{-
******************************************************************************
*                                  A F R P				     *
*									     *
*       Example:        Elevator					     *
*       Purpose:        Testing of the Elevator simulator.		     *
*	Authors:	Henrik Nilsson					     *
*									     *
*             Copyright (c) The University of Nottingham, 2004		     *
*									     *
******************************************************************************
-}

module Main where

import Data.List (sortBy, intersperse)
import Data.Maybe (catMaybes)

import FRP.Yampa
import FRP.Yampa.Utilities
import FRP.Yampa.Internals	-- Just for testing purposes.

import Elevator

smplPer = 0.01

lbps :: SF a (Event ())
lbps = afterEach [(3.0, ()), (2.0, ()), (50.0, ())]

rbps :: SF a (Event ())
rbps = afterEach [(20.0, ()), (2.0, ()), (18.0, ()), (15.001, ())]


-- Looks for interesting events by inspecting the input events
-- and the elevator position over the interval [0, t_max].

data State = Stopped | GoingUp | GoingDown deriving Eq


testElevator :: Time -> [(Time, ((Event (), Event ()), Position))]
testElevator t_max = takeWhile ((<= t_max) . fst) tios
    where
        -- Time, Input, and Output
        tios = embed (localTime &&& ((lbps &&& rbps >>^ dup)
                                     >>> second elevator))
                     (deltaEncode smplPer (repeat ()))


findEvents :: [(Time, ((Event (), Event ()), Position))]
              -> [(Time, Position, String)]
findEvents []                     = []
findEvents tios@((_, (_, y)) : _) = feAux Stopped y tios
    where
        feAux _    _    []                             = []
        feAux sPre yPre ((t, ((lbp, rbp), y)) : tios') =
            if not (null message) then 
                (t, y, message) : feAux s y tios'
            else
		feAux s y tios'
	    where
		s = if y == yPre then
		        Stopped
                    else if yPre < y then
                        GoingUp
                    else
			GoingDown

                ms = if s /= sPre then
		         case s of
			     Stopped ->   Just "elevator stopped"
			     GoingUp ->   Just "elevator started going up"
			     GoingDown -> Just "elevator started going down"
		     else
			 Nothing

		mu = if isEvent lbp then
                         Just "up button pressed"
                     else
                         Nothing

		md = if isEvent rbp then
                         Just "down button pressed"
                     else
                         Nothing

                message = concat (intersperse ", " (catMaybes [ms, mu, md]))

formatEvent :: (Time, Position, String) -> String
formatEvent (t, y, m) = "t = " ++ t' ++ ",\ty = " ++ y' ++ ":\t" ++ m
    where
	t' = show (fromIntegral (round (t * 100)) / 100)
	y' = show (fromIntegral (round (y * 100)) / 100)

ppEvents []       = return ()
ppEvents (e : es) = putStrLn (formatEvent e) >> ppEvents es

main = ppEvents (findEvents (testElevator 100))