Implement basic mima-run functionality

Bugs fixed:
- Print correct file name when load/save error occurs
- Correctly identify invalid file formats

src/Mima/Run.hs

@@ -5,6 +5,7 @@ module Mima.Run
   -- * The 'Run' monad
     Run
   , run
+  , runOrExit
   , throw
   , catch
   , handle
@@ -18,8 +19,10 @@ module Mima.Run
 import           Control.Monad.IO.Class
 import           Control.Monad.Trans.Except
 import qualified Data.ByteString.Lazy       as BS
+import           Data.Maybe
 import qualified Data.Text                  as T
 import qualified Data.Text.IO               as T
+import           System.Exit
 import           System.IO.Error
 
 newtype Run a = Run (ExceptT T.Text IO a)
@@ -28,6 +31,16 @@ newtype Run a = Run (ExceptT T.Text IO a)
 run :: Run a -> IO (Either T.Text a)
 run (Run e) = runExceptT e
 
+runOrExit :: Int -> Run () -> IO ()
+runOrExit exitCode r = do
+  result <- run r
+  case result of
+    Right () -> pure ()
+    Left e -> do
+      putStrLn "Encountered an exception:"
+      T.putStrLn e
+      exitWith $ ExitFailure exitCode
+
 throw :: T.Text -> Run a
 throw = Run . throwE
 
@@ -43,8 +56,10 @@ isRelevantError e = isAlreadyInUseError e || isDoesNotExistError e || isPermissi
 formatRelevantError :: IOError -> Maybe T.Text
 formatRelevantError e
   | isRelevantError e = Just $ T.pack $
-    "Can't open file " <> ioeGetLocation e <> ": " <> ioeGetErrorString e
+    "Can't open file " <> fileName <> ": " <> ioeGetErrorString e
   | otherwise = Nothing
+  where
+    fileName = fromMaybe "<unknown>" $ ioeGetFileName e
 
 protect :: IO a -> Run a
 protect m = do

src/Mima/Vm/State.hs

@@ -6,8 +6,8 @@ module Mima.Vm.State
   , basicState
   , AbortReason(..)
   , step
-  , run
-  , runN
+  , execute
+  , executeN
   ) where
 
 import           Control.Applicative
@@ -157,16 +157,16 @@ step ms = do
     (SmallInstruction so lv) -> doSmallOpcode so lv ms'
     (LargeInstruction lo sv) -> doLargeOpcode lo sv ms'
 
-run :: MimaState -> (MimaState, AbortReason, Integer)
-run = helper 0
+execute :: MimaState -> (MimaState, AbortReason, Integer)
+execute = helper 0
   where
     helper completed s =
       case step s of
         Left e   -> (s, e, completed)
         Right s' -> helper (completed + 1) s'
 
-runN :: Integer -> MimaState -> (MimaState, Maybe AbortReason, Integer)
-runN n = helper 0
+executeN :: Integer -> MimaState -> (MimaState, Maybe AbortReason, Integer)
+executeN n = helper 0
   where
     helper completed s =
       if completed >= n

src/Mima/Vm/Storage.hs

@@ -32,7 +32,7 @@ loadMimaState :: FilePath -> Run MimaState
 loadMimaState path = do
   bs <- readFileBS path
   case B.decodeOrFail bs of
-    Right ("", 0, a) -> pure a
+    Right ("", _, a) -> pure a
     Right _          -> throw "invalid file format"
     Left (_, _, e)   -> throw $ T.pack e