#define RATE 16

static void
aegis256_init(const uint8_t *key, const uint8_t *nonce, aes_block_t *const state)
{
    static CRYPTO_ALIGN(AES_BLOCK_LENGTH)
        const uint8_t c0_[AES_BLOCK_LENGTH] = { 0x00, 0x01, 0x01, 0x02, 0x03, 0x05, 0x08, 0x0d,
                                                0x15, 0x22, 0x37, 0x59, 0x90, 0xe9, 0x79, 0x62 };
    static CRYPTO_ALIGN(AES_BLOCK_LENGTH)
        const uint8_t c1_[AES_BLOCK_LENGTH] = { 0xdb, 0x3d, 0x18, 0x55, 0x6d, 0xc2, 0x2f, 0xf1,
                                                0x20, 0x11, 0x31, 0x42, 0x73, 0xb5, 0x28, 0xdd };

    const aes_block_t c0    = AES_BLOCK_LOAD(c0_);
    const aes_block_t c1    = AES_BLOCK_LOAD(c1_);
    const aes_block_t k0    = AES_BLOCK_LOAD(key);
    const aes_block_t k1    = AES_BLOCK_LOAD(key + AES_BLOCK_LENGTH);
    const aes_block_t n0    = AES_BLOCK_LOAD(nonce);
    const aes_block_t n1    = AES_BLOCK_LOAD(nonce + AES_BLOCK_LENGTH);
    const aes_block_t k0_n0 = AES_BLOCK_XOR(k0, n0);
    const aes_block_t k1_n1 = AES_BLOCK_XOR(k1, n1);
    int               i;

    state[0] = k0_n0;
    state[1] = k1_n1;
    state[2] = c1;
    state[3] = c0;
    state[4] = AES_BLOCK_XOR(k0, c0);
    state[5] = AES_BLOCK_XOR(k1, c1);
    for (i = 0; i < 4; i++) {
        aegis256_update(state, k0);
        aegis256_update(state, k1);
        aegis256_update(state, k0_n0);
        aegis256_update(state, k1_n1);
    }
}

static void
aegis256_mac(uint8_t *mac, size_t maclen, size_t adlen, size_t mlen, aes_block_t *const state)
{
    aes_block_t tmp;
    int         i;

    tmp = AES_BLOCK_LOAD_64x2(((uint64_t) mlen) << 3, ((uint64_t) adlen) << 3);
    tmp = AES_BLOCK_XOR(tmp, state[3]);

    for (i = 0; i < 7; i++) {
        aegis256_update(state, tmp);
    }

    if (maclen == 16) {
        tmp = AES_BLOCK_XOR(state[5], state[4]);
        tmp = AES_BLOCK_XOR(tmp, AES_BLOCK_XOR(state[3], state[2]));
        tmp = AES_BLOCK_XOR(tmp, AES_BLOCK_XOR(state[1], state[0]));
        AES_BLOCK_STORE(mac, tmp);
    } else if (maclen == 32) {
        tmp = AES_BLOCK_XOR(AES_BLOCK_XOR(state[2], state[1]), state[0]);
        AES_BLOCK_STORE(mac, tmp);
        tmp = AES_BLOCK_XOR(AES_BLOCK_XOR(state[5], state[4]), state[3]);
        AES_BLOCK_STORE(mac + 16, tmp);
    } else {
        memset(mac, 0, maclen);
    }
}

static inline void
aegis256_absorb(const uint8_t *const src, aes_block_t *const state)
{
    aes_block_t msg;

    msg = AES_BLOCK_LOAD(src);
    aegis256_update(state, msg);
}

static void
aegis256_enc(uint8_t *const dst, const uint8_t *const src, aes_block_t *const state)
{
    aes_block_t msg;
    aes_block_t tmp;

    msg = AES_BLOCK_LOAD(src);
    tmp = AES_BLOCK_XOR(msg, state[5]);
    tmp = AES_BLOCK_XOR(tmp, state[4]);
    tmp = AES_BLOCK_XOR(tmp, state[1]);
    tmp = AES_BLOCK_XOR(tmp, AES_BLOCK_AND(state[2], state[3]));
    AES_BLOCK_STORE(dst, tmp);

    aegis256_update(state, msg);
}

static void
aegis256_dec(uint8_t *const dst, const uint8_t *const src, aes_block_t *const state)
{
    aes_block_t msg;

