{-# LANGUAGE NoImplicitPrelude #-}
module Synthesizer.PiecewiseConstant.Signal (
   T,
   StrictTime,
   ShortStrictTime,
   LazyTime,
   subdivideLazy,
   subdivideLazyToShort,
   subdivideLongStrict,
   chopLongTime,
   zipWith,
   ) where

import qualified Data.EventList.Relative.TimeTime  as EventListTT
-- import qualified Data.EventList.Relative.TimeMixed as EventListTM
import qualified Data.EventList.Relative.MixedTime as EventListMT
import qualified Data.EventList.Relative.BodyTime  as EventListBT
-- import qualified Data.EventList.Relative.TimeBody  as EventList

import qualified Numeric.NonNegative.Class   as NonNeg
import qualified Numeric.NonNegative.Wrapper as NonNegW
import qualified Numeric.NonNegative.Chunky as NonNegChunky
import Numeric.NonNegative.Class ((-|), )

import Control.Monad.Trans.State (evalState, get, put, )
import Data.Traversable (traverse, )

import qualified Data.List as List
import Data.Maybe.HT (toMaybe, )

import NumericPrelude.Numeric
import NumericPrelude.Base hiding (zipWith, )
import qualified Prelude as P


type StrictTime = NonNegW.Integer
type ShortStrictTime = NonNegW.Int
type LazyTime = NonNegChunky.T StrictTime

type T = EventListBT.T StrictTime


{-# INLINE subdivideLazy #-}
subdivideLazy ::
   (NonNeg.C time) =>
   EventListBT.T (NonNegChunky.T time) body ->
   EventListBT.T time body
subdivideLazy =
   EventListBT.foldrPair
      (\y lt r ->
         List.foldr
            (\dt ->
               EventListMT.consBody y .
               EventListMT.consTime dt) r $
         NonNegChunky.toChunks (NonNegChunky.normalize lt))
      EventListBT.empty

{- |
Subdivide lazy times into chunks that fit into the number range
representable by @Int@.
-}
{-# INLINE subdivideLazyToShort #-}
subdivideLazyToShort ::
   EventListBT.T LazyTime y -> EventListBT.T ShortStrictTime y
subdivideLazyToShort =
   subdivideLazy .
   EventListBT.mapTime
      (NonNegChunky.fromChunks .
       List.concatMap chopLongTime .
       NonNegChunky.toChunks)

{- |
Returns a list of non-zero times.
-}
{-# INLINE chopLongTime #-}
chopLongTime :: StrictTime -> [ShortStrictTime]
chopLongTime n =
   let d = fromIntegral (maxBound :: Int)
       (q,r) = P.divMod (NonNegW.toNumber n) d
   in  map (NonNegW.fromNumberMsg "chopLongTime" . fromInteger) $
       List.genericReplicate q d ++
       if not $ isZero r then [r] else []


{-# INLINE subdivideLongStrict #-}
subdivideLongStrict ::
   EventListBT.T StrictTime y -> EventListBT.T ShortStrictTime y
subdivideLongStrict =
   subdivideLazy .
   EventListBT.mapTime
      (NonNegChunky.fromChunks . chopLongTime)


_subdivideMaybe ::
   EventListBT.T LazyTime y -> EventListBT.T StrictTime (Maybe y)
_subdivideMaybe =
   EventListBT.foldrPair
      (\y lt r ->
         case NonNegChunky.toChunks (NonNegChunky.normalize lt) of
            [] -> r
            (t:ts) ->
               EventListBT.cons (Just y) t $
               List.foldr (EventListBT.cons Nothing) r ts)
      EventListBT.empty

