module Queue1 where

import           StrictList as L

data Queue a = Q { left     :: StrictList a
                 , leftLen  :: !Int
                 , right    :: StrictList a
                 , rightLen :: !Int
                 } deriving (Show, Eq)

empty :: Queue a
empty = Q Empty 0 Empty 0

length :: Queue a -> Int
length (Q _ ll _ rl) = ll + rl

insert :: a -> Queue a -> Queue a
insert e (Q l ll r rl) = Q l ll (e :$ r) (rl + 1)

remove :: Queue a -> (a, Queue a)
remove (Q Empty _  r rl) = remove (Q (L.reverse r) rl Empty 0)
remove (Q l     ll r rl) = (L.head l, Q (L.tail l) (ll - 1) r rl)