Extract variable rendering (#39934)

homeassistant/helpers/script_variables.py

@@ -0,0 +1,57 @@
+"""Script variables."""
+from typing import Any, Dict, Mapping, Optional
+
+from homeassistant.core import HomeAssistant, callback
+
+from . import template
+
+
+class ScriptVariables:
+    """Class to hold and render script variables."""
+
+    def __init__(self, variables: Dict[str, Any]):
+        """Initialize script variables."""
+        self.variables = variables
+        self._has_template: Optional[bool] = None
+
+    @callback
+    def async_render(
+        self,
+        hass: HomeAssistant,
+        run_variables: Optional[Mapping[str, Any]],
+    ) -> Dict[str, Any]:
+        """Render script variables.
+
+        The run variables are used to compute the static variables, but afterwards will also
+        be merged on top of the static variables.
+        """
+        if self._has_template is None:
+            self._has_template = template.is_complex(self.variables)
+            template.attach(hass, self.variables)
+
+        if not self._has_template:
+            rendered_variables = dict(self.variables)
+
+            if run_variables is not None:
+                rendered_variables.update(run_variables)
+
+            return rendered_variables
+
+        rendered_variables = {} if run_variables is None else dict(run_variables)
+
+        for key, value in self.variables.items():
+            # We can skip if we're going to override this key with
+            # run variables anyway
+            if key in rendered_variables:
+                continue
+
+            rendered_variables[key] = template.render_complex(value, rendered_variables)
+
+        if run_variables:
+            rendered_variables.update(run_variables)
+
+        return rendered_variables
+
+    def as_dict(self) -> dict:
+        """Return dict version of this class."""
+        return self.variables