add smtp module and testing

app/services/email.py

@@ -0,0 +1,106 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from email.message import EmailMessage
+import smtplib
+
+from app.config import Settings
+
+
+class EmailConfigurationError(ValueError):
+    """Raised when SMTP settings are incomplete or disabled."""
+
+
+class EmailDeliveryError(RuntimeError):
+    """Raised when sending email fails."""
+
+
+@dataclass(frozen=True, slots=True)
+class SMTPConfig:
+    host: str
+    port: int
+    username: str
+    password: str
+    from_address: str
+    to_address: str
+    use_starttls: bool
+
+
+def get_smtp_config(settings: Settings, *, require_enabled: bool = True) -> SMTPConfig:
+    if require_enabled and not settings.smtp_enabled:
+        raise EmailConfigurationError("SMTP is disabled")
+
+    if not settings.smtp_host:
+        raise EmailConfigurationError("SMTP host is required")
+
+    if settings.smtp_port <= 0:
+        raise EmailConfigurationError("SMTP port must be greater than zero")
+
+    if not settings.smtp_from_address:
+        raise EmailConfigurationError("SMTP from address is required")
+
+    if not settings.smtp_to_address:
+        raise EmailConfigurationError("SMTP to address is required")
+
+    return SMTPConfig(
+        host=settings.smtp_host,
+        port=settings.smtp_port,
+        username=settings.smtp_username,
+        password=settings.smtp_password,
+        from_address=settings.smtp_from_address,
+        to_address=settings.smtp_to_address,
+        use_starttls=settings.smtp_use_starttls,
+    )
+
+
+def is_smtp_ready(settings: Settings) -> bool:
+    try:
+        get_smtp_config(settings, require_enabled=False)
+    except EmailConfigurationError:
+        return False
+    return True
+
+
+def send_plaintext_email(
+    settings: Settings,
+    *,
+    subject: str,
+    body: str,
+    recipient: str | None = None,
+    require_enabled: bool = True,
+) -> None:
+    smtp_config = get_smtp_config(settings, require_enabled=require_enabled)
+    message = EmailMessage()
+    message["Subject"] = subject
+    message["From"] = smtp_config.from_address
+    message["To"] = recipient or smtp_config.to_address
+    message.set_content(body)
+
+    try:
+        with smtplib.SMTP(smtp_config.host, smtp_config.port, timeout=10) as smtp:
+            smtp.ehlo()
+            if smtp_config.use_starttls:
+                smtp.starttls()
+                smtp.ehlo()
+            if smtp_config.username:
+                smtp.login(smtp_config.username, smtp_config.password)
+            smtp.send_message(message)
+    except (OSError, smtplib.SMTPException) as exc:
+        error_message = _sanitize_error_message(str(exc), smtp_config.password)
+        raise EmailDeliveryError(error_message or "SMTP delivery failed") from exc
+
+
+def send_smtp_test_email(settings: Settings) -> None:
+    send_plaintext_email(
+        settings,
+        subject="Home Automation SMTP Test",
+        body="This is a test email from Home Automation SMTP settings.",
+        require_enabled=False,
+    )
+
+
+def _sanitize_error_message(message: str, password: str) -> str:
+    sanitized = message
+    if password:
+        sanitized = sanitized.replace(password, "[redacted]")
+    return sanitized