/*
 * nanobbs, a tiny forums software.
 * Copyright (C) 2025-2026  Xavier Del Campo Romero
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#define _POSIX_C_SOURCE 200809L

#include "auth.h"
#include "db.h"
#include "defs.h"
#include "endpoints.h"
#include "jwt.h"
#include "op.h"
#include <dynstr.h>
#include <libweb/http.h>
#include <sodium.h>
#include <sqlite3.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>

struct validate
{
    bool valid;
    unsigned long id;
    enum auth_role role;
    sqlite3 *db;
    auth_fn fn;
    void *user;
};

static void free_validate(void *const p)
{
    int error;
    struct validate *const v = p;

    if (!v)
        return;
    else if ((error = sqlite3_close(v->db)) != SQLITE_OK)
        fprintf(stderr, "%s: sqlite3_close: %s\n", __func__,
            sqlite3_errstr(error));

    free(v);
}

static int check_role(const char *const s, enum auth_role *const out)
{
    static const struct r
    {
        const char *s;
        enum auth_role role;
    } roles[] =
    {
        {"admin", AUTH_ROLE_ADMIN},
        {"mod", AUTH_ROLE_MOD},
        {"user", AUTH_ROLE_USER},
        {"banned", AUTH_ROLE_BANNED}
    };

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

        if (!strcmp(s, r->s))
        {
            *out = r->role;
            return 0;
        }
    }

    fprintf(stderr, "%s: invalid role: %s\n", __func__, s);
    return -1;
}

static int end(const struct http_payload *const p,
    struct http_response *const r, void *const user, void *const args)
{
    int ret = -1;
    struct validate *const v = args;

    if (!v->valid)
        ret = v->fn(p, r, v->user, v->db, NULL);
    else
    {
        const struct http_cookie *const c = &p->cookie;
        const char *const username = c->field;
        const struct auth_user u =
        {
            .username = username,
            .role = v->role,
            .id = v->id
        };

        ret = v->fn(p, r, v->user, v->db, &u);
    }

    free(v);
    return ret;
}

static int signkey(const struct http_cookie *const c, const char *const key,
    struct validate *const v)
{
    int ret = -1;
    cJSON *j = NULL;
    unsigned char dkey[crypto_auth_hmacsha256_KEYBYTES];
    const size_t len = strlen(key), explen = sizeof dkey * 2;
    const cJSON *u;
    const char *user;

    if (len != explen)
    {
        fprintf(stderr, "%s: key size mismatch, got %zu, expected %zu\n",
            __func__, len, explen);
        goto end;
    }
    else if (sodium_hex2bin(dkey, sizeof dkey, key, len, NULL, NULL, NULL))
    {
        fprintf(stderr, "%s: sodium_hex2bin failed\n", __func__);
        goto end;
    }
    else if ((ret = jwt_decode(c->value, dkey, sizeof dkey, &j)))
    {
        if (ret < 0)
            fprintf(stderr, "%s: jwt_check failed\n", __func__);

        goto end;
    }
    else if (!(u = cJSON_GetObjectItem(j, "name"))
        || !(user = cJSON_GetStringValue(u))
        || strcmp(user, c->field))
    {
        ret = 1;
        goto end;
    }

    ret = 0;

end:
    cJSON_Delete(j);
    return ret;
}

static int row(sqlite3_stmt *const stmt, const struct http_payload *const p,
    struct http_response *const r, void *const user, void *const args)
{
    int ret = -1, error;
    struct validate *const v = args;
    sqlite3 *const db = v->db;
    char *const key = db_str(db, stmt, "signkey"), *name = NULL;
    enum auth_role role;
    unsigned id;

    if (!key)
    {
        fprintf(stderr, "%s: db_str %s failed\n", __func__, "signkey");
        goto end;
    }
    else if ((ret = db_uint(db, stmt, "id", &id)))
    {
        fprintf(stderr, "%s: db_uint %s failed\n", __func__, "id");
        goto end;
    }
    else if (!(name = db_str(db, stmt, "name")))
    {
        fprintf(stderr, "%s: db_str %s failed\n", __func__, "name");
        goto end;
    }
    else if (check_role(name, &role))
    {
        fprintf(stderr, "%s: role failed\n", __func__);
        goto end;
    }
    else if ((error = signkey(&p->cookie, key, v)))
    {
        if (error < 0)
        {
            fprintf(stderr, "%s: signkey failed\n", __func__);
            goto end;
        }
    }
    else if (!error)
    {
        v->valid = true;
        v->id = id;
        v->role = role;
    }

    ret = 0;

end:
    free(name);
    free(key);
    return ret;
}

static int check_username(const char *const name)
{
    return strspn(name, USER_SYMS) != strlen(name);
}

static int setup(const struct http_payload *const p,
    struct http_response *const r, void *const user, void *const args)
{
    int ret = -1;
    const struct http_cookie *const c = &p->cookie;
    const char *const username = c->field;
    struct validate *const v = args;
    struct dynstr d;

    dynstr_init(&d);

    if (dynstr_append(&d, "SELECT users.id, users.signkey, roles.name "
        "FROM users JOIN roles ON users.roleid = roles.id "
        "WHERE users.name = '%s';", username))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }

    const struct op_cfg op =
    {
        .error = free_validate,
        .end = end,
        .row = row,
        .args = v
    };

    if (!op_run(v->db, d.str, &op, r))
    {
        fprintf(stderr, "%s: op_run failed\n", __func__);
        goto end;
    }

    ret = 0;

end:

    if (ret)
        free_validate(v);

    dynstr_free(&d);
    return ret;
}

static int open_db(const struct http_payload *const p,
    struct http_response *const r, void *const user, void *const args)
{
    struct validate *const v = args;
    const struct cfg *const cfg = user;
    const int error = db_open(cfg->dir, &v->db);

    if (error != SQLITE_OK)
    {
        if (error != SQLITE_BUSY)
        {
            fprintf(stderr, "%s: db_open: %s\n", __func__,
                sqlite3_errstr(error));
            goto failure;
        }
    }
    else
        *r = (const struct http_response)
        {
            .step.payload = setup,
            .args = v
        };

    return 0;

failure:
    free_validate(v);
    return -1;
}

int auth_validate(const struct http_payload *const p,
    struct http_response *const r, void *const user, const auth_fn fn)
{
    int ret = -1;
    struct validate *v = NULL;
    const struct http_cookie *const c = &p->cookie;
    const char *const username = c->field;

    if (!username || !c->value || check_username(username))
    {
        ret = 1;
        goto failure;
    }
    else if (!(v = malloc(sizeof *v)))
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto failure;
    }

    *r = (const struct http_response)
    {
        .step.payload = open_db,
        .free = free_validate,
        .args = v
    };

    *v = (const struct validate)
    {
        .fn = fn,
        .user = user
    };

    return 0;

failure:
    free(v);
    return ret;
}