feat: allow solution ID to be passed as CLI arg

src/Main.idr

@@ -3,6 +3,7 @@ module Main
 import Data.SortedMap
 import Data.Problem
 import Language.Reflection
+import System
 
 import AllDays
 
@@ -30,11 +31,13 @@ getInput = go ""
 
 main : IO ()
 main = do
-  putStr "Solution: "
-  Just pr <- parseProblem <$> getLine
-    | Nothing => putStrLn "Invalid solution ID"
-  let Just func = lookup pr solMap
-    | Nothing => putStrLn "This part is not implemented yet!"
+  sol <- case !getArgs of
+           [_, s] => pure s
+           _ => putStr "Solution: " >> getLine
+  let Just pr = parseProblem sol
+        | Nothing => putStrLn "ERROR: Invalid solution"
+      Just func = lookup pr solMap
+        | Nothing => putStrLn "ERROR: This part is not implemented yet!"
 
   putStrLn "Input (end with \\):"
   input <- trim <$> getInput