{-# LANGUAGE DeriveDataTypeable, TypeSynonymInstances, FlexibleInstances #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

module Sound.Tidal.Pattern where

import qualified Data.Map.Strict as Map
import Control.Applicative (liftA2)

import Data.Maybe (isJust, fromJust, catMaybes, fromMaybe)
import Data.Ratio (numerator, denominator)
import Data.List (delete, findIndex, sort, intercalate)
import Data.Typeable (Typeable)
import Data.Data (Data) -- toConstr

import Sound.Tidal.Utils

------------------------------------------------------------------------
-- * Types

-- | Time is rational
type Time = Rational

-- | A time arc (start and end)
type Arc = (Time, Time)

-- | The second arc (the part) should be equal to or fit inside the
-- first one (the whole that it's a part of).
type Part = (Arc, Arc)

-- | An event is a value that's active during a timespan
type Event a = (Part, a)

data State = State {arc :: Arc,
                    controls :: ControlMap
                   }

-- | A function that represents events taking place over time
type Query a = (State -> [Event a])

-- | Also known as Continuous vs Discrete/Amorphous vs Pulsating etc.
data Nature = Analog | Digital
            deriving Eq

-- | A datatype that's basically a query, plus a hint about whether its events
-- are Analogue or Digital by nature
data Pattern a = Pattern {nature :: Nature, query :: Query a}

data Value = VS { svalue :: String }
           | VF { fvalue :: Double }
           | VI { ivalue :: Int }
           deriving (Eq,Ord,Typeable,Data)

type ControlMap = Map.Map String Value
type ControlPattern = Pattern ControlMap

------------------------------------------------------------------------
-- * Instances

instance Functor Pattern where
  -- | apply a function to all the values in a pattern
  fmap f p = p {query = (fmap (fmap f)) . query p}

instance Applicative Pattern where
  -- | Repeat the given value once per cycle, forever
  pure v = Pattern Digital $ \(State (s,e) _) -> map (\(s',e') -> (constrain (s,e) (s',e'),v)) $ cycleArcsInArc (s,e)
    where constrain (s,e) (s',e') = ((s',e'), (max s s', min e e'))

  (<*>) pf@(Pattern Digital _) px@(Pattern Digital _) = Pattern Digital q
    where q st = catMaybes $ concat $ map match $ query pf st
            where
              match ((fWhole, fPart), f) =
                map
                (\((xWhole, xPart),x) ->
                  do whole' <- subArc xWhole fWhole
                     part' <- subArc fPart xPart
                     return ((whole', part'), f x)
                )
                (query px $ st {arc = fPart})
  (<*>) pf@(Pattern Digital _) px@(Pattern Analog _) = Pattern Digital q
    where q st = concatMap match $ query pf st
            where
              match ((fWhole, fPart), f) =
                map
                (\(_ ,x) -> ((fWhole, fPart), f x))
                (query px $ st {arc = (fst fPart, fst fPart)})

  (<*>) pf@(Pattern Analog _) px@(Pattern Digital _) = Pattern Digital q
    where q st = concatMap match $ query px st
            where
              match ((xWhole, xPart), x) =
                map
                (\(_ ,f) -> ((xWhole, xPart), f x))
                (query pf st {arc = (fst xPart, fst xPart)})
                
  (<*>) pf px = Pattern Analog q
    where q st = concatMap match $ query pf st
            where
              match (_, f) =
                map
                (\(_ ,x) -> ((arc st, arc st), f x))
                (query px st)

-- | Like <*>, but the structure only comes from the left
(<*) :: Pattern (a -> b) -> Pattern a -> Pattern b
(<*) pf@(Pattern Digital _) px = Pattern Digital q
  where q st = concatMap match $ query pf st
         where
            match ((fWhole, fPart), f) =
              map
              (\(_, x) -> ((fWhole, fPart), f x)) $
              query px $ st {arc = xQuery fWhole}
            xQuery ((s,_)) = (s,s) -- for discrete events, match with the onset
            

pf <* px = Pattern Analog q
  where q st = concatMap match $ query pf st
          where
            match ((fWhole, fPart), f) =
              map
              (\(_, x) -> ((fWhole, fPart), f x)) $
              query px st -- for continuous events, use the original query

