1 files changed, 37 insertions, 2 deletions
diff --git a/src/Command.hs b/src/Command.hs
index 78d0d6c..bb0b26f 100644
--- a/src/Command.hs
+++ b/src/Command.hs
@@ -1,20 +1,55 @@
 module Command (
     Command(..),
+    CommandArgumentsType(..),
 
     CommandExec(..),
     getConfig,
 ) where
 
+import Control.Monad.Except
 import Control.Monad.Reader
 
+import Data.Kind
+import Data.Text (Text)
+import Data.Text qualified as T
+
+import System.Console.GetOpt
+
 import Config
 
-class Command c where
+class CommandArgumentsType (CommandArguments c) => Command c where
     commandName :: proxy c -> String
 
-    commandInit :: proxy c -> c
+    type CommandOptions c :: Type
+    type CommandOptions c = ()
+    commandOptions :: proxy c -> [OptDescr (CommandOptions c -> CommandOptions c)]
+    commandOptions _ = []
+    defaultCommandOptions :: proxy c -> CommandOptions c
+    default defaultCommandOptions :: CommandOptions c ~ () => proxy c -> CommandOptions c
+    defaultCommandOptions _ = ()
+
+    type CommandArguments c :: Type
+    type CommandArguments c = ()
+
+    commandInit :: CommandArgumentsType (CommandArguments c) => proxy c -> CommandOptions c -> CommandArguments c -> c
     commandExec :: c -> CommandExec ()
 
+class CommandArgumentsType args where
+    argsFromStrings :: [String] -> Except String args
+
+instance CommandArgumentsType () where
+    argsFromStrings [] = return ()
+    argsFromStrings _ = throwError "no argument expected"
+
+instance CommandArgumentsType Text where
+    argsFromStrings [str] = return $ T.pack str
+    argsFromStrings _ = throwError "expected single argument"
+
+instance CommandArgumentsType (Maybe Text) where
+    argsFromStrings [] = return $ Nothing
+    argsFromStrings [str] = return $ Just (T.pack str)
+    argsFromStrings _ = throwError "expected at most one argument"
+
 
 newtype CommandExec a = CommandExec (ReaderT Config IO a)
     deriving (Functor, Applicative, Monad, MonadIO)