# Message is simply an object with a source and destination
class Message():
	def __init__(self, src, dst):
		self.src = src
		self.dst = dst

# LAN is a broadcast domain - if any node on it sends a message, everyone else receives it
class LAN():
	def __init__(self, name):
		self.name = name

		# Receiver is any bridge or node on the LAN (anyone who hears the broadcast message)
		self.receivers = [] 

	# When a LAN receives a message, everyone on the LAN (nodes and bridges) except the sender should also receive it 
	def receive_broadcast(self, src, m):
		for receiver in self.receivers:
			if receiver is not src:
				receiver.receive_message(self, m)

# Store and forward device to extend LANs
class Bridge():
	def __init__(self, name, port_LAN_map):
		self.name = name

		# Sign up for all messages by adding itself as a receiver on the LANs it's connected to
		for l in port_LAN_map.values():
			l.receivers.append(self)

		self.ports = [p for p in port_LAN_map.keys()]

		# Keep track of which LANs are associated with which ports
		self.port_LAN_map = port_LAN_map

	# Takes a LAN that a message was received from and returns the corresponding port
	# that message came in on
	def in_port_from_LAN(self, in_LAN):
		in_port = None
		for port, LAN in self.port_LAN_map.items():
			if LAN == in_LAN:
				in_port = port

		assert in_port is not None, "in_port must be deduced based on which LAN sent this message"
		return in_port

	# TODO: Fix this function
	# in_LAN: LAN from which bridge received the message
	def receive_message(self, in_LAN, m):
		# Determine which port this message arrived on
		in_port = self.in_port_from_LAN(in_LAN)

		# Go through all the ports and send message to all ports except the one that message came in on
		for p in self.ports:
			if p is not in_port:
				self.port_LAN_map[p].receive_broadcast(self, m)

# The devices on LANs that send and receive messages
class Node():
	def __init__(self, name, LAN):
		self.name = name

		# Sign up for all messages by adding itself as a receiver on its LAN
		self.LAN = LAN
		self.LAN.receivers.append(self)

	# Send message on its LAN
	def send_message(self, dst):
		message = Message(self, dst)
		self.LAN.receive_broadcast(self, message)

	# Receive message and check whether it's intended for self
	def receive_message(self, in_LAN, m):
		if m.dst is self:
			print(f'{self.name}: received message from {m.src.name}. It is for me!')
		else:
			print(f'{self.name}: heard message from {m.src.name} but it is not for me')
		

def main():
	L1 = LAN("L1")
	A = Node("A", L1)
	B = Node("B", L1)
	
	L2 = LAN("L2")
	C = Node("C", L2)

	L3 = LAN("L3")
	D = Node("D", L3)

	L4 = LAN("L4")
	E = Node("E", L4)

	L5 = LAN("L5")
	F = Node("F", L5)
	G = Node("G", L5)

	# Initalize bridges with a mapping of port number: LAN
	B1 = Bridge("B1", {"P1": L1, "P2": L2, "P3": L4})
	B2 = Bridge("B2", {"P1": L1, "P2": L3, "P3": L5})
	
	# Add your messages below:


	
if __name__ == '__main__': 
	main()