#!/usr/bin/env python3
# vim:sw=4 ts=4 et:

import email
import smtplib
import ssl
import socket
import sys
import os

try:
    from xtermcolor import colorize
    COLOR_ERROR = 0xff0000
    COLOR_WARN  = 0xffff00
    COLOR_GOOD  = 0x00ff00
    def print_error(val="", *args, **kwargs):
        return print(colorize(val, COLOR_ERROR), *args, **kwargs)
    def print_warn(val="", *args, **kwargs):
        return print(colorize(val, COLOR_WARN), *args, **kwargs)
    def print_good(val="", *args, **kwargs):
        return print(colorize(val, COLOR_GOOD), *args, **kwargs)
except ImportError:
    print("Install the python3-xtermcolor package for coloured output")
    print_error = print
    print_warn = print
    print_good = print

try:
    import yaml
except ImportError:
    print_error("ERROR: python yaml module not installed - run the following and try again:", file=sys.stderr)
    print("sudo apt-get install python3-yaml", file=sys.stderr)
    sys.exit(1)

def do_tls(conn, sslv):
    # Possible values of smtp_sslv: none|peer|client_once|fail_if_no_peer_cert
    try:
        # Creating a context with the purpose of server authentication implies verifying the certificate
        if not hasattr(ssl,'create_default_context'):
            # ssl.create_default_context is in Python 3.4+
            print_warn('WARNING: cannot attempt verification of server certificate:')
            print_warn(' (need Python 3.4+ to attempt verification)')
            # Damn you, openssl. Why don't you support IPv6?
            if conn.sock.family == socket.AddressFamily.AF_INET:
                print_warn(' You can verify the certificate manually by running:')
                print_warn(' echo quit | openssl s_client -CAfile /etc/ssl/certs/ca-certificates.crt \\')
                print_warn('   -starttls smtp -connect {}:{}'.format(*conn.sock.getpeername()[0:2]))
            return conn.starttls()
        sslcontext=ssl.create_default_context(purpose=ssl.Purpose.SERVER_AUTH)
        # The None below looks like might be a typo but it's not - it represents the ActiveRecord default (to verify)
        if sslv in (None, 'peer', 'client_once', 'fail_if_no_peer_cert'):
            # defaults are good
            conn.starttls(context=sslcontext)
        elif sslv in ('none',):
            # disable cert checking
            sslcontext.check_hostname = False
            sslcontext.verify_mode = ssl.CERT_NONE
            conn.starttls(context=sslcontext)
        else:
            raise ValueError('invalid value for DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: {}'.format(sslv))
    except smtplib.SMTPException as e:
        if (sslv is None) and ('STARTTLS extension not supported by server' in e.args[0]):
            print_warn("unable to establish TLS, continuing: {}".format(e.args[0]))
        else:
            raise

### Start of execution ###
cfgfile = sys.argv[1]
try:
    destemail = sys.argv[2]
except IndexError:
    destemail = input('Enter your email address: ')
srcemail  = 'nobody+launcher-mailtest@discourse.org'

# Read in the container yaml and grab the env section
cfgdata = yaml.safe_load(open(cfgfile).read())
envdata = cfgdata['env']

# Here are the variables we'll test
smtp_addr = envdata.get('DISCOURSE_SMTP_ADDRESS')
smtp_port = envdata.get('DISCOURSE_SMTP_PORT')
smtp_user = envdata.get('DISCOURSE_SMTP_USER_NAME')
smtp_pass = envdata.get('DISCOURSE_SMTP_PASSWORD')
smtp_sslv = envdata.get('DISCOURSE_SMTP_OPENSSL_VERIFY_MODE')

# Yoink out the settings from the file - we'll print them and put them in the email
testinfo = 'DISCOURSE_SMTP_ settings:\n'
for k,v in filter(lambda x: x[0].startswith('DISCOURSE_SMTP_'), envdata.items()):
    if 'PASSWORD' in k:
        v = '(hidden)'
    testinfo += ' {} = {}\n'.format(k,v)
print(testinfo)

