<?php

/*
 * SCROTT IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * For more information, please refer to UNLICENSE
 */

/* Include database configuration file if it exists */
define("DATABASE_CONFIG_FILE", "dbconfig.php");
is_file(DATABASE_CONFIG_FILE) && require_once DATABASE_CONFIG_FILE;

require_once "class/globals.php";
require_once "class/mysql.class.php";

/*
 * This class provides a common interface to various database drivers.
 * Scrott provides facilities for interacting with any DBMS that we can
 * use in PHP.  To provide support for a new DBMS, extend this class and
 * implement the abstract functions.  Additionally, update the getInstance()
 * function in this class so that the new implementation is used under
 * appropriate configuration.
 */
abstract class database
{
    private static $instance = NULL;

    /*
     * Call this object's close function while being destructed
     */
    public function __destruct()
    {
        $this->_close();
    }

    /*
     * Return the database instance object, creating it if this is the
     * first call to this function.  This function will need maintained
     * as new DBMSs are supported.  This function will throw if the
     * database is not configured.
     */
    private static function getInstance() : database
    {
        global $_SCROTT;

        if (self::$instance)
            return self::$instance;

        if (!isset($_SCROTT['conf']))
            throw new Exception("Scrott database configuration is missing.");

        switch ($_SCROTT['dbEngine'])
        {
            case "mysql":
                $host   = $_SCROTT['dbHost'];
                $uname  = $_SCROTT['dbUname'];
                $passwd = $_SCROTT['dbPasswd'];
                $dbname = $_SCROTT['dbName'];
                self::$instance = new mysql($host, $uname, $passwd, $dbname);
                break;

            default:
                throw new Exception("Problem with Scrott database configuration.  Invalid " .
                    "database engine specified.");
                break;
        }

        return self::$instance;
    }

    /*
     * These functions are to be implemented by DBMS extensions,
     * providing a uniform interface to database engines.
     */
    protected abstract function _close() : void;
    protected abstract function _query(string $query) : array;
    protected abstract function _esc(string $str) : string;

    /*
     * Perform a database query and return the results as an array
     * of arrays.
     */
    public static function query(string $query) : array
    {
        return self::getInstance()->_query($query);
    }

    /*
     * Escape a given string for use in a database query
     */
    public static function esc(string $str) : string
    {
        return self::getInstance()->_esc($str);
    }

    /*
     * Check whether Scrott's database config is loaded
     */
    public static function checkConfig() : bool
    {
        try
        {
            $db = self::getInstance();
        }
        catch (Exception $e)
        {
            return false;
        }

        return true;
    }
}

?>