basic parsing stub using optparse-applicative

exec/Main.hs

@@ -7,6 +7,10 @@ import qualified Language.Wasm.Lexer as Lexer
 import qualified Language.Wasm.Parser as Parser
 import qualified Language.Wasm.Binary as Binary
 
+import Options.Applicative
+import Data.Semigroup ((<>))
+import Wasm.WasmParser
+
 data OutputMode = WasmBinary | JSWrapper deriving (Show, Eq)
 
 data WasmConfig = WasmConfig {
@@ -24,6 +28,15 @@ compile input output = do
     Left reason ->
       putStrLn $ "Cannot complie module: " ++ reason
 
+
 main :: IO ()
-main = do
-    putStrLn "There is no WASM!"
+main = parseArgs =<< execParser opts
+  where
+    opts = info (sample <**> helper)
+      ( fullDesc
+     <> progDesc "Print a greeting for TARGET"
+     <> header "hello - a test for optparse-applicative" )
+
+parseArgs :: WasmParser -> IO ()
+parseArgs (WasmParser h False n) = putStrLn $ "Hello, " ++ h ++ replicate n '!'
+parseArgs _ = return ()

exec/Wasm/WasmParser.hs

@@ -0,0 +1,26 @@
+module Wasm.WasmParser where
+
+import Options.Applicative
+import Data.Semigroup ((<>))
+
+data WasmParser = WasmParser
+  { hello      :: String
+  , quiet      :: Bool
+  , enthusiasm :: Int }
+
+sample :: Parser WasmParser
+sample = WasmParser
+      <$> strOption
+          ( long "hello"
+         <> metavar "TARGET"
+         <> help "Target for the greeting" )
+      <*> switch
+          ( long "quiet"
+         <> short 'q'
+         <> help "Whether to be quiet" )
+      <*> option auto
+          ( long "enthusiasm"
+         <> help "How enthusiastically to greet"
+         <> showDefault
+         <> value 1
+         <> metavar "INT" )