From 598c7a18d342bc05149b58d53819fd0b28881938 Mon Sep 17 00:00:00 2001
From: Anand Thakker <github@anandthakker.net>
Date: Sat, 12 Aug 2017 22:44:27 -0400
Subject: wip - attempt to hook up expression parsing

---
 .../style/conversion/data_driven_property_value.hpp   | 14 ++++++++++++++
 include/mbgl/style/conversion/expression.hpp          | 19 ++++++++++++++-----
 include/mbgl/style/function/camera_function.hpp       |  7 +++++++
 include/mbgl/style/function/composite_function.hpp    | 12 ++++++++++++
 include/mbgl/style/function/convert.hpp               |  1 +
 include/mbgl/style/function/source_function.hpp       |  7 +++++++
 6 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/include/mbgl/style/conversion/data_driven_property_value.hpp b/include/mbgl/style/conversion/data_driven_property_value.hpp
index 79b15dcfb0..ed8478a108 100644
--- a/include/mbgl/style/conversion/data_driven_property_value.hpp
+++ b/include/mbgl/style/conversion/data_driven_property_value.hpp
@@ -4,6 +4,8 @@
 #include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/function.hpp>
+#include <mbgl/style/conversion/expression.hpp>
+#include <mbgl/style/expression/value.hpp>
 
 namespace mbgl {
 namespace style {
@@ -21,6 +23,18 @@ struct Converter<DataDrivenPropertyValue<T>> {
                 return {};
             }
             return DataDrivenPropertyValue<T>(*constant);
+        } else if (objectMember(value, "expression")) {
+            optional<std::unique_ptr<Expression>> expression = convert<std::unique_ptr<Expression>>(*objectMember(value, "expression"), error, valueTypeToExpressionType<T>());
+            if (!expression) {
+                return {};
+            }
+            if ((*expression)->isFeatureConstant()) {
+                return DataDrivenPropertyValue<T>(CameraFunction<T>(std::move(*expression)));
+            } else if ((*expression)->isZoomConstant()) {
+                return DataDrivenPropertyValue<T>(SourceFunction<T>(std::move(*expression)));
+            } else {
+                return DataDrivenPropertyValue<T>(CompositeFunction<T>(std::move(*expression)));
+            }
         } else if (!objectMember(value, "property")) {
             optional<CameraFunction<T>> function = convert<CameraFunction<T>>(value, error);
             if (!function) {
diff --git a/include/mbgl/style/conversion/expression.hpp b/include/mbgl/style/conversion/expression.hpp
index bce7c91396..601916250d 100644
--- a/include/mbgl/style/conversion/expression.hpp
+++ b/include/mbgl/style/conversion/expression.hpp
@@ -2,6 +2,7 @@
 
 #include <memory>
 #include <mbgl/style/expression/parse.hpp>
+#include <mbgl/style/expression/type.hpp>
 #include <mbgl/style/conversion.hpp>
 
 namespace mbgl {
@@ -12,12 +13,20 @@ using namespace mbgl::style::expression;
 
 template<> struct Converter<std::unique_ptr<Expression>> {
     template <class V>
-    optional<std::unique_ptr<Expression>> operator()(const V& value, Error& error) const {
-        auto parsed = parseExpression(value, ParsingContext());
-        if (parsed.template is<std::unique_ptr<Expression>>()) {
-            return std::move(parsed.template get<std::unique_ptr<Expression>>());
+    optional<std::unique_ptr<Expression>> operator()(const V& value, Error& error, type::Type expected) const {
+        std::vector<ParsingError> errors;
+        auto parsed = parseExpression(value, ParsingContext(errors, expected));
+        if (parsed) {
+            return std::move(*parsed);
         }
-        error = { parsed.template get<CompileError>().message };
+        std::string combinedError;
+        for (const ParsingError& parsingError : errors) {
+            if (combinedError.size() > 0) {
+                combinedError += "\n";
+            }
+            combinedError += parsingError.key + ": " + parsingError.message;
+        }
+        error = { combinedError };
         return {};
     };
 };
diff --git a/include/mbgl/style/function/camera_function.hpp b/include/mbgl/style/function/camera_function.hpp
index 5a0f5ffe4a..55fd5cd7cc 100644
--- a/include/mbgl/style/function/camera_function.hpp
+++ b/include/mbgl/style/function/camera_function.hpp
@@ -19,6 +19,13 @@ public:
             IntervalStops<T>>,
         variant<
             IntervalStops<T>>>;
+    
+    CameraFunction(std::unique_ptr<expression::Expression> expression_)
+        : expression(std::move(expression_))
+    {
+        assert(!expression->isZoomConstant());
+        assert(expression->isFeatureConstant());
+    }
 
     CameraFunction(Stops stops_)
         : stops(std::move(stops_)),
diff --git a/include/mbgl/style/function/composite_function.hpp b/include/mbgl/style/function/composite_function.hpp
index f7cbab1b21..7d77d5e552 100644
--- a/include/mbgl/style/function/composite_function.hpp
+++ b/include/mbgl/style/function/composite_function.hpp
@@ -50,6 +50,18 @@ public:
     using Interpolator = expression::ExponentialInterpolator<T>;
     using Curve = expression::Curve<Interpolator>;
 
+    CompositeFunction(std::unique_ptr<expression::Expression> expression_)
+    :   expression(std::move(expression_)),
+        interpolator([&]() -> Interpolator {
+            optional<Curve*> zoomCurve = findZoomCurve(expression.get());
+            assert(zoomCurve);
+            return (*zoomCurve)->getInterpolator();
+        }())
+    {
+        assert(!expression->isZoomConstant());
+        assert(!expression->isFeatureConstant());
+    }
+
     CompositeFunction(std::string property_, Stops stops_, optional<T> defaultValue_ = {})
     :   property(std::move(property_)),
         stops(std::move(stops_)),
diff --git a/include/mbgl/style/function/convert.hpp b/include/mbgl/style/function/convert.hpp
index 67624625d4..ca021eadf6 100644
--- a/include/mbgl/style/function/convert.hpp
+++ b/include/mbgl/style/function/convert.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+
 #include <mbgl/util/enum.hpp>
 #include <mbgl/style/types.hpp>
 #include <mbgl/style/expression/array_assertion.hpp>
diff --git a/include/mbgl/style/function/source_function.hpp b/include/mbgl/style/function/source_function.hpp
index 0ae8357d7b..d65d03857a 100644
--- a/include/mbgl/style/function/source_function.hpp
+++ b/include/mbgl/style/function/source_function.hpp
@@ -29,6 +29,13 @@ public:
             CategoricalStops<T>,
             IdentityStops<T>>>;
 
+    SourceFunction(std::unique_ptr<expression::Expression> expression_)
+        : expression(std::move(expression_))
+    {
+        assert(expression->isZoomConstant());
+        assert(!expression->isFeatureConstant());
+    }
+    
     SourceFunction(std::string property_, Stops stops_, optional<T> defaultValue_ = {})
         : property(std::move(property_)),
           stops(std::move(stops_)),
-- 
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