Wip

src/Lib2.hs

@@ -11,14 +11,8 @@ module Lib2
 -- It should match the grammar from Laboratory work #1.
 -- Currently it has no constructors but you can introduce
 -- as many as needed.
-data Query
-
--- | The instances are needed basically for tests
-instance Eq Query where
-  (==) _ _= False
-
-instance Show Query where
-  show _ = ""
+data Query = Print | Add Int
+  deriving (Show, Eq)
 
 -- | Parses user's input.
 -- The function must have tests.
@@ -28,12 +22,12 @@ parseQuery _ = Left "Not implemented 2"
 -- | An entity which represents your program's state.
 -- Currently it has no constructors but you can introduce
 -- as many as needed.
-data State
+data State = Sum Int
 
 -- | Creates an initial program's state.
 -- It is called once when the program starts.
 emptyState :: State
-emptyState = error "Not implemented 1"
+emptyState = Sum 0
 
 -- | Updates a state according to a query.
 -- This allows your program to share the state

src/Lib3.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE InstanceSigs #-}
+{-# LANGUAGE EmptyCase #-}
 module Lib3
     ( stateTransition,
     StorageOp (..),
@@ -9,9 +10,10 @@ module Lib3
     renderStatements
     ) where
 
+
 import Control.Concurrent ( Chan )
-import Control.Concurrent.STM(STM, TVar)
 import qualified Lib2
+import Control.Concurrent.STM (STM, TVar, atomically, readTVar, writeTVar, readTVarIO, modifyTVar)
 
 data StorageOp = Save String (Chan ()) | Load (Chan String)
 -- | This function is started from main
@@ -70,4 +72,41 @@ renderStatements _ = error "Not implemented 5"
 -- is stored in transactinal variable
 stateTransition :: TVar Lib2.State -> Command -> Chan StorageOp ->
                    IO (Either String (Maybe String))
-stateTransition _ _ ioChan = return $ Left "Not implemented 6"
+stateTransition state command ioChan =
+  case command of
+    StatementCommand sc ->
+      updateState state sc
+    SaveCommand -> do
+      jakie <- newChan
+      st <- readTVarIO state
+      writeChan ioChan (Save (renderStatements (marshallState st)) jakie)
+      _ <- readChan jakie
+      return $ Right Nothing
+    LoadCommand -> do
+      jakie <- newChan
+      writeChan ioChan (Load jakie)
+      file <- readChan jakie
+      case parseStatements file of
+        Left e -> return $ Left e
+        Right (st, "") -> updateState state st
+        Right _ -> return $ Left "Statements are not fully parsed"
+
+updateState :: TVar Lib2.State -> Statements ->
+               IO (Either String (Maybe String))
+updateState state (Single q) = atomically $ updateState' state [q]
+updateState state (Batch b) = atomically $ updateState' state b
+
+updateState' :: TVar Lib2.State -> [Lib2.Query] -> STM (Either String (Maybe String))
+updateState' _ [] = return $ Right Nothing
+updateState' state (h:t) = do
+  case h of
+    Lib2.Print -> do
+      Lib2.Sum s <- readTVar state
+      us <- updateState' state t
+      case us of
+        Left e -> return $ Left e
+        Right Nothing -> return $ Right $ Just $ show s
+        Right (Just next) -> return $ Right $ Just $ concat [show s, "\n", next]
+    Lib2.Add v -> do
+      modifyTVar state (\(Lib2.Sum s) -> Lib2.Sum (s + v))
+      return $ Right Nothing