/*
 * 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 "endpoints.h"
#include "db.h"
#include "defs.h"
#include "form.h"
#include "op.h"
#include "utils.h"
#include <cjson/cJSON.h>
#include <dynstr.h>
#include <libweb/form.h>
#include <sodium.h>
#include <sqlite3.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct login
{
    bool valid;
    char *username, *password, *key;
    sqlite3 *db;
};

static void free_login(void *const p)
{
    int error;
    struct login *const l = p;

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

    free(l->username);
    free(l->password);
    free(l->key);
    free(l);
}

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;
    struct login *const l = args;
    sqlite3 *const db = l->db;
    const size_t len = strlen(l->password);
    char *const hashpwd = db_str(db, stmt, "password"),
        *key = db_str(db, stmt, "signkey");

    if (!hashpwd)
    {
        fprintf(stderr, "%s: missing password\n", __func__);
        goto end;
    }
    else if (!key)
    {
        fprintf(stderr, "%s: missing signkey\n", __func__);
        goto end;
    }
    else if (!crypto_pwhash_str_verify(hashpwd, l->password, len))
    {
        l->valid = true;
        l->key = key;
        key = NULL;
    }

    ret = 0;

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

static int authorize(const struct login *const l, struct http_response *const r)
{
    int ret = -1;
    char *const cookie = gencookie(l->username, l->key);

    if (!cookie)
    {
        fprintf(stderr, "%s: gencookie failed\n", __func__);
        goto end;
    }

    *r = (const struct http_response){.status = HTTP_STATUS_SEE_OTHER};

    if (http_response_add_header(r, "Location", "/")
        || http_response_add_header(r, "Set-Cookie", cookie))
    {
        fprintf(stderr, "%s: http_response_add_header failed\n", __func__);
        goto end;
    }

    ret = 0;

end:
    free(cookie);
    return ret;
}

static int end(const struct http_payload *const pl,
    struct http_response *const r, void *const user, void *const args)
{
    struct login *const l = args;
    const int error = sqlite3_close(l->db);

    l->db = NULL;

    if (error != SQLITE_OK)
    {
        fprintf(stderr, "%s: sqlite3_close: %s\n", __func__,
            sqlite3_errstr(error));
        return -1;
    }
    else if (l->valid)
    {
        if (authorize(l, r))
        {
            fprintf(stderr, "%s: authorize failed\n", __func__);
            return -1;
        }
    }
    else if (form_unauthorized("Invalid username or password", r))
    {
        fprintf(stderr, "%s: form_unauthorized failed\n", __func__);
        return -1;
    }

    free_login(l);
    return 0;
}

static int query_creds(const struct http_payload *const p,
    struct http_response *const r, void *const user, void *const args)
{
    int ret = -1;
    struct login *const l = args;
    struct dynstr d;

    dynstr_init(&d);

    if (dynstr_append(&d,
        "SELECT signkey, password FROM users WHERE name = '%s'", l->username))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }

    const struct op_cfg op =
    {
        .error = free_login,
        .end = end,
        .row = row,
        .args = l
    };

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

    ret = 0;

end:

    if (ret)
        free_login(l);

    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)
{
    const struct cfg *const cfg = user;
    struct login *const l = args;
    const int error = db_open(cfg->dir, &l->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 = query_creds,
            .args = l
        };

    return 0;

failure:
    free(l);
    return -1;
}

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

int ep_login(const struct http_payload *const p, struct http_response *const r,
    void *const user)
{
    int error, ret = -1;
    char *userdup = NULL, *passdup = NULL;
    struct form *f = NULL;
    struct login *l = NULL;
    const char *username, *password;

    if ((error = form_alloc(p->u.post.data, &f)))
    {
        if ((ret = error) < 0)
            fprintf(stderr, "%s: form_alloc failed\n", __func__);
        else
            ret = form_badreq("Invalid request", r);

        goto end;
    }
    else if (!(username = form_value(f, "username")))
    {
        fprintf(stderr, "%s: missing username\n", __func__);
        ret = form_badreq("Missing username", r);
        goto end;
    }
    else if (!(password = form_value(f, "password")))
    {
        fprintf(stderr, "%s: missing password\n", __func__);
        ret = form_badreq("Missing password", r);
        goto end;
    }
    else if (check_user(username))
    {
        fprintf(stderr, "%s: check_user failed\n", __func__);
        ret = form_unauthorized("Invalid username", r);
        goto end;
    }
    else if (!(userdup = strdup(username))
        || !(passdup = strdup(password)))
    {
        fprintf(stderr, "%s: strdup(3): %s\n", __func__, strerror(errno));
        goto end;
    }
    else if (!(l = malloc(sizeof *l)))
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto end;
    }

    *l = (const struct login)
    {
        .username = userdup,
        .password = passdup,
    };

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

    ret = 0;

end:

    if (ret)
    {
        free(userdup);
        free(passdup);
        free(l);
    }

    form_free(f);
    return 0;
}