[core] Introduce Serializable

10 files changed, 49 insertions, 42 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 88df040b1c..fde902980d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -297,6 +297,7 @@ add_library(
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/projection.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/range.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/run_loop.hpp
+    ${PROJECT_SOURCE_DIR}/include/mbgl/util/serializable.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/size.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/string.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/thread.hpp
diff --git a/include/mbgl/style/color_ramp_property_value.hpp b/include/mbgl/style/color_ramp_property_value.hpp
index 1b9385f85f..6c623cf17d 100644
--- a/include/mbgl/style/color_ramp_property_value.hpp
+++ b/include/mbgl/style/color_ramp_property_value.hpp
@@ -1,8 +1,9 @@
 #pragma once
 
-#include <mbgl/util/variant.hpp>
-#include <mbgl/style/undefined.hpp>
 #include <mbgl/style/expression/expression.hpp>
+#include <mbgl/style/undefined.hpp>
+#include <mbgl/util/serializable.hpp>
+#include <mbgl/util/variant.hpp>
 
 namespace mbgl {
 namespace style {
@@ -11,7 +12,7 @@ namespace style {
  * Special-case implementation of (a subset of) the PropertyValue<T> interface
  * used for building the HeatmapColor paint property traits class.
  */
-class ColorRampPropertyValue {
+class ColorRampPropertyValue : public Serializable {
 private:
     std::shared_ptr<expression::Expression> value;
 
@@ -42,8 +43,8 @@ public:
     bool hasDataDrivenPropertyDifference(const ColorRampPropertyValue&) const { return false; }
 
     const expression::Expression& getExpression() const { return *value; }
+    Value serialize() const final { return value->serialize(); }
 };
 
-
 } // namespace style
 } // namespace mbgl
diff --git a/include/mbgl/style/conversion_impl.hpp b/include/mbgl/style/conversion_impl.hpp
index 11d3bae9ce..692760195e 100644
--- a/include/mbgl/style/conversion_impl.hpp
+++ b/include/mbgl/style/conversion_impl.hpp
@@ -10,6 +10,7 @@
 #include <mbgl/util/feature.hpp>
 #include <mbgl/util/geojson.hpp>
 #include <mbgl/util/optional.hpp>
+#include <mbgl/util/serializable.hpp>
 #include <mbgl/util/traits.hpp>
 
 #include <mapbox/compatibility/value.hpp>
@@ -301,23 +302,15 @@ optional<T> convert(const Convertible& value, Error& error, Args&&...args) {
     return Converter<T>()(value, error, std::forward<Args>(args)...);
 }
 
-template <>
-struct ValueFactory<ColorRampPropertyValue> {
-    static Value make(const ColorRampPropertyValue& value) { return value.getExpression().serialize(); }
-};
-
-template <>
-struct ValueFactory<TransitionOptions> {
-    static Value make(const TransitionOptions& value) { return value.serialize(); }
-};
-
-template <>
-struct ValueFactory<Color> {
-    static Value make(const Color& color) { return color.serialize(); }
+template <typename T>
+struct ValueFactory<T, typename std::enable_if<std::is_base_of<Serializable, T>::value>::type> {
+    static Value make(const Serializable& value) { return value.serialize(); }
 };
 
 template <typename T>
-struct ValueFactory<T, typename std::enable_if<(!std::is_enum<T>::value && !is_linear_container<T>::value)>::type> {
+struct ValueFactory<T,
+                    typename std::enable_if<(!std::is_enum<T>::value && !is_linear_container<T>::value &&
+                                             !std::is_base_of<Serializable, T>::value)>::type> {
     static Value make(const T& arg) { return {arg}; }
 };
 
diff --git a/include/mbgl/style/expression/expression.hpp b/include/mbgl/style/expression/expression.hpp
index 51cc3b0f15..c747cd210d 100644
--- a/include/mbgl/style/expression/expression.hpp
+++ b/include/mbgl/style/expression/expression.hpp
@@ -173,7 +173,7 @@ enum class Kind : int32_t {
     Distance
 };
 
-class Expression {
+class Expression : public Serializable {
 public:
     Expression(Kind kind_, type::Type type_) : kind(kind_), type(std::move(type_)) {}
     virtual ~Expression() = default;
@@ -206,8 +206,8 @@ public:
      * complete set of outputs is statically undecidable.
      */
     virtual std::vector<optional<Value>> possibleOutputs() const = 0;
-    
-    virtual mbgl::Value serialize() const {
+
+    mbgl::Value serialize() const override {
         std::vector<mbgl::Value> serialized;
         serialized.emplace_back(getOperator());
         eachChild([&](const Expression &child) {
@@ -215,7 +215,7 @@ public:
         });
         return serialized;
     };
-    
+
     virtual std::string getOperator() const = 0;
 
 protected:
diff --git a/include/mbgl/style/filter.hpp b/include/mbgl/style/filter.hpp
index c3ce6833fb..51c42b4a88 100644
--- a/include/mbgl/style/filter.hpp
+++ b/include/mbgl/style/filter.hpp
@@ -12,7 +12,7 @@
 namespace mbgl {
 namespace style {
 
