#!/usr/bin/env python3

def validate_aliases(aliases):
	for alias in aliases:
		unknown_attributes = alias.keys() - {'addresses', 'senders', 'receivers', 'senders_and_receivers'}
		if unknown_attributes:
			raise ValueError('Unknown alias attributes: ' + ', '.join(unknown_attributes))
		for address in alias['addresses']:
			if not address.islower():
				raise ValueError(f'Aliases are not case-sensitive. Make "{address}" all-lowercase!')
			if address.strip() != address:
				raise ValueError(f'Remove surrounding whitespace in "{address}"!')

class FilterModule(object):
	def filters(self):
		return {
				'postfix_resolve_senders': self.postfix_resolve_senders,
				'postfix_resolve_receivers': self.postfix_resolve_receivers,
			}

	def postfix_resolve_senders(self, aliases, match_sender_domain, allow_sender_domains=tuple()):
		validate_aliases(aliases)
		sender_suffix = '@' + match_sender_domain
		address_sender_address_map = {}
		for alias in aliases:
			for address in alias['addresses']:
				address_sender_address_map.setdefault(address, set())
				address_sender_address_map[address] |= set(alias.get('senders', []))
				address_sender_address_map[address] |= set(alias.get('senders_and_receivers', []))
		for _ in range(100):
			done = True
			for address, senders in address_sender_address_map.items():
				for sender in set(senders):
					if sender.endswith(sender_suffix):
						continue
					done = False
					if sender not in address_sender_address_map:
						raise Exception(f'Address does not resolve to sender address: {sender}')
					senders.remove(sender)
					senders |= address_sender_address_map[sender]
			if done:
				break
		if not done:
			raise Exception('Recursion limit reached')

		address_sender_name_map = {}
		for address, senders in address_sender_address_map.items():
			address_sender_name_map[address] = set()
			for sender in senders:
				username = sender[:-len(sender_suffix)]
				address_sender_name_map[address].add(username)
				for domain in allow_sender_domains:
					address_sender_name_map[address].add(f'{username}@{domain}')
		return address_sender_name_map

	def postfix_resolve_receivers(self, aliases):
		validate_aliases(aliases)
		address_receiver_address_map = {}
		for alias in aliases:
			for address in alias['addresses']:
				address_receiver_address_map.setdefault(address, set())
				address_receiver_address_map[address] |= set(alias.get('receivers', []))
				address_receiver_address_map[address] |= set(alias.get('senders_and_receivers', []))
		return address_receiver_address_map