-- | Like <*>, but the structure only comes from the right
(*>) :: Pattern (a -> b) -> Pattern a -> Pattern b
(*>) pf px@(Pattern Digital _) = Pattern Digital q
  where q st = concatMap match $ query px st
         where
            match ((xWhole, xPart), x) =
              map
              (\(_, f) -> ((xWhole, xPart), f x)) $
              query pf $ fQuery xWhole
            fQuery ((s,_)) = st {arc = (s,s)} -- for discrete events, match with the onset
            

pf *> px = Pattern Analog q
  where q st = concatMap match $ query px st
          where
            match ((xWhole, xPart), x) =
              map
              (\(_, f) -> ((xWhole, xPart), f x)) $
              query pf st -- for continuous events, use the original query

infixl 4 <*, *>

instance Monad Pattern where
  return = pure
  p >>= f = unwrap (f <$> p)

-- | Turns a pattern of patterns into a single pattern.
-- (this is actually 'join')
--
-- 1/ For query 'arc', get the events from the outer pattern @pp@
-- 2/ Query the inner pattern using the 'part' of the outer
-- 3/ For each inner event, set the whole and part to be the intersection
--    of the outer whole and part, respectively
-- 4/ Concatenate all the events together (discarding wholes/parts that didn't intersect)
--
-- TODO - what if a continuous pattern contains a discrete one, or vice-versa?

unwrap :: Pattern (Pattern a) -> Pattern a
unwrap pp = pp {query = q}
  where q st = concatMap (\((whole, part), p) -> catMaybes $ map (munge whole part) $ query p st {arc = part}) (query pp st)
        munge oWhole oPart ((iWhole, iPart),v) = do w <- subArc oWhole iWhole
                                                    p <- subArc oPart iPart
                                                    return ((w,p),v)

-- | Turns a pattern of patterns into a single pattern. Like @unwrap@,
-- but structure only comes from the inner pattern.
innerJoin :: Pattern (Pattern a) -> Pattern a
innerJoin pp = pp {query = q}
  where q st = concatMap (\((_, part), p) -> catMaybes $ map munge $ query p st {arc = part}) (query pp st)
          where munge ((iWhole, iPart),v) = do let w = iWhole
                                               p <- subArc (arc st) iPart
                                               p' <- subArc p (arc st)
                                               return ((w,p'),v)

-- | Turns a pattern of patterns into a single pattern. Like @unwrap@,
-- but structure only comes from the outer pattern.
outerJoin :: Pattern (Pattern a) -> Pattern a
outerJoin pp = pp {query = q}
  where q st = concatMap (\((whole, part), p) -> catMaybes $ map (munge whole part) $ query p st {arc = (fst whole, fst whole)}) (query pp st)
          where munge oWhole oPart (_,v) = do let w = oWhole
                                              p <- subArc (arc st) oPart
                                              return ((w,p),v)

-- | Like @unwrap@, but cycles of the inner patterns are compressed to fit the
-- timespan of the outer whole (or the original query if it's a continuous pattern?)
-- TODO - what if a continuous pattern contains a discrete one, or vice-versa?
unwrapSqueeze :: Pattern (Pattern a) -> Pattern a
unwrapSqueeze pp = pp {query = q}
  where q st = concatMap (\((whole, part), p) -> catMaybes $ map (munge whole part) $ query (__compress whole p) st {arc = part}) (query pp st)
        munge oWhole oPart ((iWhole, iPart),v) = do whole' <- subArc oWhole iWhole
                                                    part' <- subArc oPart iPart
                                                    return ((whole',part'),v)

noOv :: String -> a
noOv meth = error $ meth ++ ": not supported for patterns"

class TolerantEq a where
   (~==) :: a -> a -> Bool

instance TolerantEq Value where
         (VS a) ~== (VS b) = a == b
         (VI a) ~== (VI b) = a == b
         (VF a) ~== (VF b) = (abs (a - b)) < 0.000001
         _ ~== _ = False

instance TolerantEq ControlMap where
  a ~== b = (Map.differenceWith (\a' b' -> if a' ~== b' then Nothing else Just a') a b) == Map.empty

instance TolerantEq (Event ControlMap) where
  (pt, x) ~== (pt', x') = pt == pt' && x ~== x'

instance TolerantEq a => TolerantEq ([a]) where
  as ~== bs = (length as == length bs) && (and $ map (\(a,b) -> a ~== b) $ zip as bs)

instance Eq (Pattern a) where
  (==) = noOv "(==)"

instance Ord a => Ord (Pattern a) where
  min = liftA2 min
  max = liftA2 max
  compare = noOv "compare"
  (<=) = noOv "(<=)"

instance Num a => Num (Pattern a) where
  negate      = fmap negate
  (+)         = liftA2 (+)
  (*)         = liftA2 (*)
  fromInteger = pure . fromInteger
  abs         = fmap abs
  signum      = fmap signum

