add ip change notification and refine sender display

app/services/public_ip.py

@@ -10,7 +10,10 @@ import httpx
 from sqlalchemy import select
 from sqlalchemy.orm import Session
 
+from app.config import Settings
 from app.models.public_ip import PublicIPHistory, PublicIPState
+from app.services.config_page import build_runtime_settings
+from app.services.email import EmailConfigurationError, EmailDeliveryError, send_public_ip_changed_email
 
 logger = logging.getLogger(__name__)
 
@@ -31,6 +34,8 @@ class PublicIPCheckResult:
     status: PublicIPResultStatus
     checked_at: datetime
     changed: bool
+    previous_ipv4: str | None = None
+    current_ipv4: str | None = None
 
 
 def check_public_ipv4(
@@ -77,7 +82,12 @@ def check_public_ipv4(
             )
         )
         session.commit()
-        return PublicIPCheckResult(status="first_seen", checked_at=checked_at, changed=False)
+        return PublicIPCheckResult(
+            status="first_seen",
+            checked_at=checked_at,
+            changed=False,
+            current_ipv4=current_ipv4,
+        )
 
     if state.current_ipv4 == current_ipv4:
         state.last_checked_at = checked_at
@@ -85,9 +95,15 @@ def check_public_ipv4(
         state.last_check_error = None
         state.last_provider = provider_name
         session.commit()
-        return PublicIPCheckResult(status="unchanged", checked_at=checked_at, changed=False)
+        return PublicIPCheckResult(
+            status="unchanged",
+            checked_at=checked_at,
+            changed=False,
+            current_ipv4=current_ipv4,
+        )
 
-    state.previous_ipv4 = state.current_ipv4
+    previous_ipv4 = state.current_ipv4
+    state.previous_ipv4 = previous_ipv4
     state.current_ipv4 = current_ipv4
     state.last_checked_at = checked_at
     state.last_changed_at = checked_at
@@ -103,7 +119,43 @@ def check_public_ipv4(
         )
     )
     session.commit()
-    return PublicIPCheckResult(status="changed", checked_at=checked_at, changed=True)
+    return PublicIPCheckResult(
+        status="changed",
+        checked_at=checked_at,
+        changed=True,
+        previous_ipv4=previous_ipv4,
+        current_ipv4=current_ipv4,
+    )
+
+
+def check_public_ipv4_and_notify(
+    session: Session,
+    *,
+    bootstrap_settings: Settings,
+    fetch_public_ipv4: PublicIPv4Fetcher | None = None,
+    provider_name: str = PUBLIC_IP_PROVIDER_NAME,
+) -> PublicIPCheckResult:
+    result = check_public_ipv4(
+        session,
+        fetch_public_ipv4=fetch_public_ipv4,
+        provider_name=provider_name,
+    )
+
+    if result.status != "changed" or result.previous_ipv4 is None or result.current_ipv4 is None:
+        return result
+
+    runtime_settings = build_runtime_settings(session, bootstrap_settings)
+    try:
+        send_public_ip_changed_email(
+            runtime_settings,
+            previous_ipv4=result.previous_ipv4,
+            current_ipv4=result.current_ipv4,
+            detected_at=result.checked_at,
+        )
+    except (EmailConfigurationError, EmailDeliveryError) as exc:
+        logger.warning("Public IPv4 change notification failed: %s", exc)
+
+    return result
 
 
 def fetch_public_ipv4_from_provider() -> str: