create and remove dhcpd host entry

config.example.json

   },
   "domain": "local.example.com",
   "reverseDomain": "1.168.192.in-addr.arpa",
-  "dhcpdFile": "/etc/dhcp/dhcpd.conf",
+  "dhcpdFilePath": "/etc/dhcp/dhcpd.conf",
+  "dhcpdReloadCommand": "systemctl restart isc-dhcp-server",
   "recordTTL": 600
 }

localhostgen.py

 import argparse
 import json
 from time import time
-
 import psycopg2
 import sys
+import re
 
 
 class LocalHostGen:
     db_config = None
     db_instance = None
+    dhcpd_replace_string = "# %%HOST%%"
 
     def __init__(self, db_config):
         self.db_config = db_config
         self.db_instance.commit()
         return record_id
 
-    def create_host(self, domain, reverse_domain, host, ip, mac, ttl):
-        if self.db_instance is None:
-            self.connect()
-        reverse_domain_record = self.get_reverse_domain_record(reverse_domain, ip)
+    def remove_host_dhcp(self, host, dhcpd_file_content):
+        return re.sub(" *host +%s +\{[^}]+} *\n" % host, "", dhcpd_file_content)
+
+    def create_host(self, domain, reverse_domain, host, ip, mac, ttl, dhcpd_file_path):
         record_full = "%s.%s" % (host, domain)
+        reverse_domain_record = self.get_reverse_domain_record(reverse_domain, ip)
 
         self.insert_host(domain, host, ip, ttl, 'A')
         self.insert_host(reverse_domain, reverse_domain_record, record_full, ttl, 'PTR')
 
-    def remove_host(self, domain, reverse_domain, host):
-        if self.db_instance is None:
-            self.connect()
+        with open(dhcpd_file_path, "r") as f:
+            dhcpd_file_content = f.read()
+
+        dhcpd_host_config = "host %s {\n" \
+                            "        hardware ethernet %s;\n" \
+                            "        fixed-address %s;\n" \
+                            "    }" % (host, mac, record_full)
+
+        dhcpd_file_content = self.remove_host_dhcp(host, dhcpd_file_content)
+        dhcpd_file_content = dhcpd_file_content.replace(self.dhcpd_replace_string, "%s\n    %s" %
+                                                        (dhcpd_host_config, self.dhcpd_replace_string))
+
+        with open(dhcpd_file_path, "w") as f:
+            f.write(dhcpd_file_content)
+
+    def remove_host(self, domain, reverse_domain, host, dhcpd_file_path):
         record_full = "%s.%s" % (host, domain)
         ip = self.get_record_content(record_full)
         if ip is not None:
             self.delete_host(record_full)
             self.delete_host(reverse_domain_record_full)
 
+        with open(dhcpd_file_path, "r") as f:
+            dhcpd_file_content = f.read()
+
+        dhcpd_file_content = self.remove_host_dhcp(host, dhcpd_file_content)
+
+        with open(dhcpd_file_path, "w") as f:
+            f.write(dhcpd_file_content)
+
 
 def eprint(*args, **kwargs):
     print(*args, file=sys.stderr, **kwargs)
         if ip is None or mac is None:
             eprint("IP and MAC are required to create a host")
             exit(1)
-        local_host_gen.create_host(config['domain'], config['reverseDomain'], host, ip, mac, ttl)
+        local_host_gen.create_host(config['domain'], config['reverseDomain'], host, ip, mac, ttl, config['dhcpdFilePath'])
     elif args.remove:
-        local_host_gen.remove_host(config['domain'], config['reverseDomain'], host)
+        local_host_gen.remove_host(config['domain'], config['reverseDomain'], host, config['dhcpdFilePath'])
 
     local_host_gen.disconnect()