instance Enum a => Enum (Pattern a) where
  succ           = fmap succ
  pred           = fmap pred
  toEnum         = pure . toEnum
  fromEnum       = noOv "fromEnum"
  enumFrom       = noOv "enumFrom"
  enumFromThen   = noOv "enumFromThen"
  enumFromTo     = noOv "enumFromTo"
  enumFromThenTo = noOv "enumFromThenTo"

instance (Num a, Ord a) => Real (Pattern a) where
  toRational = noOv "toRational"

instance (Integral a) => Integral (Pattern a) where
  quot          = liftA2 quot
  rem           = liftA2 rem
  div           = liftA2 div
  mod           = liftA2 mod
  toInteger     = noOv "toInteger"
  x `quotRem` y = (x `quot` y, x `rem` y)
  x `divMod`  y = (x `div`  y, x `mod` y)

instance (Fractional a) => Fractional (Pattern a) where
  recip        = fmap recip
  fromRational = pure . fromRational

instance (Floating a) => Floating (Pattern a) where
  pi    = pure pi
  sqrt  = fmap sqrt
  exp   = fmap exp
  log   = fmap log
  sin   = fmap sin
  cos   = fmap cos
  asin  = fmap asin
  atan  = fmap atan
  acos  = fmap acos
  sinh  = fmap sinh
  cosh  = fmap cosh
  asinh = fmap asinh
  atanh = fmap atanh
  acosh = fmap acosh

instance (RealFrac a) => RealFrac (Pattern a) where
  properFraction = noOv "properFraction"
  truncate       = noOv "truncate"
  round          = noOv "round"
  ceiling        = noOv "ceiling"
  floor          = noOv "floor"

instance (RealFloat a) => RealFloat (Pattern a) where
  floatRadix     = noOv "floatRadix"
  floatDigits    = noOv "floatDigits"
  floatRange     = noOv "floatRange"
  decodeFloat    = noOv "decodeFloat"
  encodeFloat    = ((.).(.)) pure encodeFloat
  exponent       = noOv "exponent"
  significand    = noOv "significand"
  scaleFloat n   = fmap (scaleFloat n)
  isNaN          = noOv "isNaN"
  isInfinite     = noOv "isInfinite"
  isDenormalized = noOv "isDenormalized"
  isNegativeZero = noOv "isNegativeZero"
  isIEEE         = noOv "isIEEE"
  atan2          = liftA2 atan2

instance Num (ControlMap) where
  negate      = ((applyFIS negate negate id) <$>)
  (+)         = Map.unionWith (fNum2 (+) (+))
  (*)         = Map.unionWith (fNum2 (*) (*))
  fromInteger i = Map.singleton "n" $ VI $ fromInteger i
  signum      = ((applyFIS signum signum id) <$>)
  abs         = ((applyFIS abs abs id) <$>)

instance Fractional ControlMap where
  recip        = fmap (applyFIS recip id id)
  fromRational = Map.singleton "speed" . VF . fromRational


instance {-# OVERLAPPING #-} Show Arc where
  show (s,e) = prettyRat s ++ ">" ++ prettyRat e

instance {-# OVERLAPPING #-} Show Part where
  show ((s,e),(s',e')) = h ++ "(" ++ show (s',e') ++ ")" ++ t
    where h | s == s' = ""
            | otherwise = prettyRat s ++ "-"
          t | e == e' = ""
            | otherwise = "-" ++ prettyRat e

instance {-# OVERLAPPING #-} Show a => Show (Event a) where
  show (p,v) = show p ++ "|" ++ show v

showPattern :: Show a => Arc -> Pattern a -> String
showPattern a p = intercalate "\n" $ map show $ queryArc p a

instance (Show a) => Show (Pattern a) where
  show p = showPattern (0,1) p

instance Show Value where
  show (VS s) = ('"':s) ++ "\""
  show (VI i) = show i
  show (VF f) = show f ++ "f"

instance {-# OVERLAPPING #-} Show (ControlMap) where
  show m = intercalate ", " $ map (\(name, value) -> name ++ ": " ++ show value) $ Map.toList m

prettyRat :: Rational -> String
prettyRat r | unit == 0 && frac > 0 = showFrac (numerator frac) (denominator frac)
            | otherwise =  show unit ++ showFrac (numerator frac) (denominator frac)
  where unit = floor r :: Int
        frac = (r - (toRational unit))

