module Common where

data BlockType = Empty | Allocated Int

instance Show BlockType where
  show Empty = "(empty)"
  show (Allocated blockId) = show blockId
instance Eq BlockType where
  (==) Empty Empty = True
  (==) (Allocated a) (Allocated b) = True
  (==) _ _ = False

type Block = (BlockType, Int)
length :: Block -> Int
length (_, l) = l

parseBlocks :: String -> [Block]
parseBlocks = startWithBlock 0
  where
    startWithBlock :: Int -> String -> [Block]
    startWithBlock _ [] = []
    startWithBlock blockId (size:rest)
      | size >= '0' && size <= '9' = (Allocated blockId, read [size]) : startWithEmpty (blockId + 1) rest
      | otherwise = startWithBlock blockId rest

    startWithEmpty :: Int -> String -> [Block]
    startWithEmpty _ [] = []
    startWithEmpty blockId (size:rest)
      | size >= '0' && size <= '9' = (Empty, read [size]) : startWithBlock blockId rest
      | otherwise = startWithEmpty blockId rest