/*
 * Copyright (c) 2026, Arm Limited. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *
 */

#ifndef __SFCP_DEFS_H__
#define __SFCP_DEFS_H__


#include <cdefs.h>
#include <stdbool.h>
#include <stddef.h>

#include "sfcp_trusted_subnet.h"

#ifdef __cplusplus
extern "C" {
#endif

#define SFCP_PROTOCOL_VERSION (0b10)

/*
 * Crptography
 */
struct __packed sfcp_cryptography_config_t {
	uint16_t seq_num;
	enum sfcp_cryptography_mode_t mode;
	uint8_t trusted_subnet_id;
};

struct __packed sfcp_cryptography_metadata_t {
	struct sfcp_cryptography_config_t config;
	uint8_t tag[16];
};

/*
 * Header
 */
enum sfcp_packet_type_t {
	SFCP_PACKET_TYPE_MSG_NEEDS_REPLY = 0b00,
	SFCP_PACKET_TYPE_MSG_NO_REPLY = 0b01,
	SFCP_PACKET_TYPE_REPLY = 0b10,
	SFCP_PACKET_TYPE_PROTOCOL_ERROR_REPLY = 0b11,
};

#define METADATA_PACKET_TYPE_OFFSET (6)
#define METADATA_PACKET_TYPE_MASK (0b11)
#define METADATA_USES_CRYPTOGRAPHY_OFFSET (5)
#define METADATA_USES_CRYPTOGRAPHY_MASK (0b1)
#define METADATA_USES_ID_EXTENSION_OFFSET (4)
#define METADATA_USES_ID_EXTENSION_MASK (0b1)
#define METADATA_PROTOCOL_VERSION_OFFSET (0)
#define METADATA_PROTOCOL_VERSION_MASK (0b111)

#define GET_METADATA_FIELD(_field, _metadata)          \
	(((_metadata) >> METADATA_##_field##_OFFSET) & \
	 (METADATA_##_field##_MASK))
#define SET_METADATA_FIELD(_field, _value) \
	(((_value) & METADATA_##_field##_MASK) << (METADATA_##_field##_OFFSET))
#define SET_ALL_METADATA_FIELDS(_packet_type, _uses_crypto, _uses_id, \
				_protocol_version)                    \
	(SET_METADATA_FIELD(PACKET_TYPE, (_packet_type)) |            \
	 SET_METADATA_FIELD(USES_CRYPTOGRAPHY, (_uses_crypto)) |      \
	 SET_METADATA_FIELD(USES_ID_EXTENSION, (_uses_id)) |          \
	 SET_METADATA_FIELD(PROTOCOL_VERSION, (_protocol_version)))

struct __packed sfcp_header_t {
	/*
	 * Metadata field consists of (in descending bit order):
	 * - packet_type : 1
	 * - uses_cryptography : 1
	 * - uses_id_extension: 1
	 * - reserved: 2
	 * - protocol_version: 3
	 */
	uint8_t metadata;
	uint8_t sender_id;
	uint8_t receiver_id;
	uint8_t message_id;
};

/*
 * Packet definition
 */
/*
 * C standard dictates that a fleixble array member cannot by the only element in a
 * struct and therefore we use uint8_t payload[1] to make the struct definition valid C
 */
struct __packed sfcp_id_extension_payload {
	union __packed {
		struct __packed {
			uint16_t client_id;
			uint16_t application_id;
			uint8_t payload[1];
		} id_extension_used;
		struct __packed {
			uint8_t payload[1];
		} id_extension_not_used;
	};
};

struct __packed sfcp_packet_t {
	struct sfcp_header_t header;
	union __packed {
		struct __packed {
			struct sfcp_cryptography_metadata_t
				cryptography_metadata;
			struct sfcp_id_extension_payload id_extension_payload;
		} cryptography_used;
		struct __packed {
			struct sfcp_id_extension_payload id_extension_payload;
		} cryptography_not_used;
		struct __packed {
			uint16_t client_id;
			uint16_t protocol_error;
		} error_reply;
	};
};

/*
 * Helper macros
 */
#define GET_SFCP_ID_EXTENSION_PAYLOAD(_packet, _uses_crypto)          \
	((_uses_crypto) ?                                             \
		 &(_packet)->cryptography_used.id_extension_payload : \
		 &(_packet)->cryptography_not_used.id_extension_payload)
#define GET_SFCP_GENERIC_FIELD_PTR(_packet, _uses_crypto, _uses_id_extension, \
				   _field_name)                               \
	((_uses_id_extension) ?                                               \
		 &GET_SFCP_ID_EXTENSION_PAYLOAD(_packet, _uses_crypto)        \
			  ->id_extension_used._field_name :                   \
		 &GET_SFCP_ID_EXTENSION_PAYLOAD(_packet, _uses_crypto)        \
			  ->id_extension_not_used._field_name)

#define GET_SFCP_PAYLOAD_PTR(_packet, _uses_crypto, _uses_id_extension)       \
	GET_SFCP_GENERIC_FIELD_PTR(_packet, _uses_crypto, _uses_id_extension, \
				   payload)

#define GET_SFCP_ID_EXTENSION_FIELD(_packet, _uses_crypto, _field_name) \
	GET_SFCP_ID_EXTENSION_PAYLOAD(_packet, _uses_crypto)            \
		->id_extension_used._field_name
#define GET_SFCP_CLIENT_ID(_packet, _uses_crypto) \
	GET_SFCP_ID_EXTENSION_FIELD(_packet, _uses_crypto, client_id)
#define GET_SFCP_APPLICATION_ID(_packet, _uses_crypto) \
	GET_SFCP_ID_EXTENSION_FIELD(_packet, _uses_crypto, application_id)

#define GET_SFCP_ERROR_REPLY_FIELD(_packet, _field) \
	((_packet)->error_reply._field)
#define GET_SFCP_ERROR_REPLY_CLIENT_ID(_packet) \
	GET_SFCP_ERROR_REPLY_FIELD(_packet, client_id)
#define GET_SFCP_ERROR_REPLY_PROTCOL_ERROR(_packet) \
	GET_SFCP_ERROR_REPLY_FIELD(_packet, protocol_error)

#define SFCP_PACKET_SIZE_WITHOUT_PAYLOAD(_uses_crypto, _uses_id_extension)    \
	((_uses_crypto) ?                                                     \
		 ((_uses_id_extension) ?                                      \
			  offsetof(struct sfcp_packet_t,                      \
				   cryptography_used.id_extension_payload     \
					   .id_extension_used.payload) :      \
			  offsetof(struct sfcp_packet_t,                      \
				   cryptography_used.id_extension_payload     \
					   .id_extension_not_used.payload)) : \
		 ((_uses_id_extension) ?                                      \
			  offsetof(struct sfcp_packet_t,                      \
				   cryptography_not_used.id_extension_payload \
					   .id_extension_used.payload) :      \
			  offsetof(struct sfcp_packet_t,                      \
				   cryptography_not_used.id_extension_payload \
					   .id_extension_not_used.payload)))
#define SFCP_PACKET_SIZE_ERROR_REPLY                   \
	(offsetof(struct sfcp_packet_t, error_reply) + \
	 sizeof(((struct sfcp_packet_t *)0)->error_reply))

#ifdef __cplusplus
}
#endif

#endif /* __SFCP_DEFS_H__ */