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291 lines
11 KiB
291 lines
11 KiB
{-|
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A solution to rubyquiz 30 (http://rubyquiz.com/quiz30.html).
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/A "Barrel of Monkeys" playlist is when the next song in the playlist begins/
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/with the same letter as the current song ended in./
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/Given any starting and ending song, create a playlist that connects the two songs./
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/Create playlists of specific durations and shortest and longest playlists by/
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/the number of songs and the total duration./
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/The song data is available at/ <http://rubyquiz.com/SongLibrary.xml.gz>.
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Copyright 2012 Abhinav Sarkar \<abhinav\@abhinavsarkar.net\>
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-}
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{-# LANGUAGE Arrows, NoMonomorphismRestriction, RecordWildCards #-}
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module BarrelOfMonkeys
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(Song(..), SongLibrary, Playlist(..), getSongsFromXml,
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shortestPlaylist, longestPlaylist, shortestTimePlaylist, longestTimePlaylist,
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timedPlaylist, main)
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where
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import qualified Data.Map as M
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import qualified Data.FingerTree.PSQueue as Q
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import qualified Data.Set as S
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import qualified Data.Text as T
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import AStar
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import Data.Char (toLower, isAlphaNum)
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import Data.FingerTree.PSQueue (Binding(..))
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import Data.List (foldl', maximumBy, partition, sortBy)
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import Data.Maybe (maybeToList, fromMaybe, isNothing, fromJust, catMaybes)
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import Data.Ord (comparing)
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import Control.Applicative ((<*>))
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import Control.Monad (when)
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import Options.Applicative
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import Text.Printf (printf)
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import Text.XML.HXT.Core hiding ((:->), when)
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--- types ---
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-- | A song with all the fields
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data Song = Song {
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songArtist :: T.Text, -- ^ The song artist
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songId :: Int, -- ^ The song ID
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songName :: T.Text, -- ^ The song name
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songDuration :: Int -- ^ The song duration in milliseconds
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}
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instance Eq Song where
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a == b = songId a == songId b
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instance Ord Song where
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compare = comparing songId
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instance Show Song where
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show (Song {..}) = printf "%s. %s - %s (%sms)"
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(show songId) (T.unpack songArtist) (T.unpack songName) (show songDuration)
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-- | The whole song library
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data SongLibrary = SongLibrary {
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songIdMap :: M.Map Int Song,
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fstCharMap :: M.Map Char [Song],
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lstCharMap :: M.Map Char [Song]
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}
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-- | A playlist of songs
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data Playlist = Playlist {
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playlistSongs :: [Song], -- ^ The songs in the playlist
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playlistDuration :: Int -- ^ The total duration of the playlist in milliseconds
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}
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--- XML parsing ---
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atTag tag = deep (isElem >>> hasName tag)
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getSong = atTag "Song" >>>
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proc s -> do
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sName <- (T.strip . T.pack) ^<< getAttrValue "name" -< s
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sId <- read ^<< getAttrValue "id" -< s
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sDuration <- read ^<< getAttrValue "duration" -< s
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returnA -< (sId, sName, sDuration)
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getSongs = atTag "Artist" >>>
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proc a -> do
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sArtist <- (T.strip . T.pack) ^<< getAttrValue "name" -< a
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songs <- listA getSong -< a
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returnA -< map (uncurry3 $ Song sArtist) songs
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-- | Reads the song library from the XML file given its path
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getSongsFromXml :: FilePath -> IO SongLibrary
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getSongsFromXml file =
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fmap (uncurry3 SongLibrary
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. foldl' (\(mi, mf, ml) s ->
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(M.insert (songId s) s mi,
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M.insertWith (++) (fstChar . songName $ s) [s] mf,
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M.insertWith (++) (lstChar. songName $ s) [s] ml))
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(M.empty, M.empty, M.empty)
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. concat)
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$ runX (readDocument [withValidate no , withRemoveWS yes] file >>> getSongs)
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--- playlist generation ---
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cleanSongName =
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T.dropAround (not . isAlphaNum) . head . dropWhile T.null . T.splitOn (T.pack "(")
