[android] bindings for aggregated cluster properties (#15425)

* [android] bindings for aggregated cluster properties

* [android] change the parameter type for adding clusterProperty

* [android] add changelog

* remove extra emplty line

9 files changed, 92 insertions, 5 deletions

diff --git a/platform/android/CHANGELOG.md b/platform/android/CHANGELOG.md
index 54729fbcc5..ca57e48378 100644
--- a/platform/android/CHANGELOG.md
+++ b/platform/android/CHANGELOG.md
@@ -3,6 +3,8 @@
 Mapbox welcomes participation and contributions from everyone.  If you'd like to do so please see the [`Contributing Guide`](https://github.com/mapbox/mapbox-gl-native/blob/master/CONTRIBUTING.md) first to get started.
 
 ## master
+### Features
+ - Introduce `clusterProperties` option for aggregated cluster properties. [#15425](https://github.com/mapbox/mapbox-gl-native/pull/15425)
 
 ## 8.3.0
 This release changes how offline tile requests are billed — they are now billed on a pay-as-you-go basis and all developers are able raise the offline tile limit for their users. Offline requests were previously exempt from monthly active user (MAU) billing and increasing the offline per-user tile limit to more than 6,000 tiles required the purchase of an enterprise license. By upgrading to this release, you are opting into the changes outlined in [this blog post](https://blog.mapbox.com/offline-maps-for-all-bb0fc51827be) and [#15380](https://github.com/mapbox/mapbox-gl-native/pull/15380).
diff --git a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/expressions/Expression.java b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/expressions/Expression.java
index 0f5ce76725..d6cddea066 100644
--- a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/expressions/Expression.java
+++ b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/expressions/Expression.java
@@ -1436,6 +1436,27 @@ public class Expression {
   }
 
   /**
+   * Gets the value of a cluster property accumulated so far. Can only be used in the clusterProperties
+   * option of a clustered GeoJSON source.
+   * <p>
+   * Example usage:
+   * </p>
+   * <pre>
+   * {@code
+   *  GeoJsonOptions options = new GeoJsonOptions()
+   *                              .withCluster(true)
+   *                              .withClusterProperty("max", max(accumulated(), get("max")).toArray(), get("mag").toArray());
+   * }
+   * </pre>
+   *
+   * @return expression
+   * @see <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-accumulated">Style specification</a>
+   */
+  public static Expression accumulated() {
+    return new Expression("accumulated");
+  }
+
+  /**
    * Gets the kernel density estimation of a pixel in a heatmap layer,
    * which is a relative measure of how many data points are crowded around a particular pixel.
    * Can only be used in the `heatmap-color` property.
diff --git a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/sources/GeoJsonOptions.java b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/sources/GeoJsonOptions.java
index 1e1b9bafa6..091079ab92 100644
--- a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/sources/GeoJsonOptions.java
+++ b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/sources/GeoJsonOptions.java
@@ -1,9 +1,12 @@
 package com.mapbox.mapboxsdk.style.sources;
 
 import android.support.annotation.NonNull;
+import com.mapbox.mapboxsdk.style.expressions.Expression;
 
 import java.util.HashMap;
 
+import static com.mapbox.mapboxsdk.style.expressions.Expression.ExpressionLiteral;
+
 /**
  * Builder class for composing GeoJsonSource objects.
  *
@@ -109,4 +112,28 @@ public class GeoJsonOptions extends HashMap<String, Object> {
     this.put("clusterRadius", clusterRadius);
     return this;
   }
+
+  /**
+   * An object defining custom properties on the generated clusters if clustering is enabled,
+   * aggregating values from clustered points. Has the form {"property_name": [operator, [map_expression]]} or
+   * {"property_name": [[operator, accumulated, expression], [map_expression]]}
+   *
+   * @param propertyName name of the property
+   * @param operatorExpr operatorExpr is any expression function that accepts at least 2 operands (e.g. "+" or "max").
+   *                     It accumulates the property value from clusters/points the cluster contains. It can either be
+   *                     a literal with single operator, or be a valid expression
+   * @param mapExpr map expression produces the value of a single point, it shall be a valid expression
+   * @return the current instance for chaining
+   */
+  @NonNull
+  public GeoJsonOptions withClusterProperty(String propertyName, Expression operatorExpr, Expression mapExpr) {
+    HashMap<String, Object[]> properties = containsKey("clusterProperties")
+            ? (HashMap<String, Object[]>) get("clusterProperties") : new HashMap<String, Object[]>();
+    Object operator = (operatorExpr instanceof ExpressionLiteral)
+            ? ((ExpressionLiteral)operatorExpr).toValue() : operatorExpr.toArray();
+    Object map = mapExpr.toArray();
+    properties.put(propertyName, new Object[]{operator, map});
+    this.put("clusterProperties", properties);
+    return this;
+  }
 }
diff --git a/platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/GeoJsonClusteringActivity.java b/platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/GeoJsonClusteringActivity.java
index 732a7929b8..cb2701d436 100644
--- a/platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/GeoJsonClusteringActivity.java
+++ b/platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/GeoJsonClusteringActivity.java
@@ -30,6 +30,8 @@ import java.util.List;
 import java.util.Objects;
 
 import static com.mapbox.mapboxsdk.style.expressions.Expression.all;
+import static com.mapbox.mapboxsdk.style.expressions.Expression.accumulated;
+import static com.mapbox.mapboxsdk.style.expressions.Expression.concat;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.division;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.exponential;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.get;
@@ -39,6 +41,8 @@ import static com.mapbox.mapboxsdk.style.expressions.Expression.has;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.interpolate;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.literal;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.lt;
+import static com.mapbox.mapboxsdk.style.expressions.Expression.max;
+import static com.mapbox.mapboxsdk.style.expressions.Expression.neq;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.rgb;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.stop;
 import static com.mapbox.mapboxsdk.style.expressions.Expression.toNumber;
@@ -138,6 +142,9 @@ public class GeoJsonClusteringActivity extends AppCompatActivity {
       .withCluster(true)
       .withClusterMaxZoom(14)
       .withClusterRadius(50)
+      .withClusterProperty("max", max(accumulated(), get("max")), get("mag"))
+      .withClusterProperty("sum", literal("+"), get("mag"))
+      .withClusterProperty("felt", literal("any"), neq(get("felt"), literal("null")))
     );
   }
 
