Total overhaul!

src/fan-controller.js

@@ -0,0 +1,43 @@
+import {Controller} from "./controller.js";
+
+export class FanController extends Controller {
+
+  get _value() {
+    return (this.stateObj.state !== "off")
+    ? this.stateObj.attributes.speed_list.indexOf(this.stateObj.attributes.speed)
+    : 0;
+  }
+
+  set _value(value) {
+    if (value in this.stateObj.attributes.speed_list) {
+      this._hass.callService("fan", "turn_on", {
+        entity_id: this.stateObj.entity_id,
+        speed: this.stateObj.attributes.speed_list[value],
+      });
+    } else {
+      this._hass.callService("fan", "turn_off", {
+        entity_id: this.stateObj.entity_id,
+      });
+    }
+  }
+
+  get string() {
+    if (this.stateObj.state === "off")
+      return this._hass.localize("state.default.off");
+    return this.stateObj.attributes.speed;
+  }
+
+  get hasSlider() {
+    if ("speed" in this.stateObj.attributes) return true;
+    return false;
+  }
+
+  get _max() {
+    return this.stateObj.attributes.speed_list.length -1;
+  }
+
+  get _step() {
+    return 1;
+  }
+
+}