#!/usr/bin/env python
# -*- coding: utf-8 -*-

import threading
import time

shared_resource_with_lock = 0
shared_resource_with_no_lock = 0
COUNT = 100000
shared_resource_lock = threading.Lock()

class Box(object):
    lock = threading.RLock()

    def __init__(self):
        self.total_items = 0

    def execute(self, n):
        Box.lock.acquire()
        self.total_items += n
        Box.lock.release()

    def add(self):
        Box.lock.acquire()
        self.execute(1)
        Box.lock.release()

    def remove(self):
        Box.lock.acquire()
        self.execute(-1)
        Box.lock.release()

def adder(box, items):
    while items > 0:
        print("adding 1 item in the box\n")
        box.add()
        time.sleep(5)
        items -= 1

def remover(box, items):
    while items > 0:
        print("removing 1 item in the box")
        box.remove()
        time.sleep(5)
        items -= 1

def increment_with_lock():
    global shared_resource_with_lock
    for i in range(COUNT):
        shared_resource_lock.acquire()
        shared_resource_with_lock += 1
        shared_resource_lock.release()

def decrement_with_lock():
    global shared_resource_with_lock
    for i in range(COUNT):
        shared_resource_lock.acquire()
        shared_resource_with_lock -= 1
        shared_resource_lock.release()

def increment_without_lock():
    global shared_resource_with_no_lock
    for i in range(COUNT):
        shared_resource_with_no_lock += 1

def decrement_without_lock():
    global shared_resource_with_no_lock
    for i in range(COUNT):
        shared_resource_with_no_lock -= 1

if __name__ == "__main__":
    t1 = threading.Thread(target = increment_with_lock)
    t2 = threading.Thread(target = decrement_with_lock)
    t3 = threading.Thread(target = increment_without_lock)
    t4 = threading.Thread(target = decrement_without_lock)
    t1.start()
    t2.start()
    t3.start()
    t4.start()
    t1.join()
    t2.join()
    t3.join()
    t4.join()
    print ("the value of shared variable with lock management is %s"\
    %shared_resource_with_lock)
    print ("the value of shared variable with race condition is %s"\
    %shared_resource_with_no_lock)

    items = 5
    print("putting %s items in the box " % items)
    box = Box()
    t1 = threading.Thread(target=adder, args=(box, items))
    t2 = threading.Thread(target=remover, args=(box, items))
    t1.start()
    t2.start()
    t1.join()
    t2.join()
    print ("%s items still remain in the box " % box.total_items)