#!/usr/bin/env python3
"""
ics_mail_importer.py
--------------------
Sucht in einem mailbox.org IMAP-Postfach nach E-Mails mit .ics-Anhängen
und importiert die enthaltenen Termine automatisch in einen CalDAV-Kalender.

Benötigte Pakete:
    pipenv install caldav icalendar

Einrichtung:
    1. config.ini ausfüllen (liegt im gleichen Verzeichnis)
    2. Optional: Als Cronjob einrichten (z.B. alle 30 Minuten)
       */30 * * * * /pfad/zu/python3 /pfad/zum/ics_mail_importer.py
"""

import imaplib
import email
import os
import logging
import hashlib
import configparser
from pathlib import Path
from datetime import datetime, timezone

import caldav
from icalendar import Calendar

# ─────────────────────────── Logging ───────────────────────────────────────────
LOG_FILE = Path(__file__).parent / "ics_importer.log"
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(message)s",
    handlers=[
        logging.FileHandler(LOG_FILE),
        logging.StreamHandler(),
    ],
)
log = logging.getLogger(__name__)

# ─────────────────────────── Konfiguration laden ───────────────────────────────
CONFIG_FILE = Path(__file__).parent / "config.ini"

def load_config():
    if not CONFIG_FILE.exists():
        log.error("config.ini nicht gefunden. Bitte config.ini.example umbenennen und ausfüllen.")
        raise FileNotFoundError(str(CONFIG_FILE))
    cfg = configparser.ConfigParser()
    cfg.read(CONFIG_FILE)
    return cfg

# ─────────────────────────── Duplikat-Tracking ────────────────────────────────
SEEN_FILE = Path(__file__).parent / "imported_uids.txt"

def load_seen_uids():
    if not SEEN_FILE.exists():
        return set()
    return set(SEEN_FILE.read_text().splitlines())

def save_uid(uid: str):
    with SEEN_FILE.open("a") as f:
        f.write(uid + "\n")

# ─────────────────────────── IMAP-Anhänge holen ───────────────────────────────
def fetch_ics_attachments(cfg):
    host     = cfg["imap"]["host"]
    port     = int(cfg["imap"].get("port", "993"))
    username = cfg["imap"]["username"]
    password = cfg["imap"]["password"]
    folder   = cfg["imap"].get("folder", "INBOX")

    log.info(f"Verbinde mit IMAP {host}:{port} als {username} ...")
    conn = imaplib.IMAP4_SSL(host, port)
    conn.login(username, password)
    conn.select(folder)

    search_unseen_only = cfg["imap"].getboolean("unseen_only", fallback=True)
    criteria = "(UNSEEN)" if search_unseen_only else "ALL"
    _, msg_ids = conn.search(None, criteria)

    found = []
    for mid in msg_ids[0].split():
        _, data = conn.fetch(mid, "(RFC822)")
        raw = data[0][1]
        msg = email.message_from_bytes(raw)

        for part in msg.walk():
            ct   = part.get_content_type()
            fn   = part.get_filename() or ""

            is_ics = (
                ct in ("text/calendar", "application/ics")
                or fn.lower().endswith(".ics")
            )
            if not is_ics:
                continue

            ics_bytes = part.get_payload(decode=True)
            if not ics_bytes:
                continue

            uid_hash = hashlib.sha256(ics_bytes).hexdigest()
            log.info(f"  ics-Anhang gefunden: {fn!r} (Hash {uid_hash[:12]}…)")
            found.append((uid_hash, ics_bytes))

        if cfg["imap"].getboolean("mark_as_read", fallback=False):
            conn.store(mid, "+FLAGS", "\\Seen")

    conn.close()
    conn.logout()
    log.info(f"  {len(found)} .ics-Anhang/-Anhänge gefunden.")
    return found

# ─────────────────────────── CalDAV-Import ────────────────────────────────────
def import_to_caldav(cfg, ics_bytes: bytes, uid_hash: str):
    caldav_url = cfg["caldav"]["url"]
    username   = cfg["caldav"]["username"]
    password   = cfg["caldav"]["password"]

    client   = caldav.DAVClient(url=caldav_url, username=username, password=password)
    calendar = client.calendar(url=caldav_url)

    cal = Calendar.from_ical(ics_bytes)

    imported = 0
    for component in cal.walk():
        if component.name != "VEVENT":
            continue

        single_cal = Calendar()
        single_cal.add("prodid", "-//ics_mail_importer//DE")
        single_cal.add("version", "2.0")
        single_cal.add_component(component)

        uid = str(component.get("uid", uid_hash + f"-{imported}"))
        try:
            calendar.add_event(single_cal.to_ical().decode("utf-8"))
            log.info(f"    ✓ Termin importiert: {component.get('summary', '(kein Titel)')} [{uid[:20]}]")
            imported += 1
        except Exception as e:
            log.warning(f"    ✗ Fehler beim Import von {uid[:20]}: {e}")

    return imported

# ─────────────────────────── Hauptprogramm ────────────────────────────────────
def main():
    log.info("=" * 60)
    log.info(f"ICS-Importer gestartet ({datetime.now(timezone.utc).isoformat()})")

    cfg = load_config()
    seen_uids = load_seen_uids()

    attachments = fetch_ics_attachments(cfg)

    total_imported = 0
    for uid_hash, ics_bytes in attachments:
        if uid_hash in seen_uids:
            log.info(f"  Überspringe bereits importierten Anhang {uid_hash[:12]}…")
            continue

        n = import_to_caldav(cfg, ics_bytes, uid_hash)
        total_imported += n
        save_uid(uid_hash)

    log.info(f"Fertig. {total_imported} Termine insgesamt importiert.")
    log.info("=" * 60)

if __name__ == "__main__":
    main()