#!/usr/bin/python3

import subprocess, shutil, os, sqlite3, re
import utils

def validate_email(email, mode=None):
	# There are a lot of characters permitted in email addresses, but
	# Dovecot's sqlite driver seems to get confused if there are any
	# unusual characters in the address. Bah. Also note that since
	# the mailbox path name is based on the email address, the address
	# shouldn't be absurdly long and must not have a forward slash.

	if len(email) > 255: return False

	if mode == 'user':
		# For Dovecot's benefit, only allow basic characters.
		ATEXT = r'[\w\-]'
	elif mode == 'alias':
		# For aliases, we can allow any valid email address.
		# Based on RFC 2822 and https://github.com/SyrusAkbary/validate_email/blob/master/validate_email.py,
		# these characters are permitted in email addresses.
		ATEXT = r'[\w!#$%&\'\*\+\-/=\?\^`\{\|\}~]' # see 3.2.4
	else:
		raise ValueError(mode)

	# per RFC 2822 3.2.4
	DOT_ATOM_TEXT_LOCAL = ATEXT + r'+(?:\.' + ATEXT + r'+)*'
	if mode == 'alias':
		# For aliases, Postfix accepts '@domain.tld' format for
		# catch-all addresses. Make the local part optional.
		DOT_ATOM_TEXT_LOCAL = '(?:' + DOT_ATOM_TEXT_LOCAL + ')?'

	# as above, but we can require that the host part have at least
	# one period in it, so use a "+" rather than a "*" at the end
	DOT_ATOM_TEXT_HOST = ATEXT + r'+(?:\.' + ATEXT + r'+)+'

	# per RFC 2822 3.4.1
	ADDR_SPEC = '^%s@%s$' % (DOT_ATOM_TEXT_LOCAL, DOT_ATOM_TEXT_HOST)

	return re.match(ADDR_SPEC, email)

def open_database(env, with_connection=False):
	conn = sqlite3.connect(env["STORAGE_ROOT"] + "/mail/users.sqlite")
	if not with_connection:
		return conn.cursor()
	else:
		return conn, conn.cursor()

def get_mail_users(env):
	c = open_database(env)
	c.execute('SELECT email FROM users')
	return [row[0] for row in c.fetchall()]

def get_mail_aliases(env):
	c = open_database(env)
	c.execute('SELECT source, destination FROM aliases')
	return [(row[0], row[1]) for row in c.fetchall()]

def get_mail_domains(env, filter_aliases=lambda alias : True):
	def get_domain(emailaddr):
		return emailaddr.split('@', 1)[1]
	return set(
		   [get_domain(addr) for addr in get_mail_users(env)]
		 + [get_domain(source) for source, target in get_mail_aliases(env) if filter_aliases((source, target)) ]
		 )

def add_mail_user(email, pw, env):
	if not validate_email(email, mode='user'):
		return ("Invalid email address.", 400)

	# get the database
	conn, c = open_database(env, with_connection=True)

	# hash the password
	pw = utils.shell('check_output', ["/usr/bin/doveadm", "pw", "-s", "SHA512-CRYPT", "-p", pw]).strip()

	# add the user to the database
	try:
		c.execute("INSERT INTO users (email, password) VALUES (?, ?)", (email, pw))
	except sqlite3.IntegrityError:
		return ("User already exists.", 400)

	# write databasebefore next step
	conn.commit()

	# Create the user's INBOX and Spam folders and subscribe them.

	# Check if the mailboxes exist before creating them. When creating a user that had previously
	# been deleted, the mailboxes will still exist because they are still on disk.
	try:
		existing_mboxes = utils.shell('check_output', ["doveadm", "mailbox", "list", "-u", email, "-8"], capture_stderr=True).split("\n")
	except subprocess.CalledProcessError as e:
		c.execute("DELETE FROM users WHERE email=?", (email,))
		conn.commit()
		return ("Failed to initialize the user: " + e.output.decode("utf8"), 400)

	if "INBOX" not in existing_mboxes: utils.shell('check_call', ["doveadm", "mailbox", "create", "-u", email, "-s", "INBOX"])
	if "Spam" not in existing_mboxes: utils.shell('check_call', ["doveadm", "mailbox", "create", "-u", email, "-s", "Spam"])

