{-# LANGUAGE GeneralizedNewtypeDeriving #-}

-- |
-- Module      : Database.Relational.Monad.Trans.Qualify
-- Copyright   : 2013-2019 Kei Hibino
-- License     : BSD3
--
-- Maintainer  : ex8k.hibino@gmail.com
-- Stability   : experimental
-- Portability : unknown
--
-- This module defines monad transformer which qualify uniquely SQL table forms.
--
-- This is not public interface.
module Database.Relational.Monad.Trans.Qualify (
  -- * Qualify monad
  Qualify, qualify,
  evalQualifyPrime, qualifyQuery
  ) where

import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.State (StateT, runStateT, get, modify)
import Control.Applicative (Applicative)
import Control.Monad (liftM, ap)

import qualified Database.Relational.SqlSyntax as Syntax


-- | Monad type to qualify SQL table forms.
newtype Qualify m a =
  Qualify (StateT Int m a)
  deriving (forall a. a -> Qualify m a
forall a b. Qualify m a -> Qualify m b -> Qualify m b
forall a b. Qualify m a -> (a -> Qualify m b) -> Qualify m b
forall {m :: * -> *}. Monad m => Applicative (Qualify m)
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forall (m :: * -> *) a b.
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-> Monad m
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Functor m =>
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forall (f :: * -> *).
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forall a b c.
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Qualify m a -> Qualify m b -> Qualify m b
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(a -> b -> c) -> Qualify m a -> Qualify m b -> Qualify m c
$cliftA2 :: forall (m :: * -> *) a b c.
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Applicative)

-- | Run qualify monad with initial state to get only result.
evalQualifyPrime :: Monad m => Qualify m a -> m a
evalQualifyPrime :: forall (m :: * -> *) a. Monad m => Qualify m a -> m a
evalQualifyPrime (Qualify StateT Int m a
s) = forall a b. (a, b) -> a
fst forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
`liftM` forall s (m :: * -> *) a. StateT s m a -> s -> m (a, s)
runStateT StateT Int m a
s Int
0 {- primary alias id -}

-- | Generated new qualifier on internal state.
newAlias :: Monad m => Qualify m Syntax.Qualifier
newAlias :: forall (m :: * -> *). Monad m => Qualify m Qualifier
newAlias =  forall (m :: * -> *) a. StateT Int m a -> Qualify m a
Qualify forall a b. (a -> b) -> a -> b
$ do
  Qualifier
ai <- Int -> Qualifier
Syntax.Qualifier forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
`liftM` forall (m :: * -> *) s. Monad m => StateT s m s
get
  forall (m :: * -> *) s. Monad m => (s -> s) -> StateT s m ()
modify (forall a. Num a => a -> a -> a
+ Int
1)
  forall (m :: * -> *) a. Monad m => a -> m a
return Qualifier
ai

-- | Lift to 'Qualify'
qualify :: Monad m => m a -> Qualify m a
qualify :: forall (m :: * -> *) a. Monad m => m a -> Qualify m a
qualify =  forall (m :: * -> *) a. StateT Int m a -> Qualify m a
Qualify forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (t :: (* -> *) -> * -> *) (m :: * -> *) a.
(MonadTrans t, Monad m) =>
m a -> t m a
lift

-- | Get qualifyed table form query.
qualifyQuery :: Monad m
             => query                              -- ^ Query to qualify
             -> Qualify m (Syntax.Qualified query) -- ^ Result with updated state
qualifyQuery :: forall (m :: * -> *) query.
Monad m =>
query -> Qualify m (Qualified query)
qualifyQuery query
query =
  forall a. Qualifier -> a -> Qualified a
Syntax.qualify forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
`liftM` forall (m :: * -> *). Monad m => Qualify m Qualifier
newAlias forall (m :: * -> *) a b. Monad m => m (a -> b) -> m a -> m b
`ap` forall (m :: * -> *) a. Monad m => a -> m a
return query
query