feat: Remove defer (#76)

Co-authored-by: Gulsum Atici <[email protected]>

src/charm.py

@@ -12,14 +12,14 @@
 from charms.data_platform_libs.v0.data_interfaces import DatabaseRequires  # type: ignore[import]
 from charms.sdcore_nrf_k8s.v0.fiveg_nrf import NRFProvides  # type: ignore[import]
 from charms.tls_certificates_interface.v3.tls_certificates import (  # type: ignore[import]
-    CertificateAvailableEvent,
     CertificateExpiringEvent,
     TLSCertificatesRequiresV3,
     generate_csr,
     generate_private_key,
 )
 from jinja2 import Environment, FileSystemLoader  # type: ignore[import]
-from ops.charm import CharmBase, EventBase, RelationJoinedEvent
+from ops.charm import CharmBase, RelationJoinedEvent
+from ops.framework import EventBase
 from ops.main import main
 from ops.model import ActiveStatus, BlockedStatus, ModelError, WaitingStatus
 from ops.pebble import Layer
@@ -110,67 +110,62 @@ def __init__(self, *args):
         self.framework.observe(
             self.on.fiveg_nrf_relation_joined, self._on_fiveg_nrf_relation_joined
         )
-        self.framework.observe(
-            self.on.certificates_relation_created, self._on_certificates_relation_created
-        )
-        self.framework.observe(
-            self.on.certificates_relation_joined, self._on_certificates_relation_joined
-        )
+        self.framework.observe(self.on.certificates_relation_joined, self._configure_nrf)
+        self.framework.observe(self._certificates.on.certificate_available, self._configure_nrf)
         self.framework.observe(
             self.on.certificates_relation_broken, self._on_certificates_relation_broken
         )
-        self.framework.observe(
-            self._certificates.on.certificate_available, self._on_certificate_available
-        )
         self.framework.observe(
             self._certificates.on.certificate_expiring, self._on_certificate_expiring
         )
 
-    def _configure_nrf(self, event: EventBase) -> None:
-        """Adds pebble layer and manages Juju unit status.
-
-        Args:
-            event: Juju event
-        """
+    def ready_to_configure(self) -> bool:
+        """Returns whether all preconditions are met to proceed with configuration."""
         if not self._container.can_connect():
             self.unit.status = WaitingStatus("Waiting for container to be ready")
-            event.defer()
-            return
+            return False
         for relation in [DATABASE_RELATION_NAME, "certificates"]:
             if not self._relation_created(relation):
                 self.unit.status = BlockedStatus(f"Waiting for {relation} relation to be created")
-                return
+                return False
         if not self._database_is_available():
             self.unit.status = WaitingStatus("Waiting for the database to be available")
-            return
+            return False
         if not self._get_database_uri():
             self.unit.status = WaitingStatus("Waiting for database URI")
-            event.defer()
-            return
-        if not self._container.exists(path=BASE_CONFIG_PATH):
+            return False
+        if not self._container.exists(path=BASE_CONFIG_PATH) or not self._container.exists(
+            path=CERTS_DIR_PATH
+        ):
             self.unit.status = WaitingStatus("Waiting for storage to be attached")
-            event.defer()
-            return
+            return False
         if not _get_pod_ip():
             self.unit.status = WaitingStatus("Waiting for pod IP address to be available")
-            event.defer()
+            return False
+        return True
+
+    def _configure_nrf(self, event: EventBase) -> None:
+        """Adds pebble layer and manages Juju unit status.
+
+        Args:
+            event: Juju event
+        """
+        if not self.ready_to_configure():
             return
-        if not self._certificate_is_stored():
+        if not self._private_key_is_stored():
+            self._generate_private_key()
+        if not self._csr_is_stored():
+            self._request_new_certificate()
+        provider_certificate = self._get_current_provider_certificate()
+        if not provider_certificate:
             self.unit.status = WaitingStatus("Waiting for certificates to be stored")
-            event.defer()
             return
-        needs_restart = self._generate_config_file()
-        self._configure_workload(restart=needs_restart)
+        certificate_changed = self._update_certificate(provider_certificate=provider_certificate)
+        config_file_changed = self._generate_config_file()
+        self._configure_workload(restart=(config_file_changed or certificate_changed))
         self._publish_nrf_info_for_all_requirers()
         self.unit.status = ActiveStatus()
 
-    def _on_certificates_relation_created(self, event: EventBase) -> None:
-        """Generates Private key."""
-        if not self._container.can_connect():
-            event.defer()
-            return
-        self._generate_private_key()
-
     def _on_certificates_relation_broken(self, event: EventBase) -> None:
         """Deletes TLS related artifacts and reconfigures workload."""
         if not self._container.can_connect():
@@ -181,33 +176,6 @@ def _on_certificates_relation_broken(self, event: EventBase) -> None:
         self._delete_certificate()
         self.unit.status = BlockedStatus("Waiting for certificates relation to be created")
 
-    def _on_certificates_relation_joined(self, event: EventBase) -> None:
-        """Generates CSR and requests new certificate."""
-        if not self._container.can_connect():
-            event.defer()
-            return
-        if not self._private_key_is_stored():
-            event.defer()
-            return
-        if self._certificate_is_stored():
-            return
-
-        self._request_new_certificate()
-
-    def _on_certificate_available(self, event: CertificateAvailableEvent) -> None:
-        """Pushes certificate to workload and configures workload."""
-        if not self._container.can_connect():
-            event.defer()
-            return
-        if not self._csr_is_stored():
-            logger.warning("Certificate is available but no CSR is stored")
-            return
-        if event.certificate_signing_request != self._get_stored_csr():
-            logger.debug("Stored CSR doesn't match one in certificate available event")
-            return
-        self._store_certificate(event.certificate)
-        self._configure_nrf(event)
-
     def _on_certificate_expiring(self, event: CertificateExpiringEvent) -> None:
         """Requests new certificate."""
         if not self._container.can_connect():
@@ -226,6 +194,31 @@ def _on_database_relation_broken(self, event: EventBase) -> None:
         """
         self.unit.status = BlockedStatus("Waiting for database relation")
 
+    def _get_current_provider_certificate(self) -> str | None:
+        """Compares the current certificate request to what is in the interface.
+
+        Returns The current valid provider certificate if present
+        """
+        csr = self._get_stored_csr()
+        for provider_certificate in self._certificates.get_assigned_certificates():
+            if provider_certificate.csr == csr:
+                return provider_certificate.certificate
+        return None
+
+    def _update_certificate(self, provider_certificate) -> bool:
+        """Compares the provided certificate to what is stored.
+
+        Returns True if the certificate was updated
+        """
+        existing_certificate = (
+            self._get_stored_certificate() if self._certificate_is_stored() else ""
+        )
+
+        if existing_certificate != provider_certificate:
+            self._store_certificate(certificate=provider_certificate)
+            return True
+        return False
+
     def _generate_private_key(self) -> None:
         """Generates and stores private key."""
         private_key = generate_private_key()