finalize schema/data setup

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

include/ikarus/values/schema.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include <ikarus/errors.h>
+#include <ikarus/macros.h>
+#include <ikarus/stdtypes.h>
+
+/// \file schema.h
+/// \author Folling <mail@folling.io>
+
+/// \addtogroup values Values
+
+IKARUS_BEGIN_HEADER
+
+/// \brief Schemas define the type of value.
+/// \details Schemas are used to define the type of value. They are akin to
+/// classes in programming languages.
+/// Schemas are used to validate values and structure data.
+///
+/// Given the complexity of schemas, they are transferred as json.
+/// The json representation of a schema is a map with the following keys:
+/// - `type` The type of the schema. Must be one of the following:
+///   - `Primitive` A primitive value. Has the following additional keys:
+///     - `primitive` The type of the primitive value. \see IkarusPrimitiveType.
+///   - `Constant` A constant value. Has the following additional keys:
+///     - `value` The constant value, shared across all values of the schema.
+///     \see value.h. \remark The schema is derived from the value.
+///   - `List` A list of values. Has the following additional keys:
+///     - `schema` The schema of the values in the list.
+///   - `Map` A map of key-value pairs. Has the following additional keys:
+///     - `key_schema` The schema of the keys.
+///     - `value_schema` The schema of the values.
+///   - `Tuple` A tuple of values. Has the following additional keys:
+///     - `schemas` The schemas of the values in the tuple.
+struct IkarusSchema;
+
+/// \brief The type of primitive data.
+enum IkarusValuePrimitiveType {
+	/// \brief A boolean.
+	IkarusValuePrimitiveType_Toggle = 1,
+	/// \brief A 64-bit floating point number.
+	IkarusValuePrimitiveType_Number = 2,
+	/// \brief An arbitrary length string.
+	IkarusValuePrimitiveType_Text = 3
+};
+
+/// \brief The type of schema.
+enum IkarusValueSchemaType {
+	/// \brief A primitive value. \see IkarusPrimitiveType
+	IkarusValueSchemaType_Primitive = 1,
+	/// \brief A homogeneous list of values.
+	IkarusValueSchemaType_List = 2,
+	/// \brief A mapping from Value->Value.
+	IkarusValueSchemaType_Map = 3,
+	/// \brief A heterogeneous list of values.
+	IkarusValueSchemaType_Tuple = 4
+};
+
+IKARUS_END_HEADER