Day 8

day08/Commons.hs

@@ -0,0 +1,40 @@
+module Commons where
+
+import GHC.IO.Handle (isEOF)
+import Data.Hashable (Hashable (hash), hashWithSalt)
+import Data.HashMap.Strict (HashMap, empty, insert, singleton, union)
+
+
+data Instruction = ILeft | IRight deriving Eq
+instance Hashable Instruction where
+  hashWithSalt s ILeft = s + hash False
+  hashWithSalt s IRight = s + hash True
+
+data Network = Network { instructions :: [Instruction], nodes :: HashMap (String, Instruction) String }
+
+
+parseInstructions :: String -> [Instruction]
+parseInstructions ('L': t) = ILeft: parseInstructions t
+parseInstructions ('R': t) = IRight: parseInstructions t
+parseInstructions [] = []
+
+parseNode :: String -> HashMap (String, Instruction) String
+parseNode [a, b, c, ' ', '=', ' ', '(', d, e, f, ',', ' ', g, h, i, ')'] =
+  insert ([a, b, c], ILeft) [d, e, f] $ singleton ([a, b, c], IRight) [g, h, i]
+
+parseNodes :: IO (HashMap (String, Instruction) String)
+parseNodes = do done <- isEOF
+                if done
+                   then return empty
+                   else do line <- getLine
+                           let node = parseNode line
+                           otherNodes <- parseNodes
+                           let newNodes = node `union` otherNodes
+                           return newNodes
+
+parse :: IO Network
+parse = do instructionsRaw <- getLine
+           getLine
+           let instructions = parseInstructions instructionsRaw
+           nodes <- parseNodes
+           return Network {instructions = instructions, nodes = nodes}