#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_string.h>

#include <openssl/hmac.h>

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

#define NGX_HTTP_POW_RAND_LEN 64

typedef struct {
    ngx_uint_t  version;
    ngx_uint_t  created;
    ngx_uint_t  validity;
    ngx_uint_t  hardness;
    u_char      random[NGX_HTTP_POW_RAND_LEN];
    u_char      hmac[EVP_MAX_MD_SIZE];
} ngx_http_pow_challenge;

/*
const u_char *ngx_http_pow_challenge_to_string(ngx_http_pow_challenge *c,
        ngx_str_t *str)
{
    u_char  random_hex[NGX_HTTP_POW_RAND_LEN * 2 + 1];
    u_char  hmac_hex[EVP_MAX_MD_SIZE * 2 + 1];

    ngx_hex_dump(random_hex, c->random, NGX_HTTP_POW_RAND_LEN);
    random_hex[NGX_HTTP_POW_RAND_LEN * 2] = 0;
    ngx_hex_dump(hmac_hex, c->hmac, EVP_MAX_MD_SIZE);
    hmac_hex[EVP_MAX_MD_SIZE * 2] = 0;

    char out[1024] = { 0 };

    sprintf(out,
            "version=%lu, created=%lu, validity=%lu, hardness=%lu, random=%s, hmac=%s",
            c->version, c->created, c->validity, c->hardness, random_hex,
            hmac_hex);

    printf("%s\n", out);

    return NULL;
}
*/

const bool ngx_http_pow_sign_challenge(ngx_http_pow_challenge *c, ngx_str_t *k)
{
    size_t         clen;
    const EVP_MD  *digest;

    clen = sizeof(ngx_http_pow_challenge) - EVP_MAX_MD_SIZE;
    digest = EVP_sha256();

    u_char *hmac = HMAC(digest, k->data, k->len, (const unsigned char *) c, 
            clen, c->hmac, NULL);

    return hmac == c->hmac;
}

int main(int argc, char** argv)
{
    ngx_http_pow_challenge c = {
        .version = 1,
        .created = 1234567,
        .validity = 300,
        .hardness = 22,
        .random = { 'a', 'b', 'c' },
        .hmac = { 0 }
    };

    ngx_str_t key = ngx_string("asdf");
    bool success = ngx_http_pow_sign_challenge(&c, &key);
    printf("Success: %d\n", success);
    printf("challenge:\n");
    printf("    version: %lu\n", c.version);
    printf("    created: %lu\n", c.created);
    printf("    validity: %lu\n", c.validity);
    printf("    hardness: %lu\n", c.hardness);
    printf("    random: %.*s\n", NGX_HTTP_POW_RAND_LEN, (char *) c.random);
    printf("    random: %.*s\n", EVP_MAX_MD_SIZE, (char *) c.hmac);

    // ngx_http_pow_challenge_to_string(&c, NULL);
	
    return 0;
}