	# Update things in case any new domains are added.
	return kick(env, "mail user added")

def set_mail_password(email, pw, env):
	# hash the password
	pw = utils.shell('check_output', ["/usr/bin/doveadm", "pw", "-s", "SHA512-CRYPT", "-p", pw]).strip()

	# update the database
	conn, c = open_database(env, with_connection=True)
	c.execute("UPDATE users SET password=? WHERE email=?", (pw, email))
	if c.rowcount != 1:
		return ("That's not a user (%s)." % email, 400)
	conn.commit()
	return "OK"

def remove_mail_user(email, env):
	conn, c = open_database(env, with_connection=True)
	c.execute("DELETE FROM users WHERE email=?", (email,))
	if c.rowcount != 1:
		return ("That's not a user (%s)." % email, 400)
	conn.commit()

	# Update things in case any domains are removed.
	return kick(env, "mail user removed")

def add_mail_alias(source, destination, env, do_kick=True):
	if not validate_email(source, mode='alias'):
		return ("Invalid email address.", 400)

	conn, c = open_database(env, with_connection=True)
	try:
		c.execute("INSERT INTO aliases (source, destination) VALUES (?, ?)", (source, destination))
	except sqlite3.IntegrityError:
		return ("Alias already exists (%s)." % source, 400)
	conn.commit()

	if do_kick:
		# Update things in case any new domains are added.
		return kick(env, "alias added")

def remove_mail_alias(source, env, do_kick=True):
	conn, c = open_database(env, with_connection=True)
	c.execute("DELETE FROM aliases WHERE source=?", (source,))
	if c.rowcount != 1:
		return ("That's not an alias (%s)." % source, 400)
	conn.commit()

	if do_kick:
		# Update things in case any domains are removed.
		return kick(env, "alias removed")

def kick(env, mail_result=None):
	results = []

	# Inclde the current operation's result in output.

	if mail_result is not None:
		results.append(mail_result + "\n")

	# Create hostmaster@ for the primary domain if it does not already exist.
	# Default the target to administrator@ which the user is responsible for
	# setting and keeping up to date.

	existing_aliases = get_mail_aliases(env)

	administrator = "administrator@" + env['PRIMARY_HOSTNAME']

	def ensure_admin_alias_exists(source):
		# Does this alias exists?
		for s, t in existing_aliases:
			if s == source:
				return

		# Doesn't exist.
		add_mail_alias(source, administrator, env, do_kick=False)
		results.append("added alias %s (=> %s)\n" % (source, administrator))

	ensure_admin_alias_exists("hostmaster@" + env['PRIMARY_HOSTNAME'])

	# Get a list of domains we serve mail for, except ones for which the only
	# email on that domain is a postmaster/admin alias to the administrator.

	real_mail_domains = get_mail_domains(env,
		filter_aliases = lambda alias : \
			(not alias[0].startswith("postmaster@") \
			 and not alias[0].startswith("admin@")) \
			or alias[1] != administrator \
			)

	# Create postmaster@ and admin@ for all domains we serve mail on.
	# postmaster@ is assumed to exist by our Postfix configuration. admin@
	# isn't anything, but it might save the user some trouble e.g. when
	# buying an SSL certificate.
	for domain in real_mail_domains:
		ensure_admin_alias_exists("postmaster@" + domain)
		ensure_admin_alias_exists("admin@" + domain)

	# Remove auto-generated hostmaster/postmaster/admin on domains we no
	# longer have any other email addresses for.
	for source, target in existing_aliases:
		user, domain = source.split("@")
		if user in ("postmaster", "admin") and domain not in real_mail_domains \
			and target == administrator:
			remove_mail_alias(source, env, do_kick=False)
			results.append("removed alias %s (was to %s; domain no longer used for email)\n" % (source, target))

	# Update DNS and nginx in case any domains are added/removed.

	from dns_update import do_dns_update
	results.append( do_dns_update(env) )

	from web_update import do_web_update
	results.append( do_web_update(env) )

	return "".join(s for s in results if s != "")

if __name__ == "__main__":
	import sys
	if len(sys.argv) > 2 and sys.argv[1] == "validate-email":
		# Validate that we can create a Dovecot account for a given string.
		if validate_email(sys.argv[2], mode='user'):
			sys.exit(0)
		else:
			sys.exit(1)

	if len(sys.argv) > 1 and sys.argv[1] == "update":
		from utils import load_environment
		print(kick(load_environment()))