#! /usr/lib/rads/venv/bin/python3
'''List sources of email sent by address and directory.'''

import os
import sys
import re
import glob
import gzip
import datetime
from collections import defaultdict
from argparse import ArgumentParser

__author__ = "Daniel K"
__email__ = "danielk@inmotionhosting.com"


def email_lines(all_logs=False):
    '''Return iterable over email log lines'''

    log_list = []

    if all_logs:
        log_list = glob.glob('/var/log/exim_mainlog?*')

        for log_file in log_list:

            if not os.path.exists(log_file):
                print(f"Could not find log file: {log_file}")
                sys.exit(1)

            with gzip.open(log_file, 'r') as mail_log:
                try:
                    yield from mail_log
                except OSError as error:
                    print(f"Error reading file '{log_file}': {error}")
                    sys.exit(1)

    log_file = "/var/log/exim_mainlog"

    if not os.path.exists(log_file):
        print(f"Could not find log file: {log_file}")
        sys.exit(1)

    with open(log_file, encoding='utf-8') as mail_log:
        try:
            yield from mail_log
        except OSError:
            print(f"Error reading file {log_file}")
            sys.exit(1)
        except UnicodeDecodeError as e:
            print(f"Received decoding error for {log_file}:")
            print(f"{e}")
            print("continuing...")


def get_domains(username=''):
    '''Get domain regex for username'''

    if username == '':
        return r'[^@ ]+'

    domain_list = []

    user_file = f"/var/cpanel/users/{username}"

    if not os.path.exists(user_file):
        print(
            "Could not find domains for {}. "
            "Invalid cPanel user? Cannot find {}".format(username, user_file)
        )
        sys.exit(1)

    dns_rx = re.compile(r"^DNS[0-9]*=(.*)$")

    with open(user_file, encoding='utf-8') as mail_log:
        try:
            for line in mail_log:
                dns_match = dns_rx.search(line)
                if dns_match is not None:
                    domain_list.append(dns_match.groups(1)[0])
        except OSError as error:
            print(f"Error reading file '{user_file}': {error}")
            sys.exit(1)

    return '|'.join(domain_list)


def get_sources(all_logs=False, username='', time=''):
    '''Returns touple of dicts of email sources'''

    email_logins = defaultdict(int)
    working_directories = defaultdict(int)
    spoofing = defaultdict(int)

    domains = get_domains(username)

    if time == '':
        date = ''
        duration = 0
    elif '-' in str(time):
        date = time
        duration = 0
    else:
        assert isinstance(time, int), "Time is not date or number"
        date = ''
        duration = int(time)
        target = datetime.datetime.now()

    datetime_rx = re.compile(r'\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}')
    login_rx = re.compile(
        r'(courier|dovecot)_(plain|login):(?P<login>[^@ ]+(@(?P<domain>{}))?) '
        r'.*for (?P<for>.*)$'.format(domains)
    )
    spoofing_rx = re.compile(
        r'<= (?P<sender>[^@]*@[^@ ]+)'
        r'.*(courier|dovecot)_(plain|login):'
        r'(?P<login>(?!(?P=sender))[^@ ]+(@(?P<sdom>{}))?)'
        r'.*for (?P<for>.*)$'.format(domains)
    )
    directory_rx = re.compile(fr'cwd=(?P<directory>/home/{username}[^ ]*)')

    for line in email_lines(all_logs):
        if date != '' and not line.startswith(date):
            continue

        if not datetime_rx.match(line):
            continue

        # If duration is set, skip any lines not within that duration
        if duration > 0 and not (
            duration
            > (
                target
                - datetime.datetime.strptime(line[:19], "%Y-%m-%d %H:%M:%S")
            ).total_seconds()
        ):
            continue

        rx_match = spoofing_rx.search(line.lower())
        if rx_match:
            logged_in = "{} as {}".format(
                rx_match.group('login'), rx_match.group('sender')
            )
            spoofing[logged_in] = spoofing[logged_in] + len(
                rx_match.group('for').split()
            )

        rx_match = login_rx.search(line.lower())
        if rx_match:
            address = rx_match.group('login')
            email_logins[address] = email_logins[address] + len(
                rx_match.group('for').split()
            )
            continue

        rx_match = directory_rx.search(line)
        if rx_match:
            directory = rx_match.group('directory')
            if '/usr/local/cpanel/' in directory:
                continue
            working_directories[directory] = working_directories[directory] + 1
            continue

    return (email_logins, working_directories, spoofing)


def print_sorted_dict(dictionary):
    '''Print a dictionary sorted by values'''

    for value in sorted(dictionary, key=dictionary.get):
        print(f"{dictionary[value]:>7}\t{value}")


def parse_args():
    '''Parse command line aruments'''

    parser = ArgumentParser(description=__doc__)

    parser.add_argument(
        "-a",
        "--all",
        action='store_true',
        help="Search all email logs, rather than only the recent log.",
    )

    parser.add_argument(
        'username',
        metavar='USER',
        type=str,
        nargs='?',
        help="Search for only email from a specific cPanel account",
    )

    time_group = parser.add_mutually_exclusive_group()

    time_group.add_argument(
        "-d",
        "--date",
        action='store',
        type=str,
        default='',
        help=(
            "Search for entries from a certain date. "
            "Must be in the format of YYYY-MM-DD."
        ),
    )

    time_group.add_argument(
        "-s",
        "--seconds",
        action='store',
        type=int,
        default=0,
        help=(
            "Search entries which were made within the specified "
            "number of seconds. Overrides --all."
        ),
    )

    time_group.add_argument(
        "-r",
        "--recent",
        action='store_true',
        help=(
            "Search recent entries, from the last hour. "
            "This is the same as -s 3600. Also overrides --all"
        ),
    )

    args = parser.parse_args()

    all_logs = args.all

    if args.username is None:
        username = ''
    else:
        username = args.username

    date_rx = re.compile(r"\d{4}-\d{2}-\d{2}")

    if args.recent:
        time = 3600
        all_logs = False
    elif args.date != '':
        if not date_rx.match(args.date):
            print(f"Date is not in the correct format: {args.date}")
            sys.exit(1)
        time = args.date
    elif args.seconds > 0:
        time = args.seconds
        all_logs = False
    else:
        time = ''

    return all_logs, username, time


def main():
    '''Main function for script'''

    (all_logs, username, time) = parse_args()

    (email_logins, working_directories, spoofing) = get_sources(
        all_logs, username, time
    )

    print("Email Logins:")
    print_sorted_dict(email_logins)

    print("\nSource directories:")
    print_sorted_dict(working_directories)

    print("\nPossibly spoofed emails:")
    if not len(spoofing) == 0:
        print_sorted_dict(spoofing)
    else:
        print("\tNo obvious spoofs found")


if __name__ == "__main__":
    main()