[homekit] fix unit conversions on step values for temperatures (openhab#18233)

getConfigurationAsQuantity was using toUnitRelative appropriately,
but the final conversion to Celsius was not, resulting in a 1 °F
step being interpreted as a -17.5 °C step!

Signed-off-by: Cody Cutrer <[email protected]>

Author: ccutrer

bundles/org.openhab.io.homekit/src/main/java/org/openhab/io/homekit/internal/HomekitTaggedItem.java

@@ -18,6 +18,7 @@
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
+import javax.measure.Quantity;
 import javax.measure.Unit;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -450,36 +451,44 @@ public double getConfigurationAsDouble(String key, double defaultValue) {
      * @param defaultValue default value
      * @return value
      */
-    public QuantityType<?> getConfigurationAsQuantity(String key, QuantityType defaultValue,
+    public <T extends Quantity<T>> QuantityType<T> getConfigurationAsQuantity(String key, QuantityType<T> defaultValue,
             boolean relativeConversion) {
         String stringValue = getConfiguration(key, new String());
         if (stringValue.isEmpty()) {
             return defaultValue;
         }
-        var parsedValue = new QuantityType(stringValue);
-        QuantityType<?> convertedValue;
+        var parsedValue = new QuantityType<>(stringValue);
+        QuantityType<T> convertedValue;
 
         if (relativeConversion) {
-            convertedValue = parsedValue.toUnitRelative(defaultValue.getUnit());
+            if (parsedValue.getUnit().isCompatible(defaultValue.getUnit())) {
+                convertedValue = ((QuantityType<T>) parsedValue).toUnitRelative(defaultValue.getUnit());
+            } else {
+                convertedValue = null;
+            }
         } else {
-            convertedValue = parsedValue.toInvertibleUnit(defaultValue.getUnit());
+            convertedValue = (QuantityType<T>) parsedValue.toInvertibleUnit(defaultValue.getUnit());
         }
         // not convertible? just assume it's in the item's unit
         if (convertedValue == null) {
             Unit unit;
             if (getBaseItem() instanceof NumberItem numberItem && (unit = numberItem.getUnit()) != null) {
                 var bdValue = new BigDecimal(stringValue);
-                parsedValue = new QuantityType(bdValue, unit);
+                parsedValue = new QuantityType<>(bdValue, unit);
                 if (relativeConversion) {
-                    convertedValue = parsedValue.toUnitRelative(defaultValue.getUnit());
+                    if (parsedValue.getUnit().isCompatible(defaultValue.getUnit())) {
+                        convertedValue = ((QuantityType<T>) parsedValue).toUnitRelative(defaultValue.getUnit());
+                    } else {
+                        convertedValue = null;
+                    }
                 } else {
-                    convertedValue = parsedValue.toInvertibleUnit(defaultValue.getUnit());
+                    convertedValue = (QuantityType<T>) parsedValue.toInvertibleUnit(defaultValue.getUnit());
                 }
             }
         }
         // still not convertible? just assume it's in the default's unit
         if (convertedValue == null) {
-            return new QuantityType(parsedValue.toBigDecimal(), defaultValue.getUnit());
+            return new QuantityType<>(parsedValue.toBigDecimal(), defaultValue.getUnit());
         }
         return convertedValue;
     }

bundles/org.openhab.io.homekit/src/main/java/org/openhab/io/homekit/internal/accessories/HomekitCharacteristicFactory.java

@@ -610,11 +610,6 @@ public static double convertFromCelsius(double degrees) {
         return convertAndRound(degrees, SIUnits.CELSIUS, getSystemTemperatureUnit());
     }
 
-    public static double getTemperatureStep(HomekitTaggedItem taggedItem, double defaultValue) {
-        return taggedItem.getConfigurationAsQuantity(HomekitTaggedItem.STEP,
-                new QuantityType(defaultValue, SIUnits.CELSIUS), true).doubleValue();
-    }
-
     private static Supplier<CompletableFuture<Integer>> getAngleSupplier(HomekitTaggedItem taggedItem,
             int defaultValue) {
         return () -> CompletableFuture.completedFuture(getAngleFromItem(taggedItem, defaultValue));
@@ -899,7 +894,7 @@ private static CoolingThresholdTemperatureCharacteristic createCoolingThresholdC
                         Objects.requireNonNull(new QuantityType(CoolingThresholdTemperatureCharacteristic.DEFAULT_STEP,
                                 SIUnits.CELSIUS).toUnit(getSystemTemperatureUnit())),
                         true)
-                .toUnit(SIUnits.CELSIUS).doubleValue();
+                .toUnitRelative(SIUnits.CELSIUS).doubleValue();
         return new CoolingThresholdTemperatureCharacteristic(minValue, maxValue, step,
                 getTemperatureSupplier(taggedItem, minValue), setTemperatureConsumer(taggedItem),
                 getSubscriber(taggedItem, COOLING_THRESHOLD_TEMPERATURE, updater),
@@ -979,7 +974,7 @@ private static CurrentTemperatureCharacteristic createCurrentTemperatureCharacte
                                 new QuantityType(CurrentTemperatureCharacteristic.DEFAULT_STEP, SIUnits.CELSIUS)
                                         .toUnit(getSystemTemperatureUnit())),
                         true)
-                .toUnit(SIUnits.CELSIUS).doubleValue();
+                .toUnitRelative(SIUnits.CELSIUS).doubleValue();
         return new CurrentTemperatureCharacteristic(minValue, maxValue, step,
                 getTemperatureSupplier(taggedItem, minValue), getSubscriber(taggedItem, TARGET_TEMPERATURE, updater),
                 getUnsubscriber(taggedItem, TARGET_TEMPERATURE, updater));
@@ -1073,7 +1068,7 @@ private static HeatingThresholdTemperatureCharacteristic createHeatingThresholdC
                         Objects.requireNonNull(new QuantityType(HeatingThresholdTemperatureCharacteristic.DEFAULT_STEP,
                                 SIUnits.CELSIUS).toUnit(getSystemTemperatureUnit())),
                         true)
-                .toUnit(SIUnits.CELSIUS).doubleValue();
+                .toUnitRelative(SIUnits.CELSIUS).doubleValue();
         return new HeatingThresholdTemperatureCharacteristic(minValue, maxValue, step,
                 getTemperatureSupplier(taggedItem, minValue), setTemperatureConsumer(taggedItem),
                 getSubscriber(taggedItem, HEATING_THRESHOLD_TEMPERATURE, updater),
@@ -1573,7 +1568,7 @@ private static TargetTemperatureCharacteristic createTargetTemperatureCharacteri
                                 new QuantityType(TargetTemperatureCharacteristic.DEFAULT_STEP, SIUnits.CELSIUS)
                                         .toUnit(getSystemTemperatureUnit())),
                         true)
-                .toUnit(SIUnits.CELSIUS).doubleValue();
+                .toUnitRelative(SIUnits.CELSIUS).doubleValue();
         return new TargetTemperatureCharacteristic(minValue, maxValue, step,
                 getTemperatureSupplier(taggedItem, minValue), setTemperatureConsumer(taggedItem),
                 getSubscriber(taggedItem, TARGET_TEMPERATURE, updater),