f a)
-> (forall a b. f (a -> b) -> f a -> f b)
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-> (forall a b. f a -> f b -> f b)
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-> Applicative f
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Restrictings c m a -> Restrictings c m b -> Restrictings c m a
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Restrictings c m a -> Restrictings c m b -> Restrictings c m a
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Restrictings c m a -> Restrictings c m b -> Restrictings c m b
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Applicative m =>
Restrictings c m a -> Restrictings c m b -> Restrictings c m b
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pure :: forall a. a -> Restrictings c m a
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Applicative)

-- | Lift to 'Restrictings'
restrictings :: Monad m => m a -> Restrictings c m a
restrictings :: forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings =  forall (t :: (* -> *) -> * -> *) (m :: * -> *) a.
(MonadTrans t, Monad m) =>
m a -> t m a
lift

-- | Add whole query restriction.
updateRestriction :: Monad m => Predicate c -> Restrictings c m ()
updateRestriction :: forall (m :: * -> *) c.
Monad m =>
Predicate c -> Restrictings c m ()
updateRestriction =  forall c (m :: * -> *) a.
WriterT (DList (Predicate c)) m a -> Restrictings c m a
Restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *) w. Monad m => w -> WriterT w m ()
tell forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (f :: * -> *) a. Applicative f => a -> f a
pure

-- | 'MonadRestrict' instance.
instance (Monad q, Functor q) => MonadRestrict c (Restrictings c q) where
  restrict :: Predicate c -> Restrictings c q ()
restrict = forall (m :: * -> *) c.
Monad m =>
Predicate c -> Restrictings c m ()
updateRestriction

-- | Restricted 'MonadQualify' instance.
instance MonadQualify q m => MonadQualify q (Restrictings c m) where
  liftQualify :: forall a. q a -> Restrictings c m a
liftQualify = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (q :: * -> *) (m :: * -> *) a.
MonadQualify q m =>
q a -> m a
liftQualify

-- | Restricted 'MonadQuery' instance.
instance MonadQuery q => MonadQuery (Restrictings c q) where
  setDuplication :: Duplication -> Restrictings c q ()
setDuplication     = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *). MonadQuery m => Duplication -> m ()
setDuplication
  restrictJoin :: Predicate Flat -> Restrictings c q ()
restrictJoin       = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *). MonadQuery m => Predicate Flat -> m ()
restrictJoin
  query' :: forall p r.
Relation p r -> Restrictings c q (PlaceHolders p, Record Flat r)
query'             = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *) p r.
MonadQuery m =>
Relation p r -> m (PlaceHolders p, Record Flat r)
query'
  queryMaybe' :: forall p r.
Relation p r
-> Restrictings c q (PlaceHolders p, Record Flat (Maybe r))
queryMaybe'        = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *) p r.
MonadQuery m =>
Relation p r -> m (PlaceHolders p, Record Flat (Maybe r))
queryMaybe'

-- | Restricted 'MonadAggregate' instance.
instance MonadAggregate m => MonadAggregate (Restrictings c m) where
  groupBy :: forall r. Record Flat r -> Restrictings c m (Record Aggregated r)
groupBy  = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *) r.
MonadAggregate m =>
Record Flat r -> m (Record Aggregated r)
groupBy
  groupBy' :: forall r.
AggregateKey (Record Aggregated r)
-> Restrictings c m (Record Aggregated r)
groupBy' = forall (m :: * -> *) a c. Monad m => m a -> Restrictings c m a
restrictings forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (m :: * -> *) r.
MonadAggregate m =>
AggregateKey (Record Aggregated r) -> m (Record Aggregated r)
groupBy'

-- | Run 'Restrictings' to get 'QueryRestriction'
extractRestrict :: (Monad m, Functor m) => Restrictings c m a -> m (a, [Predicate c])
extractRestrict :: forall (m :: * -> *) c a.
(Monad m, Functor m) =>
Restrictings c m a -> m (a, [Predicate c])
extractRestrict (Restrictings WriterT (DList (Predicate c)) m a
rc) = forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> a (d, b) (d, c)
second forall a. DList a -> [a]
toList forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall w (m :: * -> *) a. WriterT w m a -> m (a, w)
runWriterT WriterT (DList (Predicate c)) m a
rc