"""Construction et remise des emails.

`deliver_many` est le point d'injection unique (remplacé dans les tests).
La remise est « best effort » : une erreur SMTP est journalisée (le message du
serveur, pas de PII) et ne remonte pas — l'appel HTTP n'échoue pas pour ça.
Pour diagnostiquer : `python -m app.email.check <destinataire>`."""

import logging
import smtplib
import ssl
from collections.abc import Iterable
from email.message import EmailMessage

from app.config import Settings, get_settings

logger = logging.getLogger("app.email")


def build_message(to: str, subject: str, body: str) -> EmailMessage:
    message = EmailMessage()
    message["From"] = get_settings().smtp_from
    message["To"] = to
    message["Subject"] = subject
    message.set_content(body)
    return message


def open_smtp(settings: Settings) -> smtplib.SMTP:
    """Ouvre une session SMTP authentifiée. Lève en cas d'échec."""
    use_ssl = settings.smtp_ssl
    use_starttls = settings.smtp_starttls
    if settings.smtp_port == 465 and not use_ssl:
        # Le port 465 (SMTPS, RFC 8314) parle TLS d'emblée : STARTTLS échoue.
        logger.info("Port 465 → SSL implicite (SMTP_SSL/STARTTLS ignorés).")
        use_ssl, use_starttls = True, False

    context = ssl.create_default_context()
    if use_ssl:
        smtp: smtplib.SMTP = smtplib.SMTP_SSL(
            settings.smtp_host, settings.smtp_port, timeout=30, context=context
        )
    else:
        smtp = smtplib.SMTP(settings.smtp_host, settings.smtp_port, timeout=30)
        if use_starttls:
            smtp.starttls(context=context)
    if settings.smtp_user:
        smtp.login(settings.smtp_user, settings.smtp_password)
    return smtp


def deliver_many(messages: list[EmailMessage]) -> None:
    settings = get_settings()
    if not settings.email_enabled:
        # RGPD : ni destinataire ni corps dans les logs.
        logger.info(
            "Emails non envoyés (EMAIL_ENABLED=false) — %d message(s)",
            len(messages),
        )
        return
    if not messages:
        return

    try:
        smtp = open_smtp(settings)
    except (OSError, smtplib.SMTPException) as exc:
        logger.error(
            "SMTP indisponible (%s:%s, ssl=%s starttls=%s) : %s",
            settings.smtp_host,
            settings.smtp_port,
            settings.smtp_ssl,
            settings.smtp_starttls,
            exc,
        )
        return

    with smtp:
        for message in messages:
            try:
                smtp.send_message(message)
            except smtplib.SMTPException as exc:
                # Ex. « 550 sender not authorized », « 535 auth failed ».
                logger.error(
                    "Email refusé par le serveur (From=%s) : %s",
                    message["From"],
                    exc,
                )


def send(to: str, subject: str, body: str) -> None:
    deliver_many([build_message(to, subject, body)])


def send_many(items: Iterable[tuple[str, str, str]]) -> None:
    """`items` = itérable de `(destinataire, sujet, corps)`."""
    deliver_many([build_message(*item) for item in items])