day4: Solve part1

src/AoC/Y2023/D04.hs

@@ -1,6 +1,56 @@
-module AoC.Y2023.D04 (solve) where
+module AoC.Y2023.D04 where
 
+import AoC.Parser
 import AoC.Riddle
+import Text.Megaparsec (sepBy, (<?>))
+import Text.Megaparsec.Char (char, space, string)
+import Text.Megaparsec.Char.Lexer qualified as L
+
+type Cards = [Int]
+
+data Game = Game
+  { winningCards :: Cards
+  , playedCards :: Cards
+  }
+  deriving stock (Show)
+
+-- | parse list of cards
+--
+-- >>> parseText pCards "5 6 42 23"
+-- Right [5,6,42,23]
+pCards :: Parser Cards
+pCards = L.decimal `sepBy` ws
+
+-- | parse a game
+--
+-- >>> parseText pGame "Game 1: 5 6 42 23 | 78 56 42"
+pGame :: Parser Game
+pGame = do
+  _ <- string "Card "
+  _ <- L.decimal :: Parser Int
+  _ <- string ": "
+  w <- many $ L.decimal <* ws
+  _ <- string "|"
+  h <- L.decimal `sepBy` ws
+  pure $ Game w h
+
+-- sets <- pCards `sepBy` (char '|' >> ws)
+-- case sets of
+--   [w, h] -> pure $ Game w h
+--   _ -> fail "expected two sets of cards"
+
+pPuzzle :: Parser [Game]
+pPuzzle = linewise pGame
 
 solve :: (MonadIO m) => Text -> m (Either Text Solution)
-solve _ = pure $ Left "not yet implemented"
+solve riddle = case parseText pPuzzle riddle of
+  Right puzzle ->
+    let
+      part1 :: Integer
+      part1 = 42
+
+      part2 :: Integer
+      part2 = part1
+     in
+      pure $ Right [part1, part2]
+  Left e -> pure $ Left e