Implement Expressions (#9439)

Ports https://github.com/mapbox/mapbox-gl-js/pull/4777 (and its several follow-ups)

platform/node/src/node_expression.hpp

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/expression/expression.hpp>
+#include <exception>
+#include <memory>
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#pragma GCC diagnostic ignored "-Wshadow"
+#include <nan.h>
+#pragma GCC diagnostic pop
+
+using namespace mbgl::style::expression;
+
+namespace node_mbgl {
+
+v8::Local<v8::Value> toJS(const Value&);
+
+class NodeExpression : public Nan::ObjectWrap {
+public:
+    static void Init(v8::Local<v8::Object>);
+
+private:
+    NodeExpression(std::unique_ptr<Expression> expression_) :
+        expression(std::move(expression_))
+    {};
+
+    static void New(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void Parse(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void Evaluate(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void GetType(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void IsFeatureConstant(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void IsZoomConstant(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static Nan::Persistent<v8::Function> constructor;
+
+    std::unique_ptr<Expression> expression;
+};
+
+} // namespace node_mbgl