/*****************************************************************************
 *
 *
 *Copyright (c) 2021-2029 Semidrive Incorporated.  All rights reserved.
 *Software License Agreement
 *
 ******************************************************************************
 */
#include <ecdh.h>
#include <pke.h>

/* Function: ECDH compute key
 * Parameters:
 *     local_prikey --------------- input, local private key, big-endian
 *     peer_pubkey ---------------- input, peer public key, big-endian
 *     key ------------------------ output, output key
 *     keyByteLen ----------------- input, byte length of output key
 *     KDF ------------------------ input, KDF function to get key
 * Return:
 *     ECDH_SUCCESS(success); other(error)
 * Caution:
 */
uint32_t ecdh_compute_key(eccp_curve_t *curve, uint8_t *local_prikey,
                          uint8_t *peer_pubkey, uint8_t *key,
                          uint32_t keyByteLen, KDF_FUNC kdf)
{
    uint32_t k[ECCP_MAX_WORD_LEN] = {0};
    uint32_t Px[ECCP_MAX_WORD_LEN] = {0};
    uint32_t Py[ECCP_MAX_WORD_LEN] = {0};
    uint32_t byteLen, wordLen;
    uint32_t ret;

    if (NULL == curve || NULL == local_prikey || NULL == peer_pubkey ||
        NULL == key) {
        return ECDH_POINTOR_NULL;
    } else if (0 == keyByteLen) {
        return ECDH_INVALID_INPUT;
    } else {
        ;
    }

    byteLen = GET_BYTE_LEN(curve->eccp_n_bitLen);
    wordLen = GET_WORD_LEN(curve->eccp_n_bitLen);

    /*make sure private key is in [1, n-1]*/
    reverse_byte_array((uint8_t *)local_prikey, (uint8_t *)k, byteLen);

    if (uint32_bignum_check_zero(k, wordLen)) {
        return ECDH_INVALID_INPUT;
    } else if (uint32_bignumcmp(k, wordLen, curve->eccp_n, wordLen) >= 0) {
        return ECDH_INVALID_INPUT;
    } else {
        ;
    }

    /*check public key*/
    byteLen = GET_BYTE_LEN(curve->eccp_p_bitLen);
    reverse_byte_array(peer_pubkey, (uint8_t *)Px, byteLen);
    reverse_byte_array(peer_pubkey + byteLen, (uint8_t *)Py, byteLen);
    ret = eccp_pointVerify(curve, Px, Py);

    if (PKE_SUCCESS != ret) {
        return ret;
    } else {
        ;
    }

    ret = eccp_pointMul(curve, k, Px, Py, Px, Py);

    if (PKE_SUCCESS != ret) {
        return ret;
    } else {
        ;
    }

    reverse_byte_array((uint8_t *)Px, (uint8_t *)Px, byteLen);

    if (kdf) {
        kdf(Px, byteLen, key, keyByteLen);
    } else {
        if (keyByteLen > byteLen) {
            keyByteLen = byteLen;
        } else {
            ;
        }

        memcpy_(key, Px, keyByteLen);
    }

    return ECDH_SUCCESS;
}