{-# OPTIONS -fglasgow-exts #-}

module Eg.Music.Simulator where

import Control.Monad (when)
import Data.Dynamic

data Simulator = Simulator
  { nextSearchComplete :: Integer
  , nextPlayStarted :: Integer
  , nextPlayComplete :: Integer
  , simulatorTime :: Integer
  , searchCompleteAction :: IO ()
  , playStartedAction :: IO ()
  , playCompleteAction :: IO ()
  }
  deriving Typeable

newSimulator = Simulator 0 0 0 0 (return ()) (return ()) (return ()) 

sooner sim event soon =
  if event > simulatorTime sim && event < soon
  then event else soon

nextEvent sim bound =
  sooner sim (nextSearchComplete sim)
  . sooner sim (nextPlayStarted sim)
  . sooner sim (nextPlayComplete sim)
  $ bound

perform sim = do
  let time = simulatorTime sim
  when (time == nextSearchComplete sim) (searchCompleteAction sim)
  when (time == nextPlayStarted sim) (playStartedAction sim)
  when (time == nextPlayComplete sim) (playCompleteAction sim)
  return ()

advance sim future =
  if simulatorTime sim < future
    then do
      let sim' = sim { simulatorTime = nextEvent sim future }
      perform sim'
      advance sim' future
    else return sim

schedule sim secs = simulatorTime sim + round (1000.0 * secs)
delay sim secs = advance sim (schedule sim secs)
waitSearchComplete sim = advance sim (nextSearchComplete sim)
waitPlayStarted sim = advance sim (nextPlayStarted sim)
waitPlayComplete sim = advance sim (nextPlayComplete sim)