showFrac :: Integer -> Integer -> String
showFrac 0 _ = ""
showFrac 1 2 = "½"
showFrac 1 3 = "⅓"
showFrac 2 3 = "⅔"
showFrac 1 4 = "¼"
showFrac 3 4 = "¾"
showFrac 1 5 = "⅕"
showFrac 2 5 = "⅖"
showFrac 3 5 = "⅗"
showFrac 4 5 = "⅘"
showFrac 1 6 = "⅙"
showFrac 5 6 = "⅚"
showFrac 1 7 = "⅐"
showFrac 1 8 = "⅛"
showFrac 3 8 = "⅜"
showFrac 5 8 = "⅝"
showFrac 7 8 = "⅞"
showFrac 1 9 = "⅑"
showFrac 1 10 = "⅒"

showFrac n d = fromMaybe plain $ do n' <- up n
                                    d' <- down d
                                    return $ n' ++ d'
  where plain = " " ++ show n ++ "/" ++ show d
        up 1 = Just "¹"
        up 2 = Just "²"
        up 3 = Just "³"
        up 4 = Just "⁴"
        up 5 = Just "⁵"
        up 6 = Just "⁶"
        up 7 = Just "⁷"
        up 8 = Just "⁸"
        up 9 = Just "⁹"
        up 0 = Just "⁰"
        up _ = Nothing
        down 1 = Just "₁"
        down 2 = Just "₂"
        down 3 = Just "₃"
        down 4 = Just "₄"
        down 5 = Just "₅"
        down 6 = Just "₆"
        down 7 = Just "₇"
        down 8 = Just "₈"
        down 9 = Just "₉"
        down 0 = Just "₀"
        down _ = Nothing

------------------------------------------------------------------------
-- * Internal functions

empty :: Pattern a
empty = Pattern {nature = Digital, query = const []}

queryArc :: Pattern a -> Arc -> [Event a]
queryArc p a = query p $ State a Map.empty 

-- | Get the timespan of an event's 'whole'
eventWhole :: Event a -> Arc
eventWhole = fst . fst

-- | Get the onset of an event's 'whole'
eventWholeOnset :: Event a -> Time
eventWholeOnset = fst . fst . fst

-- | Get the timespan of an event's 'part'
eventPart :: Event a -> Arc
eventPart = snd . fst

eventValue :: Event a -> a
eventValue = snd

eventHasOnset :: Event a -> Bool
eventHasOnset e = (fst $ eventWhole e) == (fst $ eventPart e)

isDigital :: Pattern a -> Bool
isDigital = (== Digital) . nature

isAnalog :: Pattern a -> Bool
isAnalog = not . isDigital

-- | Splits the given 'Arc' into a list of 'Arc's, at cycle boundaries.
arcCycles :: Arc -> [Arc]
arcCycles (s,e) | s >= e = []
                | sam s == sam e = [(s,e)]
                | otherwise = (s, nextSam s) : (arcCycles (nextSam s, e))

-- | Like arcCycles, but returns zero-width arcs
arcCyclesZW :: Arc -> [Arc]
arcCyclesZW (s,e) | s == e = [(s,e)]
                  | otherwise = arcCycles (s,e)

-- | Map the given function over both the start and end @Time@ values
-- of the given @Arc@.
mapArc :: (Time -> Time) -> Arc -> Arc
mapArc f (s,e) = (f s, f e)

-- | Similar to 'mapArc' but time is relative to the cycle (i.e. the
-- sam of the start of the arc)
mapCycle :: (Time -> Time) -> Arc -> Arc
mapCycle f (s,e) = (sam' + (f $ s - sam'), sam' + (f $ e - sam'))
         where sam' = sam s

-- | Splits queries that span cycles. For example `query p (0.5, 1.5)` would be
-- turned into two queries, `(0.5,1)` and `(1,1.5)`, and the results
-- combined. Being able to assume queries don't span cycles often
-- makes transformations easier to specify.
splitQueries :: Pattern a -> Pattern a
splitQueries p = p {query = \st -> concatMap (\a -> query p st {arc = a}) $ arcCyclesZW (arc st)}

-- | The 'sam' (start of cycle) for the given time value
sam :: Time -> Time
sam = fromIntegral . (floor :: Time -> Int)

-- | Turns a number into a (rational) time value. An alias for 'toRational'.
toTime :: Real a => a -> Rational
toTime = toRational

-- | The end point of the current cycle (and starting point of the next cycle)
nextSam :: Time -> Time
nextSam = (1+) . sam

