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module Main (main) where
import System.Environment ( getArgs )
main :: IO ()
main = getArgs >>= readFile . head >>= print . solveDay7
solveDay7 :: String -> String
solveDay7 = formatSolutions . solveDay7Parts . parseDay7Input
where formatSolutions (x,y) = show x ++ ", " ++ show y
data File = File String Int
data Directory = Directory String [Directory] [File]
data Command = CdRoot | CdUp | Cd String | Ls String
newtype Path = Path [String] -- Just a list of directory names. Root is LAST element.
pushDirectory :: Path -> String -> Path
pushDirectory (Path p) = Path . (:p)
popDirectory :: Path -> (Path, String)
popDirectory (Path (p:ps)) = (Path ps, p)
popDirectory _ = error "Cannot pop a directory from an empty path."
parseDay7Input :: String -> Directory
parseDay7Input = buildDirectoryFromCommands . parseCommands
parseCommands :: String -> [Command]
parseCommands = map parseCommand . splitAtDollarSign
splitAtDollarSign :: String -> [String]
splitAtDollarSign [] = []
splitAtDollarSign ('$':' ':bs) = []:splitAtDollarSign bs
splitAtDollarSign (b:bs) = prependToFirst (splitAtDollarSign bs) b
where prependToFirst (l:ls) b = (b:l):ls
prependToFirst [] b = [[b]]
parseCommand :: String -> Command
parseCommand ('c':'d':' ':'/':_) = CdRoot
parseCommand ('c':'d':' ':'.':'.':_) = CdUp
parseCommand ('c':'d':' ':path) = Cd $ stripTrailingNewline path
parseCommand ('l':'s':'\n':files) = Ls $ stripTrailingNewline files
parseCommand e = error ("Invalid command: " ++ e)
stripTrailingNewline :: String -> String
stripTrailingNewline ['\n'] = []
stripTrailingNewline [] = []
stripTrailingNewline (a:as) = a:stripTrailingNewline as
buildDirectoryFromCommands :: [Command] -> Directory
buildDirectoryFromCommands = error "unimplemented"
applyCommandToDirectory :: (Path, Directory) -> Command -> (Path, Directory)
applyCommandToDirectory (oldPath, oldDir) CdRoot = (Path [], oldDir)
applyCommandToDirectory (oldPath, oldDir) CdUp = (fst . popDirectory $ oldPath, oldDir)
-- todo: other arms
solveDay7Parts :: Directory -> (Int, Int)
solveDay7Parts = error "unimplemented"
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