remove nameservers model; update db with hosts and host_ips on _fetch_cache

src/registrar/models/domain.py

@@ -10,6 +10,8 @@ from django_fsm import FSMField, transition, TransitionNotAllowed  # type: ignor
 from django.db import models
 from django.utils import timezone
 from typing import Any
+from registrar.models.host import Host
+from registrar.models.host_ip import HostIP
 
 
 from registrar.utility.errors import (
@@ -1605,6 +1607,7 @@ class Domain(TimeStampedModel, DomainHelper):
             cache = self._extract_data_from_response(data_response)
             cleaned = self._clean_cache(cache, data_response)
             self._update_hosts_and_contacts(cleaned, fetch_hosts, fetch_contacts)
+            self._update_hosts_and_ips_in_db(cleaned, fetch_hosts)
             self._update_dates(cleaned)
 
             self._cache = cleaned
@@ -1651,7 +1654,7 @@ class Domain(TimeStampedModel, DomainHelper):
         return dnssec_data
 
     def _update_hosts_and_contacts(self, cleaned, fetch_hosts, fetch_contacts):
-        """Capture and store old hosts and contacts from cache if the don't exist"""
+        """Capture and cache old hosts and contacts from cache if they don't exist in cleaned"""
         old_cache_hosts = self._cache.get("hosts")
         old_cache_contacts = self._cache.get("contacts")
 
@@ -1666,6 +1669,51 @@ class Domain(TimeStampedModel, DomainHelper):
             if old_cache_contacts is not None:
                 cleaned["contacts"] = old_cache_contacts
 
+    def _update_hosts_and_ips_in_db(self, cleaned, fetch_hosts):
+        """Update hosts and host_ips in database if retrieved from registry.
+
+        Parameters:
+            self: the domain to be updated with hosts and ips from cleaned
+            cleaned: dict containing hosts.  Hosts are provided as a list of dicts, e.g.
+                [{"name": "ns1.example.com",}, {"name": "ns1.example.gov"}, "addrs": ["0.0.0.0"])]
+            fetch_hosts: boolean indicating whether or not fetch_hosts was called
+        """
+        if fetch_hosts:
+            cleaned_hosts = cleaned["hosts"]
+            # Get all existing hosts from the database for this domain
+            existing_hosts_in_db = Host.objects.filter(domain=self)
+            # Identify hosts to delete
+            cleaned_host_names = set(cleaned_host["name"] for cleaned_host in cleaned_hosts)
+            hosts_to_delete_from_db = [
+                existing_host for existing_host in existing_hosts_in_db if existing_host.name not in cleaned_host_names
+            ]
+            # Delete hosts and their associated HostIP instances
+            for host_to_delete in hosts_to_delete_from_db:
+                # Delete associated HostIP instances
+                HostIP.objects.filter(host=host_to_delete).delete()
+                # Delete the host itself
+                host_to_delete.delete()
+            # Update or create Hosts and HostIPs
+            for cleaned_host in cleaned_hosts:
+                # Check if the cleaned_host already exists
+                host_in_db, host_created = Host.objects.get_or_create(domain=self, name=cleaned_host["name"])
+                # Get cleaned list of ips for update
+                cleaned_ips = cleaned_host["addrs"]
+                if not host_created:
+                    # Get all existing ips from the database for this host
+                    existing_ips_in_db = HostIP.objects.filter(host=host_in_db)
+                    # Identify IPs to delete
+                    ips_to_delete_from_db = [
+                        existing_ip for existing_ip in existing_ips_in_db if existing_ip.address not in cleaned_ips
+                    ]
+                    # Delete IPs
+                    for ip_to_delete in ips_to_delete_from_db:
+                        # Delete the ip
+                        ip_to_delete.delete()
+                # Update or create HostIP instances
+                for ip_address in cleaned_ips:
+                    HostIP.objects.get_or_create(address=ip_address, host=host_in_db)
+
     def _update_dates(self, cleaned):
         """Update dates (expiration and creation) from cleaned"""
         requires_save = False