Adds "compiler" and CLI argument handling

src/Main.hs

@@ -1,5 +1,6 @@
 module Main where
 
+import Compiler
 import Eval     (evalTricu, result)
 import Library  (library)
 import Parser   (parseTricu)
@@ -7,16 +8,40 @@ import REPL     (repl)
 import Research (T)
 
 import Text.Megaparsec (runParser)
+import System.Console.CmdArgs
 
 import qualified Data.Map as Map
 
+data TricuArgs
+  = Repl
+  | Compile { file :: FilePath }
+  deriving (Show, Data, Typeable)
+
+replMode :: TricuArgs
+replMode = Repl
+  &= help "Start interactive REPL"
+  &= auto
+  &= name "repl"
+
+compileMode :: TricuArgs
+compileMode = Compile { file = def &= typ "FILE" &= help "Relative or absolute path to compile" }
+  &= help "Compile a file and return the result of the expression in the final line"
+  &= explicit
+  &= name "compile"
+
 main :: IO ()
 main = do
-  putStrLn "Welcome to the tricu Interpreter"
-  putStrLn "You can exit at any time by typing and entering: "
-  putStrLn ":_exit"
-  repl library
+  args <- cmdArgs $ modes [replMode, compileMode]
+    &= help "tricu: Exploring Tree Calculus"
+    &= program "tricu"
+    &= summary "tricu - compiler and repl"
+
+  case args of
+    Repl -> do
+      putStrLn "Welcome to the tricu REPL"
+      putStrLn "You can exit with `CTRL+D` or the `:_exit` command.`"
+      repl Map.empty
+    Compile filePath -> do
+      result <- evaluateFile filePath
+      print result
 
-runTricu :: String -> T
-runTricu s = result (evalTricu Map.empty $ parseTricu s)
-runTricuEnv env s = result (evalTricu env $ parseTricu s)