2 files changed, 123 insertions, 2 deletions

diff --git a/src/core/model/Typesystem.cpp b/src/core/model/Typesystem.cpp
index 688cb60..6ae92b4 100644
--- a/src/core/model/Typesystem.cpp
+++ b/src/core/model/Typesystem.cpp
@@ -17,6 +17,7 @@
 */
 
 #include "Typesystem.hpp"
+#include "Ontology.hpp"
 
 #include <core/common/RttiBuilder.hpp>
 #include <core/common/Utils.hpp>
@@ -640,6 +641,48 @@ bool StructType::hasAttribute(const std::string &name) const
 	return indexOf(name) >= 0;
 }
 
+/* Class ReferenceType */
+
+ReferenceType::ReferenceType(Manager &mgr, const std::string &name,
+                             Handle<Descriptor> descriptor)
+    : Type(mgr, name, nullptr, false), descriptor(acquire(descriptor))
+{
+}
+
+bool ReferenceType::doBuild(Variant &data, Logger &logger,
+                            const MagicCallback &magicCallback) const
+{
+	// Null references are valid references
+	if (data.isNull()) {
+		return true;
+	}
+
+	if (data.isObject()) {
+		// TODO: Check: object is an instance of the entity descriptor
+		return true;
+	} else if (data.isString()) {
+		// TODO: Lookup referenced object
+		if (!Utils::isNamespacedIdentifier(data.asString())) {
+			throw LoggableException("Reference must be a valid identifier",
+			                        data);
+		}
+	}
+	return false;
+}
+
+bool ReferenceType::doCheckIsa(Handle<const Type> type) const
+{
+	// TODO: Implement correctly, check descriptor inheritance
+	return type->isa(&RttiTypes::ReferenceType);
+}
+
+Handle<Descriptor> ReferenceType::getDescriptor() { return descriptor; }
+
+void ReferenceType::setDescriptor(Handle<Descriptor> descriptor)
+{
+	this->descriptor = acquire(descriptor);
+}
+
 /* Class ArrayType */
 
 bool ArrayType::doBuild(Variant &data, Logger &logger,
@@ -811,6 +854,8 @@ const Rtti EnumType = RttiBuilder<ousia::EnumType>("EnumType").parent(&Type);
 const Rtti StructType = RttiBuilder<ousia::StructType>("StructType")
                             .parent(&Type)
                             .composedOf(&Attribute);
+const Rtti ReferenceType =
+    RttiBuilder<ousia::ReferenceType>("ReferenceType").parent(&Type);
 const Rtti ArrayType = RttiBuilder<ousia::ArrayType>("ArrayType").parent(&Type);
 const Rtti UnknownType =
     RttiBuilder<ousia::UnknownType>("UnknownType").parent(&Type);
@@ -823,4 +868,4 @@ const Rtti Typesystem =
 const Rtti SystemTypesystem = RttiBuilder<ousia::SystemTypesystem>(
                                   "SystemTypesystem").parent(&Typesystem);
 }
-}
\ No newline at end of file
+}
diff --git a/src/core/model/Typesystem.hpp b/src/core/model/Typesystem.hpp
index ac29c81..ce3cee0 100644
--- a/src/core/model/Typesystem.hpp
+++ b/src/core/model/Typesystem.hpp
@@ -47,6 +47,7 @@ class CharReader;
 class Rtti;
 class Typesystem;
 class SystemTypesystem;
+class Descriptor;
 
 /**
  * The abstract Type class represents a type descriptor. Each Type node is part
@@ -980,6 +981,76 @@ public:
 };
 
 /**
+ * The ReferenceType class represents a reference to an entity in the document.
+ * The type of the entity can be specified by the user in the form of a
+ * ontology descriptor.
+ */
+class ReferenceType : public Type {
+private:
+	/**
+	 * Contains the reference at the descriptor element or nullptr if no such
+	 * element was given (the reference is a general reference) or the reference
+	 * type could not be resolved.
+	 */
+	Owned<Descriptor> descriptor;
+
+protected:
+	/**
+	 * Makes sure the given variant is either an array or a string that can be
+	 * resolved to an object of the given structure type.
+	 *
+	 * @param data is a Variant containing the data that should be checked.
+	 * @param logger is the Logger instance into which errors should be written.
+	 * @return true if the conversion was successful, false otherwise.
+	 */
+	bool doBuild(Variant &data, Logger &logger,
+	             const MagicCallback &magicCallback) const override;
+
+	/**
+	 * Returns true if this type is equivalent to another given ReferenceType,
+	 * uses the inheritance hierarchy of the underlying descriptor.
+	 *
+	 * @param type is the type that should be checked for the "isa"
+	 * relationship.
+	 * @return true if the given type is equivalent to this type, false
+	 * otherwise.
+	 */
+	bool doCheckIsa(Handle<const Type> type) const override;
+
+public:
+	/**
+	 * Constructor of the ReferenceType class.
+	 *
+	 * @param mgr is the parent Manager instance.
+	 * @param name is the name of the type.
+	 * @param descriptor is the entity descriptor specifying the ontological
+	 * type of the reference objects.
+	 */
+	ReferenceType(Manager &mgr, const std::string &name,
+	              Handle<Descriptor> descriptor);
+
+	/**
+	 * Create a new, empty variant containing an invalid (null) reference.
+	 *
+	 * @return a null reference.
+	 */
+	Variant create() const override { return Variant{}; }
+
+	/**
+	 * Returns the descriptor containing the ontological type of which an
+	 * instance is being referenced.
+	 *
+	 * @return the descriptor or nullptr if no descriptor has been set.
+	 */
+	Handle<Descriptor> getDescriptor();
+
+	/**
+	 * Sets the descriptor to the given value.
+	 */
+	void setDescriptor(Handle<Descriptor> descriptor);
+};
+
+/**
  * The ArrayType class represents an array with elements of a fixed inner type.
  * ArrayTypes are anonymous (they have an empty name) and always have the
  * Typesystem instance of the inner type as parent. ArrayType instances are
@@ -1446,6 +1517,11 @@ extern const Rtti EnumType;
 extern const Rtti StructType;
 
 /**
+ * Type information for the ReferenceType class.
+ */
+extern const Rtti ReferenceType;
+
+/**
  * Type information for the ArrayType class.
  */
 extern const Rtti ArrayType;
@@ -1477,4 +1553,4 @@ extern const Rtti SystemTypesystem;
 }
 }
 
-#endif /* _OUSIA_MODEL_TYPESYSTEM_HPP_ */
\ No newline at end of file
+#endif /* _OUSIA_MODEL_TYPESYSTEM_HPP_ */