Total overhaul!

src/light-controller.js

@@ -0,0 +1,37 @@
+import {Controller} from "./controller.js";
+
+export class LightController extends Controller {
+
+  get _value() {
+    return (this.stateObj.state === "on")
+    ? Math.ceil(this.stateObj.attributes.brightness*100.0/255)
+    : 0;
+  }
+
+  set _value(value) {
+    value = Math.ceil(value/100.0*255);
+    if (value) {
+      this._hass.callService("light", "turn_on", {
+        entity_id: this.stateObj.entity_id,
+        brightness: value,
+      });
+    } else {
+      this._hass.callService("light", "turn_off", {
+        entity_id: this.stateObj.entity_id,
+      });
+    }
+  }
+
+  get string() {
+    if (this.stateObj.state === "off")
+      return this._hass.localize("state.default.off");
+    return `${this.value} %`;
+  }
+
+  get hasSlider() {
+    if ("brightness" in this.stateObj.attributes) return true;
+    if (("supported_features" in this.stateObj.attributes) &&
+      (this.stateObj.attributes.supported_features & 1)) return true;
+    return false;
+  }
+}