#!/usr/bin/python3

import sys
import subprocess
import json
import logging
import argparse
import email
import mailparser

_LOG_LEVEL_STRINGS = ['CRITICAL', 'ERROR', 'WARNING', 'INFO', 'DEBUG']

def _log_level_string_to_int(log_level_string):
    if not log_level_string in _LOG_LEVEL_STRINGS:
        message = 'invalid choice: {0} (choose from {1})'.format(log_level_string, _LOG_LEVEL_STRINGS)
        raise argparse.ArgumentTypeError(message)

    log_level_int = getattr(logging, log_level_string, logging.INFO)
    # check the logging log_level_choices have not changed from our expected values
    assert isinstance(log_level_int, int)

    return log_level_int

WL_PATH_DEF = "/etc/rspamd/local.d/whitelist.txt"
RC_PATH_DEF = "/usr/bin/rspamc"

parser = argparse.ArgumentParser(description="""Learn messages via rspamc and manage a sender whitelist. Depends on https://github.com/SpamScope/mail-parser.\n\nUse with local.d/multimap.conf:\nSENDER_FROM_WHITELIST {{
  type = "from";
  map = "file://{}"; # default; set this via -w/--whitelist-path
  prefilter = true;
  action = "accept";
  filter = "email";
}}""".format(WL_PATH_DEF), formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument("message_class", help="What to classify the message as: 'ham' or 'spam'")
parser.add_argument("--input", "-i", nargs='?', type=argparse.FileType('r'), default=sys.stdin, help="Mail message input; read from stdin by default")
parser.add_argument("-w", "--whitelist-path", help="Path to whitelist file *NEEDS TO BE WRITABLE BY THE CURRENT USER*; Default: {}".format(WL_PATH_DEF), default=WL_PATH_DEF)
parser.add_argument("-r", "--rspamc-path", help="Path to rspamc binary; Default: {}".format(RC_PATH_DEF), default=RC_PATH_DEF)
parser.add_argument("--log-file", help="Path to log file; Default: stdout", default=None)
parser.add_argument('--log-level',
                    default='INFO',
                    dest='log_level',
                    type=_log_level_string_to_int,
                    nargs='?',
                    help='Set the logging output level. {0}; Default: INFO'.format(_LOG_LEVEL_STRINGS))
parser.add_argument('--mailparse-log-level',
                    default='WARNING',
                    dest='mp_log_level',
                    type=_log_level_string_to_int,
                    nargs='?',
                    help='Set the mailparse logging output level. {0}; Default: INFO'.format(_LOG_LEVEL_STRINGS))

log = logging.getLogger()

if __name__ == "__main__":
    # parse argv
    args = parser.parse_args(args=None if sys.argv[1:] else ['--help'])

    # set up logging
    formatter = logging.Formatter('%(asctime)s:%(levelname)s: %(message)s')
    if args.log_file:
        fileHandler = logging.FileHandler("{}".format(args.log_file))
        fileHandler.setFormatter(formatter)
        log.addHandler(fileHandler)
    else:
        consoleHandler = logging.StreamHandler()
        consoleHandler.setFormatter(formatter)
        log.addHandler(consoleHandler)

    log.setLevel(args.log_level)
    logging.getLogger("mailparser").setLevel(args.mp_log_level)
    log.debug("Called rspamd_learn.py")

    # main
    try:
        cls = args.message_class
        if cls not in ("spam", "ham"):
            raise ValueError("First argument must be 'ham' or 'spam'")

        what = args.input.read()
        if not what:
            raise ValueError("Either pass the to-be-processed message as stdin or via -i/--input")

        # use mailparser to get sender addresses
        mail = mailparser.parse_from_string(what)
        from_lines = mail.from_[:]
        for k in ("return_path", "envelope_from", "sender", "x_mail_from"):
            val = getattr(mail, k)
            if not val:
                continue
            if not isinstance(val, list):
                val = [val]
            from_lines += email.utils.getaddresses(val)

        # parse current whitelist and update it according to the current message
        with open(args.whitelist_path, "r+", encoding="utf-8") as f:
            # this might be a tad naive
            whitelist_orig = f.read().split()
            whitelist = whitelist_orig[:]
            for omit, addr in list(set(from_lines)):
                if cls == "spam" and addr in whitelist:
                    action = "remove"
                elif cls == "ham" and addr not in whitelist:
                    action = "append"
                else:
                    log.debug("whitelist: {} already marked as {}".format(addr, cls))
                    continue

                log.info("{}: {}".format(cls, addr))
                getattr(whitelist, action)(addr)

            if whitelist_orig != whitelist:
                f.truncate(0)
                f.seek(0)
                f.writelines("\n".join(whitelist)+"\n")

        # rspamc learn message
        ret = subprocess.check_output([args.rspamc_path, "learn_{}".format(cls)], input=what, universal_newlines=True)
        log.debug("Rspamc result: {}".format(ret))

    except Exception as e:
        log.exception(e)
        sys.exit(1)