diff --git a/app/Main.hs b/app/Main.hs
index c8dbf9f..2ee4c7a 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -1,4 +1,27 @@
 module Main (main) where
 
+import Control.Monad
+import Ormolu.Parser
+import System.Environment (getArgs)
+import qualified Outputable as GHC
+
 main :: IO ()
-main = return ()
+main = do
+  (path:_) <- getArgs
+  input <- readFile path
+  (ws, r) <- parseModule [] path input
+  unless (null ws) $
+    putStrLn "dynamic option warnings:"
+    -- TODO print ws
+  case r of
+    Left (srcSpan, err) -> do
+      putStrLn (showOutputable srcSpan)
+      putStrLn err
+    Right (anns, parsedModule) -> do
+      putStrLn "\nannotations:\n"
+      putStrLn (showOutputable anns)
+      putStrLn "\nparsed module:\n"
+      putStrLn (showOutputable parsedModule)
+
+showOutputable :: GHC.Outputable o => o -> String
+showOutputable = GHC.showSDocUnsafe . GHC.ppr
diff --git a/ormolu.cabal b/ormolu.cabal
index a4a978f..15034c2 100644
--- a/ormolu.cabal
+++ b/ormolu.cabal
@@ -25,7 +25,11 @@ flag dev
 
 library
   hs-source-dirs:     src
-  build-depends:      base
+  build-depends:      base        >= 4.8 && < 5.0
+                    , data-default-class
+                    , ghc         >= 8.4.3
+                    , ghc-boot-th >= 8.4.3
+                    , ghc-exactprint >= 0.5.6
   exposed-modules:    Ormolu
                     , Ormolu.Parser
                     , Ormolu.Printer
@@ -45,7 +49,7 @@ test-suite tests
   main-is:            Main.hs
   hs-source-dirs:     tests
   type:               exitcode-stdio-1.0
-  build-depends:      base
+  build-depends:      base        >= 4.8 && < 5.0
                     , ormolu
   if flag(dev)
     ghc-options:      -Wall -Werror
@@ -56,7 +60,8 @@ test-suite tests
 executable ormolu
   main-is:            Main.hs
   hs-source-dirs:     app
-  build-depends:      base
+  build-depends:      base        >= 4.8 && < 5.0
+                    , ghc         >= 8.4.3
                     , ormolu
   if flag(dev)
     ghc-options:      -Wall -Werror -Wcompat
diff --git a/src/Ormolu/Parser.hs b/src/Ormolu/Parser.hs
index 65de79a..96a4cd3 100644
--- a/src/Ormolu/Parser.hs
+++ b/src/Ormolu/Parser.hs
@@ -1,3 +1,22 @@
 module Ormolu.Parser
-  (  )
+  ( parseModule )
 where
+
+import Language.Haskell.GHC.ExactPrint.Parsers hiding (parseModule)
+import Language.Haskell.GHC.ExactPrint.Types
+import Ormolu.Type
+import qualified CmdLineParser as GHC
+import qualified DynFlags as GHC
+import qualified GHC hiding (parseModule)
+
+-- | Parse a complete module from string.
+
+parseModule
+  :: [DynOption]        -- ^ Dynamic options that affect parsing
+  -> FilePath           -- ^ File name (only for source location annotations)
+  -> String             -- ^ Input for parser
+  -> IO ([GHC.Warn], Either (GHC.SrcSpan, String) (Anns, GHC.ParsedSource))
+parseModule dynOpts path input = ghcWrapper $ do
+  dynFlags0 <- initDynFlagsPure path input
+  (dynFlags1, _, ws) <- GHC.parseDynamicFilePragma dynFlags0 (dynOption <$> dynOpts)
+  return (ws, parseModuleFromStringInternal dynFlags1 path input)
diff --git a/src/Ormolu/Type.hs b/src/Ormolu/Type.hs
index 3a4ecef..302a874 100644
--- a/src/Ormolu/Type.hs
+++ b/src/Ormolu/Type.hs
@@ -1,3 +1,35 @@
 module Ormolu.Type
-  (  )
+  ( Config (..)
+  , DynOption (..)
+  , dynOption
+  )
 where
+
+import Data.Default.Class
+import qualified SrcLoc as GHC
+
+-- | Ormolu configuration.
+
+data Config = Config
+  { cfgLineWidth :: Int
+  , cfgIndentStep :: Int
+  , cfgDynOptions :: [DynOption]
+  }
+
+instance Default Config where
+  def = Config
+    { cfgLineWidth = 80
+    , cfgIndentStep = 2
+    , cfgDynOptions = []
+    }
+
+-- | A wrapper for dynamic options.
+
+newtype DynOption = DynOption
+  { unDynOption :: String
+  } deriving (Eq, Ord, Show)
+
+-- | Convert 'DynOption' to @'GHC.Located' 'String'@.
+
+dynOption :: DynOption -> GHC.Located String
+dynOption (DynOption o) = GHC.L GHC.noSrcSpan o