#include <stdint.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>

#include "core.h"
#include "crypto_aead_chacha20poly1305.h"
#include "crypto_aead_xchacha20poly1305.h"
#include "crypto_core_hchacha20.h"
#include "crypto_onetimeauth_poly1305.h"
#include "crypto_stream_chacha20.h"
#include "crypto_verify_16.h"
#include "randombytes.h"
#include "utils.h"

#include "private/chacha20_ietf_ext.h"
#include "private/common.h"

static const unsigned char _pad0[16] = { 0 };

static int
_encrypt_detached(unsigned char *c,
                  unsigned char *mac,
                  unsigned long long *maclen_p,
                  const unsigned char *m,
                  unsigned long long mlen,
                  const unsigned char *ad,
                  unsigned long long adlen,
                  const unsigned char *nsec,
                  const unsigned char *npub,
                  const unsigned char *k)
{
    crypto_onetimeauth_poly1305_state state;
    unsigned char                     block0[64U];
    unsigned char                     slen[8U];

    (void) nsec;
    crypto_stream_chacha20_ietf_ext(block0, sizeof block0, npub, k);
    crypto_onetimeauth_poly1305_init(&state, block0);
    sodium_memzero(block0, sizeof block0);

    crypto_onetimeauth_poly1305_update(&state, ad, adlen);
    crypto_onetimeauth_poly1305_update(&state, _pad0, (0x10 - adlen) & 0xf);

    crypto_stream_chacha20_ietf_ext_xor_ic(c, m, mlen, npub, 1U, k);

    crypto_onetimeauth_poly1305_update(&state, c, mlen);
    crypto_onetimeauth_poly1305_update(&state, _pad0, (0x10 - mlen) & 0xf);

    STORE64_LE(slen, (uint64_t) adlen);
    crypto_onetimeauth_poly1305_update(&state, slen, sizeof slen);

    STORE64_LE(slen, (uint64_t) mlen);
    crypto_onetimeauth_poly1305_update(&state, slen, sizeof slen);

    crypto_onetimeauth_poly1305_final(&state, mac);
    sodium_memzero(&state, sizeof state);

    if (maclen_p != NULL) {
        *maclen_p = crypto_aead_chacha20poly1305_ietf_ABYTES;
    }
    return 0;
}

static int
_decrypt_detached(unsigned char *m,
                  unsigned char *nsec,
                  const unsigned char *c,
                  unsigned long long clen,
                  const unsigned char *mac,
                  const unsigned char *ad,
                  unsigned long long adlen,
                  const unsigned char *npub,
                  const unsigned char *k)
{
    crypto_onetimeauth_poly1305_state state;
    unsigned char                     block0[64U];
    unsigned char                     slen[8U];
    unsigned char                     computed_mac[crypto_aead_chacha20poly1305_ietf_ABYTES];
    unsigned long long                mlen;
    int                               ret;

    (void) nsec;
    crypto_stream_chacha20_ietf_ext(block0, sizeof block0, npub, k);
    crypto_onetimeauth_poly1305_init(&state, block0);
    sodium_memzero(block0, sizeof block0);

    crypto_onetimeauth_poly1305_update(&state, ad, adlen);
    crypto_onetimeauth_poly1305_update(&state, _pad0, (0x10 - adlen) & 0xf);

    mlen = clen;
    crypto_onetimeauth_poly1305_update(&state, c, mlen);
    crypto_onetimeauth_poly1305_update(&state, _pad0, (0x10 - mlen) & 0xf);

    STORE64_LE(slen, (uint64_t) adlen);
    crypto_onetimeauth_poly1305_update(&state, slen, sizeof slen);

    STORE64_LE(slen, (uint64_t) mlen);
    crypto_onetimeauth_poly1305_update(&state, slen, sizeof slen);

    crypto_onetimeauth_poly1305_final(&state, computed_mac);
    sodium_memzero(&state, sizeof state);

    COMPILER_ASSERT(sizeof computed_mac == 16U);
    ret = crypto_verify_16(computed_mac, mac);
    sodium_memzero(computed_mac, sizeof computed_mac);
    if (m == NULL) {
        return ret;
    }
    if (ret != 0) {
        memset(m, 0, mlen);
        return -1;
    }
    crypto_stream_chacha20_ietf_ext_xor_ic(m, c, mlen, npub, 1U, k);

    return 0;
}

int
crypto_aead_xchacha20poly1305_ietf_encrypt_detached(unsigned char *c,
                                                    unsigned char *mac,
                                                    unsigned long long *maclen_p,
                                                    const unsigned char *m,
                                                    unsigned long long mlen,
                                                    const unsigned char *ad,
                                                    unsigned long long adlen,
                                                    const unsigned char *nsec,
                                                    const unsigned char *npub,
                                                    const unsigned char *k)
{
    unsigned char k2[crypto_core_hchacha20_OUTPUTBYTES];
    unsigned char npub2[crypto_aead_chacha20poly1305_ietf_NPUBBYTES] = { 0 };
    int           ret;

