content: {-# LANGUAGE FlexibleContexts #-}
  {-# LANGUAGE RecordWildCards, FlexibleInstances, DefaultSignatures #-}
  
  
  ------------------------------------------------------------------------------
  -- |
  -- Module:      Database.PostgreSQL.Simple.FromRow
  -- Copyright:   (c) 2012 Leon P Smith
  -- License:     BSD3
  -- Maintainer:  Leon P Smith <leon@melding-monads.com>
  -- Stability:   experimental
  --
  -- The 'FromRow' typeclass, for converting a row of results
  -- returned by a SQL query into a more useful Haskell representation.
  --
  -- Predefined instances are provided for tuples containing up to ten
  -- elements.  The instances for 'Maybe' types return 'Nothing' if all
  -- the columns that would have been otherwise consumed are null,  otherwise
  -- it attempts a regular conversion.
  --
  ------------------------------------------------------------------------------
  
  module Database.PostgreSQL.Simple.FromRow
       ( FromRow(..)
       , RowParser
       , field
       , fieldWith
       , numFieldsRemaining
       ) where
  
  import           Prelude hiding (null)
  import           Control.Applicative (Applicative(..), (<$>), (<|>), (*>), liftA2)
  import           Control.Monad (replicateM, replicateM_)
  import           Control.Monad.Trans.State.Strict
  import           Control.Monad.Trans.Reader
  import           Control.Monad.Trans.Class
  import           Data.ByteString (ByteString)
  import qualified Data.ByteString.Char8 as B
  import           Data.Vector (Vector)
  import qualified Data.Vector as V
  import           Database.PostgreSQL.Simple.Types (Only(..))
  import qualified Database.PostgreSQL.LibPQ as PQ
  import           Database.PostgreSQL.Simple.Internal
  import           Database.PostgreSQL.Simple.Compat
  import           Database.PostgreSQL.Simple.FromField
  import           Database.PostgreSQL.Simple.Ok
  import           Database.PostgreSQL.Simple.Types ((:.)(..), Null)
  import           Database.PostgreSQL.Simple.TypeInfo
  
  import           GHC.Generics
  
  
  -- | A collection type that can be converted from a sequence of fields.
  -- Instances are provided for tuples up to 10 elements and lists of any length.
  --
  -- Note that instances can be defined outside of postgresql-simple,  which is
  -- often useful.   For example, here's an instance for a user-defined pair:
  --
  -- @
  -- data User = User { name :: String, fileQuota :: Int }
  --
  -- instance 'FromRow' User where
  --     fromRow = User \<$\> 'field' \<*\> 'field'
  -- @
  --
  -- The number of calls to 'field' must match the number of fields returned
  -- in a single row of the query result.  Otherwise,  a 'ConversionFailed'
  -- exception will be thrown.
  --
  -- Note that 'field' evaluates its result to WHNF, so the caveats listed in
  -- mysql-simple and very early versions of postgresql-simple no longer apply.
  -- Instead, look at the caveats associated with user-defined implementations
  -- of 'fromField'.
  
  class FromRow a where
      fromRow :: RowParser a
      default fromRow :: (Generic a, GFromRow (Rep a)) => RowParser a
      fromRow = to <$> gfromRow
  
  getvalue :: PQ.Result -> PQ.Row -> PQ.Column -> Maybe ByteString
  getvalue result row col = unsafeDupablePerformIO (PQ.getvalue' result row col)
  
  nfields :: PQ.Result -> PQ.Column
  nfields result = unsafeDupablePerformIO (PQ.nfields result)
  
  getTypeInfoByCol :: Row -> PQ.Column -> Conversion TypeInfo
  getTypeInfoByCol Row{..} col =
      Conversion $ \conn -> do
        oid <- PQ.ftype rowresult col
        Ok <$> getTypeInfo conn oid
  
  getTypenameByCol :: Row -> PQ.Column -> Conversion ByteString
  getTypenameByCol row col = typname <$> getTypeInfoByCol row col
  
  fieldWith :: FieldParser a -> RowParser a
  fieldWith fieldP = RP $ do
      let unCol (PQ.Col x) = fromIntegral x :: Int
      r@Row{..} <- ask
      column <- lift get
      lift (put (column + 1))
      let ncols = nfields rowresult
      if (column >= ncols)
      then lift $ lift $ do
          vals <- mapM (getTypenameByCol r) [0..ncols-1]
          let err = ConversionFailed
                  (show (unCol ncols) ++ " values: " ++ show (map ellipsis vals))
                  Nothing
                  ""
                  ("at least " ++ show (unCol column + 1)
                    ++ " slots in target type")
                  "mismatch between number of columns to \
                  \convert and number in target type"
          conversionError err
      else do
        let !result = rowresult
            !typeOid = unsafeDupablePerformIO (PQ.ftype result column)
            !field = Field{..}
        lift (lift (fieldP field (getvalue result row column)))
  
  field :: FromField a => RowParser a
  field = fieldWith fromField
  
  ellipsis :: ByteString -> ByteString
  ellipsis bs
      | B.length bs > 15 = B.take 10 bs `B.append` "[...]"
      | otherwise        = bs
  
  numFieldsRemaining :: RowParser Int
  numFieldsRemaining = RP $ do
      Row{..} <- ask
      column <- lift get
      return $! (\(PQ.Col x) -> fromIntegral x) (nfields rowresult - column)
  
