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

Konfiguration über .env-Datei mit python-dotenv.
"""

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

from dotenv import load_dotenv
import caldav
from icalendar import Calendar

BASE_DIR = Path(__file__).resolve().parent
load_dotenv(BASE_DIR / ".env")

LOG_FILE = BASE_DIR / "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__)

SEEN_FILE = BASE_DIR / "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")


def fetch_ics_attachments():
    host = os.getenv("IMAP_HOST", "imap.mailbox.org")
    port = int(os.getenv("IMAP_PORT", "993"))
    username = os.getenv("IMAP_USERNAME")
    password = os.getenv("IMAP_PASSWORD")
    folder = os.getenv("IMAP_FOLDER", "INBOX")

    if not username or not password:
        raise RuntimeError("IMAP_USERNAME oder IMAP_PASSWORD fehlt in .env")

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

    unseen_only = os.getenv("IMAP_UNSEEN_ONLY", "true").lower() == "true"
    criteria = "(UNSEEN)" if 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))

        mark_read = os.getenv("IMAP_MARK_AS_READ", "false").lower() == "true"
        if mark_read:
            conn.store(mid, "+FLAGS", "\\Seen")

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


def import_to_caldav(ics_bytes: bytes, uid_hash: str):
    caldav_url = os.getenv("CALDAV_URL")
    username = os.getenv("CALDAV_USERNAME")
    password = os.getenv("CALDAV_PASSWORD")

    if not caldav_url or not username or not password:
        raise RuntimeError(
            "CALDAV_URL, CALDAV_USERNAME oder CALDAV_PASSWORD fehlt in .env"
        )

    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


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

    seen_uids = load_seen_uids()
    attachments = fetch_ics_attachments()

    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(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()