    msg = AES_BLOCK_LOAD(src);
    msg = AES_BLOCK_XOR(msg, state[5]);
    msg = AES_BLOCK_XOR(msg, state[4]);
    msg = AES_BLOCK_XOR(msg, state[1]);
    msg = AES_BLOCK_XOR(msg, AES_BLOCK_AND(state[2], state[3]));
    AES_BLOCK_STORE(dst, msg);

    aegis256_update(state, msg);
}

static void
aegis256_declast(uint8_t *const dst, const uint8_t *const src, size_t len, aes_block_t *const state)
{
    uint8_t     pad[RATE];
    aes_block_t msg;

    memset(pad, 0, sizeof pad);
    memcpy(pad, src, len);

    msg = AES_BLOCK_LOAD(pad);
    msg = AES_BLOCK_XOR(msg, state[5]);
    msg = AES_BLOCK_XOR(msg, state[4]);
    msg = AES_BLOCK_XOR(msg, state[1]);
    msg = AES_BLOCK_XOR(msg, AES_BLOCK_AND(state[2], state[3]));
    AES_BLOCK_STORE(pad, msg);

    memset(pad + len, 0, sizeof pad - len);
    memcpy(dst, pad, len);

    msg = AES_BLOCK_LOAD(pad);

    aegis256_update(state, msg);
}

static int
encrypt_detached(uint8_t *c, uint8_t *mac, size_t maclen, const uint8_t *m, size_t mlen,
                 const uint8_t *ad, size_t adlen, const uint8_t *npub, const uint8_t *k)
{
    aes_block_t                state[6];
    CRYPTO_ALIGN(RATE) uint8_t src[RATE];
    CRYPTO_ALIGN(RATE) uint8_t dst[RATE];
    size_t                     i;

    aegis256_init(k, npub, state);

    for (i = 0; i + RATE <= adlen; i += RATE) {
        aegis256_absorb(ad + i, state);
    }
    if (adlen % RATE) {
        memset(src, 0, RATE);
        memcpy(src, ad + i, adlen % RATE);
        aegis256_absorb(src, state);
    }
    for (i = 0; i + RATE <= mlen; i += RATE) {
        aegis256_enc(c + i, m + i, state);
    }
    if (mlen % RATE) {
        memset(src, 0, RATE);
        memcpy(src, m + i, mlen % RATE);
        aegis256_enc(dst, src, state);
        memcpy(c + i, dst, mlen % RATE);
    }

    aegis256_mac(mac, maclen, adlen, mlen, state);

    return 0;
}

static int
decrypt_detached(uint8_t *m, const uint8_t *c, size_t clen, const uint8_t *mac, size_t maclen,
                 const uint8_t *ad, size_t adlen, const uint8_t *npub, const uint8_t *k)
{
    aes_block_t                state[6];
    CRYPTO_ALIGN(RATE) uint8_t src[RATE];
    CRYPTO_ALIGN(RATE) uint8_t dst[RATE];
    CRYPTO_ALIGN(16) uint8_t   computed_mac[32];
    const size_t               mlen = clen;
    size_t                     i;
    int                        ret;

    aegis256_init(k, npub, state);

    for (i = 0; i + RATE <= adlen; i += RATE) {
        aegis256_absorb(ad + i, state);
    }
    if (adlen % RATE) {
        memset(src, 0, RATE);
        memcpy(src, ad + i, adlen % RATE);
        aegis256_absorb(src, state);
    }
    if (m != NULL) {
        for (i = 0; i + RATE <= mlen; i += RATE) {
            aegis256_dec(m + i, c + i, state);
        }
    } else {
        for (i = 0; i + RATE <= mlen; i += RATE) {
            aegis256_dec(dst, c + i, state);
        }
    }
    if (mlen % RATE) {
        if (m != NULL) {
            aegis256_declast(m + i, c + i, mlen % RATE, state);
        } else {
            aegis256_declast(dst, c + i, mlen % RATE, state);
        }
    }

    COMPILER_ASSERT(sizeof computed_mac >= 32);
    aegis256_mac(computed_mac, maclen, adlen, mlen, state);
    ret = -1;
    if (maclen == 16) {
        ret = crypto_verify_16(computed_mac, mac);
    } else if (maclen == 32) {
        ret = crypto_verify_32(computed_mac, mac);
    }
    if (ret != 0 && m != NULL) {
        memset(m, 0, mlen);
    }
    return ret;
}
