finalize schema/data setup

Signed-off-by: Folling <mail@folling.io>

include/ikarus/values/data.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <ikarus/errors.h>
+#include <ikarus/macros.h>
+#include <ikarus/stdtypes.h>
+
+/// \file data.h
+/// \author Folling <mail@folling.io>
+
+/// \addtogroup values Values
+
+IKARUS_BEGIN_HEADER
+
+/// \brief Data stores the actual information of a value.
+/// \details Data is schemaless and can store any kind of data. Only when the
+/// data is combined with a schema does it become a value. \see value.h.
+/// Given the complexity of data, they are transferred as json.
+/// The json representation of a data is a map with the following keys:
+/// - `type` The type of the data. \see IkarusValueDataType. Must be one of the
+/// following:
+///   - `Primitive` A primitive value. Has two additional key:
+///     - `primitive` The type of the primitive. Must be one of the following:
+///     - `data` The stored data. Must be either a bool, double, or string.
+///   - `Constant` A constant value. Has no additional keys, as the constant
+///   value is shared across all values.
+///   - `List` A list of values. Has the following additional keys:
+///     - `data` An array of stored data.
+///   - `Map` A map of key-value pairs. Has the following additional keys:
+///     - `data` An array of key-value pairs.
+///   - `Tuple` A tuple of values. Has the following additional keys:
+///     - `data` An array of stored data.
+/// Note that each sub-data is also a data, allowing for arbitrarily nested data
+/// structures.
+struct IkarusValueData;
+
+/// \brief The type of data.
+enum IkarusValueDataType {
+	/// \brief A primitive value. \see IkarusValuePrimitiveType.
+	IkarusValueDataType_Primitive = 1,
+	/// \brief A list of values.
+	IkarusValueDataType_List = 2,
+	/// \brief A map of key-value pairs.
+	IkarusValueDataType_Map = 3,
+	/// \brief A tuple of values.
+	IkarusValueDataType_Tuple = 4,
+};
+
+IKARUS_END_HEADER