1 files changed, 73 insertions, 0 deletions
diff --git a/include/mbgl/style/expression/parse/array_assertion.hpp b/include/mbgl/style/expression/parse/array_assertion.hpp
new file mode 100644
index 0000000000..1549a468f6
--- /dev/null
+++ b/include/mbgl/style/expression/parse/array_assertion.hpp
@@ -0,0 +1,73 @@
+#pragma once
+
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/expression/array_assertion.hpp>
+#include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/expression/type.hpp>
+#include <mbgl/util/optional.hpp>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+struct ParseArrayAssertion {
+    template <class V>
+    static ParseResult parse(const V& value, ParsingContext ctx) {
+        using namespace mbgl::style::conversion;
+        
+        static std::unordered_map<std::string, type::Type> itemTypes {
+            {"string", type::String},
+            {"number", type::Number},
+            {"boolean", type::Boolean}
+        };
+    
+        auto length = arrayLength(value);
+        if (length < 2 || length > 4) {
+            ctx.error("Expected 1, 2, or 3 arguments, but found " + std::to_string(length - 1) + " instead.");
+            return ParseResult();
+        }
+        
+        optional<type::Type> itemType;
+        optional<std::size_t> N;
+        if (length > 2) {
+            optional<std::string> itemTypeName = toString(arrayMember(value, 1));
+            auto it = itemTypeName ? itemTypes.find(*itemTypeName) : itemTypes.end();
+            if (it == itemTypes.end()) {
+                ctx.error(
+                    R"(The item type argument of "array" must be one of string, number, boolean)",
+                    1
+                );
+                return ParseResult();
+            }
+            itemType = it->second;
+        } else {
+            itemType = {type::Value};
+        }
+        
+        if (length > 3) {
+            auto n = toNumber(arrayMember(value, 2));
+            if (!n || *n != ceilf(*n)) {
+                ctx.error(
+                    R"(The length argument to "array" must be a positive integer literal.)",
+                    2
+                );
+                return ParseResult();
+            }
+            N = optional<std::size_t>(*n);
+        }
+        
+        auto input = parseExpression(arrayMember(value, length - 1), ParsingContext(ctx, length - 1, {type::Value}));
+        if (!input) {
+            return input;
+        }
+
+        return ParseResult(std::make_unique<ArrayAssertion>(
+            type::Array(*itemType, N),
+            std::move(*input)
+        ));
+    }
+};
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl