[ios] Create expression with expressionWithFormat. Revert changes in NSExpression of sum. Add a TestCase of featureAccumulated.

6 files changed, 62 insertions, 22 deletions

diff --git a/platform/darwin/src/MGLShapeSource.h b/platform/darwin/src/MGLShapeSource.h
index c4421e3ddf..08891ee90c 100644
--- a/platform/darwin/src/MGLShapeSource.h
+++ b/platform/darwin/src/MGLShapeSource.h
@@ -41,6 +41,18 @@ FOUNDATION_EXTERN MGL_EXPORT const MGLShapeSourceOption MGLShapeSourceOptionClus
  */
 FOUNDATION_EXTERN MGL_EXPORT const MGLShapeSourceOption MGLShapeSourceOptionClusterRadius;
 
+/**
+ An `NSDictionary` objcet containing custom properties on the generated clusters if clustering is enabled,
+ aggregating values from clustered points. Has the form {"property_name": [recude_operator, [map_expression]]} or
+ {"property_name": [[reduce_operator, accumulated, expression], [map_expression]]}
+
+ recude_operator is any expression function that accepts at least 2 operands (e.g. "sum" or "max", etc.).
+ 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 with two expression arguments: `accumulated` and
+ an other valid expression produces value of the same type of `accumulated`
+
+ map_expression produces the value of a single point, it shall be a valid expression
+ */
 FOUNDATION_EXTERN MGL_EXPORT const MGLShapeSourceOption MGLShapeSourceOptionClusterProperties;
 /**
  An `NSNumber` object containing an integer; specifies the maximum zoom level at
diff --git a/platform/darwin/src/MGLShapeSource.mm b/platform/darwin/src/MGLShapeSource.mm
index c1ac6fbbbe..8ec92880cb 100644
--- a/platform/darwin/src/MGLShapeSource.mm
+++ b/platform/darwin/src/MGLShapeSource.mm
@@ -109,7 +109,17 @@ mbgl::style::GeoJSONOptions MGLGeoJSONOptionsFromDictionary(NSDictionary<MGLShap
                 [NSException raise:NSInvalidArgumentException
                             format:@"Failed to convert MGLShapeSourceOptionClusterProperties map expression."];
             }
-            NSExpression *reduceExpre = expArray[0];
+
+            NSString *reduceOperator = expArray[0];
+            NSExpression *reduceExpre;
+            // If reduceOperator is only a string instead of expression, create the integrated full expression before parsing
+            if ([reduceOperator isKindOfClass:[NSString class]]) {
+                NSString *reduceExpression = [NSString stringWithFormat:@"%@({ $featureAccumulated, %@})", reduceOperator, key];
+                reduceExpre =  [NSExpression expressionWithFormat:reduceExpression];
+            } else {
+                reduceExpre = expArray[0];
+            }
+
             auto reduce = MGLClusterPropertyFromNSExpression(reduceExpre);
             if (!reduce) {
                 [NSException raise:NSInvalidArgumentException
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.h b/platform/darwin/src/NSExpression+MGLAdditions.h
index 2a33367e9c..2109310e69 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.h
+++ b/platform/darwin/src/NSExpression+MGLAdditions.h
@@ -86,6 +86,13 @@ FOUNDATION_EXTERN MGL_EXPORT const MGLExpressionInterpolationMode MGLExpressionI
 
