"""SMTP e-mail adapter built on top of aiosmtplib."""

from email.message import EmailMessage
from typing import Protocol

import aiosmtplib
import structlog

log = structlog.get_logger(__name__)


class SMTPEmailSenderError(Exception):
    """Raised when the SMTP delivery fails."""


class SMTPSendFn(Protocol):
    async def __call__(
        self,
        message: EmailMessage,
        *,
        hostname: str,
        port: int,
        username: str | None,
        password: str | None,
        use_tls: bool,
        start_tls: bool,
        timeout: float,
    ) -> object: ...


class SMTPEmailSender:
    def __init__(
        self,
        *,
        smtp_host: str,
        smtp_port: int,
        username: str,
        password: str,
        from_address: str,
        use_tls: bool = True,
        timeout_seconds: float = 10.0,
        send: SMTPSendFn | None = None,
    ) -> None:
        self._smtp_host = smtp_host
        self._smtp_port = smtp_port
        self._username = username
        self._password = password
        self._from_address = from_address
        self._use_tls = use_tls
        self._timeout_seconds = timeout_seconds
        self._send = send or _default_send

    async def send_email(
        self,
        *,
        to: str,
        subject: str,
        body: str,
        attachment_bytes: bytes,
        attachment_filename: str,
    ) -> None:
        message = self._build_message(
            to=to,
            subject=subject,
            body=body,
            attachment_bytes=attachment_bytes,
            attachment_filename=attachment_filename,
        )
        try:
            await self._send(
                message,
                hostname=self._smtp_host,
                port=self._smtp_port,
                username=self._username or None,
                password=self._password or None,
                use_tls=self._use_tls and self._smtp_port == 465,
                start_tls=self._use_tls and self._smtp_port != 465,
                timeout=self._timeout_seconds,
            )
        except Exception as exc:
            log.warning(
                "smtp_send_failed",
                smtp_host=self._smtp_host,
                smtp_port=self._smtp_port,
                to=to,
                error=str(exc),
            )
            raise SMTPEmailSenderError(
                f"SMTP send to {to} failed: {exc}"
            ) from exc

    def _build_message(
        self,
        *,
        to: str,
        subject: str,
        body: str,
        attachment_bytes: bytes,
        attachment_filename: str,
    ) -> EmailMessage:
        message = EmailMessage()
        message["From"] = self._from_address
        message["To"] = to
        message["Subject"] = subject
        message.set_content(body)
        message.add_attachment(
            attachment_bytes,
            maintype="application",
            subtype="pdf",
            filename=attachment_filename,
        )
        return message


async def _default_send(
    message: EmailMessage,
    *,
    hostname: str,
    port: int,
    username: str | None,
    password: str | None,
    use_tls: bool,
    start_tls: bool,
    timeout: float,
) -> object:
    return await aiosmtplib.send(
        message,
        hostname=hostname,
        port=port,
        username=username,
        password=password,
        use_tls=use_tls,
        start_tls=start_tls,
        timeout=timeout,
    )