Dovecot Wildcard Email Sorter

mail.py

#! /home/dgt/venv/bin/python3
"""
Dovecot Wildcard Email Sorter

Used to sort inbound email to a wildcard address into category subfolders.

Used by me on Mythic Beasts hosted webmail.

Copyright 2021 Dan Trickey

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

"""
from pathlib import Path
from re import compile
from typing import Dict, List, Set

from jinja2 import Template
from pydantic import BaseModel
from ruamel.yaml import YAML

# Settings
HOMEDIR = Path("/home/dgt")
MAILCONF = HOMEDIR / "mail.yml"
PREFIX = "trickey"
MAILDIR = HOMEDIR / "popboxes/dan%trickey.uk/Maildir"
SUBSCRIPTIONS = MAILDIR / "subscriptions"
FORWARD_TEMPLATE_PATH = HOMEDIR / "forward-template.j2"
SUB_TEMPLATE_PATH = HOMEDIR / "subscriptions.j2"

# Static
FORWARD_RE = compile(f"^\.forward-{PREFIX}-([a-z0-9]+)$")
MAILBOX_RE = compile(f"^\.INBOX.([A-Za-z0-9]+)$")
yaml = YAML(typ='safe')

with FORWARD_TEMPLATE_PATH.open("r") as fh:
    FORWARD_TEMPLATE = Template(fh.read())

with SUB_TEMPLATE_PATH.open("r") as fh:
    SUB_TEMPLATE = Template(fh.read())

class MailConfig(BaseModel):
    folders: Dict[str, List[str]]
    
    @classmethod
    def load(cls) -> 'MailConfig':
        with MAILCONF.open("r") as fh:
            mc = cls(**yaml.load(fh))
            mc.verify_config()
            return mc
    @property
    def all_addresses(self) -> List[str]:
        return [i for s in self.folders.values() for i in s]
    
    def verify_config(self) -> None:
        all_addresses_set = set(self.all_addresses)
    
        # Check for duplicate addresses
        if len(self.all_addresses) != len(all_addresses_set):
            raise ValueError("Duplicate addresses in config.")
    
        # Check for default in use. We cannot use this.
        if "default" in all_addresses_set:
            raise ValueError("default is a reserved mailbox and cannot be assigned.")
    
    def get_folder(self, address: str) -> str:
        for f, v in self.folders.items():
            if address in v:
                return f
        raise IndexError("Unable to find folder for address")

class ForwardManager:

    def __init__(self) -> None:
        self._addresses: Set[str] = set()
        glob = HOMEDIR.glob(f".forward-{PREFIX}-*")
        for i in glob:
            res = FORWARD_RE.match(i.stem)
            if res:
                address, = res.groups()
                self._addresses.add(address)
            else:
                raise ValueError(f"{i.stem} does not match the right format")
        
        # Check that default is there, and remove it.
        if "default" not in self._addresses:
            raise ValueError("No default forward rule.")
        self._addresses.remove("default")

    @property
    def addresses(self) -> Set[str]:
        return self._addresses

class MailboxManager:

    def __init__(self) -> None:
        self._mailboxes: Set[str] = set()
        glob = MAILDIR.glob(".INBOX.*")
        for i in glob:
            res = MAILBOX_RE.match(i.name)
            if res:
                mailbox_name, = res.groups()
                self._mailboxes.add(mailbox_name)
            else:
                raise ValueError(f"{i.name} does not match the right format")

    @property
    def mailboxes(self) -> Set[str]:
        return self._mailboxes

if __name__ == "__main__":
    mc = MailConfig.load()
    fm = ForwardManager()
    mb = MailboxManager()

    missing_addresses = set(mc.all_addresses) - fm.addresses
    spurious_addresses = fm.addresses - set(mc.all_addresses)
    existing_addresses = set(mc.all_addresses) & fm.addresses

    print("Finding .forward files")
    print(f"\t{len(mc.all_addresses)} addresses configured.")
    print(f"\t{len(existing_addresses)} configured and defined.")
    print(f"\tNeed to add {len(missing_addresses)} address definitions")

    if len(spurious_addresses) > 0:
        print(f"\tSpurious addresses: {spurious_addresses}")
        raise ValueError("Unable to handle spurious addresses.")


    # Check that existing forward files are correct
    print("Checking existing .forward files are correct.")
    for i in existing_addresses:
        path = HOMEDIR / f".forward-{PREFIX}-{i}"
        print(f"\tChecking .forward-{PREFIX}-{i} => {mc.get_folder(i)}")
        with path.open("r") as fh:
            dat = fh.read()
        render = FORWARD_TEMPLATE.render(maildir=MAILDIR, folder=mc.get_folder(i))
        if dat != render:
            raise ValueError(f"{i} does not match template.")
        
    missing_mailboxes = set(mc.folders.keys()) - mb.mailboxes
    spurious_mailboxes = mb.mailboxes - set(mc.folders.keys())
    existing_mailboxes = set(mc.folders.keys()) & mb.mailboxes
    print("Finding Mailboxes")
    print(f"\t{len(mc.folders)} mailboxes configured.")
    print(f"\t{len(existing_mailboxes)} configured and defined.")
    print(f"\tNeed to add {len(missing_mailboxes)} mailboxes")

    if len(spurious_mailboxes) > 0:
        print(f"\t{len(spurious_mailboxes)} spurious mailboxes found.")
        raise ValueError("Unable to handle spurious mailboxes.")

    # Add missing mailboxes
    print(f"Adding {len(missing_mailboxes)} mailboxes.")
    for i in missing_mailboxes:
        path = MAILDIR / f".INBOX.{i}"
        print(f"\tAdding {path}")
        path.mkdir()

    # Add forward files for addresses
    print(f"Adding {len(missing_addresses)} .forward files.")
    for i in missing_addresses:
        print(f"\tAdding .forward-{PREFIX}-{i} => {mc.get_folder(i)}")
        render = FORWARD_TEMPLATE.render(maildir=MAILDIR, folder=mc.get_folder(i)) 
        path = HOMEDIR / f".forward-{PREFIX}-{i}"
        with path.open("w") as fh:
            fh.write(render) 
    
    
    # Update subscriptions file
    print("Updating dovecot subscriptions file.")
    render = SUB_TEMPLATE.render(folders=mc.folders.keys())
    sub_path = MAILDIR / "subscriptions"
    with sub_path.open("w") as fh:
        fh.write(render)