Adding the new rewrite

app/notifications/__init__.py

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+"""Notification channels."""

app/notifications/email.py

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+"""SMTP email sending with retry, batching, and HTML templates."""
+from __future__ import annotations
+
+import logging
+import smtplib
+import ssl
+from datetime import datetime
+from email.message import EmailMessage
+from pathlib import Path
+from typing import Any
+
+from jinja2 import Environment, FileSystemLoader, select_autoescape
+from tenacity import (
+    RetryError,
+    retry,
+    retry_if_exception_type,
+    stop_after_attempt,
+    wait_exponential,
+)
+
+from ..config import SMTPConfig
+from ..settings import settings
+
+logger = logging.getLogger(__name__)
+
+_TEMPLATE_DIR = Path(__file__).parent.parent / "templates" / "emails"
+_env = Environment(
+    loader=FileSystemLoader(str(_TEMPLATE_DIR)),
+    autoescape=select_autoescape(["html", "xml"]),
+)
+
+SEVERITY_COLORS = {
+    "CRITICAL": "#c0392b",
+    "WARNING": "#e67e22",
+    "INFO": "#2980b9",
+}
+
+
+class EmailSendError(Exception):
+    pass
+
+
+def _resolve_password(smtp_cfg: SMTPConfig) -> str | None:
+    # Password is never stored in Redis; always from env var
+    return settings.smtp_password
+
+
+@retry(
+    reraise=True,
+    stop=stop_after_attempt(3),
+    wait=wait_exponential(multiplier=1, min=1, max=10),
+    retry=retry_if_exception_type((smtplib.SMTPException, OSError)),
+)
+def _send_raw(smtp_cfg: SMTPConfig, msg: EmailMessage) -> None:
+    password = _resolve_password(smtp_cfg)
+    if smtp_cfg.use_ssl:
+        context = ssl.create_default_context()
+        with smtplib.SMTP_SSL(
+            smtp_cfg.host, smtp_cfg.port, context=context, timeout=30
+        ) as server:
+            if smtp_cfg.username and password:
+                server.login(smtp_cfg.username, password)
+            server.send_message(msg)
+    else:
+        with smtplib.SMTP(smtp_cfg.host, smtp_cfg.port, timeout=30) as server:
+            if smtp_cfg.use_tls:
+                server.starttls(context=ssl.create_default_context())
+            if smtp_cfg.username and password:
+                server.login(smtp_cfg.username, password)
+            server.send_message(msg)
+
+
+def send_alert_email(
+    smtp_cfg: SMTPConfig,
+    ups_name: str,
+    alerts: list[dict[str, Any]],
+    dashboard_url: str = "http://localhost:8000/",
+) -> None:
+    """Send a single HTML email coalescing multiple alerts for a UPS."""
+    if not smtp_cfg.to_addrs or not alerts:
+        return
+    top_severity = _pick_top_severity(alerts)
+    subject = f"{smtp_cfg.subject_prefix} [{top_severity}] {ups_name}"
+    template = _env.get_template("alert.html")
+    html = template.render(
+        ups_name=ups_name,
+        alerts=alerts,
+        top_severity=top_severity,
+        color=SEVERITY_COLORS.get(top_severity, "#555"),
+        dashboard_url=dashboard_url,
+        sent_at=datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
+    )
+    text_body = "\n".join(
+        f"[{a.get('severity', 'INFO')}] {a.get('message', '')}" for a in alerts
+    )
+    msg = EmailMessage()
+    msg["Subject"] = subject
+    msg["From"] = smtp_cfg.from_addr or (smtp_cfg.username or "ups@example.local")
+    msg["To"] = ", ".join(smtp_cfg.to_addrs)
+    msg.set_content(text_body)
+    msg.add_alternative(html, subtype="html")
+    try:
+        _send_raw(smtp_cfg, msg)
+    except RetryError as e:
+        raise EmailSendError(f"SMTP send failed after retries: {e}") from e
+    except Exception as e:  # noqa: BLE001 - surface as domain error
+        raise EmailSendError(f"SMTP send failed: {e}") from e
+
+
+def send_test_email(smtp_cfg: SMTPConfig) -> None:
+    if not smtp_cfg.to_addrs:
+        raise EmailSendError("No recipients configured")
+    msg = EmailMessage()
+    msg["Subject"] = f"{smtp_cfg.subject_prefix} Test email"
+    msg["From"] = smtp_cfg.from_addr or (smtp_cfg.username or "ups@example.local")
+    msg["To"] = ", ".join(smtp_cfg.to_addrs)
+    msg.set_content(
+        "This is a test message from your APC UPS Dashboard.\n"
+        f"Sent at {datetime.now().isoformat()}"
+    )
+    try:
+        _send_raw(smtp_cfg, msg)
+    except Exception as e:  # noqa: BLE001
+        raise EmailSendError(str(e)) from e
+
+
+def send_daily_summary(
+    smtp_cfg: SMTPConfig,
+    summary: dict[str, Any],
+) -> None:
+    if not smtp_cfg.to_addrs:
+        return
+    template = _env.get_template("summary.html")
+    html = template.render(summary=summary, sent_at=datetime.now().isoformat())
+    msg = EmailMessage()
+    msg["Subject"] = f"{smtp_cfg.subject_prefix} Daily summary"
+    msg["From"] = smtp_cfg.from_addr or (smtp_cfg.username or "ups@example.local")
+    msg["To"] = ", ".join(smtp_cfg.to_addrs)
+    msg.set_content(str(summary))
+    msg.add_alternative(html, subtype="html")
+    try:
+        _send_raw(smtp_cfg, msg)
+    except Exception as e:  # noqa: BLE001
+        logger.warning("Daily summary send failed: %s", e)
+
+
+def _pick_top_severity(alerts: list[dict[str, Any]]) -> str:
+    order = {"CRITICAL": 3, "WARNING": 2, "INFO": 1}
+    best = "INFO"
+    best_rank = 0
+    for a in alerts:
+        sev = a.get("severity", "INFO")
+        rank = order.get(sev, 0)
+        if rank > best_rank:
+            best = sev
+            best_rank = rank
+    return best