restructure into smaller files & add IWYU/clang-tidy

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

include/ikarus/id.h

@@ -0,0 +1,66 @@
+// IMPLEMENTATION_DETAIL_DATABASE
+
+/// \file id.h
+/// \author Folling <mail@folling.io>
+
+#pragma once
+
+#include <ikarus/macros.h>
+#include <ikarus/objects/object_type.h>
+#include <ikarus/stdtypes.h>
+
+IKARUS_BEGIN_HEADER
+
+/// \defgroup id Ids
+/// \brief Ids are used to identify objects in the database.
+/// \details They are stored as 64 bit integers with the following layout:
+/// - first 8 bits: #IkarusObjectType - 255 possible values, 0 for special values
+/// - last 56 bits: incremented counter generated by the database
+/// @{
+
+/// \brief A wrapper around a 64 bit integer that represents the id of an object.
+/// \details They are stored as 64 bit integers with the following layout:
+/// - first bit: ignored, technically we could use it, but SQLite doesn't support u64 integers.
+///   To avoid ordering fiascos and potential index performance degradation we just skip the first bit.
+/// - next 7 bits: #IkarusObjectType - 127 possible values, 0 for special values
+/// - last 56 bits: incremented counter generated by the database
+struct IkarusId {
+    /// \private \brief The value of the id.
+    int64_t data;
+};
+
+/// \brief A special id returned by failed functions.
+IkarusId const IKARUS_ID_NONE{0};
+/// \brief A special id used to indicate an optional id not being specified.
+IkarusId const IKARUS_ID_UNSPECIFIED{1};
+
+/// \private \brief Generates a new id for the given object type.
+/// \param data The data from which the id will be constructed.
+/// \return The generated id.
+/// \pre data must be valid under the format described in Id. It should also point to an object in the database.
+IkarusId ikarus_id_from_data(int64_t data);
+
+/// \brief Checkes whether two ids are equal
+/// \param left the left side of the comparison
+/// \param right the right side of the comparison
+/// \return True if the bits from the left id are equal to the bits of the right id
+bool ikarus_id_is_equal(IkarusId left, IkarusId right);
+
+/// \brief Fetches the object type of the given id.
+/// \param id The id to fetch the object type for.
+/// \return The object type of the given id.
+IKA_API IkarusObjectType ikarus_id_get_object_type(IkarusId id);
+
+/// \brief Checks if the given id is IKARUS_ID_NONE.
+/// \param id The id to check.
+/// \return True if the id is IKARUS_ID_NONE, false otherwise.
+IKA_API bool ikarus_id_is_none(IkarusId id);
+
+/// \brief Checks if the given id is IKARUS_ID_UNSPECIFIED.
+/// \param id The id to check.
+/// \return True if the id is IKARUS_ID_UNSPECIFIED, false otherwise.
+IKA_API bool ikarus_id_is_unspecified(IkarusId id);
+
+/// @}
+
+IKARUS_END_HEADER