[core, ios, macos] Added layers and sources properties to MGLStyle

Added new layers and sources properties to MGLStyle that contain all the style’s layers and sources, respectively. These properties are KVC-compliant with all the mutable to-many methods. Layers are ordered from topmost to bottommost, for consistency with Cocoa APIs where front/first means top and back/last means bottom.

Also added storage for mbgl::style::Source in MGLSource proper for wrapping AnnotationSource. Until the style finishes loading, its name property is set to nil.

Fixes #6003.

include/mbgl/map/map.hpp

@@ -157,11 +157,13 @@ class Map : private util::noncopyable {
     void removeAnnotation(AnnotationID);
 
     // Sources
+    std::vector<style::Source*> getSources();
     style::Source* getSource(const std::string& sourceID);
     void addSource(std::unique_ptr<style::Source>);
     std::unique_ptr<style::Source> removeSource(const std::string& sourceID);
 
     // Layers
+    std::vector<style::Layer*> getLayers();
     style::Layer* getLayer(const std::string& layerID);
     void addLayer(std::unique_ptr<style::Layer>, const optional<std::string>& beforeLayerID = {});
     std::unique_ptr<style::Layer> removeLayer(const std::string& layerID);

platform/darwin/src/MGLBackgroundStyleLayer.mm

@@ -51,6 +51,9 @@ - (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLaye
 - (void)removeFromMapView:(MGLMapView *)mapView
 {
     auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    if (!removedLayer) {
+        return;
+    }
     _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::BackgroundLayer> &>(removedLayer));
     _rawLayer = _pendingLayer.get();
 }

platform/darwin/src/MGLCircleStyleLayer.mm

@@ -83,6 +83,9 @@ - (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLaye
 - (void)removeFromMapView:(MGLMapView *)mapView
 {
     auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    if (!removedLayer) {
+        return;
+    }
     _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::CircleLayer> &>(removedLayer));
     _rawLayer = _pendingLayer.get();
 }

platform/darwin/src/MGLFillStyleLayer.mm

@@ -78,6 +78,9 @@ - (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLaye
 - (void)removeFromMapView:(MGLMapView *)mapView
 {
     auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    if (!removedLayer) {
+        return;
+    }
     _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::FillLayer> &>(removedLayer));
     _rawLayer = _pendingLayer.get();
 }

platform/darwin/src/MGLLineStyleLayer.mm

@@ -90,6 +90,9 @@ - (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLaye
 - (void)removeFromMapView:(MGLMapView *)mapView
 {
     auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    if (!removedLayer) {
+        return;
+    }
     _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::LineLayer> &>(removedLayer));
     _rawLayer = _pendingLayer.get();
 }

platform/darwin/src/MGLRasterStyleLayer.mm

@@ -50,6 +50,9 @@ - (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLaye
 - (void)removeFromMapView:(MGLMapView *)mapView
 {
     auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    if (!removedLayer) {
+        return;
+    }
     _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::RasterLayer> &>(removedLayer));
     _rawLayer = _pendingLayer.get();
 }

platform/darwin/src/MGLSource.mm

@@ -2,6 +2,14 @@
 
 #include <mbgl/style/source.hpp>
 
+@interface MGLSource ()
+
+// Even though this class is abstract, MGLStyle uses it to represent some
+// special internal source types like mbgl::AnnotationSource.
+@property (nonatomic) mbgl::style::Source *rawSource;
+
+@end
+
 @implementation MGLSource
 
 - (instancetype)initWithIdentifier:(NSString *)identifier
@@ -12,6 +20,20 @@ - (instancetype)initWithIdentifier:(NSString *)identifier
     return self;
 }
 
+- (void)addToMapView:(MGLMapView *)mapView {
+    [NSException raise:NSInvalidArgumentException format:
+     @"The source %@ cannot be added to the style. "
+     @"Make sure the source was created as a member of a concrete subclass of MGLSource.",
+     self];
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView {
+    [NSException raise:NSInvalidArgumentException format:
+     @"The source %@ cannot be removed from the style. "
+     @"Make sure the source was created as a member of a concrete subclass of MGLSource.",
+     self];
+}
+
 - (NSString *)description {
     return [NSString stringWithFormat:@"<%@: %p; identifier = %@>",
             NSStringFromClass([self class]), (void *)self, self.identifier];

platform/darwin/src/MGLStyle.h

@@ -176,6 +176,11 @@ static const NSInteger MGLStyleDefaultVersion = 9;
 
 #pragma mark Managing Sources
 
+/**
+ A set containing the style’s sources.
+ */
+@property (nonatomic, strong) NS_MUTABLE_SET_OF(MGLSource *) *sources;
+
 /**
  Returns a source with the given identifier in the current style.
 
@@ -200,6 +205,12 @@ static const NSInteger MGLStyleDefaultVersion = 9;
 
 #pragma mark Managing Style Layers
 
+/**
+ The layers included in the style, arranged according to their front-to-back
+ ordering on the screen.
+ */
+@property (nonatomic, strong) NS_MUTABLE_ARRAY_OF(MGLStyleLayer *) *layers;
+
 /**
  Returns a style layer with the given identifier in the current style.
  
@@ -217,13 +228,31 @@ static const NSInteger MGLStyleDefaultVersion = 9;
  */
 - (void)addLayer:(MGLStyleLayer *)layer;
 
+/**
+ Inserts a new layer into the style at the given index.
+ 
+ @param layer The layer to insert.
+ @param index The index at which to insert the layer. An index of 0 would send
+    the layer to the back; an index equal to the number of objects in the
+    `layers` property would bring the layer to the front.
+ */
+- (void)insertLayer:(MGLStyleLayer *)layer atIndex:(NSUInteger)index;
+
 /**
  Inserts a new layer below another layer.
 
- @param layer Layer to be inserted.
- @param belowLayer A layer that's already on the map view.
+ @param layer The layer to insert.
+ @param sibling An existing layer in the style.
+ */
+- (void)insertLayer:(MGLStyleLayer *)layer belowLayer:(MGLStyleLayer *)sibling;
+
+/**
+ Inserts a new layer above another layer.
+
+ @param layer The layer to insert.
+ @param sibling An existing layer in the style.
  */
-- (void)insertLayer:(MGLStyleLayer *)layer belowLayer:(MGLStyleLayer *)otherLayer;
+- (void)insertLayer:(MGLStyleLayer *)layer aboveLayer:(MGLStyleLayer *)sibling;
 
 /**
  Removes a layer from the map view.