#define _POSIX_C_SOURCE 200809L

#include "hex.h"
#include <dynstr.h>
#include <cjson/cJSON.h>
#include <sodium.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <termios.h>
#include <unistd.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

static cJSON *dump_db(const char *const dir)
{
    int fd = -1;
    cJSON *ret = NULL, *c = NULL;
    char *buf = NULL;
    struct dynstr d;
    struct stat sb;

    dynstr_init(&d);

    if (dynstr_append(&d, "%s/db.json", dir))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }
    else if ((fd = open(d.str, O_RDONLY)) < 0)
    {
        fprintf(stderr, "%s: open(2) %s: %s\n", __func__, d.str,
            strerror(errno));
        goto end;
    }
    else if (fstat(fd, &sb))
    {
        fprintf(stderr, "%s: fstat(2) %s: %s\n", __func__, d.str,
            strerror(errno));
        goto end;
    }
    else if (sb.st_size > SIZE_MAX - 1)
    {
        fprintf(stderr, "%s: size for %s (%ju) exceeds maximum size (%zu)\n",
            __func__, d.str, (uintmax_t)sb.st_size, SIZE_MAX);
        goto end;
    }
    else if (!(buf = malloc(sb.st_size + 1)))
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto end;
    }

    size_t rem = sb.st_size;
    char *p = buf;

    while (rem)
    {
        const ssize_t r = read(fd, p, rem);

        if (r < 0)
        {
            fprintf(stderr, "%s: read(2): %s\n", __func__, strerror(errno));
            goto end;
        }

        rem -= r;
        p += r;
    }

    buf[sb.st_size] = '\0';

    if (!(c = cJSON_Parse(buf)))
    {
        fprintf(stderr, "%s: cJSON_Parse failed\n", __func__);
        goto end;
    }

    ret = c;

end:

    if (fd >= 0 && close(fd))
    {
        fprintf(stderr, "%s: close(2): %s\n", __func__, strerror(errno));
        ret = NULL;
    }

    if (!ret)
        cJSON_Delete(c);

    dynstr_free(&d);
    free(buf);
    return ret;
}

static int getuser(char *const username, const size_t n)
{
    fputs("Username:\n", stderr);

    if (!fgets(username, n, stdin))
    {
        fputs("Failed to obtain username\n", stderr);
        return -1;
    }
    else if (strcspn(username, " \t") != strlen(username))
    {
        fputs("Username cannot contain whitespaces\n", stderr);
        return -1;
    }

    *strchr(username, '\n') = '\0';
    return 0;
}

static int checkuser(const char *const username, const cJSON *const c)
{
    const cJSON *entry, *const users = cJSON_GetObjectItem(c, "users");

    if (!users)
    {
        fputs("Could not find users in database\n", stderr);
        return -1;
    }
    else if (!cJSON_IsArray(users))
    {
        fputs("Expected JSON array for users\n", stderr);
        return -1;
    }

    cJSON_ArrayForEach(entry, users)
    {
        const cJSON *const u = cJSON_GetObjectItem(entry, "name");
        const char *dbuser;

        if (!u || !(dbuser = cJSON_GetStringValue(u)))
        {
            fputs("Missing username field in database\n", stderr);
            return -1;
        }
        else if (!strcmp(username, dbuser))
        {
            fprintf(stderr, "User %s already in database\n", username);
            return -1;
        }
    }

    return 0;
}

static int getpass(char *const password, const size_t n)
{
    int ret = -1;
    struct termios t, ne;

    fputs("Password:\n", stderr);

    if (tcgetattr(STDIN_FILENO, &t))
    {
        fprintf(stderr, "%s: tcgetattr(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    ne = t;
    ne.c_lflag ^= ECHO;

    if (tcsetattr(STDIN_FILENO, TCSANOW, &ne))
    {
        fprintf(stderr, "%s: tcgetattr(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (!fgets(password, n, stdin))
    {
        fputs("Failed to obtain username\n", stderr);
        goto restore;
    }