 /**
  `NSExpression` variable that corresponds to the
+ <a href="https://docs.mapbox.com/mapbox-gl-js/style-spec/#accumulated"><code>id</code></a>
+ expression operator in the Mapbox Style Specification.
+ */
+@property (class, nonatomic, readonly) NSExpression *featureAccumulatedVariableExpression;
+
+/**
+ `NSExpression` variable that corresponds to the
  <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-properties"><code>properties</code></a>
  expression operator in the Mapbox Style Specification.
  */
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 3d77b1ea1f..b502851722 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -1066,14 +1066,8 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 NSExpression *count = [NSExpression expressionForFunction:@"count:" arguments:self.arguments];
                 return [NSExpression expressionForFunction:@"divide:by:" arguments:@[sum, count]].mgl_jsonExpressionObject;
             } else if ([function isEqualToString:@"sum:"]) {
-                id context = self.arguments.firstObject;
-                if ([context isKindOfClass:[NSExpression class]]) {
-                    NSArray *arguments = [self.arguments valueForKeyPath:@"mgl_jsonExpressionObject"];
-                    return [@[@"+"] arrayByAddingObjectsFromArray:arguments];
-                } else {
-                    NSArray *arguments = [self.arguments.firstObject.collection valueForKeyPath:@"mgl_jsonExpressionObject"];
-                    return [@[@"+"] arrayByAddingObjectsFromArray:arguments];
-                }
+                NSArray *arguments = [self.arguments.firstObject.collection valueForKeyPath:@"mgl_jsonExpressionObject"];
+                return [@[@"+"] arrayByAddingObjectsFromArray:arguments];
             } else if ([function isEqualToString:@"count:"]) {
                 NSArray *arguments = self.arguments.firstObject.mgl_jsonExpressionObject;
                 return @[@"length", arguments];
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index f1fe3ea878..b3558e2bf4 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -180,6 +180,13 @@ using namespace std::string_literals;
         XCTAssertEqualObjects([expression expressionValueWithObject:nil context:context], @1);
     }
     {
+        NSExpression *expression = [NSExpression expressionForVariable:@"featureAccumulated"];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, @[@"accumulated"]);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"$featureAccumulated"].mgl_jsonExpressionObject, @[@"accumulated"]);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:@[@"accumulated"]], expression);
+    }
+
+    {
         NSExpression *expression = [NSExpression expressionForVariable:@"geometryType"];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, @[@"geometry-type"]);
         XCTAssertEqualObjects([NSExpression expressionWithFormat:@"$geometryType"].mgl_jsonExpressionObject, @[@"geometry-type"]);
diff --git a/platform/ios/app/MBXViewController.m b/platform/ios/app/MBXViewController.m
index 6d56e39364..c319b43682 100644
--- a/platform/ios/app/MBXViewController.m
+++ b/platform/ios/app/MBXViewController.m
@@ -1319,26 +1319,36 @@ CLLocationCoordinate2D randomWorldCoordinate() {
     NSURL *geoJSONURL = [NSURL fileURLWithPath:filePath];
 //    MGLShapeSource *source = [[MGLShapeSource alloc] initWithIdentifier:@"mutable-data-source-url-id" URL:geoJSONURL options:nil];
     
-    NSExpression *reduceExpression = [NSExpression expressionForFunction:@"sum:" arguments:@[[NSExpression expressionForVariable:@"featureAccumulated"],  [NSExpression expressionForKeyPath:@"sumVal"]]];
-
-    NSExpression *mapExpression = [NSExpression expressionForKeyPath:@"mag"];
-
-    NSArray<NSExpression *> *expressArray = @[reduceExpression, mapExpression];
-    NSDictionary *clusterProperty = @{@"sumVal" : expressArray};
-
-    MGLShapeSource *source = [[MGLShapeSource alloc] initWithIdentifier:@"mutable-data-source-id" URL:geoJSONURL options:@{
-                                                                                                                        MGLShapeSourceOptionClustered: @(YES),
-                                                                                                                        MGLShapeSourceOptionClusterRadius: @(15),
-                                                                                                                        MGLShapeSourceOptionClusterProperties: clusterProperty
-                                                                                                                        }];
+    // Input property with format {"property_name": [[reduce_operator, accumulated, expression], [map_expression]]}
+//    NSExpression *reduceExpression1 = [NSExpression expressionForFunction:@"sum:" arguments:@[[NSExpression expressionForVariable:@"featureAccumulated"], [NSExpression expressionForKeyPath:@"sumVal"]]];
+    NSExpression *reduceExpression1 =  [NSExpression expressionWithFormat:@"sum({ $featureAccumulated, sumVal })"];
+    NSExpression *mapExpression1 = [NSExpression expressionForKeyPath:@"mag"];
+    NSArray *expressArray1 = @[reduceExpression1, mapExpression1];
     
+    // Input propety with format {"property_name": [[literal(reduce_operator)], [map_expression]]}
+    NSString *reduceExpression2 = @"max";
+    NSExpression *mapExpression2 = [NSExpression expressionForKeyPath:@"mag"];
+    NSArray *expressArray2 = @[reduceExpression2, mapExpression2];
+    
+    NSDictionary *clusterProperty = @{@"sumVal" : expressArray1,
+                                      @"maxVal" : expressArray2
+                                      };
+
+    MGLShapeSource *source = [[MGLShapeSource alloc] initWithIdentifier:@"mutable-data-source-id"
+                                                                    URL:geoJSONURL
+                                                                options:@{
+                                                                         MGLShapeSourceOptionClustered: @(YES),
+                                                                         MGLShapeSourceOptionClusterRadius: @(15),
+                                                                         MGLShapeSourceOptionClusterProperties: clusterProperty
+                                                                         }];
+
     [self.mapView.style addSource:source];
     
     // Create image cluster style layer
     MGLSymbolStyleLayer *clusterLayer = [[MGLSymbolStyleLayer alloc] initWithIdentifier:@"clusteredPortsNumbers" source:source];
     clusterLayer.textColor = [NSExpression expressionForConstantValue:[UIColor redColor]];
     clusterLayer.textFontSize = [NSExpression expressionForConstantValue:@(30)];
-    clusterLayer.text = [NSExpression expressionWithFormat:@"CAST(point_count, 'NSString')"];
+    clusterLayer.text = [NSExpression expressionWithFormat:@"CAST(maxVal, 'NSString')"];
     
     [self.mapView.style addLayer:clusterLayer];
 }