Huami: Fix sending air quality index

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/Weather.java

@@ -632,6 +632,26 @@ public class Weather {
         }
     }
 
+    public static String getAqiLevelString(int aqi) {
+        // Uses the [2023 Plume index](https://plumelabs.files.wordpress.com/2023/06/plume_aqi_2023.pdf) as a reference
+        if (aqi < 0) {
+            return "(n/a)";
+        }
+        if (aqi < 20) {
+            return "excellent";
+        } else if (aqi < 50) {
+            return "fair";
+        } else if (aqi < 100) {
+            return "poor";
+        } else if (aqi < 150) {
+            return "unhealthy";
+        } else if (aqi < 250) {
+            return "very unhealthy";
+        } else {
+            return "dangerous";
+        }
+    }
+
     public static byte mapToZeTimeConditionOld(int openWeatherMapCondition) {
 /* deducted values:
     0 = partly cloudy

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/huami/HuamiSupport.java

@@ -3173,7 +3173,8 @@ public abstract class HuamiSupport extends AbstractBTLEDeviceSupport implements
             TransactionBuilder builder;
             builder = performInitialized("Sending air quality index");
             int length = 8;
-            String aqiString = "(n/a)";
+            int aqi = weatherSpec.airQuality != null ? weatherSpec.airQuality.aqi : -1;
+            String aqiString = Weather.getAqiLevelString(aqi);
             if (supportsConditionString) {
                 length += aqiString.getBytes().length + 1;
             }
@@ -3182,7 +3183,7 @@ public abstract class HuamiSupport extends AbstractBTLEDeviceSupport implements
             buf.put((byte) 4);
             buf.putInt(weatherSpec.timestamp);
             buf.put((byte) (tz_offset_hours * 4));
-            buf.putShort((short) -1);
+            buf.putShort((short) aqi);
             if (supportsConditionString) {
                 buf.put(aqiString.getBytes());
                 buf.put((byte) 0);