Expose maximum/minimum/step values of a numeric characteristics

Closes #123

lib/ruby_home/characteristic.rb

@@ -72,6 +72,28 @@ def valid_values
       constraints.fetch("ValidValues", {}).keys.map(&:to_i)
     end
 
+    def minimum_value
+      return unless numeric_constraints?
+
+      constraints["MinimumValue"]
+    end
+
+    def maximum_value
+      return unless numeric_constraints?
+
+      constraints["MaximumValue"]
+    end
+
+    def step_value
+      return unless numeric_constraints?
+
+      constraints["StepValue"]
+    end
+
+    def numeric_constraints?
+      format == "uint32" || format == "float"
+    end
+
     def method_missing(method_name, *args, &block)
       value.send(method_name, *args, &block)
     end

lib/ruby_home/http/serializers/characteristic_serializer.rb

@@ -17,6 +17,7 @@ def record_hash(characteristic)
         }
           .merge(value_hash(characteristic))
           .merge(valid_values_hash(characteristic))
+          .merge(numeric_constraints(characteristic))
       end
 
       private
@@ -42,6 +43,16 @@ def valid_values_hash(characteristic)
           {"valid-values" => characteristic.valid_values}
         end
       end
+
+      def numeric_constraints(characteristic)
+        return {} unless characteristic.numeric_constraints?
+
+        {
+          "minValue" => characteristic.minimum_value,
+          "maxValue" => characteristic.maximum_value,
+          "minStep" => characteristic.step_value,
+        }.compact
+      end
     end
   end
 end