"""
Email SMTP sender – invio notifiche via SMTP con TLS/SSL o STARTTLS.

Config non sensibile (config):
  {
    "smtp_host":       "smtp.example.com",
    "smtp_port":       465,
    "smtp_use_tls":    true,        # SSL/TLS diretto (porta 465)
    "smtp_use_starttls": false,     # STARTTLS (porta 587) – alternativo a use_tls
    "from_email":      "noreply@example.com",
    "from_name":       "PEChub Notifiche",
    "to_email":        "destinatario@example.com"
  }

Config sensibile (config_enc → config_secret):
  { "smtp_password": "..." }

Dipendenza: aiosmtplib (gia' in backend/pyproject.toml)
"""

from datetime import datetime
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

import aiosmtplib

DEFAULT_TIMEOUT = 15.0


class EmailSMTPError(Exception):
    """Errore durante l'invio di un'email di notifica."""

    def __init__(self, message: str, smtp_code: int | None = None):
        super().__init__(message)
        self.smtp_code = smtp_code


async def send_email_notification(
    smtp_host: str,
    smtp_port: int,
    smtp_user: str,
    smtp_password: str,
    from_email: str,
    to_email: str,
    subject: str,
    body_text: str,
    body_html: str | None = None,
    from_name: str = "PEChub Notifiche",
    use_tls: bool = True,
    use_starttls: bool = False,
    timeout: float = DEFAULT_TIMEOUT,
) -> None:
    """
    Invia un'email di notifica via SMTP.

    Args:
        smtp_host:    host SMTP
        smtp_port:    porta SMTP
        smtp_user:    username autenticazione
        smtp_password: password autenticazione
        from_email:   indirizzo mittente
        to_email:     indirizzo destinatario
        subject:      oggetto email
        body_text:    testo plain
        body_html:    testo HTML (opzionale)
        from_name:    nome visualizzato mittente
        use_tls:      usa SSL/TLS diretto (porta 465)
        use_starttls: usa STARTTLS (porta 587) – alternativo a use_tls
        timeout:      timeout connessione in secondi

    Raises:
        EmailSMTPError: in caso di errori di autenticazione, connessione o invio
    """
    msg = MIMEMultipart("alternative")
    msg["Subject"] = subject
    msg["From"] = f"{from_name} <{from_email}>" if from_name else from_email
    msg["To"] = to_email
    msg["Date"] = datetime.utcnow().strftime("%a, %d %b %Y %H:%M:%S +0000")
    msg["X-Mailer"] = "PEChub/1.0"

    msg.attach(MIMEText(body_text, "plain", "utf-8"))
    if body_html:
        msg.attach(MIMEText(body_html, "html", "utf-8"))

    try:
        await aiosmtplib.send(
            msg,
            hostname=smtp_host,
            port=smtp_port,
            username=smtp_user,
            password=smtp_password,
            use_tls=use_tls,
            start_tls=use_starttls,
            timeout=timeout,
        )
    except aiosmtplib.SMTPAuthenticationError as exc:
        raise EmailSMTPError(
            f"Autenticazione SMTP fallita per {smtp_user}@{smtp_host}: {exc}",
            smtp_code=535,
        ) from exc
    except aiosmtplib.SMTPConnectError as exc:
        raise EmailSMTPError(
            f"Connessione SMTP fallita a {smtp_host}:{smtp_port}: {exc}"
        ) from exc
    except aiosmtplib.SMTPServerDisconnected as exc:
        raise EmailSMTPError(
            f"Server SMTP {smtp_host} ha chiuso la connessione: {exc}"
        ) from exc
    except aiosmtplib.SMTPException as exc:
        raise EmailSMTPError(f"Errore SMTP: {exc}") from exc
    except Exception as exc:
        raise EmailSMTPError(f"Errore invio email: {exc}") from exc


async def send_test_email(
    smtp_host: str,
    smtp_port: int,
    smtp_user: str,
    smtp_password: str,
    from_email: str,
    to_email: str,
    channel_name: str = "PEChub",
    from_name: str = "PEChub Notifiche",
    use_tls: bool = True,
    use_starttls: bool = False,
) -> None:
    """
    Invia un'email di test per verificare la configurazione del canale.

    Raises:
        EmailSMTPError: se la connessione o l'autenticazione falliscono
    """
    ts = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    subject = f"[PEChub] Test canale email: {channel_name}"
    body_text = (
        f"PEChub – Test canale Email\n\n"
        f"Il canale '{channel_name}' e' configurato correttamente.\n\n"
        f"Data/ora: {ts}\n"
        f"Destinatario: {to_email}"
    )
    body_html = (
        f"<h2>PEChub – Test canale Email</h2>"
        f"<p>Il canale <strong>{channel_name}</strong> e' configurato correttamente.</p>"
        f"<p>Data/ora: <em>{ts}</em><br>"
        f"Destinatario: {to_email}</p>"
        f"<hr><p style='font-size:11px;color:#888'>Inviato da PEChub Notification Engine</p>"
    )
    await send_email_notification(
        smtp_host=smtp_host,
        smtp_port=smtp_port,
        smtp_user=smtp_user,
        smtp_password=smtp_password,
        from_email=from_email,
        to_email=to_email,
        subject=subject,
        body_text=body_text,
        body_html=body_html,
        from_name=from_name,
        use_tls=use_tls,
        use_starttls=use_starttls,
    )