-- | The position of a time value relative to the start of its cycle.
cyclePos :: Time -> Time
cyclePos t = t - sam t

-- | @isIn a t@ is @True@ if @t@ is inside
-- the arc represented by @a@.
isIn :: Arc -> Time -> Bool
isIn (s,e) t = t >= s && t < e

-- | `True` if an `Event`'s starts is within given `Arc`
onsetIn :: Arc -> Event a -> Bool
onsetIn a e = isIn a (eventWholeOnset e)

-- | @subArc i j@ is the timespan that is the intersection of @i@ and @j@.
-- The definition is a bit fiddly as results might be zero-width, but
-- not at the end of an non-zero-width arc - e.g. (0,1) and (1,2) do
-- not intersect, but (1,1) (1,1) does.
subArc :: Arc -> Arc -> Maybe Arc
subArc (s, e) (s',e') | and [s'' == e'', s'' == e, s < e] = Nothing
                      | and [s'' == e'', s'' == e', s' < e'] = Nothing
                      | s'' <= e'' = Just (s'', e'')
                      | otherwise = Nothing
  where s'' = max s s'
        e'' = min e e'

-- | The arc of the whole cycle that the given time value falls within
timeToCycleArc :: Time -> Arc
timeToCycleArc t = (sam t, (sam t) + 1)

-- | A list of cycle numbers which are included in the given arc
cyclesInArc :: Integral a => Arc -> [a]
cyclesInArc (s,e) | s > e = []
                  | s == e = [floor s]
                  | otherwise = [floor s .. (ceiling e)-1]

-- | A list of arcs of the whole cycles which are included in the given arc
cycleArcsInArc :: Arc -> [Arc]
cycleArcsInArc = map (timeToCycleArc . (toTime :: Int -> Time)) . cyclesInArc

-- | Apply a function to the arcs/timespans (both whole and parts) of the result
withResultArc :: (Arc -> Arc) -> Pattern a -> Pattern a
withResultArc f p = p {query = map (mapFst (mapBoth f)) . query p}

-- | Apply a function to the time (both start and end of the timespans
-- of both whole and parts) of the result
withResultTime :: (Time -> Time) -> Pattern a -> Pattern a
withResultTime = withResultArc . mapBoth

-- | Apply a function to the timespan of the query
withQueryArc :: (Arc -> Arc) -> Pattern a -> Pattern a
withQueryArc f p = p {query = query p . (\(State a m) -> State (f a) m)}

-- | Apply a function to the time (both start and end) of the query
withQueryTime :: (Time -> Time) -> Pattern a -> Pattern a
withQueryTime = withQueryArc . mapBoth

-- | @withEvent f p@ returns a new @Pattern@ with each event mapped over
-- function @f@.
withEvent :: (Event a -> Event b) -> Pattern a -> Pattern b
withEvent f p = p {query = map f . query p}

-- | @withEvent f p@ returns a new @Pattern@ with f applied to the resulting list of events for each query
-- function @f@.
withEvents :: ([Event a] -> [Event b]) -> Pattern a -> Pattern b
withEvents f p = p {query = f . query p}

-- | @withPart f p@ returns a new @Pattern@ with function @f@ applied
-- to the part.
withPart :: (Arc -> Arc) -> Pattern a -> Pattern a
withPart f = withEvent (\((w,p),v) -> ((w,f p),v))

-- | Compares two lists of events, attempting to combine fragmented events in the process
-- for a 'truer' compare
compareDefrag :: (Eq a, Ord a) => [Event a] -> [Event a] -> Bool
compareDefrag as bs = (sort $ defragParts as) == (sort $ defragParts bs)

-- | Returns a list of events, with any adjacent parts of the same whole combined
defragParts :: Eq a => [Event a] -> [Event a]
defragParts [] = []
defragParts (e:[]) = (e:[])
defragParts (e:es) | isJust i = defraged:(defragParts (delete e' es))
                   | otherwise = e:(defragParts es)
  where i = findIndex (isAdjacent e) es
        e' = es !! (fromJust i)
        defraged = ((eventWhole e, part),eventValue e)
        part = (start,end)
        start = min (fst $ eventPart e) (fst $ eventPart e')
        end = max (snd $ eventPart e) (snd $ eventPart e')

-- | Returns 'True' if the two given events are adjacent parts of the same whole
isAdjacent :: Eq a => Event a -> Event a -> Bool
isAdjacent e e' = (eventWhole e == eventWhole e')
                  && (eventValue e == eventValue e')
                  && (((snd $ eventPart e) == (fst $ eventPart e'))
                      ||
                      ((snd $ eventPart e') == (fst $ eventPart e))
                     )

