"""Author RAG — Notifications Service (SMTP Email).

Sends OTP login codes and system alerts via Gmail SMTP.
Per implementation plan feature #2: Author login OTP via email.
"""

import smtplib
import ssl
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

import structlog

from app.config import get_settings

logger = structlog.get_logger(__name__)
cfg = get_settings()


async def send_login_otp(to_email: str, otp_code: str, author_name: str = "") -> bool:
    """Send a 6-digit OTP code to the author's email for login.

    Args:
        to_email: Recipient email address.
        otp_code: 6-digit TOTP code.
        author_name: Author's display name.

    Returns:
        True if sent successfully, False on failure.
    """
    subject = f"Your {cfg.APP_NAME} Login Code: {otp_code}"
    body = f"""
Hi {author_name or "there"},

Your login verification code is:

    {otp_code}

This code expires in 30 seconds. Do not share it with anyone.

If you didn't request this, please ignore this email.

— {cfg.APP_NAME} Team
"""
    return await _send_email(to_email, subject, body)


async def send_token_warning(to_email: str, author_name: str, usage_pct: float) -> bool:
    """Send a token budget warning when usage crosses a threshold."""
    subject = f"[{cfg.APP_NAME}] Token Budget Warning — {usage_pct:.0%} Used"
    body = f"""
Hi {author_name},

Your chatbot has used {usage_pct:.0%} of your monthly token budget.

Log in to your dashboard to view usage details or contact support to upgrade.

— {cfg.APP_NAME} Team
"""
    return await _send_email(to_email, subject, body)


async def _send_email(to: str, subject: str, body: str) -> bool:
    """Send a plain-text email via SMTP.

    Args:
        to: Recipient email.
        subject: Email subject.
        body: Plain text body.

    Returns:
        True on success.
    """
    if not cfg.SMTP_USERNAME or not cfg.SMTP_PASSWORD:
        logger.warning("SMTP not configured — email not sent", to=to, subject=subject)
        return False

    msg = MIMEMultipart("alternative")
    msg["Subject"] = subject
    msg["From"] = f"{cfg.EMAIL_FROM_NAME} <{cfg.EMAIL_FROM_ADDRESS or cfg.SMTP_USERNAME}>"
    msg["To"] = to
    msg.attach(MIMEText(body, "plain"))

    try:
        context = ssl.create_default_context()
        with smtplib.SMTP_SSL(cfg.SMTP_HOST, cfg.SMTP_PORT, context=context) as server:
            server.login(str(cfg.SMTP_USERNAME), cfg.SMTP_PASSWORD)
            server.sendmail(str(cfg.SMTP_USERNAME), to, msg.as_string())
        logger.info("Email sent", to=to, subject=subject)
        return True
    except Exception as e:
        logger.error("Failed to send email", to=to, error=str(e))
        return False