import socket
from subprocess import Popen, STDOUT, PIPE
from threading import Thread
ips = []
def start_new_math_thread(conn, addr):
	t = MathServerCommunicationThread(conn, addr)
	t.start()

class ProcessOutputThread(Thread): #OOPS
	def __init__(self, proc, conn):
		Thread.__init__(self)
		self.proc = proc
		self.conn = conn
		
	def run(self):
		while not self.proc.stdout.closed and not self.conn._closed:
			try:
				self.conn.sendall(self.proc.stdout.readline())
			except:
				pass
			
class MathServerCommunicationThread(Thread):
	def __init__(self, conn, addr):
		Thread.__init__(self)
		self.conn = conn
		self.addr = addr
	
	def run(self):
		print("{} connected with back port {}".format(self.addr[0], self.addr[1]))
		self.conn.sendall("Simple Math Server developed by LAHTP \n\nGive any math expressions, and I will answer you :) \n\n$ ".encode())

		## APPLICATION LAYER 7
		p = Popen(['bc'], stdout=PIPE, stdin=PIPE, stderr=STDOUT)
		output = ProcessOutputThread(p, self.conn)
		output.start()

		while not p.stdout.closed or not self.conn._closed:
			try: ## PRESENTATION LAYER 6
				data = self.conn.recv(1024)
				if not data:
					break
				else:
					try: 
						data = data.decode()
						query = data.strip()
						if query == 'quit' or query == 'exit':
							p.communicate(query.encode(), timeout=1)
							if p.poll() is not None:
								ips.remove(self.addr[0])
								print(self.addr[0],"Disconnected")
								break
						query = query + '\n'
						p.stdin.write(query.encode())
						p.stdin.flush()
					except:
						pass
			except:
				pass
		self.conn.close()

HOST = ''
PORT = 3075


## SESSION LAYER 5
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen() # Look for calling bell
while True: # To accept many incoming connections.
	conn, addr = s.accept() # Open door
 
	# only one connection for one IP
	if addr[0] not in ips:
		ips.append(addr[0])
		start_new_math_thread(conn, addr)
	else:
		print("Ip {} rejected because of already in connection".format(addr[0]))
		conn.sendall("You already connected, one request per IP\n".encode())
		conn.close()

s.close()