95 lines
2.8 KiB
Haskell
95 lines
2.8 KiB
Haskell
{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE FlexibleContexts #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE LambdaCase #-}
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{-# LANGUAGE KindSignatures #-}
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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{-# LANGUAGE TypeApplications #-}
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module Database.PostgreSQL.Opium
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-- * Queries
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--
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-- | TODO: Add @newtype Query = Query Text@ with @IsString@ instance to make constructing query strings at run time harder.
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( fetch
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, fetch_
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, execute
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, execute_
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-- * Classes to Implement
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, FromRow (..)
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, FromField (..)
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, ToParamList (..)
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, ToField (..)
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-- * Utility Stuff
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, Error (..)
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, ErrorPosition (..)
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, RawField (..)
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)
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where
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import Control.Monad.IO.Class (liftIO)
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import Control.Monad.Trans.Except (ExceptT (..), except, runExceptT)
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import Data.Proxy (Proxy (..))
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import Data.Text (Text)
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import Database.PostgreSQL.LibPQ
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( Connection
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, Result
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)
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import qualified Data.Text.Encoding as Encoding
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import qualified Database.PostgreSQL.LibPQ as LibPQ
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import Database.PostgreSQL.Opium.Error (Error (..), ErrorPosition (..))
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import Database.PostgreSQL.Opium.FromField (FromField (..), RawField (..))
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import Database.PostgreSQL.Opium.FromRow (FromRow (..))
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import Database.PostgreSQL.Opium.ToField (ToField (..))
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import Database.PostgreSQL.Opium.ToParamList (ToParamList (..))
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-- The order of the type parameters is important, because it is more common to use type applications for providing the row type.
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fetch
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:: forall a b. (ToParamList b, FromRow a)
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=> Connection
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-> Text
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-> b
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-> IO (Either Error [a])
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fetch conn query params = runExceptT $ do
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result <- execParams conn query params
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columnTable <- ExceptT $ getColumnTable @a Proxy result
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nRows <- liftIO $ LibPQ.ntuples result
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mapM (ExceptT . fromRow result columnTable) [0..nRows - 1]
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fetch_ :: forall a. FromRow a => Connection -> Text -> IO (Either Error [a])
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fetch_ conn query = fetch conn query ()
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execute
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:: forall a. ToParamList a
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=> Connection
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-> Text
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-> a
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-> IO (Either Error ())
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execute conn query params = runExceptT $ do
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_ <- execParams conn query params
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pure ()
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execute_ :: Connection -> Text -> IO (Either Error ())
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execute_ conn query = execute conn query ()
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execParams
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:: ToParamList a
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=> Connection
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-> Text
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-> a
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-> ExceptT Error IO Result
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execParams conn query params = do
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let queryBytes = Encoding.encodeUtf8 query
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liftIO (LibPQ.execParams conn queryBytes (toParamList params) LibPQ.Binary) >>= \case
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Nothing ->
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except $ Left ErrorNoResult
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Just result -> do
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status <- liftIO $ LibPQ.resultStatus result
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mbMessage <- liftIO $ LibPQ.resultErrorMessage result
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case mbMessage of
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Just "" -> pure result
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Nothing -> pure result
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Just message -> except $ Left $ ErrorInvalidResult status $ Encoding.decodeUtf8 message
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