module Main where

type Title = String
type Videolist = [(Title,(Int,Int))] --[(title,(available,rent))]

movies::Videolist
movies = [("Am Limit",(1,0)), ("Kill Bill vol. 1", (3,1)),("Matrix",(2,2))]

rentable :: Title -> Videolist -> Bool
rentable _ [] =  False
rentable title ((t,(a,r)):rest) = if title == t then a>r else rentable title rest

hasFilm :: Title -> Videolist -> Bool
hasFilm _ [] = False
hasFilm title ((t,(_,_)):rest) = (t == title) || hasFilm title rest

rent:: Title -> Videolist -> Videolist
rent _ [] = error "Film nicht vorhanden"
rent x ((t,(a,r)):rest) | not (hasFilm x ((t,(a,r)):rest)) = error "Film nicht vorhanden"
                        | not (rentable x ((t,(a,r)):rest)) = error "Film nicht verfuegbar"
                        | otherwise = if x == t then (t,(a,r+1)):rest else (t, (a, r)) : rent x rest



insert:: Title -> Videolist -> (Videolist,Bool)
--insert title [] = ([(title,(1,0))],False)
insert title ((t,(a,r)):rest) | not (hasFilm title ((t,(a,r)):rest) )  = ((title, (1, 0)) : ((t, (a, r)) : rest),False)
                              | otherwise = if title == t then ((t,(a+1,r)):rest, True) else insert title rest

main::IO()
main = do
        putStr "search Am Limit"