/*
 * Copyright (c) 2015-16  David Lamparter, for NetDEF, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#ifndef _QOBJ_H
#define _QOBJ_H

#include <stdint.h>
#include <stdlib.h>
#include <stddef.h>

/* reserve a specific amount of bytes for a struct, which can grow up to
 * that size (or be dummy'd out if not needed)
 *
 * note the padding's array size will be an error if it gets negative or zero;
 * this is intentional to prevent the struct from growing beyond the allocated
 * space.
 */
#define RESERVED_SPACE_STRUCT(name, fieldname, size) \
	struct { \
		struct name fieldname; \
		char padding ## fieldname[size - sizeof(struct name)]; \
	};

/* don't need struct definitions for these here.  code actually using
 * these needs to define the struct *before* including this header.
 * HAVE_QOBJ_xxx should be defined to +1 in that case, like this:
 *
 * #if defined(HAVE_QOBJ_NODETYPE_CLI) && HAVE_QOBJ_NODETYPE_CLI < 0
 * #error include files are in wrong order
 * #else
 * #define HAVE_QOBJ_NODETYPE_CLI 1
 * struct qobj_nodetype_cli { ... }
 * #endif
 */
#ifndef HAVE_QOBJ_NODETYPE_CLI
#define HAVE_QOBJ_NODETYPE_CLI -1
struct qobj_nodetype_cli { int dummy; };
#endif

#ifndef HAVE_QOBJ_NODETYPE_CAPNP
#define HAVE_QOBJ_NODETYPE_CAPNP -1
struct qobj_nodetype_capnp { int dummy; };
#endif

/* each different kind of object will have a global variable of this type,
 * which can be used by various other pieces to store type-related bits.
 * type equality can be tested as pointer equality. (cf. QOBJ_GET_TYPESAFE)
 */
struct qobj_nodetype {
	ptrdiff_t node_member_offset;
	RESERVED_SPACE_STRUCT(qobj_nodetype_cli, cli, 256)
	RESERVED_SPACE_STRUCT(qobj_nodetype_capnp, capnp, 256)
};

/* anchor to be embedded somewhere in the object's struct */
struct qobj_node {
	uint64_t nid;
	struct qobj_nodetype *type;
};

#define QOBJ_FIELDS \
	struct qobj_node qobj_node;

/* call these at the end of any _create function (QOBJ_REG)
 * and beginning of any _destroy function (QOBJ_UNREG) */
#define QOBJ_REG(n, structname) \
	qobj_reg(&n->qobj_node, &qobj_t_ ## structname)
#define QOBJ_UNREG(n) \
	qobj_unreg(&n->qobj_node)

/* internals - should not be directly used without a good reason*/
void qobj_reg(struct qobj_node *node, struct qobj_nodetype *type);
void qobj_unreg(struct qobj_node *node);
struct qobj_node *qobj_get(uint64_t id);
void *qobj_get_typed(uint64_t id, struct qobj_nodetype *type);

/* type declarations */
#define DECLARE_QOBJ_TYPE(structname) \
	extern struct qobj_nodetype qobj_t_ ## structname;
#define DEFINE_QOBJ_TYPE(structname) \
	struct qobj_nodetype qobj_t_ ## structname = { \
		.node_member_offset = \
			(ptrdiff_t)offsetof(struct structname, qobj_node) \
	};
#define DEFINE_QOBJ_TYPE_INIT(structname, ...) \
	struct qobj_nodetype qobj_t_ ## structname = { \
		.node_member_offset = \
			(ptrdiff_t)offsetof(struct structname, qobj_node), \
		__VA_ARGS__ \
	};

/* ID dereference with typecheck.
 * will return NULL if id not found or wrong type. */
#define QOBJ_GET_TYPESAFE(id, structname) \
	((struct structname *)qobj_get_typed((id), &qobj_t_ ## structname))

#define QOBJ_ID(ptr) \
	((ptr)->qobj_node.nid)

void qobj_init(void);
void qobj_finish(void);

#endif /* _QOBJ_H */