Lexer integration.

src/Bang/CommandLine.hs

@@ -0,0 +1,64 @@
+module Bang.CommandLine(
+         BangCommand(..)
+       , BangOperation(..)
+       , LexerOptions(..)
+       , getCommand
+       , helpString
+       )
+ where
+
+import Options.Applicative
+import Options.Applicative.Help
+
+data BangCommand = BangCommand {
+       cmdVerbosity  :: Verbosity
+     , cmdOutputFile :: FilePath
+     , cmdCommand    :: BangOperation
+     }
+ deriving (Show)
+
+data Verbosity = Silent | Normal | Verbose
+ deriving (Eq, Show)
+
+verboseOption :: Parser Verbosity
+verboseOption = flag Normal Silent  (short 'q' <> long "quiet")
+            <|> flag Normal Verbose (short 'v' <> long "verbose")
+
+outputFile :: Parser FilePath
+outputFile = strOption (short 'o' <> long "output-file" <> metavar "FILE"
+                      <> help "The file to output as a result of this action."
+                      <> value "/dev/stdout" <> showDefault)
+
+data BangOperation = Help
+                   | Version
+                   | Lex LexerOptions
+ deriving (Show)
+
+bangOperation :: Parser BangOperation
+bangOperation = subparser $
+  command "help" (pure Help `withInfo` "Describe common commands.") <>
+  command "version" (pure Version `withInfo` "Display version information.") <>
+  command "lex" (parseLex `withInfo` "Lex a file into its component tokens.")
+
+withInfo :: Parser a -> String -> ParserInfo a 
+withInfo opts desc = info (helper <*> opts) (progDesc desc)
+
+data LexerOptions = LexerOptions {
+       lexInputFile :: FilePath
+     }
+ deriving (Show)
+
+parseLex :: Parser BangOperation
+parseLex = Lex <$> parseLexOptions
+
+parseLexOptions :: Parser LexerOptions
+parseLexOptions = LexerOptions <$> argument str (metavar "FILE")
+
+parseOptions :: Parser BangCommand
+parseOptions = BangCommand <$> verboseOption <*> outputFile <*> bangOperation
+
+helpString :: String
+helpString = show (parserHelp (ParserPrefs "" False False True 80) parseOptions)
+
+getCommand :: IO BangCommand
+getCommand = execParser (parseOptions `withInfo` "Run a bang language action.")