"""IMAP mailbox handling and SMTP sending for chancen@destengs.com."""
from __future__ import annotations

import email
import email.utils
import imaplib
import smtplib
import ssl
from email.message import EmailMessage
from email.policy import default as default_policy

IMAP_HOST, IMAP_PORT = "mail.destengs.com", 993
SMTP_HOST, SMTP_PORT = "mail.destengs.com", 587
KEYWORD = "$ProjektChecked"


class MailBox:
    def __init__(self, user, password, conn=None):
        self.user, self.password = user, password
        self.conn = conn or self._connect()
        self.conn.select("INBOX")
        self._trash = None

    def _connect(self):
        conn = imaplib.IMAP4_SSL(IMAP_HOST, IMAP_PORT)
        conn.login(self.user, self.password)
        return conn

    def ensure_alive(self):
        """Reconnect if the server dropped the connection (idle timeout)."""
        try:
            typ, _ = self.conn.noop()
            if typ == "OK":
                return
        except Exception:      # noqa: BLE001
            pass
        try:
            self.conn.logout()
        except Exception:      # noqa: BLE001
            pass
        self.conn = self._connect()
        self.conn.select("INBOX")

    def unchecked_uids(self):
        typ, data = self.conn.uid("SEARCH", None, f"UNKEYWORD {KEYWORD}")
        if typ != "OK" or not data or not data[0]:
            return []
        return [u.decode() for u in data[0].split()]

    def fetch(self, uid):
        typ, data = self.conn.uid("FETCH", uid, "(BODY.PEEK[])")
        if typ != "OK" or not data or not data[0] or not isinstance(data[0], tuple):
            raise RuntimeError(f"FETCH {uid} fehlgeschlagen: {typ}")
        return email.message_from_bytes(data[0][1], policy=default_policy)

    def flag_checked(self, uid):
        self.conn.uid("STORE", uid, "+FLAGS", f"({KEYWORD})")

    def trash_folder(self):
        if self._trash:
            return self._trash
        typ, data = self.conn.list()
        candidates = []
        for raw in data or []:
            line = raw.decode() if isinstance(raw, bytes) else str(raw)
            name = line.rsplit(" ", 1)[-1].strip('"')
            if "\\Trash" in line.split(")")[0]:
                self._trash = name
                return name
            candidates.append(name)
        for cand in ("Trash", "INBOX.Trash"):
            if cand in candidates:
                self._trash = cand
                return cand
        self._trash = "Trash"
        return self._trash

    def move_to_trash(self, uid):
        folder = self.trash_folder()
        typ, _ = self.conn.uid("MOVE", uid, folder)
        if typ != "OK":
            self.conn.uid("COPY", uid, folder)
            self.conn.uid("STORE", uid, "+FLAGS", "(\\Deleted)")
            self.conn.expunge()

    def close(self):
        try:
            self.conn.logout()
        except Exception:
            pass


def _sent_folder(conn):
    """Find the server's Sent folder via special-use flag, fallback names."""
    typ, data = conn.list()
    candidates = []
    for raw in data or []:
        line = raw.decode() if isinstance(raw, bytes) else str(raw)
        name = line.rsplit(" ", 1)[-1].strip('"')
        if "\\Sent" in line.split(")")[0]:
            return name
        candidates.append(name)
    for cand in ("Sent", "INBOX.Sent"):
        if cand in candidates:
            return cand
    return "Sent"


def append_sent(user, password, msg, conn=None):
    """Store a copy of an outgoing message in the Sent folder (best effort)."""
    own = conn is None
    conn = conn or imaplib.IMAP4_SSL(IMAP_HOST, IMAP_PORT)
    try:
        if own:
            conn.login(user, password)
        folder = _sent_folder(conn)
        conn.append(folder, "(\\Seen)", None, msg.as_bytes())
    finally:
        if own:
            try:
                conn.logout()
            except Exception:
                pass


def send_mail(user, password, to, subject, body):
    msg = EmailMessage()
    msg["From"], msg["To"], msg["Subject"] = user, to, subject
    msg["Date"] = email.utils.formatdate(localtime=True)
    msg["Message-ID"] = email.utils.make_msgid(domain="destengs.com")
    msg.set_content(body)
    with smtplib.SMTP(SMTP_HOST, SMTP_PORT, timeout=30) as server:
        server.starttls(context=ssl.create_default_context())
        server.login(user, password)
        server.send_message(msg)
    try:
        append_sent(user, password, msg)
    except Exception:      # noqa: BLE001 — copy is best effort; the mail went out
        pass