backend/services/email_alerter.py

"""
Email alerter — sends notifications when data sources go stale.

Activated by setting env vars: SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASSWORD, ALERT_EMAIL_TO.
Respects a per-source cooldown to avoid spamming.
"""

from __future__ import annotations

import logging
import os
import smtplib
import time
from email.mime.text import MIMEText
from typing import Any

from config.settings import ALERT_COOLDOWN_MIN

log = logging.getLogger("solarwine.alerter")


class EmailAlerter:
    """Sends email alerts when data sources are in 'red' status."""

    def __init__(self):
        self._last_alert: dict[str, float] = {}  # source_name -> epoch of last alert
        self._smtp_host = os.environ.get("SMTP_HOST", "")
        self._smtp_port = int(os.environ.get("SMTP_PORT", "587"))
        self._smtp_user = os.environ.get("SMTP_USER", "")
        self._smtp_password = os.environ.get("SMTP_PASSWORD", "")
        self._alert_to = os.environ.get("ALERT_EMAIL_TO", "")
        self._alert_from = os.environ.get("ALERT_EMAIL_FROM", self._smtp_user)

    @property
    def enabled(self) -> bool:
        return bool(self._smtp_host and self._alert_to)

    def check_and_alert(self, status: dict[str, Any]) -> list[str]:
        """Check status and send alerts for red sources. Returns list of alerted sources."""
        if not self.enabled:
            return []

        alerted: list[str] = []
        sources = status.get("sources", {})

        for source_name, info in sources.items():
            if info.get("status") != "red":
                # Source recovered — clear cooldown so next outage triggers immediately
                self._last_alert.pop(source_name, None)
                continue

            # Check cooldown
            now = time.time()
            last = self._last_alert.get(source_name, 0)
            if (now - last) < ALERT_COOLDOWN_MIN * 60:
                continue

            # Send alert
            message = info.get("message", f"{source_name} is down")
            age = info.get("age_minutes")
            subject = f"[SolarWine] Data flow alert: {source_name}"
            age_line = f"Age: {age:.0f} min\n" if age is not None else ""
            body = (
                f"Data source: {source_name}\n"
                f"Status: RED\n"
                f"{age_line}"
                f"Detail: {message}\n"
                f"\nChecked at: {status.get('checked_at', 'unknown')}\n"
                f"Overall system status: {status.get('overall', 'unknown')}\n"
                f"\n---\nSolarWine Data Flow Monitor"
            )

            if self._send_email(subject, body):
                self._last_alert[source_name] = now
                alerted.append(source_name)

        return alerted

    def _send_email(self, subject: str, body: str) -> bool:
        """Send an email via SMTP. Returns True on success."""
        try:
            msg = MIMEText(body, "plain", "utf-8")
            msg["Subject"] = subject
            msg["From"] = self._alert_from
            msg["To"] = self._alert_to

            with smtplib.SMTP(self._smtp_host, self._smtp_port, timeout=10) as server:
                server.starttls()
                if self._smtp_user and self._smtp_password:
                    server.login(self._smtp_user, self._smtp_password)
                server.sendmail(self._alert_from, self._alert_to.split(","), msg.as_string())

            log.info("Alert email sent: %s → %s", subject, self._alert_to)
            return True
        except Exception as exc:
            log.error("Failed to send alert email: %s", exc)
            return False