    *strchr(password, '\n') = '\0';
    putchar('\n');
    ret = 0;

restore:

    if (tcsetattr(STDIN_FILENO, TCSANOW, &t))
    {
        fprintf(stderr, "%s: tcgetattr(3): %s\n", __func__, strerror(errno));
        ret = -1;
    }

    return ret;
}

static int getquota(unsigned long long *const q)
{
    char s[256], *end;

    fputs("Quota, in MiB (leave empty for unlimited quota):\n", stderr);

    if (!fgets(s, sizeof s, stdin))
    {
        fprintf(stderr, "%s: fgets(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    *strchr(s, '\n') = '\0';

    if (!*s)
    {
        *q = 0;
        return 0;
    }

    errno = 0;
    *q = strtoull(s, &end, 10);

    if (errno)
    {
        fprintf(stderr, "%s: strtoull(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (*end)
    {
        fprintf(stderr, "Invalid quota: %s\n", s);
        return -1;
    }

    return 0;
}

static int getmethod(char *const method, const size_t n)
{
    fputs("Password hashing (sha256 [deprecated], argon2id): "
        "[argon2id]\n", stderr);

    if (!fgets(method, n, stdin))
    {
        fprintf(stderr, "%s: fgets(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    *strchr(method, '\n') = '\0';

    if (!*method)
        strcpy(method, "argon2id");

    return 0;
}

static cJSON *createobj(cJSON *const c, const char *const username,
    const char *const key, const char *const method,
    const unsigned long long quota)
{
    cJSON *const ret = cJSON_CreateObject();
    char sq[sizeof "18446744073709551615"];
    const int n = snprintf(sq, sizeof sq, "%llu", quota);

    if (!ret)
    {
        fprintf(stderr, "%s: cJSON_CreateObject failed\n", __func__);
        goto failure;
    }
    else if (n < 0 || n >= sizeof sq)
    {
        fprintf(stderr, "%s: snprintf(3) failed with %d\n", __func__, n);
        goto failure;
    }
    else if (!cJSON_AddStringToObject(ret, "name", username)
        || !cJSON_AddStringToObject(ret, "key", key)
        || !cJSON_AddStringToObject(ret, "method", method)
        || (quota && !cJSON_AddStringToObject(ret, "quota", sq)))
    {
        fprintf(stderr, "%s: cJSON_AddStringToObject failed\n", __func__);
        goto failure;
    }

    return ret;

failure:
    cJSON_Delete(ret);
    return NULL;
}

static int runsha256(const char *const password, cJSON *const o)
{
    int ret = -1;
    enum {ROUNDS = 1000};
    unsigned char salt[32], sha256[crypto_hash_sha256_BYTES];
    const size_t plen = strlen(password), bufsz = sizeof salt + plen;
    char hexsha256[sizeof sha256 * 2 + 1], hexsalt[sizeof salt * 2 + 1];
    unsigned char *const buf = malloc(bufsz);

    randombytes_buf(salt, sizeof salt);

    if (!buf)
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto end;
    }

    memcpy(buf, salt, sizeof salt);
    memcpy(buf + sizeof salt, password, plen);

    if (crypto_hash_sha256(sha256, buf, bufsz))
    {
        fprintf(stderr, "%s: crypto_hash_sha256 failed\n", __func__);
        goto end;
    }

    fprintf(stderr, "1/%d", ROUNDS);

    for (int i = 1; i < ROUNDS; i++)
    {
        if (crypto_hash_sha256(sha256, sha256, sizeof sha256))
        {
            fprintf(stderr, "%s: crypto_hash_sha256 failed\n", __func__);
            goto end;
        }

        fprintf(stderr, "\r%d/%d", i + 1, ROUNDS);
    }

    fputc('\n', stderr);

    if (hex_encode(salt, hexsalt, sizeof salt, sizeof hexsalt)
        || hex_encode(sha256, hexsha256, sizeof sha256, sizeof hexsha256))
    {
        fprintf(stderr, "%s: hex_encode failed\n", __func__);
        goto end;
    }
    else if (!cJSON_AddStringToObject(o, "salt", hexsalt)
        || !cJSON_AddStringToObject(o, "password", hexsha256))
    {
        fprintf(stderr, "%s: cJSON_AddStringToObject failed\n", __func__);
        goto end;
    }

    ret = 0;

end:
    free(buf);
    return ret;
}

static int runargon2id(const char *const password, cJSON *const o)
{
    char hashpwd[crypto_pwhash_STRBYTES];

    if (crypto_pwhash_str(hashpwd, password, strlen(password),
        crypto_pwhash_OPSLIMIT_INTERACTIVE, crypto_pwhash_MEMLIMIT_INTERACTIVE))
    {
        fprintf(stderr, "%s: crypto_pwhash_str failed\n", __func__);
        return -1;
    }
    else if (!cJSON_AddStringToObject(o, "password", hashpwd))
    {
        fprintf(stderr, "%s: cJSON_AddStringToObject failed\n", __func__);
        return -1;
    }

