Broken existentially quantified printer config

3 files changed, 82 insertions, 10 deletions

diff --git a/server/src/Thermoprint/Server.hs b/server/src/Thermoprint/Server.hs
index 39bf0a1..4e8d962 100644
--- a/server/src/Thermoprint/Server.hs
+++ b/server/src/Thermoprint/Server.hs
@@ -3,10 +3,11 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE TypeOperators     #-}
 {-# LANGUAGE FlexibleContexts  #-}
+{-# LANGUAGE ViewPatterns      #-}
 
 module Thermoprint.Server
        ( thermoprintServer
-       , Config(..)
+       , Config(..), withPrinters
        , module Data.Default.Class
        , module Servant.Server.Internal.Enter
        , module Thermoprint.Server.Printer
@@ -19,7 +20,8 @@ import Data.Map (Map)
 import qualified Data.Map as Map
 
 import Data.Maybe (maybe)
-import Data.Foldable (mapM_, forM_)
+import Data.Foldable (mapM_, forM_, foldlM)
+import Data.Monoid
 
 import Control.Monad.Trans.Resource
 import Control.Monad.Trans.Control
@@ -27,6 +29,8 @@ import Control.Monad.Logger
 import Control.Monad.Reader
 import Control.Monad.IO.Class
 
+import Control.Monad.Writer
+
 import Control.Concurrent
        
 import Data.Text (Text)
@@ -62,9 +66,9 @@ instance Default Config where
 
 
 thermoprintServer :: ( MonadLoggerIO m
-                     , MonadIO m
-                     , MonadBaseControl IO m
                      , MonadReader ConnectionPool m
+                     , MonadResource m
+                     , MonadBaseControl IO m
                      ) => (m :~> IO) -- ^ 'dyre' controls the base of the monad-transformer-stack ('IO') but we let the user specify the rest of it. Therefore we require a specification of how to enter the stack.
                      -> Config -> IO ()
 -- ^ Run the server
@@ -79,3 +83,12 @@ thermoprintServer io = Dyre.wrapMain $ Dyre.defaultParams
         mapM_ ($(logWarnS) "DB") =<< runSqlPool (runMigrationSilent migrateAll) =<< ask
         forM_ printers $ liftBaseDiscard forkIO . runPrinter
         liftIO . Warp.runSettings warpSettings . serve thermoprintAPI . flip enter API.thermoprintServer =<< handlerNat printers
+
+withPrinters :: MonadResource m => Config -> [PrinterSpec] -> m Config
+-- ^ Helper for comfortably specifying a set of 'Printer's
+withPrinters cfg = fmap (\ps -> cfg { printers = printers cfg <> ps }) . foldlM (\ps p -> Map.insert (nextKey ps) <$> printer p <*> pure ps) Map.empty
+  where
+    nextKey :: Map PrinterId a -> PrinterId
+    nextKey (Map.keys -> keys)
+      | null keys = 0
+      | otherwise = succ $ maximum keys
diff --git a/server/src/Thermoprint/Server/Printer.hs b/server/src/Thermoprint/Server/Printer.hs
index f34b2fa..cd12297 100644
--- a/server/src/Thermoprint/Server/Printer.hs
+++ b/server/src/Thermoprint/Server/Printer.hs
@@ -1,14 +1,18 @@
 {-# LANGUAGE RankNTypes                    #-}
+{-# LANGUAGE ImpredicativeTypes            #-}
 {-# LANGUAGE MultiParamTypeClasses         #-}
 {-# LANGUAGE FlexibleContexts              #-}
 {-# LANGUAGE RecordWildCards               #-}
 {-# LANGUAGE OverloadedStrings             #-}
 {-# LANGUAGE TemplateHaskell               #-}
 {-# LANGUAGE StandaloneDeriving            #-}
+{-# LANGUAGE ExistentialQuantification     #-}
+{-# LANGUAGE RecordWildCards               #-}
 {-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}
 
