fix(homebridge): bound charge-limit Brightness characteristic to 50-100 (#121)

Set the Brightness characteristic's min/max/step to match the telemetry
clamp so HomeKit rejects an out-of-range write before it reaches the API.

Author: Bre77

.changeset/hb-charge-limit-bounds.md

@@ -0,0 +1,5 @@
+---
+"homebridge-teslemetry": patch
+---
+
+Set the Brightness characteristic's min/max/step on the charge-limit control to 50-100 (step 1), matching the telemetry clamp already applied to `ChargeLimitSoc` readings, so HomeKit itself rejects a client write outside the vehicle's supported charge-limit range instead of forwarding it to the API.

packages/homebridge-teslemetry/src/vehicle-services/charge-limit.ts

@@ -30,6 +30,14 @@ export class ChargeLimitService extends BaseService {
     // Charge limit is always "on" (we just control the brightness/percentage)
     this.service.updateCharacteristic(this.platform.Characteristic.On, true);
 
+    // Match the Brightness characteristic's bounds to the telemetry clamp
+    // below so HomeKit rejects/bounds writes outside the vehicle's supported range.
+    this.service.getCharacteristic(this.platform.Characteristic.Brightness).setProps({
+      minValue: 50,
+      maxValue: 100,
+      minStep: 1,
+    });
+
     // Subscribe to charge limit updates
     this.subscribeSignal(
       "ChargeLimitSoc",

packages/homebridge-teslemetry/test/chargeLimit.test.ts

@@ -31,6 +31,44 @@ test("ChargeLimitSoc below 50 is clamped to 50", () => {
 	assert.equal(hapService.getCharacteristic(Characteristic.Brightness).value, 50);
 });
 
+test("the Brightness characteristic's props are bounded to the vehicle's supported charge limit range", () => {
+	const { hapService } = setup();
+	const props = hapService.getCharacteristic(Characteristic.Brightness).props;
+	assert.equal(props.minValue, 50);
+	assert.equal(props.maxValue, 100);
+	assert.equal(props.minStep, 1);
+});
+
+test("a client write above the max is rejected by HAP before reaching setChargeLimit()", async () => {
+	const { hapService, vehicle } = setup();
+	let apiCalled = false;
+	(vehicle.api as any).setChargeLimit = () => {
+		apiCalled = true;
+		return Promise.resolve({});
+	};
+
+	await assert.rejects(
+		hapService.getCharacteristic(Characteristic.Brightness).handleSetRequest(150 as never, {} as never),
+	);
+
+	assert.equal(apiCalled, false);
+});
+
+test("a client write below the min is rejected by HAP before reaching setChargeLimit()", async () => {
+	const { hapService, vehicle } = setup();
+	let apiCalled = false;
+	(vehicle.api as any).setChargeLimit = () => {
+		apiCalled = true;
+		return Promise.resolve({});
+	};
+
+	await assert.rejects(
+		hapService.getCharacteristic(Characteristic.Brightness).handleSetRequest(10 as never, {} as never),
+	);
+
+	assert.equal(apiCalled, false);
+});
+
 test("setting Brightness rounds the value and calls setChargeLimit()", async () => {
 	const { hapService, vehicle } = setup();
 	let received: unknown;