/* ecc.h - ECDH helpers */

/*
 * Copyright (c) 2016 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <stdbool.h>
#include <stdint.h>

#include <zephyr/sys/slist.h>

/** Key size used in Bluetooth's ECC domain. */
#define BT_ECC_KEY_SIZE            32
/** Length of a Bluetooth ECC public key coordinate. */
#define BT_PUB_KEY_COORD_LEN       (BT_ECC_KEY_SIZE)
/** Length of a Bluetooth ECC public key. */
#define BT_PUB_KEY_LEN             (2 * (BT_PUB_KEY_COORD_LEN))
/** Length of a Bluetooth ECC private key. */
#define BT_PRIV_KEY_LEN            (BT_ECC_KEY_SIZE)
/** Length of a Bluetooth Diffie-Hellman key. */
#define BT_DH_KEY_LEN              (BT_ECC_KEY_SIZE)

/*  @brief Container for public key callback */
struct bt_pub_key_cb {
	/** @brief Callback type for Public Key generation.
	 *
	 *  Used to notify of the local public key or that the local key is not
	 *  available (either because of a failure to read it or because it is
	 *  being regenerated).
	 *
	 *  @param key The local public key, or NULL in case of no key.
	 */
	void (*func)(const uint8_t key[BT_PUB_KEY_LEN]);

	/* Internal */
	sys_snode_t node;
};

/*  @brief Check if public key is equal to the debug public key.
 *
 *  Compare the Public key to the Bluetooth specification defined debug public
 *  key.
 *
 *  @param cmp_pub_key The public key to compare.
 *
 *  @return True if the public key is the debug public key.
 */
bool bt_pub_key_is_debug(uint8_t *cmp_pub_key);

/*  @brief Check if public key is valid.
 *
 *  Verify that the public key is valid, e.g. that its coordinates lie on the elliptic curve.
 *
 *  @param key The public key to validate.
 *
 *  @return True if the public key is valid.
 */
bool bt_pub_key_is_valid(const uint8_t key[BT_PUB_KEY_LEN]);

/*  @brief Generate a new Public Key.
 *
 *  Generate a new ECC Public Key. Provided cb must persists until callback
 *  is called. Callee adds the callback structure to a linked list. Registering
 *  multiple callbacks requires multiple calls to bt_pub_key_gen() and separate
 *  callback structures. This method cannot be called directly from result
 *  callback. After calling all the registered callbacks the linked list
 *  is cleared.
 *
 *  @param cb Callback to notify the new key.
 *
 *  @return Zero on success or negative error code otherwise
 */
int bt_pub_key_gen(struct bt_pub_key_cb *cb);

/*  @brief Cleanup public key callbacks when HCI is disrupted.
 *
 *  Clear the pub_key_cb_slist and clear the BT_DEV_PUB_KEY_BUSY flag.
 */
void bt_pub_key_hci_disrupted(void);

/*  @brief Get the current Public Key.
 *
 *  Get the current ECC Public Key.
 *
 *  @return Current key, or NULL if not available.
 */
const uint8_t *bt_pub_key_get(void);

/*  @typedef bt_dh_key_cb_t
 *  @brief Callback type for DH Key calculation.
 *
 *  Used to notify of the calculated DH Key.
 *
 *  @param key The DH Key, or NULL in case of failure.
 */
typedef void (*bt_dh_key_cb_t)(const uint8_t key[BT_DH_KEY_LEN]);

/*  @brief Calculate a DH Key from a remote Public Key.
 *
 *  Calculate a DH Key from the remote Public Key.
 *
 *  @param remote_pk Remote Public Key.
 *  @param cb Callback to notify the calculated key.
 *
 *  @return Zero on success or negative error code otherwise
 */
int bt_dh_key_gen(const uint8_t remote_pk[BT_PUB_KEY_LEN], bt_dh_key_cb_t cb);