-- library & type definitions for Thomas
-- richard buckland
-- task 2, comp1711 2003 s1
-- ver 0.2  17 April 2003
--          21 April 2003 - assumptions moved to Assumptions.txt
-- ver 1.0  22 April 2003 - fixed typo in comments re behaviour
--                          of reversed fork tracks when receive
--                          a command

module ThomasLib where

-------------------------------------
-- types used in Network interface --
-------------------------------------

type TrackData = ([Track],[Light],[Control])

data Track = Simple TrackName From To    |
             Fork   TrackName From To To |
             Stop   TrackName From
   deriving (Eq,Ord,Show,Read)

type TrackName = String
type From      = TrackName
type To        = TrackName

   -- Simple = straight or curved section of track
   -- Fork   = Y section, precisely one of the 'To'
   --          segments is connected to the 'From'
   --          segment depending on the position
   --          of the switch.
   -- Stop   = a track terminator

type Light   = [Track]

   -- the fat controller has a number of lights on his control
   -- panel.  A light is on (True) if and only if there is a
   -- train on any of the [Track] corresponding to that light.

   -- For simplicity we will say a train is "on" a section of track
   -- if and only if the very front of the train is on the track.
   -- Thus a train is only "on" one Track at any time.  In this
   -- simulator we will regard each train as being a point (ie
   -- we will ignore its length)

type Control = [(Track,Normal)]
type Normal = Bool

   -- The fat controller has a number of On/Off control buttons on his
   -- control panel.  If a control button is changed from to True to
   -- False, or visa versa, then a motor changes each Track in the
   -- Control's track list depending on whether the motor for that
   -- track is "normal" or "reversed".  This means:
   --
   --
   -- 1. For "Normal" tracks:
   --  Simple tracks:
   --     Control Button==True  = Stop train on this segment
   --     Control Button==False = Let train pass thru
   --  Fork tracks:
   --     Control Button==True  = connect 'From' to first 'To'
   --     Control Button==False = connect 'From' to second 'To'
   --
   -- 2. For "reversed" tracks:
   --  Simple tracks:
   --     Control Button==True  = Let train pass thru
   --     Control Button==False = Stop train on this segment
   --  Fork tracks:
   --     Control Button==True  = connect 'From' to second 'To'
   --     Control Button==False = connect 'From' to first 'To'



type Train     = (TrainName,[Truck])
data TrainName = Thomas | Gordon | James | Henry
   deriving (Eq,Ord,Show,Read)
data Truck = Coal | Milk | Mail
   deriving (Eq,Ord,Show,Read)

   -- each train has a name and pulls some trucks
   -- each truck can carry one sort of good only


type Market      = ([Source],[Destination])
type Source      = (Truck,Track)
type Destination = (Truck,Track,Profit)
type Profit      = Float

  -- there are certain locations on the network where
  -- trucks can load up with their goods.  This happens
  -- automatically the instant the train reaches the
  -- location.  There is no need to stop and no option
  -- not to load up when passing a source location.

  -- there are certain locations on the network where
  -- trucks can unload (deliver) their goods.   This
  -- happens automatically the instant the train reaches
  -- such a location.  There is no need to stop.  There
  -- is no option not to sell when passing such a location.
  -- When a truck unloads the train receives the
  -- corresponding profit.

type Speed      = Int

-- each track is exactly 4 units long.  In each tick of time
-- a train travels 0,1,2,3 or 4 units depending on the speed
-- of the train for that tick.  The speed will be an integer
-- in the range 0..4.  Speeds greater than 4 are erroneous and
-- will not occur.

type Command    = (ControlNum,On)
type ControlNum = Int
type On         = Bool

-- the Fat Controler issues commands by setting switches on his
-- panel.  (1,True) means set control button #1 to True.
-- Control button #1 is the second Control in the [Control] given
-- in the trackdata ("second" as list elements are numbered
-- from 0 remember)

type Message    = String