    crypto_core_hchacha20(k2, npub, k, NULL);
    memcpy(npub2 + 4, npub + crypto_core_hchacha20_INPUTBYTES,
           crypto_aead_chacha20poly1305_ietf_NPUBBYTES - 4);
    ret = _encrypt_detached(c, mac, maclen_p, m, mlen, ad, adlen,
                            nsec, npub2, k2);
    sodium_memzero(k2, crypto_core_hchacha20_OUTPUTBYTES);

    return ret;
}

int
crypto_aead_xchacha20poly1305_ietf_encrypt(unsigned char *c,
                                           unsigned long long *clen_p,
                                           const unsigned char *m,
                                           unsigned long long mlen,
                                           const unsigned char *ad,
                                           unsigned long long adlen,
                                           const unsigned char *nsec,
                                           const unsigned char *npub,
                                           const unsigned char *k)
{
    unsigned long long clen = 0ULL;
    int                ret;

    if (mlen > crypto_aead_xchacha20poly1305_ietf_MESSAGEBYTES_MAX) {
        sodium_misuse();
    }
    ret = crypto_aead_xchacha20poly1305_ietf_encrypt_detached
        (c, c + mlen, NULL, m, mlen, ad, adlen, nsec, npub, k);
    if (clen_p != NULL) {
        if (ret == 0) {
            clen = mlen + crypto_aead_xchacha20poly1305_ietf_ABYTES;
        }
        *clen_p = clen;
    }
    return ret;
}

int
crypto_aead_xchacha20poly1305_ietf_decrypt_detached(unsigned char *m,
                                                    unsigned char *nsec,
                                                    const unsigned char *c,
                                                    unsigned long long clen,
                                                    const unsigned char *mac,
                                                    const unsigned char *ad,
                                                    unsigned long long adlen,
                                                    const unsigned char *npub,
                                                    const unsigned char *k)
{
    unsigned char k2[crypto_core_hchacha20_OUTPUTBYTES];
    unsigned char npub2[crypto_aead_chacha20poly1305_ietf_NPUBBYTES] = { 0 };
    int           ret;

    crypto_core_hchacha20(k2, npub, k, NULL);
    memcpy(npub2 + 4, npub + crypto_core_hchacha20_INPUTBYTES,
           crypto_aead_chacha20poly1305_ietf_NPUBBYTES - 4);
    ret = _decrypt_detached(m, nsec, c, clen, mac, ad, adlen, npub2, k2);
    sodium_memzero(k2, crypto_core_hchacha20_OUTPUTBYTES);

    return ret;
}

int
crypto_aead_xchacha20poly1305_ietf_decrypt(unsigned char *m,
                                           unsigned long long *mlen_p,
                                           unsigned char *nsec,
                                           const unsigned char *c,
                                           unsigned long long clen,
                                           const unsigned char *ad,
                                           unsigned long long adlen,
                                           const unsigned char *npub,
                                           const unsigned char *k)
{
    unsigned long long mlen = 0ULL;
    int                ret  = -1;

    if (clen >= crypto_aead_xchacha20poly1305_ietf_ABYTES) {
        ret = crypto_aead_xchacha20poly1305_ietf_decrypt_detached
            (m, nsec,
             c, clen - crypto_aead_xchacha20poly1305_ietf_ABYTES,
             c + clen - crypto_aead_xchacha20poly1305_ietf_ABYTES,
             ad, adlen, npub, k);
    }
    if (mlen_p != NULL) {
        if (ret == 0) {
            mlen = clen - crypto_aead_xchacha20poly1305_ietf_ABYTES;
        }
        *mlen_p = mlen;
    }
    return ret;
}

size_t
crypto_aead_xchacha20poly1305_ietf_keybytes(void)
{
    return crypto_aead_xchacha20poly1305_ietf_KEYBYTES;
}

size_t
crypto_aead_xchacha20poly1305_ietf_npubbytes(void)
{
    return crypto_aead_xchacha20poly1305_ietf_NPUBBYTES;
}

size_t
crypto_aead_xchacha20poly1305_ietf_nsecbytes(void)
{
    return crypto_aead_xchacha20poly1305_ietf_NSECBYTES;
}

size_t
crypto_aead_xchacha20poly1305_ietf_abytes(void)
{
    return crypto_aead_xchacha20poly1305_ietf_ABYTES;
}

size_t
crypto_aead_xchacha20poly1305_ietf_messagebytes_max(void)
{
    return crypto_aead_xchacha20poly1305_ietf_MESSAGEBYTES_MAX;
}

void
crypto_aead_xchacha20poly1305_ietf_keygen(unsigned char k[crypto_aead_xchacha20poly1305_ietf_KEYBYTES])
{
    randombytes_buf(k, crypto_aead_xchacha20poly1305_ietf_KEYBYTES);
}