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

module Hsm.Log
  ( Severity(Attention, Info, Trace)
  , Log
  , makeLoggerIO
  , logMsg
  , logBlock
  , runLog
  ) 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, 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)

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

type instance DispatchOf (Log d) = Static WithSideEffects

newtype instance StaticRep (Log d) =
  Log Severity

makeLoggerIO ::
     forall d es. (KnownSymbol d, Log d :> es)
  => Eff es (Severity -> String -> IO ())
makeLoggerIO = getStaticRep >>= \(Log level) -> return $ loggerIO level
  where
    loggerIO level severity message =
      when (severity <= level) $ do
        time <- formatISO8601Millis <$> getCurrentTime
        threadId <- show . fromThreadId <$> myThreadId
        putStrLn $ unwords [time, fmtDomainAndThreadId threadId, fmtSeverity, fmtMessage]
      where
        fmtDomainAndThreadId threadId = white $ symbolVal (Proxy @d) <> ":" <> threadId
        fmtSeverity =
          case severity of
            Attention -> red "ATTENTION"
            Info -> green "INFO"
            Trace -> blue "TRACE"
        fmtMessage = applyWhen (severity == Attention) red message

logMsg ::
     forall d es. (KnownSymbol d, Log d :> es)
  => Severity
  -> String
  -> Eff es ()
logMsg severity message = makeLoggerIO >>= \loggerIO -> unsafeEff_ $ loggerIO severity message

logBlock ::
     forall d es. (KnownSymbol d, Log d :> es)
  => Severity
  -> String
  -> Eff es ()
logBlock severity message = logMsg severity $ separator <> intercalate separator (lines message)
  where
    separator = "\n ... "

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