import time
from myque import myque
class elevator:
  def __init__(self,layers):
    self.building_layers = layers
    self.direction = 'up'
    self.cur_layer = 1
    self.up_queue = myque()
    self.down_queue = myque(True)
    self.switcher = 'open'
  def stop(self):
    self.switcher='stop'
  def push_button(self,layer,direction=None):
    if self.cur_layer>layer:
      self.down_queue.insert(layer)
    elif self.cur_layer<layer:
      self.up_queue.insert(layer)
    else:
      if self.direction=='up':
        self.down_queue.insert(layer)
      else:
        self.up_queue.insert(layer)
  def handle_queue(self,direction):
    self.direction = direction
    if direction == 'up':
      inc = 1
    else:
      inc = -1
    que = getattr(self , direction + '_queue')
    while que.length():
      while self.cur_layer != que.front():
        print '/nelevator in ',self.cur_layer
        time.sleep(1)
        self.cur_layer += inc
      print '/nelevator arrives at ',self.cur_layer
      que.pop_front()
  def run(self):
    while self.switcher=='open':
      if self.up_queue.empty() and self.down_queue.empty():
        """elevator now is waiting, stop at a layer"""
        time.sleep(1)
        continue
      """go up"""
      self.handle_queue('up')
      """go down"""
      self.handle_queue('down')

import threading
class myque:
  def __init__(self,reverse=False):
    self.mode = reverse
    self.buf = []
    self.lock = threading.Lock()
  def insert(self,object):
    self.lock.acquire()
    self.buf.append(object)
    self.buf.sort(reverse = self.mode)
    self.lock.release()
  def front(self):
    return self.buf[0]
  def pop_front(self):
    self.lock.acquire()
    self.buf.pop(0)
    self.lock.release()
  def length(self):
    self.lock.acquire()
    size = len(self.buf)
    self.lock.release()
    return size
  def empty(self):
    self.lock.acquire()
    size = len(self.buf)
    self.lock.release()
    return size==0

import threading
from elevator import elevator
def init_elevator(building_layers):
  e = elevator(building_layers)
  t = threading.Thread(target = e.run)
  t.setDaemon(True)
  t.start()
  return (e,t)
def main():
  myelevator,ctl_thread = init_elevator(17)
  while True:
    str=raw_input("Input valid layer :")
    try:
      layer = int(str)
    except Exception:
      if str=='quit':
        myelevator.stop()
        ctl_thread.join()
        break
      else:
        print 'invalid input',str
        continue
    if layer not in range(1,myelevator.building_layers+1):
      continue
    myelevator.push_button(layer)
if __name__=='__main__':
  main()