# Ensure at least smtp-addr is specified - everything else is optional
if smtp_addr is None:
    print_error("ERROR: DISCOURSE_SMTP_ADDRESS not specified", file=sys.stderr)
    sys.exit(1)

if (smtp_user is None and smtp_pass is not None) or (smtp_user is not None and smtp_pass is None):
    print_error("ERROR: both username and password must be specified for auth", file=sys.stderr)
    sys.exit(1)

# Do we have a known good set of parameters?
known_good_settings = {
    ('smtp.mandrillapp.com', 587): 'Mandrill',
}
try:
    print_good('You are correctly configured to use: {}'.format(known_good_settings[smtp_addr,smtp_port]))
except KeyError:
    pass

# Try and ensure the test is valid
if destemail.split('@',1)[1] in smtp_addr:
    print_warn('WARNING: {} may be allowed to relay mail to {}, this may not be a valid test!'.format(smtp_addr, destemail))

# Outbound port smtp?
if smtp_port == 25 or smtp_port is None:
    print_warn('WARNING: many networks block outbound port 25 - consider an alternative (587?)')

# Outbound port smtps?
if smtp_port == 465:
    print_warn("WARNING: I can't yet handle testing port 465.")
    print_warn(" It's probably wrong though - most servers use 587 or 25 for submission.")

# Outbound port submission?
if smtp_port == 587:
    if smtp_user is None:
        print_warn('WARNING: trying to use the submission (587) port without authenticating will probably fail')

# Build the message and send!
msg = email.message.Message()
msg.add_header('From', 'nobody+launcher-mailtest@discourse.org')
msg.add_header('To', destemail)
msg.add_header('Subject', 'discourse launcher mailtest for {}'.format(os.path.basename(cfgfile)))
msg.set_payload(testinfo)

try:
    smtp = smtplib.SMTP(smtp_addr, smtp_port, timeout=5)
    #smtp.debuglevel=1
    do_tls(smtp,smtp_sslv)
    if smtp_user:
        smtp.login(smtp_user, smtp_pass)
    result = smtp.sendmail('nobody+launcher-mailtest@discourse.org', destemail, msg.as_string())
except socket.gaierror as e:
    print_error("ERROR: {}".format(e.args[-1]), file=sys.stderr)
    print(" Ensure that the host '{}' exists".format(smtp_addr), file=sys.stderr)
    sys.exit(1)
except socket.timeout as e:
    print_error("ERROR: {}".format(e.args[-1]), file=sys.stderr)
    print(" Ensure that the host '{}' is up and port {} is reachable".format(smtp_addr, smtp_port), file=sys.stderr)
    print(" If your settings are known-good, ensure outbound port {} is not blocked".format(smtp_port), file=sys.stderr)
    sys.exit(1)
except smtplib.SMTPConnectError as e:
    print_error("ERROR: {}".format(e.args[-1]), file=sys.stderr)
    print(" Ensure that the host '{}' is up and port {} is reachable".format(smtp_addr, smtp_port), file=sys.stderr)
    sys.exit(1)
except ssl.SSLError as e:
    print_error("ERROR: unable to establish TLS: {}".format(e.args[-1]), file=sys.stderr)
    if 'certificate verify failed' in e.args[-1]:
        print(" Fix the host certificate or disable validation".format(smtp_addr), file=sys.stderr)
    sys.exit(1)
except smtplib.SMTPRecipientsRefused as e:
    print_error("ERROR: {}".format(e.args[-1].popitem()[1][1].decode()), file=sys.stderr)
    print(" You must provide a username/password to send to this host", file=sys.stderr)
    sys.exit(1)
except smtplib.SMTPAuthenticationError as e:
    print_error("ERROR: {}".format(e.args[-1].decode()), file=sys.stderr)
    print(" Check to ensure your username and password are correct", file=sys.stderr)
    sys.exit(1)
except smtplib.SMTPException as e:
    print_error("ERROR: {}".format(e.args[-1]), file=sys.stderr)
    if 'SMTP AUTH extension not supported by server' in e.args[0]:
        print(" Authorization is not available - you may need to use TLS", file=sys.stderr)
    sys.exit(1)
except ValueError:
    print_error("ERROR: {}".format(e.args[-1]), file=sys.stderr)
    sys.exit(1)
    
print_good("Success!")