-- | Apply one of three functions to a Value, depending on its type
applyFIS :: (Double -> Double) -> (Int -> Int) -> (String -> String) -> Value -> Value
applyFIS f _ _ (VF f') = VF $ f f'
applyFIS _ f _ (VI i ) = VI $ f i
applyFIS _ _ f (VS s ) = VS $ f s

-- | Apply one of two functions to a Value, depending on its type (int
-- or float; strings are ignored)
fNum2 :: (Int -> Int -> Int) -> (Double -> Double -> Double) -> Value -> Value -> Value
fNum2 fInt _      (VI a) (VI b) = VI $ fInt a b
fNum2 _    fFloat (VF a) (VF b) = VF $ fFloat a b
fNum2 _    fFloat (VI a) (VF b) = VF $ fFloat (fromIntegral a) b
fNum2 _    fFloat (VF a) (VI b) = VF $ fFloat a (fromIntegral b)
fNum2 _    _      x      _      = x

getI :: Value -> Maybe Int
getI (VI i) = Just i
getI _  = Nothing

getF :: Value -> Maybe Double
getF (VF f) = Just f
getF _  = Nothing

getS :: Value -> Maybe String
getS (VS s) = Just s
getS _  = Nothing

__compress :: Arc -> Pattern a -> Pattern a
__compress (s,e) p | s > e = empty
                   | s > 1 || e > 1 = empty
                   | s < 0 || e < 0 = empty
                   | otherwise = s `rotR` _fastGap (1/(e-s)) p

__compressTo :: Arc -> Pattern a -> Pattern a
__compressTo (s,e) p = __compress (cyclePos s, e-(sam s)) p

_fastGap :: Time -> Pattern a -> Pattern a
_fastGap 0 _ = empty
_fastGap r p = splitQueries $ 
  withResultArc (\(s,e) -> (sam s + ((s - sam s)/r'),
                             sam s + ((e - sam s)/r')
                            )
                 ) $ p {query = f}
  where r' = max r 1
        -- zero width queries of the next sam should return zero in this case..
        f st@(State a _) | fst a' == nextSam (fst a) = []
                         | otherwise = query p st {arc = a'}
          where mungeQuery t = sam t + (min 1 $ r' * cyclePos t)
                a' = mapBoth mungeQuery a

-- | Shifts a pattern back in time by the given amount, expressed in cycles
rotL :: Time -> Pattern a -> Pattern a
rotL t p = withResultTime (subtract t) $ withQueryTime (+ t) p

-- | Shifts a pattern forward in time by the given amount, expressed in cycles
rotR :: Time -> Pattern a -> Pattern a
rotR t = rotL (0-t)

-- ** Event filters

-- | Remove events from patterns that to not meet the given test
filterValues :: (a -> Bool) -> Pattern a -> Pattern a
filterValues f p = p {query = (filter (f . snd)) . query p}

-- | Turns a pattern of 'Maybe' values in to a pattern of values,
-- dropping the events of 'Nothing'.
filterJust :: Pattern (Maybe a) -> Pattern a
filterJust p = fromJust <$> (filterValues (isJust) p)

filterWhen :: (Time -> Bool) -> Pattern a -> Pattern a
filterWhen test p = p {query = filter (test . eventWholeOnset) . query p}

playFor :: Time -> Time -> Pattern a -> Pattern a
playFor s e = filterWhen (\t -> and [t >= s, t < e])

-- ** Temporal parameter helpers

tParam :: (a -> Pattern b -> Pattern c) -> (Pattern a -> Pattern b -> Pattern c)
tParam f tv p = innerJoin $ (`f` p) <$> tv

tParam2 :: (a -> b -> Pattern c -> Pattern d) -> (Pattern a -> Pattern b -> Pattern c -> Pattern d)
tParam2 f a b p = unwrap $ (\x y -> f x y p) <$> a <*> b

tParam3 :: (a -> b -> c -> Pattern d -> Pattern e) -> (Pattern a -> Pattern b -> Pattern c -> Pattern d -> Pattern e)
tParam3 f a b c p = unwrap $ (\x y z -> f x y z p) <$> a <*> b <*> c

tParamSqueeze :: (a -> Pattern b -> Pattern c) -> (Pattern a -> Pattern b -> Pattern c)
tParamSqueeze f tv p = unwrapSqueeze $ (`f` p) <$> tv