Create a Metrics module

src/Main.hs

@@ -0,0 +1,53 @@
+module Main
+    ( main
+    ) where
+
+import qualified Data.Text.Lazy.Builder as Text.Builder
+import qualified Data.Text.Lazy.IO as Text.Lazy
+import Graphics.Fountainhead (dumpFontFile)
+import System.Exit (exitWith)
+import GHC.IO.Exception (ExitCode(..))
+import Options.Applicative
+    ( Parser
+    , ParserInfo(..)
+    , (<**>)
+    , argument
+    , command
+    , execParser
+    , helper
+    , info
+    , fullDesc
+    , metavar
+    , progDesc
+    , str
+    , subparser
+    )
+
+data Operation
+    = Dump
+    | Afm
+    deriving (Eq, Show)
+
+data Options = Options Operation FilePath
+    deriving (Eq, Show)
+
+operationOptions :: ParserInfo Options
+operationOptions = info (options <**> helper) fullDesc
+  where
+    options = Options
+        <$> commands
+        <*> argument str (metavar "FONTFILE")
+    commands = subparser
+        $ command "dump" (info (pure Dump) (progDesc "Dumping the contents of a TrueType Font file."))
+        <> command "afm" (info (pure Afm) (progDesc "Generating Adobe Font Metrics files for TrueType fonts."))
+
+main :: IO ()
+main = execParser operationOptions >>= handleArguments
+  where
+    handleArguments (Options Dump fontFile)
+        = putStrLn ("Dumping File:" <> fontFile <> "\n\n")
+        >> dumpFontFile fontFile
+        >>= either print (Text.Lazy.putStrLn . Text.Builder.toLazyText)
+    handleArguments (Options Afm _)
+        = putStrLn "The program expects exactly one argument, the font file path."
+        >> exitWith (ExitFailure 2)