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fstChar = toLower . T.head . cleanSongName
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lstChar = toLower . T.last . cleanSongName
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nextSongs :: Song -> SongLibrary -> [Song]
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nextSongs song = fromMaybe [] . M.lookup (lstChar . songName $ song) . fstCharMap
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prevSongs :: Song -> SongLibrary -> [Song]
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prevSongs song = fromMaybe [] . M.lookup (fstChar . songName $ song) . lstCharMap
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playlist :: SongLibrary -> (Song -> [(Song, Int)]) -> Int -> Int -> Maybe Playlist
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playlist library nextSong startId endId = do
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start <- M.lookup startId $ songIdMap library
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end <- M.lookup endId $ songIdMap library
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let pl = concatMap snd . maybeToList . astar start end nextSong $ (\_ _ -> 0)
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return $ Playlist pl (playlistTime pl)
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-- | Creates the shortest and longest playlist by the number of song and
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-- the shortest and longest playlist by the length of the playlist
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shortestPlaylist, longestPlaylist, shortestTimePlaylist, longestTimePlaylist
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:: SongLibrary -- ^ The song library
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-> Int -- ^ The start song ID
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-> Int -- ^ The end song ID
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-> Maybe Playlist -- ^ (@Just@ resultant playlist) if it exists else @Nothing@
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shortestPlaylist library =
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playlist library (\song -> map (\s -> (s, 1)) . nextSongs song $ library)
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longestPlaylist library =
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playlist library (\song -> map (\s -> (s, -1)) . nextSongs song $ library)
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shortestTimePlaylist library startId =
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playlist library (\song ->
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map (\s -> (s, songDuration . fromJust . M.lookup startId . songIdMap $ library))
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. nextSongs song $ library) startId
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longestTimePlaylist library startId =
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playlist library (\song ->
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map (\s -> (s, negate . songDuration . fromJust . M.lookup startId . songIdMap $ library))
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. nextSongs song $ library) startId
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playlistTime = sum . map songDuration
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playlistTimes :: SongLibrary -> Int -> Int -> M.Map Int Int
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playlistTimes library startId endId = let
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songIds = zip (M.keys . songIdMap $ library) (repeat maxBound)
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queue = Q.fromAscList . map (uncurry (:->)) $ songIds
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distances = M.fromAscList songIds
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endSongDuration = songDuration . fromJust . song $ endId
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in M.map (\n -> if n == maxBound then 0 else n)
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$ loop (M.insert endId endSongDuration distances)
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(Q.adjust (const endSongDuration) endId queue)
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where
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song sId = M.lookup sId . songIdMap $ library
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loop distances queue = case Q.findMin queue of
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Nothing -> distances
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Just (sId :-> p) -> let
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queue' = Q.deleteMin queue
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in if p == maxBound
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then distances
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else let
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prev = prevSongs (fromJust $ song sId) library
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(distances', queue'') =
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foldl (\(d, q) Song{..} -> let
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alt = fromJust (M.lookup sId d) + songDuration
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old = fromJust $ M.lookup songId d
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in if alt < old
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then (M.insert songId alt d, Q.adjust (const alt) songId q)
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else (d, q))
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(distances, queue') prev
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in loop distances' queue''
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-- | Creates a playlist with its duration as close a possible to the given duration
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timedPlaylist ::
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SongLibrary -- ^ The song library
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-> Int -- ^ The required duration in milliseconds
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-> Int -- ^ The start song ID
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-> Int -- ^ The end song ID
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-> Int -- ^ Maximum number of child nodes to consider while
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-- traversing the graph to create the playlist. Used for
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-- tuning the runtime of the function
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-> Maybe Playlist -- ^ (@Just@ resultant playlist) if it exists else @Nothing@
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timedPlaylist library time startId endId maxChild =
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fst $ timedPlaylist_ library time startId endId S.empty M.empty
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(playlistTimes library startId endId) maxChild
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timedPlaylist_ library time startId endId seen rejected shortestTimeMap maxChild
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| isNothing song = (Nothing, rejected)
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| startId == endId = (Just $ Playlist [jSong] (songDuration jSong), rejected)
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| fromMaybe 0 (M.lookup startId rejected) > time = (Nothing, rejected)
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| fromMaybe 0 (M.lookup startId shortestTimeMap) > time =