-class Filter {
+class Filter : public Serializable {
 public:
     optional<std::shared_ptr<const expression::Expression>> expression;
 private:
@@ -41,14 +41,10 @@ public:
     friend bool operator!=(const Filter& lhs, const Filter& rhs) {
         return !(lhs == rhs);
     }
-    
-    mbgl::Value serialize() const {
-        if (legacyFilter) {
-            return *legacyFilter;
-        }
-        else if (expression) {
-            return (**expression).serialize();
-        }
+
+    mbgl::Value serialize() const final {
+        if (legacyFilter) return *legacyFilter;
+        if (expression) return (**expression).serialize();
         return NullValue();
     }
 };
diff --git a/include/mbgl/style/layer.hpp b/include/mbgl/style/layer.hpp
index 13a2ec014f..b1bc647b8b 100644
--- a/include/mbgl/style/layer.hpp
+++ b/include/mbgl/style/layer.hpp
@@ -5,6 +5,7 @@
 #include <mbgl/style/types.hpp>
 #include <mbgl/util/immutable.hpp>
 #include <mbgl/util/optional.hpp>
+#include <mbgl/util/serializable.hpp>
 
 #include <mapbox/std/weak.hpp>
 #include <mapbox/util/type_wrapper.hpp>
@@ -82,7 +83,7 @@ struct LayerTypeInfo {
  *
  *     auto circleLayer = LayerManager::get()->createLayer("circle", ...);
  */
-class Layer {
+class Layer : public Serializable {
 public:
     Layer(const Layer& ) = delete;
     Layer& operator=(const Layer&) = delete;
@@ -114,7 +115,7 @@ public:
     optional<conversion::Error> setProperty(const std::string& name, const conversion::Convertible& value);
 
     virtual StyleProperty getProperty(const std::string&) const = 0;
-    virtual Value serialize() const;
+    Value serialize() const override;
 
     // Private implementation
     // TODO : We should not have public mutable data members.
diff --git a/include/mbgl/style/source.hpp b/include/mbgl/style/source.hpp
index 031803b4bf..324528a744 100644
--- a/include/mbgl/style/source.hpp
+++ b/include/mbgl/style/source.hpp
@@ -70,7 +70,7 @@ struct SourceTypeInfo {
  *
  *     auto vectorSource = std::make_unique<VectorSource>("my-vector-source");
  */
-class Source {
+class Source : public Serializable {
 public:
     Source(const Source&) = delete;
     Source& operator=(const Source&) = delete;
@@ -168,7 +168,7 @@ public:
 
     const SourceTypeInfo* getTypeInfo() const noexcept;
 
-    virtual Value serialize() const;
+    Value serialize() const override;
 
 protected:
     explicit Source(Immutable<Impl>);
diff --git a/include/mbgl/style/transition_options.hpp b/include/mbgl/style/transition_options.hpp
index 8ead79eb21..e78dddf01d 100644
--- a/include/mbgl/style/transition_options.hpp
+++ b/include/mbgl/style/transition_options.hpp
@@ -2,13 +2,12 @@
 
 #include <mbgl/util/chrono.hpp>
 #include <mbgl/util/optional.hpp>
-
-#include <mapbox/compatibility/value.hpp>
+#include <mbgl/util/serializable.hpp>
 
 namespace mbgl {
 namespace style {
 
-class TransitionOptions {
+class TransitionOptions : public Serializable {
 public:
     optional<Duration> duration;
     optional<Duration> delay;
@@ -33,7 +32,7 @@ public:
         return duration || delay;
     }
 
-    mapbox::base::Value serialize() const {
+    mapbox::base::Value serialize() const final {
         mapbox::base::ValueObject result;
         if (duration) {
             result.emplace("duration", std::chrono::duration_cast<std::chrono::milliseconds>(*duration).count());
diff --git a/include/mbgl/util/color.hpp b/include/mbgl/util/color.hpp
index 8a03abfcdb..63ade67bcf 100644
--- a/include/mbgl/util/color.hpp
+++ b/include/mbgl/util/color.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
-#include <mbgl/util/optional.hpp>
 #include <mbgl/util/feature.hpp>
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/serializable.hpp>
 
 #include <cassert>
 #include <string>
@@ -10,7 +11,7 @@
 namespace mbgl {
 
 // Stores a premultiplied color, with all four channels ranging from 0..1
-class Color {
+class Color : public Serializable {
 public:
     Color() = default;
     Color(float r_, float g_, float b_, float a_)
@@ -41,7 +42,7 @@ public:
     std::string stringify() const;
     std::array<double, 4> toArray() const;
     mbgl::Value toObject() const;
-    mbgl::Value serialize() const;
+    mbgl::Value serialize() const final;
 };
 
 inline bool operator==(const Color& colorA, const Color& colorB) {
diff --git a/include/mbgl/util/serializable.hpp b/include/mbgl/util/serializable.hpp
new file mode 100644
index 0000000000..2a977e3c3c
--- /dev/null
+++ b/include/mbgl/util/serializable.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <mapbox/compatibility/value.hpp>
+
+namespace mbgl {
+
+using Value = mapbox::base::Value;
+
+class Serializable {
+public:
+    virtual ~Serializable() = default;
+    virtual Value serialize() const = 0;
+};
+
+} // namespace mbgl