    return 0;
}

static int runmethod(const char *const method, const char *const password,
    cJSON *const o)
{
    static const struct m
    {
        const char *s;
        int (*fn)(const char *, cJSON *);
    } methods[] =
    {
        {.s = "sha256", .fn = runsha256},
        {.s = "argon2id", .fn = runargon2id}
    };

    for (size_t i = 0; i < sizeof methods / sizeof *methods; i++)
    {
        const struct m *const m = &methods[i];

        if (!strcmp(m->s, method))
            return m->fn(password, o);
    }

    fprintf(stderr, "Invalid password hashing method: %s\n", method);
    return -1;
}

static int save_db(const cJSON *const c, const char *const dir)
{
    int ret = -1;
    FILE *f = NULL;
    char *s = NULL;
    struct dynstr d;

    dynstr_init(&d);

    if (dynstr_append(&d, "%s/db.json", dir))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }
    else if (!(f = fopen(d.str, "wb")))
    {
        fprintf(stderr, "%s: fopen(3) %s: %s\n", __func__, d.str,
            strerror(errno));
        goto end;
    }
    else if (!(s = cJSON_Print(c)))
    {
        fprintf(stderr, "%s: cJSON_Print failed\n", __func__);
        goto end;
    }
    else if (fprintf(f, "%s", s) < 0)
    {
        fprintf(stderr, "%s: fprintf(3) failed\n", __func__);
        goto end;
    }

    ret = 0;

end:

    if (f && fclose(f))
    {
        fprintf(stderr, "%s: fclose(3) %s: %s\n", __func__, d.str ? d.str : "",
            strerror(errno));
        ret = -1;
    }

    cJSON_free(s);
    dynstr_free(&d);
    return ret;
}

static int mkuserdir(const char *const dir, const char *const username)
{
    int ret = -1;
    struct dynstr d;

    dynstr_init(&d);

    if (dynstr_append(&d, "%s/user", dir))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }
    else if (mkdir(d.str, 0700) && errno != EEXIST)
    {
        fprintf(stderr, "%s: mkdir(2) %s: %s\n", __func__, d.str,
            strerror(errno));
        goto end;
    }
    else if (dynstr_append(&d, "/%s", username))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }
    else if (mkdir(d.str, 0700) && errno != EEXIST)
    {
        fprintf(stderr, "%s: mkdir(2) %s: %s\n", __func__, d.str,
            strerror(errno));
        goto end;
    }

    ret = 0;

end:
    dynstr_free(&d);
    return ret;
}

int main(int argc, char *argv[])
{
    int ret = EXIT_FAILURE;
    cJSON *c = NULL, *o, *users;
    unsigned long long quota;
    unsigned char key[32];
    char username[256], password[sizeof username], method[sizeof username],
        hexkey[sizeof key * 2 + 1];
    const char *dir;

    if (argc != 2)
    {
        fprintf(stderr, "%s <dir>\n", *argv);
        goto end;
    }
    else if (sodium_init())
    {
        fprintf(stderr, "%s: sodium_init failed\n", __func__);
        goto end;
    }
    else if (!(c = dump_db((dir = argv[1]))))
    {
        fprintf(stderr, "%s: dump_db failed\n", __func__);
        goto end;
    }

    randombytes_buf(key, sizeof key);

    if (hex_encode(key, hexkey, sizeof key, sizeof hexkey))
    {
        fprintf(stderr, "%s: hex_encode failed\n", __func__);
        goto end;
    }

    if (getuser(username, sizeof username)
        || checkuser(username, c)
        || getpass(password, sizeof password)
        || getquota(&quota)
        || getmethod(method, sizeof method)
        || !(o = createobj(c, username, hexkey, method, quota)))
        goto end;
    else if (runmethod(method, password, o))
    {
        cJSON_Delete(o);
        goto end;
    }
    else if (!(users = cJSON_GetObjectItem(c, "users")))
    {
        fputs("Missing \"users\" array in database\n", stderr);
        goto end;
    }
    else if (!cJSON_IsArray(users))
    {
        fputs("Database item \"users\" not an array\n", stderr);
        goto end;
    }
    else if (!cJSON_AddItemToArray(users, o))
    {
        fprintf(stderr, "%s: cJSON_AddItemToArray failed\n", __func__);
        cJSON_Delete(o);
        goto end;
    }
    else if (mkuserdir(dir, username)
        || save_db(c, dir))
        goto end;

    ret = EXIT_SUCCESS;

end:
    cJSON_Delete(c);
    return ret;
}