#!/usr/bin/env python3
"""
ics_mail_importer_env_v2.py
---------------------------
Sucht in einem mailbox.org IMAP-Postfach nach E-Mails mit .ics-Anhängen
und importiert die enthaltenen Termine automatisch in einen CalDAV-Kalender.

Wichtige Eigenschaften:
- Konfiguration über .env-Datei mit python-dotenv
- Duplikat-Schutz über Hash der ICS-Anhänge
- E-Mails werden beim Abrufen nicht automatisch als gelesen markiert
- Nur E-Mails mit erfolgreich verarbeitetem ICS-Anhang werden optional als gelesen markiert
"""

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 env_bool(name: str, default: str = "false") -> bool:
    return os.getenv(name, default).strip().lower() in {"1", "true", "yes", "on"}


def import_ics_to_caldav(ics_bytes: bytes, uid_hash: str) -> int:
    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 process_mailbox():
    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")

    unseen_only = env_bool("IMAP_UNSEEN_ONLY", "true")
    mark_as_read = env_bool("IMAP_MARK_AS_READ", "false")

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

    conn.select(folder)
    criteria = "UNSEEN" if unseen_only else "ALL"
    typ, data = conn.uid("search", None, criteria)
    if typ != "OK":
        raise RuntimeError("IMAP-Suche fehlgeschlagen")

    message_uids = data[0].split()
    log.info(f"{len(message_uids)} Nachricht(en) zur Prüfung gefunden.")

    imported_hashes = load_seen_uids()
    total_imported = 0
    processed_mail_count = 0

    for msg_uid in message_uids:
        typ, fetched = conn.uid("fetch", msg_uid, "(BODY.PEEK[])")
        if typ != "OK" or not fetched or not fetched[0]:
            log.warning(f"Konnte Nachricht UID {msg_uid.decode()} nicht abrufen.")
            continue

        raw = fetched[0][1]
        msg = email.message_from_bytes(raw)

        mail_had_ics = False
        mail_had_successful_import = False

        subject = msg.get("Subject", "(ohne Betreff)")
        log.info(f"Prüfe Mail UID {msg_uid.decode()} – Betreff: {subject}")

        for part in msg.walk():
            content_type = part.get_content_type()
            filename = part.get_filename() or ""
            is_ics = (
                content_type in ("text/calendar", "application/ics")
                or filename.lower().endswith(".ics")
            )
            if not is_ics:
                continue

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

            mail_had_ics = True
            uid_hash = hashlib.sha256(ics_bytes).hexdigest()

            if uid_hash in imported_hashes:
                log.info(
                    f"  Überspringe bereits importierten ICS-Anhang {filename!r} ({uid_hash[:12]}…)"
                )
                continue

            log.info(f"  ICS-Anhang gefunden: {filename!r} ({uid_hash[:12]}…)")

            try:
                imported_count = import_ics_to_caldav(ics_bytes, uid_hash)
                if imported_count > 0:
                    save_uid(uid_hash)
                    imported_hashes.add(uid_hash)
                    total_imported += imported_count
                    mail_had_successful_import = True
                else:
                    log.warning(
                        f"  Kein VEVENT importiert für Anhang {filename!r}; Mail bleibt ungelesen."
                    )
            except Exception as e:
                log.warning(
                    f"  Fehler beim Verarbeiten von {filename!r}: {e}; Mail bleibt ungelesen."
                )

        if mark_as_read and mail_had_successful_import:
            store_typ, _ = conn.uid("store", msg_uid, "+FLAGS", "(\\Seen)")
            if store_typ == "OK":
                processed_mail_count += 1
                log.info(
                    f"Mail UID {msg_uid.decode()} erfolgreich verarbeitet und als gelesen markiert."
                )
            else:
                log.warning(
                    f"Mail UID {msg_uid.decode()} wurde importiert, konnte aber nicht als gelesen markiert werden."
                )
        elif mark_as_read and mail_had_ics and not mail_had_successful_import:
            log.info(
                f"Mail UID {msg_uid.decode()} hatte ICS-Anhang, aber keinen erfolgreichen Import; bleibt ungelesen."
            )

    conn.close()
    conn.logout()

    log.info(f"Fertig. {total_imported} Termin(e) importiert.")
    log.info(f"{processed_mail_count} Mail(s) als gelesen markiert.")


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


if __name__ == "__main__":
    main()