# Vending machine simulation

from time import sleep

from random import random, choice

class Machine:

priceList = {'A':10, 'B':15, 'C':20}

def __init__(self, items=None, deposit=50):

self.income = 0

self.items = items or {'A':5, 'B':5, 'C':5}

self.deposit = deposit

def insertCoin(self, n):

print('insert coin %d' % n)

self.income += n

return 'loadCoin'

def _refund(self):

if self.income:

print('return coin %d' % self.income)

self.income = 0

# send back coin TODO: API call

def cancel(self):

print('cancel')

self._refund()

return 'ready'

def _buyItem(self, name):

if self.items[name] > 0 and self.income >= self.priceList[name]:

print('send a goods: %s' % name)

self.items[name] -= 1

self.income -= self.priceList[name]

# TODO: Need to confirm if there is enough balance

self._refund()

return 0 # success

elif self.income < self.priceList[name]:

print('Insufficient amount, needs %d coin(s)' % (self.priceList[name]-self.income))

return 1 # Insufficient amount

elif self.items[name] <= 0:

print('item %s is sold out' % name)

return 2 # sold out

else:

print('something wrong, back to state<insertCoin>')

return -1

def buyItem(self, name):

respond = self._buyItem(name)

if respond == 0:

return 'ready'

else:

return 'loadCoin'

def randwalk(state):

cmdTable = {}

cmdTable['ready'] = ['insertCoin', 'cancel']

cmdTable['loadCoin'] = ['insertCoin', 'cancel', 'buyItem']

coinList = [1, 5, 10, 50]

itemList = ['A', 'B', 'C'] # other way: get machine.items at runtime

cmd = choice(cmdTable[state])

if cmd == 'insertCoin':

return cmd, choice(coinList)

elif cmd == 'buyItem':

return cmd, choice(itemList)

else:

return cmd

m = Machine()

s = 'ready'

cmd = ''

while True:

print('state=%s' % s)

cmd = randwalk(s)

if type(cmd) is tuple:

print('cmd=%s' % cmd[0])

s = getattr(m, cmd[0])(cmd[1]) # call m.cmd(arg) & get next state

else:

print('cmd=%s' % cmd)

s = getattr(m, cmd)()

sleep(1)