<?php

    class Database
    {
        private static $singleton;

        private $mysqli;
        private $result;

        private $queryCount;
        private $fetchCount;
        private $totalQueryTime;

        /* @var Database */
        public static function GetInstance()
        {
            if (!Database::$singleton)
                Database::$singleton = new Database();

            return Database::$singleton;
        }

        public function __construct()
        {
            $this->mysqli = mysqli_connect("localhost", "root", "vertrigo", "cardgame");
            $this->queryCount = 0;
            $this->fetchCount = 0;
            $this->totalQueryTime = 0;

            if (!$this->mysqli)
                $this->TraceError("Failed to connect to server");
        }

        public function __destruct()
        {
            mysqli_close($this->mysqli);
        }

        public function Filter($q, $stripXSS = true)
        {
            return $stripXSS ? htmlspecialchars(mysqli_real_escape_string($this->mysqli, $q)) : mysqli_real_escape_string($this->mysqli, $q);
        }

        /*
         * Execute query to database.
         *
         * Query format:
         *  SELECT * FROM table WHERE id = '%1%'
         * Where %1 is argument index from $args array.
         *
         * $args are automatically escaped.
         */
        public function Query($q, $args)
        {
            for ($i = 0; $i < sizeof($args); $i++)
                $q = str_replace("%$i%", $this->Filter($args[$i]), $q);

            $start = microtime(true);
            $this->result = mysqli_query($this->mysqli, $q);
            $this->totalQueryTime += microtime(true) - $start;

            if (!$this->result)
                $this->TraceError("Failed to execute query $q");

            $this->queryCount++;

            return true;
        }

        protected function TraceError($error)
        {
            if (error_reporting() & E_ERROR) {
                $backtrace = debug_backtrace();

                echo "<div style='background-color: #FF9999; padding: 15px; border: 1px solid #FF3333; color: black'>";
                echo "<b>Database trace:</b><br><br>";
                echo "An error in database is occured:<br>";
                echo "Error text: $error<br>";
                echo "mysqli last error: " . mysqli_error($this->mysqli) . "<br><br>";
                echo "Backtrace:<br><br>";
                echo "<ul>";

                foreach ($backtrace as $trace)
                    echo "<li><b>$trace[class]$trace[type]$trace[function] in file $trace[file] at line $trace[line]</b></li>";

                echo "</ul>";
                echo "</div>";
            }
        }

        public static function TraceInfo()
        {
            if (error_reporting() & E_ERROR) {
                $instance = Database::GetInstance();

                echo "Database debug info:<br><br>";
                echo "Query count: $instance->queryCount<br>";
                echo "Fetch count: $instance->fetchCount<br>";
                echo "Total query time: $instance->totalQueryTime ms.";
            }
        }

        public function Fetch($q, $args)
        {
            if ($this->Query($q, $args)) {
                $ret = array();

                while ($arr = mysqli_fetch_array($this->result))
                    $ret[] = $arr;

                $this->fetchCount++;

                return $ret;
            }

            return array();
        }

        public function GetInsertID()
        {
            return mysqli_insert_id($this->mysqli);
        }

        public function GetRowCount()
        {
            return mysqli_num_rows($this->result);
        }

        public function GetAffectedRows()
        {
            return mysqli_affected_rows($this->mysqli);
        }

    }