from __future__ import annotations

import logging
from typing import Any

import resend
from flask import current_app


class EmailConfigurationError(RuntimeError):
    """Raised when transactional email has not been configured."""


class EmailDeliveryError(RuntimeError):
    """Raised when Resend rejects or cannot deliver an email request."""


def send_transactional_email(*, to: str, subject: str, html: str) -> dict[str, Any]:
    """Send one application-generated email through Resend."""
    api_key = current_app.config["RESEND_API_KEY"]
    from_email = current_app.config["RESEND_FROM_EMAIL"]
    if not api_key or not from_email:
        raise EmailConfigurationError(
            "邮件服务尚未配置，请设置 RESEND_API_KEY 和 RESEND_FROM_EMAIL。"
        )

    resend.api_key = api_key
    try:
        return resend.Emails.send(
            {
                "from": from_email,
                "to": [to],
                "subject": subject,
                "html": html,
            }
        )
    except Exception as exc:
        logging.exception("Resend 邮件发送失败: %s", exc)
        raise EmailDeliveryError("邮件发送失败，请稍后重试。") from exc