from __future__ import annotations

import smtplib
from email.utils import parseaddr

from django.conf import settings
from django.core.mail.backends.base import BaseEmailBackend

from apps.core.services.microsoft365 import (
    Microsoft365OAuthError,
    acquire_exchange_access_token,
    xoauth2_b64,
)
from apps.sources.services.tls import trusted_tls_context


class Microsoft365OAuthEmailBackend(BaseEmailBackend):
    """Send mail through Exchange Online with app-only SASL XOAUTH2."""

    def send_messages(self, email_messages) -> int:
        if not email_messages:
            return 0
        sent = 0
        try:
            token = acquire_exchange_access_token()
            username = settings.M365_MAILBOX_USER.strip()
            if not username:
                raise Microsoft365OAuthError(
                    "M365_MAILBOX_USER is verplicht voor Microsoft 365-mailuitvoer."
                )
            with smtplib.SMTP(
                settings.EMAIL_HOST or "smtp.office365.com",
                settings.EMAIL_PORT,
                timeout=settings.M365_SMTP_TIMEOUT_SECONDS,
            ) as client:
                client.ehlo()
                client.starttls(context=trusted_tls_context())
                client.ehlo()
                code, _ = client.docmd("AUTH", f"XOAUTH2 {xoauth2_b64(username, token)}")
                if code != 235:
                    raise Microsoft365OAuthError("Microsoft 365 SMTP OAuth geweigerd.")
                for message in email_messages:
                    recipients = message.recipients()
                    if not recipients:
                        continue
                    sender = parseaddr(message.from_email or settings.DEFAULT_FROM_EMAIL)[1]
                    client.sendmail(
                        sender or username,
                        recipients,
                        message.message().as_bytes(linesep="\r\n"),
                    )
                    sent += 1
        except Exception:
            if self.fail_silently:
                return sent
            raise
        return sent