import Data.List

main :: IO()
main = do
    print $ rf (Song "Mozart""The Marriage of Figaro Overture" 270) -- == "Summertime"
    print $ rf (Song "Gershwin""Summertime" 300) -- == "Rhapsody in Blue"
    print $ rf (Song "Gershwin""Rhapsody in Blue" 1100) -- == "Rhapsody in Blue"

type SongName = String

songs = [
    (Song "Mozart""The Marriage of Figaro Overture" 270),
    (Song "Gershwin""Summertime" 300),
    (Song "Queen""Bohemian Rhapsody" 355),
    (Song "Gershwin""Rhapsody in Blue" 1100)]

type AuthorName = String
type SongLength = Int

data Song = Song AuthorName SongName SongLength -- that is the main line we need
    deriving (Eq, Show)

data Playlist = Playlist [Song]

rf = recommender (Playlist songs)

-- aN = authorName, sN = songName, sL = songLength
-- pl is a list, actually it represented PlayList

-- we are gonna split function in two parts
-- in the first we need to have filter and dropWhile
-- in the second part we are just gonna need filter

recommender :: Playlist -> (Song -> SongName)
recommender (Playlist pl) = (\p@(Song aN sN sL) -> if null $ recommendALgorithm1 aN sL then if null $ recommendAlgorithm2 aN sL then p else head recommendAlgorithm2 aN sL else head $ recommendALgorithm1 aN sL)
    where
        -- here we need to use filter and dropWhile, and check if length is bigger, if it's bigger than we move on to another fucntion

        recommnedAlgorithm1 :: AuthorName -> Int ->
        recommendAlgorithm1 aN l = filter (\(Song authorName sN sL) -> sL > l && aN == authorName) pl

        recommentAlgorithm2 :: AuthorName -> Int ->
        recommendAlgorithm2 aN l = (\p@(Song authorName sN sL) -> if length (dropWhile (/= p) pl) < 1 then p else head $ tail recommendAlgorithm2 aN l)