module Storage(
    Store,

    createStore,
    setPref,
    checkPref
    ) where




import Data.Int ( Int8 )
import Preferences ( Preference )
import qualified Data.Vector.Unboxed.Mutable as Vec




data Store = Store { getPointer    :: Vec.IOVector Int8
                   , getBallotSize :: Int }




createStore :: Int -> Int -> IO Store
createStore maxCapacity ballotSize = do
    v <- Vec.new (maxCapacity * ballotSize)
    return (Store v ballotSize)




setPref :: Store -> Int -> Preference -> IO ()
setPref prefStore ballot (position,rank) = do
    let place = (ballot - 1) * (getBallotSize prefStore) + (position - 1)
    Vec.write (getPointer prefStore) place (fromIntegral rank)




checkPref :: Store -> Int -> Preference -> IO Bool
checkPref prefStore ballot (position,rank) = do
    let place = (ballot - 1) * (getBallotSize prefStore) + (position - 1)
    value <- Vec.read (getPointer prefStore) place
    return (value == fromIntegral rank)