 module Thermoprint.Server.Printer
        ( Printer(..), printer
+       , IsPrinter(..), PrinterSpec(..)
        , Queue(..)
        , runPrinter
        ) where
@@ -41,8 +45,23 @@ import Control.Monad (forever)
 
 import Control.Concurrent.STM
 
-data Printer = Printer
-  { print :: forall m. (MonadIO m) => Printout -> m (Maybe PrintingError)
+import Data.Default.Class
+
+import Prelude hiding (print)
+
+class IsPrinter a where
+  toMethod :: forall m. (MonadResource m) => a -> (forall m1. (MonadResource m1) => m (Printout -> m1 (Maybe PrintingError)))
+
+instance (MonadResource m) => IsPrinter (Printer m) where
+  toMethod Printer{..} = return print
+
+instance (MonadResource m) => IsPrinter (PrinterSpec m) where
+  toMethod (PS p) = toMethod p
+
+data PrinterSpec m = forall p. IsPrinter p => PS p 
+
+data Printer m = Printer
+  { print :: Printout -> m (Maybe PrintingError)
   , queue :: TVar Queue
   }
 
@@ -54,17 +73,25 @@ data Queue = Queue
   }
   deriving (Typeable, Generic, NFData)
 
-printer :: (MonadIO m) => (forall m. (MonadIO m) => Printout -> m (Maybe PrintingError)) -> m Printer
-printer f = Printer f <$> liftIO (newTVarIO $ Queue Seq.empty Nothing Seq.empty)
+instance Default Queue where
+  def = Queue
+    { pending = Seq.empty
+    , current = Nothing
+    , history = Seq.empty
+    }
+
+printer :: (MonadResource m, MonadResource m1, IsPrinter p) => p -> m (Printer m1)
+-- ^ Version of 'Printer' handling the initialisation of the 'TVar'
+printer p = Printer <$> toMethod p <*> liftIO (newTVarIO def)
 
 atomically' :: MonadIO m => STM a -> m a
 atomically' = liftIO . atomically
 
 runPrinter :: ( MonadReader ConnectionPool m
-              , MonadIO m
               , MonadLogger m
+              , MonadResource m
               , MonadBaseControl IO m
-              ) => Printer -> m ()
+              ) => Printer m -> m ()
 -- ^ Loop 'forever' pushing entries from the 'Queue' associated to a 'Printer' into its 'print'-method
 runPrinter Printer{..} = forever $ do
   jobId <- atomically' $ do
diff --git a/server/src/Thermoprint/Server/Printer/Debug.hs b/server/src/Thermoprint/Server/Printer/Debug.hs
new file mode 100644
index 0000000..81e43a3
--- /dev/null
+++ b/server/src/Thermoprint/Server/Printer/Debug.hs
@@ -0,0 +1,32 @@
+{-# LANGUAGE EmptyDataDecls    #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RankNTypes        #-}
+
+module Thermoprint.Server.Printer.Debug
+       ( Debug
+       ) where
+
+import Control.Monad.IO.Class
+import Control.Monad.Trans.Resource
+
+import Data.Text.Lazy (Text)
+import qualified Data.Text.Lazy as TL
+import qualified Data.Text.Lazy.IO as TL
+
+import Thermoprint.Printout
+import Thermoprint.Server.Printer
+
+import Data.List (intersperse)
+import Data.Foldable (toList)
+import Data.Monoid
+
+data Debug
+
+-- instance IsPrinter Debug where
+--   toMethod _ = (>> return Nothing) . liftIO . TL.putStrLn . cotext'
+
+-- cotext' :: Printout -> Text
+-- cotext' = mconcat . intersperse "\n\n" . map (mconcat . map cotext'' . toList) . toList
+--   where
+--     cotext'' (Cooked b) = cotext b
+--     cotext'' (Raw _)    = "[Raw]"