module Day7.Parser (
  parseTerminalLines,
  TerminalCommand (..),
  ListingEntry (..),
  DirName,
  FileName,
  Size
) where

import Text.ParserCombinators.Parsec

type DirName = String
type FileName = String
type Size = Int

data ListingEntry = DirListing DirName | FileListing FileName Size
  deriving (Show, Eq)

data TerminalCommand = In DirName | Out | Root | Listing [ListingEntry]
 deriving (Show, Eq)
 
parseTerminalLines :: String -> Either ParseError  [TerminalCommand]
parseTerminalLines = parse terminal "(error)"

terminal :: GenParser Char st [TerminalCommand]
terminal = many command

command :: GenParser Char st TerminalCommand
command = do
  _ <- string "$ "
  cd <|> ls

ls :: GenParser Char st TerminalCommand
ls = do
  _ <- string "ls\n"
  entries <- many listingEntry
  return $ Listing entries

listingEntry :: GenParser Char st ListingEntry
listingEntry = dirListing <|> fileListing

dirListing :: GenParser Char st ListingEntry
dirListing = do
  _ <- string "dir "
  dirName <-  many $ noneOf "\n"
  _ <- char '\n'
  return $ DirListing dirName

fileListing :: GenParser Char st ListingEntry
fileListing = do
  fileSize <- many1 digit
  _ <- char ' '
  fileName <- many $ noneOf "\n"
  _ <- char '\n'
  return $ FileListing fileName (read fileSize)

cd :: GenParser Char st TerminalCommand
cd = do
  _ <- string "cd "
  name <- many $ noneOf "\n"
  _ <- char '\n'
  return (nameToDir name)

nameToDir :: DirName -> TerminalCommand
nameToDir "/" = Root
nameToDir ".." = Out
nameToDir ds = In ds