Add matching and entry point code

app/Main.hs

@@ -1,6 +1,26 @@
 module Main where
 
+import System.Environment (getArgs)
+import Text.Parsec.Error (ParseError)
+import System.Exit
+
 import Pattern
+import Data.Dates
 
 main :: IO ()
-main = return ()
+main = do
+  args <- getArgs
+  dt <- getCurrentDateTime
+  case processArgs args dt of
+    Just True -> exitWith ExitSuccess
+    Just False -> exitWith (ExitFailure 1)
+    Nothing -> exitWith (ExitFailure 2)
+
+processArgs :: [String] -> DateTime -> Maybe Bool
+processArgs [pattern] dt = safeMatch pattern dt
+processArgs [pattern, time] dt = matchGivenTime pattern (parseDate dt time)
+processArgs _ _ = Nothing
+
+matchGivenTime :: String -> Either ParseError DateTime -> Maybe Bool
+matchGivenTime _ (Left _) = Nothing
+matchGivenTime pattern (Right dt) = safeMatch pattern dt