@@ -182,9 +189,9 @@ public class GeoJsonClusteringActivity extends AppCompatActivity {
   }
 
   private SymbolLayer createClusterTextLayer() {
-    return new SymbolLayer("count", "earthquakes")
+    return new SymbolLayer("property", "earthquakes")
       .withProperties(
-        textField(Expression.toString(get("point_count"))),
+        textField(concat(get("point_count"), literal(", "), get("max"))),
         textSize(12f),
         textColor(Color.WHITE),
         textIgnorePlacement(true),
diff --git a/platform/android/src/java_types.cpp b/platform/android/src/java_types.cpp
index dd165470cf..7a1ba93a58 100644
--- a/platform/android/src/java_types.cpp
+++ b/platform/android/src/java_types.cpp
@@ -18,6 +18,10 @@ namespace java {
 
     jni::jclass* Map::jclass;
     jni::jmethodID* Map::getMethodId;
+    jni::jmethodID* Map::keySetMethodId;
+
+    jni::jclass* Set::jclass;
+    jni::jmethodID* Set::toArrayMethodId;
 
     void registerNatives(JNIEnv& env) {
         ObjectArray::jclass = jni::NewGlobalRef(env, &jni::FindClass(env, "[Ljava/lang/Object;")).release();
@@ -34,6 +38,10 @@ namespace java {
 
         Map::jclass = jni::NewGlobalRef(env, &jni::FindClass(env, "java/util/Map")).release();
         Map::getMethodId = &jni::GetMethodID(env, *Map::jclass, "get", "(Ljava/lang/Object;)Ljava/lang/Object;");
+        Map::keySetMethodId = &jni::GetMethodID(env, *Map::jclass, "keySet", "()Ljava/util/Set;");
+
+        Set::jclass = jni::NewGlobalRef(env, &jni::FindClass(env, "java/util/Set")).release();
+        Set::toArrayMethodId = &jni::GetMethodID(env, *Set::jclass, "toArray", "()[Ljava/lang/Object;");
     }
 
 }
diff --git a/platform/android/src/java_types.hpp b/platform/android/src/java_types.hpp
index edec5cb550..c7c93ce71b 100644
--- a/platform/android/src/java_types.hpp
+++ b/platform/android/src/java_types.hpp
@@ -29,6 +29,12 @@ namespace java {
     struct Map {
         static jni::jclass* jclass;
         static jni::jmethodID* getMethodId;
+        static jni::jmethodID* keySetMethodId;
+    };
+
+    struct Set {
+        static jni::jclass* jclass;
+        static jni::jmethodID* toArrayMethodId;
     };
 
     void registerNatives(JNIEnv&);
diff --git a/platform/android/src/style/android_conversion.hpp b/platform/android/src/style/android_conversion.hpp
index 8559720b2f..d38dbfa684 100644
--- a/platform/android/src/style/android_conversion.hpp
+++ b/platform/android/src/style/android_conversion.hpp
@@ -47,9 +47,18 @@ public:
     }
 
     template <class Fn>
-    static optional<Error> eachMember(const mbgl::android::Value&, Fn&&) {
-        // TODO
-        mbgl::Log::Warning(mbgl::Event::Android, "eachMember not implemented");
+    static optional<Error> eachMember(const mbgl::android::Value& value, Fn&& fn) {
+        assert(value.isObject());
+        mbgl::android::Value keys = value.keyArray();
+        std::size_t length = arrayLength(keys);
+        for(std::size_t i = 0; i < length; ++i){
+            const auto k = keys.get(i).toString();
+            auto v = value.get(k.c_str());
+            optional<Error> result = fn(k, std::move(v));
+            if (result) {
+                return result;
+            }
+        }
         return {};
     }
 
diff --git a/platform/android/src/style/value.cpp b/platform/android/src/style/value.cpp
index f916909687..2f04840729 100644
--- a/platform/android/src/style/value.cpp
+++ b/platform/android/src/style/value.cpp
@@ -63,6 +63,12 @@ namespace android {
         return Value(env, jni::Local<jni::Object<>>(env, member));
     }
 
+    Value Value::keyArray() const{
+        jni::jobject* set = jni::CallMethod<jni::jobject*>(env, value.get(), *java::Map::keySetMethodId);
+        jni::jobject* array = jni::CallMethod<jni::jobject*>(env, set, *java::Set::toArrayMethodId);
+        return Value(env, jni::Local<jni::Object<>>(env, array));
+    }
+
     int Value::getLength() const {
         auto array = (jni::jarray<jni::jobject>*) value.get();
         return jni::GetArrayLength(env, *array);
diff --git a/platform/android/src/style/value.hpp b/platform/android/src/style/value.hpp
index 0c702bb465..b507c5ed11 100644
--- a/platform/android/src/style/value.hpp
+++ b/platform/android/src/style/value.hpp
@@ -31,6 +31,7 @@ public:
     long toLong() const;
     bool toBool() const;
     Value get(const char* key) const;
+    Value keyArray() const;
     int getLength() const;
     Value get(const int index ) const;