<?php

/*
 * DB Class
 */
class DB
{
    private static $_instance;
    private $_connection;
    private $_dbhost = DB_HOST;
    private $_dbuser = DB_USER;
    private $_dbpass = DB_PASS;
    private $_dbname = DB_NAME;
    private $_dbcharset = DB_CHARSET;

    public static function getInstance()
    {
        if (!self::$_instance) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    private function __construct()
    {
        $this->_connection = new mysqli($this->_dbhost, $this->_dbuser, $this->_dbpass, $this->_dbname);

        if (mysqli_connect_errno()) {
            trigger_error('Database connection failed: ' . mysqli_connect_error(), E_USER_ERROR);
        }

        $this->_connection->set_charset($this->_dbcharset);
    }

    function getConnection()
    {
        return $this->_connection;
    }

    function query($sql)
    {
        $args = func_get_args();
        $sql = array_shift($args);
        $link = $this->_connection;

        $args = array_map(function ($param) use ($link) {
            return $link->escape_string($param);
        }, $args);

        $sql = str_replace(array('%', '?'), array('%%', '%s'), $sql);

        array_unshift($args, $sql);

        $sql = call_user_func_array('sprintf', $args);

        $this->_query = $this->_connection->query($sql);
        if($this->_query === false) throw new Exception('Database error: ' . $this->_connection->error);

        return $this;
    }

    function changeDb($db_name)
    {
        $this->_connection->select_db($db_name);
    }

    function data_seek($offset = 0)
    {
        return $this->_query->data_seek($offset);
    }

    function field_seek($field)
    {
        return $this->_query->field_seek($field);
    }

    function insert_id()
    {
        return $this->_query->insert_id;
    }

    function fetch_field_direct($field)
    {
        return $this->_query->fetch_field_direct($field);
    }

    function assoc()
    {
        return $this->_query->fetch_assoc();
    }

    function fetch_field()
    {
        while ($row = $this->_query->fetch_field()) $_result[] = $row->name;
        return $_result;
    }

    function fetch_row()
    {
        return $this->_query->fetch_row();
    }

    function fetch_object($class_name = "stdClass", $param = null)
    {
        if(is_null($param))
        {
            return $this->_query->fetch_object($class_name);
        }
        else
        {
            return $this->_query->fetch_object($class_name, $param);
        }
    }

    function all()
    {
        while($row = $this->_query->fetch_assoc()) $_result[] = $row;
        return $_result;
    }

    function __destruct()
    {
        $this->_connection->close();
    }
}