# E-2 MCS 275 Fri 16 Apr 2010 : ex2q4.py

# Define a Thread class to model floating disks on a canvas.

# Before sleeping one second the disks move their position at random.
# After each move the disks check whether they have collided
# with another disk.  Disks no longer move after a collision.
# Disks also stop moving after 15 moves.

from threading import *
from random import randint
from time import sleep

class Disk(Thread):
   """
   Floating disks on canvas.
   """
   def __init__(self,n,p,L):
      """
      Disk n is initialized with a start position with coordinates in p
      and a list L of all positions of all other disks.
      We have the L[n] with equal the position of the n-th disk.
      """
      Thread.__init__(self,name=n)
      self.position = p
      self.stopped = False 
      self.others = L
      self.moves = 15

   def collision(self):
      """
      Returns k if the position of the disk is the same of
      some other disk at position k, otherwise returns -1.
      """
      n = int(self.getName())
      for i in range(0,len(self.others)):
         if i != n:
            if self.position == self.others[i]: return i
      return -1

   def run(self):
      """
      If not yet stopped or if no other disk has collided with it,
      the disk will make a random move.
      """
      sleep(1)
      n = self.getName()
      while not self.stopped and (self.moves > 0):
         k = self.collision()
         if k != -1:
            self.stopped = True
            print 'Thread ' + n + ' collided with ' + str(k)
         else:
            a = randint(-1,+1); b = randint(-1,+1)
            self.position[0] = self.position[0] + a
            self.position[1] = self.position[1] + b
            s = 'Thread ' + n + ' moves to ' + str(self.position)
            self.others[int(n)] = self.position
            self.moves = self.moves - 1
            k = self.collision()
            if k != -1:
               self.stopped = True
               s = s + ' collided with ' + str(k)
            print s

def main():
   """
   Prompts user for number of disks, 
   generates as many disks as the number entered.
   """
   n = input('give number of threads : ')
   print 'creating', n, 'threads ...'
   L = []; T = []
   for i in range(0,n):
      L.append([i,0])
      T.append(Disk(str(i),[i,0],L))
   print 'starting', n, 'threads ...'
   for t in T: t.start()

main()