src/RMCA/Translator/Filter.hs

   1 -- Contains function for scheduling and filtering events given the
   2 -- correct informations.
   3
   4 module RMCA.Translator.Filter where
   5
   6 import Data.Bifunctor          as BF
   7 import Data.List               (sortBy)
   8 import Data.Ord
   9 import RMCA.Translator.Message
  10
  11 -- Takes a list of time stamped "things", a sample rate and a buffer
  12 -- size. The function argument is a function that needs to tell which
  13 -- arguments are kept in the case where two would come into
  14 -- contact. On the left are the events that can be thrown into the
  15 -- buffer, on the right are the events that will need to wait. Both
  16 -- list are sorted.
  17 --
  18 -- /!\ The frame number is relative. A preprocessing operation
  19 -- removing all events too soon to be happening and shifting them is
  20 -- necessary.
  21 schedule :: Frames
  22          -> [(Frames, a)]
  23          -> ([(Frames,a)], [(Frames,a)])
  24 schedule size = BF.first scatterEvents
  25                 . break ((>= size) . fst) . sortBy (comparing fst)
  26
  27 -- When to events are at the same frame, shift them so that they are
  28 -- all separated by one frame. Then take every list and make sure that
  29 -- the first frame of the next list is at least one frame after the
  30 -- last frame of that list.
  31 scatterEvents :: [(Frames, a)] -> [(Frames, a)]
  32 scatterEvents (x@(n,_):(m,b):xs) = x:scatterEvents ((m',b):xs)
  33   where m' = m + max 0 (1 + n - m)
  34 scatterEvents [x] = [x]
  35 scatterEvents _ = []