dhcp: track pending config changes with hash, update UI button

daemon/handlers/dnsmasq.py

@@ -1,5 +1,6 @@
 """Dnsmasq daemon handler."""
 
+import hashlib
 import logging
 from copy import deepcopy
 from datetime import UTC, datetime
@@ -49,6 +50,20 @@ DEFAULT_CFG: dict[str, Any] = {
     "dns": {"upstreams": ["8.8.8.8", "1.1.1.1"], "domain": None, "custom_records": []},
 }
 
+# Internal field for tracking applied config version
+_APPLY_HASH_KEY = "_last_applied_hash"
+
+
+def _config_hash(cfg: dict[str, Any]) -> str:
+    """Compute a hash of the config, excluding the _last_applied_hash field.
+
+    Used to detect whether the JSON config has changed since the last apply.
+    """
+    import json
+
+    clean = {k: v for k, v in cfg.items() if k != _APPLY_HASH_KEY}
+    return hashlib.sha256(json.dumps(clean, sort_keys=True).encode()).hexdigest()
+
 
 def _get_state() -> dict[str, Any] | None:
     """Retrieve cached dnsmasq state from the state store."""
@@ -172,14 +187,17 @@ def apply_config(_request: Any, _body: Any) -> dict[str, Any]:
     conf_text = _generate_conf(cfg)
     ensure_dirs(CONFIG_DIR, DATA_DIR, FRAGMENTS_DIR)
     run(["mkdir", "-p", "/etc/dnsmasq.d"], sudo=True)
-    run_proc(
-        ["tee", DNSMASQ_CONF, "--"],
-        sudo=True,
-        check=True,
-        input=conf_text,
-    )
+    tmp = Path("/tmp") / "vacuum-wall-dnsmasq.tmp"
+    with open(tmp, "w") as f:
+        f.write(conf_text)
+    run(["cp", str(tmp), DNSMASQ_CONF], sudo=True)
+    tmp.unlink(missing_ok=True)
     run(["systemctl", "reload", "dnsmasq"], sudo=True)
     logger.info("dnsmasq config written and reloaded")
+    # Store the config hash so state collector can detect pending changes
+    cfg_after = _get_config()
+    cfg_after[_APPLY_HASH_KEY] = _config_hash(cfg_after)
+    _save_config(cfg_after)
     refresh_state(["dnsmasq"])
     return {"applied": True}