{- |
When a lazy time value is split into chunks
then do not just replicate the sample for the whole time,
but insert 'Nothing's.
-}
{-# INLINE subdivideMaybe #-}
subdivideMaybe ::
   EventListTT.T LazyTime y ->
   EventListTT.T StrictTime (Maybe y)
subdivideMaybe =
   EventListTT.foldr
      (\lt r ->
         uncurry EventListMT.consTime $
         case NonNegChunky.toChunks (NonNegChunky.normalize lt) of
            [] ->
               (NonNegW.fromNumber zero, r)
            (t:ts) ->
               (t, List.foldr (EventListBT.cons Nothing) r ts))
      (\y r -> EventListMT.consBody (Just y) r)
      EventListBT.empty

{-# INLINE unionMaybe #-}
unionMaybe ::
   EventListTT.T StrictTime (Maybe y) ->
   EventListTT.T LazyTime y
unionMaybe =
   EventListTT.foldr
      (\t ->
         EventListMT.mapTimeHead
            (NonNegChunky.fromChunks . (t:) . NonNegChunky.toChunks))
      (\my ->
         case my of
            Nothing -> id
            Just y ->
               EventListMT.consTime NonNegChunky.zero .
               EventListMT.consBody y)
      (EventListTT.pause NonNegChunky.zero)

zipWithCore ::
   (a -> b -> c) ->
   a -> b ->
   EventListTT.T StrictTime (Maybe a) ->
   EventListTT.T StrictTime (Maybe b) ->
   EventListTT.T StrictTime (Maybe c)
zipWithCore f =
   let switch ac ar g =
          flip (EventListMT.switchBodyL EventListBT.empty) ar $ \am ar1 ->
          g (maybe (False,ac) ((,) True) am) ar1
       cont j ac bc as bs =
          EventListMT.consBody (toMaybe j $ f ac bc) $
          recourse ac bc as bs
       recourse ac bc as bs =
          flip EventListMT.switchTimeL as $ \at ar ->
          flip EventListMT.switchTimeL bs $ \bt br ->
          let ct = min at bt
          in  -- ToDo: redundant comparison of 'at' and 'bt'
              EventListMT.consTime ct $
              case compare at bt of
                 LT ->
                    switch ac ar $ \(ab,a) ar1 ->
                       cont ab a bc ar1 (EventListMT.consTime (bt-|ct) br)
                 GT ->
                    switch bc br $ \(bb,b) br1 ->
                       cont bb ac b (EventListMT.consTime (at-|ct) ar) br1
                 EQ ->
                    switch ac ar $ \(ab,a) ar1 ->
                    switch bc br $ \(bb,b) br1 ->
                       cont (ab||bb) a b ar1 br1
   in  recourse

zipWith ::
   (a -> b -> c) ->
   EventListBT.T StrictTime a ->
   EventListBT.T StrictTime b ->
   EventListBT.T StrictTime c
zipWith f as0 bs0 =
   flip (EventListMT.switchBodyL EventListBT.empty) as0 $ \a0 as1 ->
   flip (EventListMT.switchBodyL EventListBT.empty) bs0 $ \b0 bs1 ->
   let c0 = f a0 b0
   in  EventListMT.consBody c0 $
       flip evalState c0 $
       traverse (\mc -> maybe (return ()) put mc >> get) $
       zipWithCore f a0 b0 (fmap Just as1) (fmap Just bs1)

_zipWithLazy ::
   (a -> b -> c) ->
   EventListBT.T LazyTime a ->
   EventListBT.T LazyTime b ->
   EventListBT.T LazyTime c
_zipWithLazy f as0 bs0 =
   flip (EventListMT.switchBodyL EventListBT.empty) as0 $ \a0 as1 ->
   flip (EventListMT.switchBodyL EventListBT.empty) bs0 $ \b0 bs1 ->
   EventListMT.consBody (f a0 b0) $ unionMaybe $
   zipWithCore f a0 b0 (subdivideMaybe as1) (subdivideMaybe bs1)
{-
*Synthesizer.PiecewiseConstant.ALSA.MIDI Data.EventList.Relative.MixedTime> zipWithLazy (,) ('a' ./ 2 /. 'b' ./ 7 /. EventListBT.empty) ('c' ./ (1 P.+ 1) /. 'd' ./ 1 /. EventListBT.empty)
-}