Z-Wave prevent I/O event loop (#6369)

* Prevent Z-Wave I/O in event loop

* Move value_handler to util class.

* Add docstring

homeassistant/components/zwave/util.py

@@ -0,0 +1,54 @@
+"""Zwave util methods."""
+import logging
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def value_handler(value, method=None, class_id=None, index=None,
+                  label=None, data=None, member=None, instance=None,
+                  **kwargs):
+    """Get the values for a given command_class with arguments.
+
+    May only be used inside callback.
+
+    """
+    values = []
+    if class_id is None:
+        values.extend(value.node.get_values(**kwargs).values())
+    else:
+        if not isinstance(class_id, list):
+            class_id = [class_id]
+        for cid in class_id:
+            values.extend(value.node.get_values(
+                class_id=cid, **kwargs).values())
+    _LOGGER.debug('method=%s, class_id=%s, index=%s, label=%s, data=%s,'
+                  ' member=%s, instance=%d, kwargs=%s',
+                  method, class_id, index, label, data, member, instance,
+                  kwargs)
+    _LOGGER.debug('values=%s', values)
+    results = None
+    for value in values:
+        if index is not None and value.index != index:
+            continue
+        if label is not None:
+            label_found = False
+            for entry in label:
+                if value.label == entry:
+                    label_found = True
+                    break
+            if not label_found:
+                continue
+        if method == 'set':
+            value.data = data
+            return
+        if data is not None and value.data != data:
+            continue
+        if instance is not None and value.instance != instance:
+            continue
+        if member is not None:
+            results = getattr(value, member)
+        else:
+            results = value
+        break
+    _LOGGER.debug('final result=%s', results)
+    return results