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Lib: Changes to the DSL

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1. Fix the logger DSL and add top level helpers
2. Drop the servant server part in the DSL. As aptly explained by Arun,
"It won't accomplish a lot to DSL-ise the starting of that execution
flow -- it's not expressing any business logic, just setting up the
scaffolding within which our business logic will be executed".

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
This commit is contained in:
Sanchayan Maity 2020-07-27 20:32:43 +05:30
parent 7547bcefad
commit 38d9cd6072
1 changed files with 10 additions and 29 deletions
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39
src/Lib.hs
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@ -9,10 +9,7 @@ module Lib where
import Control.Exception
import Control.Monad.Free.Church
import Database.PostgreSQL.Simple
import Data.Proxy
import Data.Text
import Servant.API
import Servant.Server
data SqlDBMethodF next where
SqlDBMethod :: FromRow r => (Connection -> Query -> IO [r]) -> ([r] -> next) -> SqlDBMethodF next
@ -37,25 +34,6 @@ interpretSqlDBMethod _ _ (SqlThrowException exception _) = throwIO exception
runDB :: Connection -> Query -> SqlDb a -> IO a
runDB conn squery = foldF $ interpretSqlDBMethod conn squery
type SampleAPI = Get '[JSON] Text
data ServeF next where
ServeMethod :: (forall api. HasServer api '[] => (Proxy api -> IO a)) -> (a -> next) -> ServeF next
instance Functor ServeF where
fmap f (ServeMethod runner next) = ServeMethod runner (f . next)
type Serve = F ServeF
serveMethod :: (forall api. HasServer api '[] => (Proxy api -> IO a)) -> Serve a
serveMethod action = liftF $ ServeMethod action id
interpretServeMethod :: HasServer api '[] => Proxy api -> ServeF a -> IO a
interpretServeMethod api (ServeMethod runner next) = next <$> runner api
runServe :: HasServer api '[] => Proxy api -> Serve a -> IO a
runServe api = foldF $ interpretServeMethod api
data LoggerMethodF next where
LogMessage :: Text -> (() -> next) -> LoggerMethodF next
@ -65,22 +43,20 @@ instance Functor LoggerMethodF where
type Logger = F LoggerMethodF
logMessage :: Text -> Logger ()
logMessage logMsg = liftF $ LogMessage logMsg id
logMessage msg = liftF $ LogMessage msg id
interpretLoggerMethod :: LoggerMethodF a -> IO a
interpretLoggerMethod (LogMessage msg next) = next <$> print msg
runLogger :: Logger a -> IO a
runLogger :: Logger () -> IO ()
runLogger = foldF interpretLoggerMethod
data DSLMethod next where
LogMsg :: Logger () -> (() -> next) -> DSLMethod next
ServeHttp :: HasServer api '[] => Proxy api -> Serve a -> (a -> next) -> DSLMethod next
RunQuery :: FromRow r => Connection -> Query -> SqlDb [r] -> ([r] -> next) -> DSLMethod next
instance Functor DSLMethod where
fmap f (LogMsg msg next) = LogMsg msg (f . next)
fmap f (ServeHttp api act next) = ServeHttp api act (f . next)
fmap f (RunQuery conn squery act next) = RunQuery conn squery act (f . next)
type DSL = F DSLMethod
@ -88,10 +64,15 @@ type DSL = F DSLMethod
interpretDSLMethod :: DSLMethod a -> IO a
interpretDSLMethod (LogMsg logger next) =
fmap next $ runLogger logger
interpretDSLMethod (ServeHttp api server next) =
fmap next $ runServe api server
interpretDSLMethod (RunQuery conn squery sql next) =
fmap next $ runDB conn squery sql
runDSL :: DSL a -> IO a
runDSL :: DSL () -> IO ()
runDSL = foldF interpretDSLMethod
-- Smart constructors providing a convenient interface.
logMsg :: Text -> DSL ()
logMsg msg = liftF $ LogMsg (logMessage msg) id
runQuery :: (MonadFree DSLMethod m, FromRow r) => Connection -> Query -> m [r]
runQuery conn squery = liftF $ RunQuery conn squery (sqlDbMethod query_) id