import sys
sys.path.append("/usr/local/lib/python2.3/site-packages/")
import random
import pyipc
import time
import os

from string import atoi

# python Dining_Philosophers.py (N Philosophers) (t time in sec)
if len(sys.argv) < 3 or len(sys.argv) > 3:
    print "Usage: python Dining_Philosophers.py N t"
    print "N: The number of Philosophers"
    print "t: Duration of program in seconds"

# argv[1] is (N Philosophers)
# argv[2] is (t time in sec)
philosopher_N = sys.argv[1]
chopstick_N = sys.argv[1]
# number of philosophers = number of chopsticks
time_t = sys.argv[2]

children_list = []

# converts the command line arguments into integers
philosopher_N = atoi(philosopher_N)
chopstick_N = atoi(chopstick_N)
time_t = atoi(time_t)

def thinking(phil_id):
    print "Philosopher ", phil_id, " is thinking"

    random.seed()
    time.sleep( random.randint(1, 5) )
    
    return

def hungry(phil_id, chopsticks):
    print "Philosopher ", phil_id, " is hungry"

    chopsticks.wait(chopstick_N)
    
    if phil_id == 0:
        chopsticks.wait(chopstick_N - 1)
        #grab the left chopstick
    else:
        chopsticks.wait(phil_id - 1)
        # grab the left chopstick

    chopsticks.wait(phil_id)
    # grab the right chopstick

    chopsticks.signal(chopstick_N)

    return

def eating(phil_id):
    print "Philosopher ", phil_id, " is eating"

    random.seed()
    time.sleep( random.randint(1, 5) )

    if phil_id == 0:
        chopsticks.signal(chopstick_N - 1)
    else:
        chopsticks.signal(phil_id - 1)

    chopsticks.signal(phil_id)

    return

# -----------------------------
# Creating the Chopsticks
# -----------------------------

uniq_key = pyipc.ftok("Dining_Philosophers.py", 7)
chopsticks = pyipc.SemaphoreGroup(uniq_key, chopstick_N + 1)
# I make N + 1 semaphores because I use one extra semaphore 
# to prevent the situation when all the philosophers
# decide to grab their left chopstick at the same time

# -----------------------------
# The Birth of the Philosophers
# -----------------------------
phil_id = 0
# Variable that holds a unique id for each philosopher
# Sets the oldest philosopher to phil_id 0

for i in range( philosopher_N - 1 ):
    #this loop creates N - 1 philosophers
    pid = os.fork()
    if pid == 0:
        phil_id = i + 1
        break
    else:
        children_list.append(pid)
        continue

# ----------------------------
# The Philosophers live their lives
# ----------------------------
total_time = time.time() + time_t
while time.time() < total_time:
    thinking(phil_id)
    hungry(phil_id, chopsticks)
    eating(phil_id)

if phil_id == 0:
# oldest philosopher waits for everyone to die
# and does all the cleaning up
    for child in children_list:
        os.waitpid(child, 0)
    pyipc.removeIPC(chopsticks)