  null :: RowParser Null
  null =  field
  
  instance (FromField a) => FromRow (Only a) where
      fromRow = Only <$> field
  
  instance (FromField a) => FromRow (Maybe (Only a)) where
      fromRow =  (null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b) => FromRow (a,b) where
      fromRow = (,) <$> field <*> field
  
  instance (FromField a, FromField b) => FromRow (Maybe (a,b)) where
      fromRow =  (null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c) => FromRow (a,b,c) where
      fromRow = (,,) <$> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c) => FromRow (Maybe (a,b,c)) where
      fromRow =  (null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d) =>
      FromRow (a,b,c,d) where
      fromRow = (,,,) <$> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d) =>
      FromRow (Maybe (a,b,c,d)) where
      fromRow =  (null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
      FromRow (a,b,c,d,e) where
      fromRow = (,,,,) <$> field <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
      FromRow (Maybe (a,b,c,d,e)) where
      fromRow =  (null *> null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f) =>
      FromRow (a,b,c,d,e,f) where
      fromRow = (,,,,,) <$> field <*> field <*> field <*> field <*> field
                        <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f) =>
      FromRow (Maybe (a,b,c,d,e,f)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g) =>
      FromRow (a,b,c,d,e,f,g) where
      fromRow = (,,,,,,) <$> field <*> field <*> field <*> field <*> field
                         <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g) =>
      FromRow (Maybe (a,b,c,d,e,f,g)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h) =>
      FromRow (a,b,c,d,e,f,g,h) where
      fromRow = (,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                          <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i) =>
      FromRow (a,b,c,d,e,f,g,h,i) where
      fromRow = (,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                           <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j) =>
      FromRow (a,b,c,d,e,f,g,h,i,j) where
      fromRow = (,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                            <*> field <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k) where
      fromRow = (,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                             <*> field <*> field <*> field <*> field <*> field
                             <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l) where
      fromRow = (,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                              <*> field <*> field <*> field <*> field <*> field
                              <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m) where
      fromRow = (,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                               <*> field <*> field <*> field <*> field <*> field
                               <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n) where
      fromRow = (,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                <*> field <*> field <*> field <*> field <*> field
                                <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o) where
      fromRow = (,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                 <*> field <*> field <*> field <*> field <*> field
                                 <*> field <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p) where
      fromRow = (,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                  <*> field <*> field <*> field <*> field <*> field
                                  <*> field <*> field <*> field <*> field <*> field
                                  <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q) where
      fromRow = (,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                    <*> field <*> field <*> field <*> field <*> field
                                    <*> field <*> field <*> field <*> field <*> field
                                    <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q, FromField r) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r) where
      fromRow = (,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                    <*> field <*> field <*> field <*> field <*> field
                                    <*> field <*> field <*> field <*> field <*> field
                                    <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q, FromField r) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q, FromField r, FromField s) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s) where
      fromRow = (,,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                     <*> field <*> field <*> field <*> field <*> field
                                     <*> field <*> field <*> field <*> field <*> field
                                     <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q, FromField r, FromField s) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q, FromField r, FromField s, FromField t) =>
      FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t) where
      fromRow = (,,,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
                                      <*> field <*> field <*> field <*> field <*> field
                                      <*> field <*> field <*> field <*> field <*> field
                                      <*> field <*> field <*> field <*> field <*> field
  
  instance (FromField a, FromField b, FromField c, FromField d, FromField e,
            FromField f, FromField g, FromField h, FromField i, FromField j,
            FromField k, FromField l, FromField m, FromField n, FromField o,
            FromField p, FromField q, FromField r, FromField s, FromField t) =>
      FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t)) where
      fromRow =  (null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *>
                  null *> null *> null *> null *> null *> pure Nothing)
             <|> (Just <$> fromRow)
  
  instance FromField a => FromRow [a] where
      fromRow = do
        n <- numFieldsRemaining
        replicateM n field
  
  instance FromField a => FromRow (Maybe [a]) where
      fromRow = do
        n <- numFieldsRemaining
        (replicateM_ n null *> pure Nothing) <|> (Just <$> replicateM n field)
  
  instance FromField a => FromRow (Vector a) where
      fromRow = do
        n <- numFieldsRemaining
        V.replicateM n field
  
  instance FromField a => FromRow (Maybe (Vector a)) where
      fromRow = do
        n <- numFieldsRemaining
        (replicateM_ n null *> pure Nothing) <|> (Just <$> V.replicateM n field)
  
  instance (FromRow a, FromRow b) => FromRow (a :. b) where
      fromRow = (:.) <$> fromRow <*> fromRow
  
  
  
  -- Type class for default implementation of FromRow using generics
  class GFromRow f where
      gfromRow :: RowParser (f p)
  
  instance GFromRow f => GFromRow (M1 c i f) where
      gfromRow = M1 <$> gfromRow
  
  instance (GFromRow f, GFromRow g) => GFromRow (f :*: g) where
      gfromRow = liftA2 (:*:) gfromRow gfromRow
  
  instance (FromField a) => GFromRow (K1 R a) where
      gfromRow = K1 <$> field
  
  instance GFromRow U1 where
      gfromRow = pure U1
  