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(Nothing, M.insertWith max startId time rejected)
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| songDuration jSong > time = (Nothing, rejected)
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| otherwise = let
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(rest, rejected', _) =
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foldl
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(\(pls, rej, count) sId -> if count >= maxChild
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then (pls, rej, count)
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else let
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(pl, rej') = timedPlaylist_ library (time - songDuration jSong)
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sId endId seen' rej shortestTimeMap maxChild
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in case pl of
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Nothing -> (pl : pls, rej', count)
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Just _ -> (pl : pls, rej', count + 1))
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([], rejected, 0) nextSongIds
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rest' = catMaybes rest
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in if null rest'
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then if null nextSeen
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then (Nothing, M.insertWith max startId time rejected')
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else (Nothing, rejected')
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else let Playlist plSongs plDur = maximumBy (comparing playlistDuration) rest'
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in (Just $ Playlist (jSong : plSongs) (plDur + songDuration jSong), rejected')
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where
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song = M.lookup startId . songIdMap $ library
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jSong = fromJust song
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(nextSongIds, nextSeen) =
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partition (not . flip S.member seen) . map songId
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. sortBy (comparing (negate . songDuration)) . nextSongs jSong $ library
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seen' = S.insert startId seen
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--- command line parsing ---
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data Command = Shortest Bool
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| Longest Bool
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| Timed Int Int
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deriving (Show)
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optParser = subparser $
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command "shortest"
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(info
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(helper
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<*> ((\bt sl st et -> (sl, st, et, Shortest bt))
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<$> byTimeP "Shortest" <*> songLibFileP <*> startIdP <*> endIdP))
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(progDesc "Creates shortest playlist"))
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& command "longest"
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(info
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(helper
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<*> ((\bt sl st et -> (sl, st, et, Longest bt))
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<$> byTimeP "Longest" <*> songLibFileP <*> startIdP <*> endIdP))
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(progDesc "Creates longest playlist"))
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& command "timed"
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(info
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(helper
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<*> ((\sl tm mc st et -> (sl, st, et, Timed tm mc))
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<$> songLibFileP <*> timeP <*> maxChildP <*> startIdP <*> endIdP))
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(progDesc "Creates longest playlist with the maximum specified time"))
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where
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songLibFileP = argument str (metavar "song_library_xml_file")
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byTimeP optimum = switch (short 't' & help (optimum ++ " by playlist time"))
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startIdP = argument auto (metavar "start_song_id")
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endIdP = argument auto (metavar "end_song_id")
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timeP = argument auto (metavar "playlist_time")
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maxChildP = argument auto (metavar "max_children")
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opts = info (helper <*> optParser) $
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progDesc "Creates \"Barrel of Monkey\" playlists starting and ending by given songs"
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--- main ---
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main = do
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(songLibFile, startId, endId, command) <- execParser opts
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library <- getSongsFromXml songLibFile
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when (isNothing . M.lookup startId . songIdMap $ library)
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(error "Start id not found in the library")
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when (isNothing . M.lookup endId . songIdMap $ library)
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(error "End id not found in the library")
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case command of
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Shortest byTime ->
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if byTime
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then printPlaylist $ shortestTimePlaylist library startId endId
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else printPlaylist $ shortestPlaylist library startId endId
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Longest byTime ->
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if byTime
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then printPlaylist $ longestTimePlaylist library startId endId
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else printPlaylist $ longestPlaylist library startId endId
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Timed time maxChild ->
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printPlaylist $ timedPlaylist library time startId endId maxChild
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where
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printPlaylist playlist = case playlist of
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Nothing -> putStrLn "No playlist found"
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Just Playlist{..} -> do
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putStrLn . unlines . map show $ playlistSongs
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putStrLn ("Duration: " ++ show playlistDuration ++ " ms")
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