# backend/common/emails.py
import logging
from typing import Iterable, Mapping, Optional

from django.conf import settings
from django.core.mail import EmailMultiAlternatives
from django.template.loader import render_to_string
from django.utils.html import strip_tags

logger = logging.getLogger(__name__)


def send_templated_mail(
    subject: str,
    to: Iterable[str],
    template_base: str,
    context: Mapping,
    from_email: Optional[str] = None,
    attachments: Optional[list[tuple[str, bytes, str]]] = None,
) -> int:
    """
    Отправляет письмо в HTML + plain текстах по шаблонам:
      templates/<template_base>.html
      templates/<template_base>.txt (опционально)
    attachments: список троек (name, content_bytes, mimetype)
    """
    to_list = list(to)

    logger.info(
        "Email delivery started",
        extra={
            "event": "email.delivery.started",
            "template": template_base,
            "recipient_count": len(to_list),
            "attachment_count": len(attachments or []),
        },
    )

    try:
        html_body = render_to_string(f"{template_base}.html", context)
        logger.debug(
            "Email HTML template rendered",
            extra={
                "event": "email.template.rendered",
                "template": template_base,
                "body_bytes": len(html_body.encode()),
            },
        )
    except Exception:
        logger.exception(
            "Email HTML template rendering failed",
            extra={
                "event": "email.template.failed",
                "template": template_base,
                "format": "html",
            },
        )
        raise

    # .txt файл опционален — если его нет, берём strip_tags от html
    try:
        text_body = render_to_string(f"{template_base}.txt", context)
        logger.debug(
            "Email text template rendered",
            extra={
                "event": "email.template.rendered",
                "template": template_base,
                "format": "text",
            },
        )
    except Exception:
        text_body = strip_tags(html_body)
        logger.debug(
            "Email text body generated from HTML",
            extra={
                "event": "email.template.fallback",
                "template": template_base,
                "format": "text",
            },
        )

    email = EmailMultiAlternatives(
        subject=subject,
        body=text_body,
        from_email=from_email or settings.DEFAULT_FROM_EMAIL,
        to=to_list,
    )
    email.attach_alternative(html_body, "text/html")

    if attachments:
        for name, data, mimetype in attachments:
            email.attach(name, data, mimetype)
            logger.debug(
                "Email attachment added",
                extra={
                    "event": "email.attachment.added",
                    "attachment_bytes": len(data),
                    "mime_type": mimetype,
                },
            )

    try:
        result = email.send(fail_silently=False)
        logger.info(
            "Email delivery completed",
            extra={
                "event": "email.delivery.completed",
                "template": template_base,
                "recipient_count": len(to_list),
                "sent_count": result,
            },
        )
        return result
    except Exception as error:
        logger.exception(
            "Email delivery failed",
            extra={
                "event": "email.delivery.failed",
                "template": template_base,
                "recipient_count": len(to_list),
                "error_type": type(error).__name__,
            },
        )
        raise