add ip change notification and refine sender display

tests/test_public_ip.py

@@ -6,7 +6,9 @@ from fastapi.testclient import TestClient
 from sqlalchemy import create_engine
 from sqlalchemy.orm import Session, sessionmaker
 
-from app.services.public_ip import PublicIPCheckResult, check_public_ipv4
+from app.config import Settings
+from app.services.email import EmailDeliveryError
+from app.services.public_ip import PublicIPCheckResult, check_public_ipv4, check_public_ipv4_and_notify
 
 
 def _make_session(database_url: str) -> Session:
@@ -152,8 +154,8 @@ def test_public_ip_check_endpoint_hides_ip_values(client: TestClient, monkeypatc
 
     monkeypatch.setattr(
         public_ip_route,
-        "check_public_ipv4",
-        lambda session: PublicIPCheckResult(
+        "check_public_ipv4_and_notify",
+        lambda session, bootstrap_settings: PublicIPCheckResult(
             status="changed",
             checked_at=fixed_checked_at,
             changed=True,
@@ -172,3 +174,85 @@ def test_public_ip_check_endpoint_hides_ip_values(client: TestClient, monkeypatc
     assert "current_ipv4" not in response.text
     assert "previous_ipv4" not in response.text
     assert "203.0.113.10" not in response.text
+
+
+def _notification_settings() -> Settings:
+    return Settings(
+        _env_file=None,
+        app_env="development",
+        app_hostname="localhost:8000",
+        app_database_url="sqlite:///./data/app.db",
+        location_database_url="sqlite:///./data/locationRecorder.db",
+        poo_database_url="sqlite:///./data/pooRecorder.db",
+        auth_bootstrap_username="admin",
+        auth_bootstrap_password="secret-password",
+        smtp_enabled=True,
+        smtp_host="smtp.example.com",
+        smtp_port=587,
+        smtp_username="smtp-user",
+        smtp_password="super-secret-password",
+        smtp_from_address="sender@example.com",
+        smtp_to_address="recipient@example.com",
+        smtp_use_starttls=True,
+    )
+
+
+def test_public_ip_notification_sends_only_when_changed(auth_database, monkeypatch) -> None:
+    session = _make_session(auth_database["app_url"])
+    sent = []
+    monkeypatch.setattr(
+        "app.services.public_ip.send_public_ip_changed_email",
+        lambda settings, *, previous_ipv4, current_ipv4, detected_at: sent.append(
+            (previous_ipv4, current_ipv4, detected_at)
+        ),
+    )
+    try:
+        first_seen = check_public_ipv4_and_notify(
+            session,
+            bootstrap_settings=_notification_settings(),
+            fetch_public_ipv4=lambda: "203.0.113.10",
+        )
+        unchanged = check_public_ipv4_and_notify(
+            session,
+            bootstrap_settings=_notification_settings(),
+            fetch_public_ipv4=lambda: "203.0.113.10",
+        )
+        changed = check_public_ipv4_and_notify(
+            session,
+            bootstrap_settings=_notification_settings(),
+            fetch_public_ipv4=lambda: "198.51.100.25",
+        )
+    finally:
+        session.close()
+
+    assert first_seen.status == "first_seen"
+    assert unchanged.status == "unchanged"
+    assert changed.status == "changed"
+    assert len(sent) == 1
+    assert sent[0][0] == "203.0.113.10"
+    assert sent[0][1] == "198.51.100.25"
+    assert sent[0][2] == changed.checked_at
+
+
+def test_public_ip_notification_failure_does_not_break_changed_result(auth_database, monkeypatch) -> None:
+    session = _make_session(auth_database["app_url"])
+    monkeypatch.setattr(
+        "app.services.public_ip.send_public_ip_changed_email",
+        lambda settings, *, previous_ipv4, current_ipv4, detected_at: (_ for _ in ()).throw(
+            EmailDeliveryError("smtp down")
+        ),
+    )
+    try:
+        check_public_ipv4(session, fetch_public_ipv4=lambda: "203.0.113.10")
+        result = check_public_ipv4_and_notify(
+            session,
+            bootstrap_settings=_notification_settings(),
+            fetch_public_ipv4=lambda: "198.51.100.25",
+        )
+    finally:
+        session.close()
+
+    assert result.status == "changed"
+    assert result.changed is True
+    assert result.previous_ipv4 == "203.0.113.10"
+    assert result.current_ipv4 == "198.51.100.25"