{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

module Hsm.Log
  ( Severity(Attention, Info, Trace)
  , Log
  , getLevel
  , logMsg
  , makeLoggerIO
  , runLog
  , runLogs
  ) where

import Control.Monad (when)
import Data.Function (applyWhen)
import Data.List (intercalate)
import Data.Proxy (Proxy(Proxy))
import Data.Time.Clock (getCurrentTime)
import Data.Time.ISO8601 (formatISO8601Millis)
import Effectful (Dispatch(Static), DispatchOf, Eff, Effect, IOE, (:>))
import Effectful.Dispatch.Static (SideEffects(WithSideEffects), StaticRep, evalStaticRep, getStaticRep, unEff, unsafeEff, unsafeEff_)
import GHC.Conc.Sync (fromThreadId, myThreadId)
import GHC.TypeLits (KnownSymbol, Symbol, symbolVal)
import String.ANSI (blue, green, red, white)

data Severity
  = Attention
  | Info
  | Trace
  deriving (Enum, Eq, Ord)

coloredShow :: Severity -> String
coloredShow Attention = red "ATTENTION"
coloredShow Info = green "INFO"
coloredShow Trace = blue "TRACE"

data Log (d :: Symbol) (a :: * -> *) (b :: *)

type instance DispatchOf (Log d) = Static WithSideEffects

newtype instance StaticRep (Log d) =
  Log Severity

getLevel :: Log d :> es => Eff es Severity
getLevel = getStaticRep >>= \(Log level) -> return level

logMsg ::
     forall d es. (KnownSymbol d, Log d :> es)
  => Severity
  -> String
  -> Eff es ()
logMsg severity message = do
  level <- getLevel
  when (severity <= level) . unsafeEff_ $ do
    time <- formatISO8601Millis <$> getCurrentTime
    domainAndThreadId <- myThreadId >>= \tid -> return . white $ symbolVal (Proxy @d) <> ":" <> show (fromThreadId tid)
    putStrLn $ unwords [time, domainAndThreadId, coloredShow severity, applyWhen (severity == Attention) red . intercalate "\n ... " $ lines message]

makeLoggerIO ::
     forall d es. (KnownSymbol d, Log d :> es)
  => Eff es (Severity -> String -> IO ())
makeLoggerIO = unsafeEff $ \env -> return $ \severity message -> unEff (logMsg severity message) env

runLog ::
     forall d es a. IOE :> es
  => Severity
  -> Eff (Log d : es) a
  -> Eff es a
runLog = evalStaticRep . Log

class Logs (ds :: [Symbol]) (es :: [Effect]) where
  type Insert ds es :: [Effect]
  runLogs :: Severity -> Eff (Insert ds es) a -> Eff es a

instance Logs ('[] :: [Symbol]) (es :: [Effect]) where
  type Insert '[] es = es
  runLogs _ = id

instance (IOE :> Insert ds es, KnownSymbol d, Logs ds es) => Logs (d : ds :: [Symbol]) (es :: [Effect]) where
  type Insert (d : ds) es = Log d : Insert ds es
  runLogs level = runLogs @ds level . runLog @d level