feat: implemented the program

app/Main.hs

@@ -0,0 +1,36 @@
+module Main (main) where
+import qualified Data.Text.IO as Text
+import Text.Megaparsec (errorBundlePretty, runParser)
+import qualified Data.Text as Text
+import qualified Sudoku
+import qualified Sudoku.Solve as Solve
+import qualified Sudoku.Render as Render
+import Sudoku.State (State)
+import Options.Applicative (subparser, command, info, Parser, progDesc, execParser)
+import System.Exit (exitFailure)
+
+data Mode
+  = Solve
+  | Hints
+
+parseMode :: Parser Mode
+parseMode = subparser
+  (     command "solve" (info (pure Solve) (progDesc "Solve the supplied sudoku entirely."))
+  <>    command "hints" (info (pure Hints) (progDesc "Show hints for the sudoku."))
+  )
+
+main :: IO ()
+main = do
+  mode <- execParser (info parseMode mempty)
+  input <- Text.getContents
+  sudoku <- case runParser Sudoku.parse "<stdin>" input of
+    Left errorBundle -> (Text.putStr . Text.pack . errorBundlePretty $ errorBundle) >> exitFailure
+    Right s -> pure s
+
+  Text.putStr $ case mode of
+    Solve -> Text.pack . show $ Solve.solve State sudoku
+    Hints -> let
+      hints = Solve.hints State sudoku
+
+      in Render.hints hints
+