// Copyright 1999 Regents of The University of Michigan
// This makes all public classes defined for the simulator package available to this class
import umich.coabs.simulator.*;
import java.awt.*;

/**
   This class is a decision maker that controls the single transport
   in its entities list.  The transport explores the network by
   avoiding locations it has already visited and actively searching
   for evacuees, stopping at each location to allow evacuees to embark
   or disembark.  It has a very simple state machine and can get stuck
   if one of its actions fails.

   @author Brad Clement, bradc@umich.edu 
*/
public class SmartestTransportDM extends DecisionMaker {
  int state = 0;  // the state of the state machine
  Location destination;  // global variable for keeping track of where 
                         // it wants to go
  LinkedList visitedLocations;

  /**
     Just passes basics up to the costructor of the parent class, 
     <tt>DecisionMaker</tt>
  */
  public SmartestTransportDM(String i, LinkedList e, Control c) {
    super(i, e, c);
    visitedLocations = new LinkedList();
  }

  /**
     This is the method that is called on each decision cycle by the
     Control object of the simulator.  It controls the behavior of the
     transport in its <tt>entities</tt> list.  Sometimes the
     transports will not successfully move to a location.  The results
     of these action failures are defined in the Transport class.  The
     default is nothing changes, and a message is printed.
     Additionally, this decision maker often winds up in the wrong
     state and gets stuck when an action fails.  For example, this can
     happen when two transports try to go opposite ways on a one-lane
     road or when a transport tries to traverse a route that has been
     destroyed.
  */
  public void TakeStep() {
    ListElement elem, elem1;  // for stepping through lists
    LinkedList candidates = new LinkedList();  // candidate routes to take
    int i, n;
    Route r;  // the chosen route to traverse
    Route tr;  // temporary route var
    Location tl;  // temporary route var
    double time = 0.0;  // used to wait for a specified time
    Transport me = (Transport)entities.head.data;  // get the transport at 
                                                   // the front of the 
                                                   // entities list
    boolean seeEvacs = false;  // true when an adjacent location has evacuees
    boolean seeSafety = false;  // true when an adjacent location is safe

    // Take step for state 0
    if (state == 0) {
      visitedLocations.Add(me.getCurLocation());
      // Find candidate routes preferring those to locations with evacuees, 
      // then safety points when carrying evacuees, then locations never 
      // visited
      for (elem=me.getCurLocation().getRoutes().head; elem!=null; 
	   elem=elem.next) {
	tr = (Route)elem.data;
	// Get location at end of route
	if (tr.getEndpt1() == me.getCurLocation())
	  tl = tr.getEndpt2();
	else
	  tl = tr.getEndpt1();
	// If this is a safety location, and we haven't spotted evacuees
	if (!seeEvacs && (tl.getColor() == Color.green)) {
	  // If this is the first safety location we've spotted, dump current 
	  // candidates and set flag
	  if (!seeSafety && (me.getEvacuees().size > 0)) {
	    candidates.Empty();
	    seeSafety = true;
	  }
	  // Add route to safety location to candidates
	  candidates.Add(tr);
	} else 
	  // Not a safety location or we're only looking for evacuees
	  // If we haven't visited this location before
	  if (visitedLocations.Find(tl) == null) {
	    // If there are evacuees there
	    if (tl.getEvacuees().size > 0) {
	      // If this is the first time we've spotted evacuees, dump 
	      // current candidates and set flag
	      if (!seeEvacs) {
		candidates.Empty();
		seeEvacs = true;
	      }
	      // Add route to location with evacuees to candidates
	      candidates.Add(tr);
	    }
	    // Add route if we're only after places we haven't been before
	    if (!seeEvacs && !seeSafety) candidates.Add(tr);
	  }
      }
      if (candidates.size == 0) {
	candidates = me.getCurLocation().getRoutes();
      }
      // Pick a random route to traverse; assign it to r
      n = (int) (candidates.size * java.lang.Math.random());
      if (n == candidates.size)
	--n;
      elem = candidates.head;
      for (i = 0; i < n; i++)
	elem = elem.next;
      r = (Route) elem.data;
      // Get the location at the other end of the route
      if (r.getEndpt1() == me.getCurLocation())
	destination = r.getEndpt2();
      else
	destination = r.getEndpt1();
      // Move the transport along the chosen route; additionally destroy 
      // the route with 0.0 probability
      if (java.lang.Math.random() < 1.0)
	me.Move(destination, r);
      else
	me.MoveAndDestroy(destination, r);
      // Go to next state
      state = 1;
    } else
      // Take step for state 1
      if (state == 1) {
	// If transport has arrived at its destination, set a timer to 
	// wait at the current location to let evacuees embark or disembark
	if (me.getCurLocation() == destination) {
	  time = ctrl.getTime();
	  state = 2;
	}
      } else
	// Take step for state 2
	if (state == 2) {
	  // If time is up go back to state 0 to move to another location
	  if (ctrl.getTime() - time >= 4.0)
	    state = 0;
	}
  }
}