sync: add cross-subsystem event bus for config consistency

Add EventBus with loop guards to keep firewall, dnsmasq, wireguard,
and network configs consistent. Handlers emit SyncEvent after mutations;
subscribers compute diffs and write JSON without manual cascade loops.

daemon/handlers/dnsmasq.py

@@ -26,7 +26,8 @@ from daemon.iface import (
     POST_DNSMASQ_UPSTREAMS,
 )
 from daemon.server import NotFoundError, refresh_state, registry
-from lib.common import deep_merge, ensure_dirs, load_json, run, run_proc, save_json
+from lib.common import deep_merge, ensure_dirs, load_json, run, save_json
+from lib.sync import SyncEvent, bus
 
 logger = logging.getLogger(__name__)
 
@@ -156,7 +157,10 @@ def save_config_handler(_request: Any, body: dict[str, Any] | None) -> dict[str,
     if not body:
         raise ValueError("Request body required")
     _save_config(body)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent("dnsmasq", "config_saved", {"action": "config_saved"})
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"config_saved": True}
 
 
@@ -172,7 +176,10 @@ def patch_config(_request: Any, body: dict[str, Any] | None) -> dict[str, Any]:
     current = _get_config()
     merged = deep_merge(current, body)
     _save_config(merged)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent("dnsmasq", "config_saved", {"action": "config_patched"})
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"config_saved": True}
 
 
@@ -198,8 +205,11 @@ def apply_config(_request: Any, _body: Any) -> dict[str, Any]:
     cfg_after = _get_config()
     cfg_after[_APPLY_HASH_KEY] = _config_hash(cfg_after)
     _save_config(cfg_after)
-    refresh_state(["dnsmasq"])
-    return {"applied": True}
+    sync_result = bus.emit(
+        SyncEvent("dnsmasq", "config_saved", {"action": "config_applied"})
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
+    return {"applied": True, "synced": sync_result.affected_subsystems}
 
 
 @registry.register(GET_DNSMASQ_STATUS)
@@ -260,7 +270,12 @@ def set_dhcp_range(_request: Any, body: dict[str, Any] | None) -> dict[str, Any]
             entry["dns"] = body["dns"]
         ranges.append(entry)
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent(
+            "dnsmasq", "config_saved", {"action": "range_added", "interface": iface}
+        )
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"interface": iface, "start": start, "end": end}
 
 
@@ -295,7 +310,12 @@ def remove_dhcp_range(_request: Any, body: dict[str, Any] | None) -> dict[str, A
             f"DHCP range for interface '{iface}' ({start}-{end}) not found"
         )
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent(
+            "dnsmasq", "config_saved", {"action": "range_removed", "interface": iface}
+        )
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"interface": iface, "start": start, "end": end}
 
 
@@ -334,14 +354,26 @@ def add_static_lease(_request: Any, body: dict[str, Any] | None) -> dict[str, An
             if hostname is not None:
                 leases[i]["hostname"] = hostname
             _save_config(cfg)
-            refresh_state(["dnsmasq"])
+            sync_result = bus.emit(
+                SyncEvent(
+                    "dnsmasq",
+                    "config_saved",
+                    {"action": "static_lease_added", "mac": mac},
+                )
+            )
+            refresh_state(["dnsmasq", *sync_result.affected_subsystems])
             return {"mac": mac, "ip": ip, "hostname": hostname}
     entry: dict[str, Any] = {"mac": mac, "ip": ip}
     if hostname:
         entry["hostname"] = hostname
     leases.append(entry)
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent(
+            "dnsmasq", "config_saved", {"action": "static_lease_added", "mac": mac}
+        )
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"mac": mac, "ip": ip, "hostname": hostname}
 
 
@@ -366,7 +398,12 @@ def remove_static_lease(_request: Any, body: dict[str, Any] | None) -> dict[str,
     if len(cfg["dhcp"]["static_leases"]) == before:
         raise NotFoundError(f"Static lease for MAC '{mac}' not found")
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent(
+            "dnsmasq", "config_saved", {"action": "static_lease_removed", "mac": mac}
+        )
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"mac": mac}
 
 
@@ -392,14 +429,26 @@ def add_dns_record(_request: Any, body: dict[str, Any] | None) -> dict[str, Any]
             if hostname is not None:
                 records[i]["hostname"] = hostname
             _save_config(cfg)
-            refresh_state(["dnsmasq"])
+            sync_result = bus.emit(
+                SyncEvent(
+                    "dnsmasq",
+                    "config_saved",
+                    {"action": "dns_record_added", "name": name},
+                )
+            )
+            refresh_state(["dnsmasq", *sync_result.affected_subsystems])
             return {"name": name, "address": address, "hostname": hostname}
     entry: dict[str, Any] = {"name": name, "address": address}
     if hostname:
         entry["hostname"] = hostname
     records.append(entry)
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent(
+            "dnsmasq", "config_saved", {"action": "dns_record_added", "name": name}
+        )
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"name": name, "address": address, "hostname": hostname}
 
 
@@ -422,7 +471,12 @@ def remove_dns_record(_request: Any, body: dict[str, Any] | None) -> dict[str, A
     if len(cfg["dns"]["custom_records"]) == before:
         raise NotFoundError(f"DNS record '{name}' not found")
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent(
+            "dnsmasq", "config_saved", {"action": "dns_record_removed", "name": name}
+        )
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"name": name}
 
 
@@ -438,7 +492,10 @@ def set_upstreams(_request: Any, body: dict[str, Any] | None) -> dict[str, Any]:
     cfg = _get_config()
     cfg["dns"]["upstreams"] = list(body["servers"])
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent("dnsmasq", "config_saved", {"action": "upstreams_set"})
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"upstreams": cfg["dns"]["upstreams"]}
 
 
@@ -455,5 +512,8 @@ def set_domain(_request: Any, body: dict[str, Any] | None) -> dict[str, Any]:
     cfg = _get_config()
     cfg["dns"]["domain"] = domain if domain else None
     _save_config(cfg)
-    refresh_state(["dnsmasq"])
+    sync_result = bus.emit(
+        SyncEvent("dnsmasq", "config_saved", {"action": "domain_set"})
+    )
+    refresh_state(["dnsmasq", *sync_result.affected_subsystems])
     return {"domain": cfg["dns"]["domain"]}