<?php

/**
 * Database driver
 *
 * @var string
 */
public $dbdriver = 'mysqli';

/**
 * Compression flag
 *
 * @var bool
 */
public $compress = FALSE;

/**
 * DELETE hack flag
 *
 * Whether to use the MySQL "delete hack" which allows the number
 * of affected rows to be shown. Uses a preg_replace when enabled,
 * adding a bit more processing to all queries.
 *
 * @var bool
 */
public $delete_hack = TRUE;

/**
 * Strict ON flag
 *
 * Whether we're running in strict SQL mode.
 *
 * @var bool
 */
public $stricton;

// --------------------------------------------------------------------

/**
 * Identifier escape character
 *
 * @var string
 */
protected $_escape_char = '`';

// --------------------------------------------------------------------

/**
 * MySQLi object
 *
 * Has to be preserved without being assigned to $conn_id.
 *
 * @var MySQLi
 */
protected $_mysqli;

// --------------------------------------------------------------------

/**
 * Database connection
 *
 * @param   bool    $persistent
 * @return  object
 */
public function db_connect($persistent = FALSE)
{
    // Do we have a socket path?
    if ($this->hostname[0] === '/')
    {
        $hostname = NULL;
        $port = NULL;
        $socket = $this->hostname;
    }
    else
    {
        $hostname = ($persistent === TRUE)
            ? 'p:'.$this->hostname : $this->hostname;
        $port = empty($this->port) ? NULL : $this->port;
        $socket = NULL;
    }

    $client_flags = ($this->compress === TRUE) ? MYSQLI_CLIENT_COMPRESS : 0;
    $this->_mysqli = mysqli_init();

    $this->_mysqli->options(MYSQLI_OPT_CONNECT_TIMEOUT, 10);

    if (isset($this->stricton))
    {
        if ($this->stricton)
        {
            $this->_mysqli->options(MYSQLI_INIT_COMMAND, 'SET SESSION sql_mode = CONCAT(@@sql_mode, ",", "STRICT_ALL_TABLES")');
        }
        else
        {
            $this->_mysqli->options(MYSQLI_INIT_COMMAND,
                'SET SESSION sql_mode =
                REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
                @@sql_mode,
                "STRICT_ALL_TABLES,", ""),
                ",STRICT_ALL_TABLES", ""),
                "STRICT_ALL_TABLES", ""),
                "STRICT_TRANS_TABLES,", ""),
                ",STRICT_TRANS_TABLES", ""),
                "STRICT_TRANS_TABLES", "")'
            );
        }
    }

    if (is_array($this->encrypt))
    {
        $ssl = array();
        empty($this->encrypt['ssl_key'])    OR $ssl['key']    = $this->encrypt['ssl_key'];
        empty($this->encrypt['ssl_cert'])   OR $ssl['cert']   = $this->encrypt['ssl_cert'];
        empty($this->encrypt['ssl_ca'])     OR $ssl['ca']     = $this->encrypt['ssl_ca'];
        empty($this->encrypt['ssl_capath']) OR $ssl['capath'] = $this->encrypt['ssl_capath'];
        empty($this->encrypt['ssl_cipher']) OR $ssl['cipher'] = $this->encrypt['ssl_cipher'];

        if ( ! empty($ssl))
        {
            if (isset($this->encrypt['ssl_verify']))
            {
                if ($this->encrypt['ssl_verify'])
                {
                    defined('MYSQLI_OPT_SSL_VERIFY_SERVER_CERT') && $this->_mysqli->options(MYSQLI_OPT_SSL_VERIFY_SERVER_CERT, TRUE);
                }
                // Apparently (when it exists), setting MYSQLI_OPT_SSL_VERIFY_SERVER_CERT
                // to FALSE didn't do anything, so PHP 5.6.16 introduced yet another
                // constant ...
                //
                // https://secure.php.net/ChangeLog-5.php#5.6.16
                // https://bugs.php.net/bug.php?id=68344
                elseif (defined('MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT'))
                {
                    $client_flags |= MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT;
                }
            }

            $client_flags |= MYSQLI_CLIENT_SSL;
            $this->_mysqli->ssl_set(
                isset($ssl['key'])    ? $ssl['key']    : NULL,
                isset($ssl['cert'])   ? $ssl['cert']   : NULL,
                isset($ssl['ca'])     ? $ssl['ca']     : NULL,
                isset($ssl['capath']) ? $ssl['capath'] : NULL,
                isset($ssl['cipher']) ? $ssl['cipher'] : NULL
            );
        }
    }

    if ($this->_mysqli->real_connect($hostname, $this->username, $this->password, $this->database, $port, $socket, $client_flags))
    {
        // Prior to version 5.7.3, MySQL silently downgrades to an unencrypted connection if SSL setup fails
        if (
            ($client_flags & MYSQLI_CLIENT_SSL)
            && version_compare($this->_mysqli->client_info, '5.7.3', '<=')
            && empty($this->_mysqli->query("SHOW STATUS LIKE 'ssl_cipher'")->fetch_object()->Value)
        )
        {
            $this->_mysqli->close();
            $message = 'MySQLi was configured for an SSL connection, but got an unencrypted connection instead!';
            log_message('error', $message);
            return ($this->db_debug) ? $this->display_error($message, '', TRUE) : FALSE;
        }

        return $this->_mysqli;
    }

    return FALSE;
}

// --------------------------------------------------------------------

/**
 * Reconnect
 *
 * Keep / reestablish the db connection if no queries have been
 * sent for a length of time exceeding the server's idle timeout
 *
 * @return  void
 */
public function reconnect()
{
    if ($this->conn_id !== FALSE && $this->conn_id->ping() === FALSE)
    {
        $this->conn_id = FALSE;
    }
}

// --------------------------------------------------------------------

/**
 * Select the database
 *
 * @param   string  $database
 * @return  bool
 */
public function db_select($database = '')
{
    if ($database === '')
    {
        $database = $this->database;
    }

    if ($this->conn_id->select_db($database))
    {
        $this->database = $database;
        $this->data_cache = array();
        return TRUE;
    }

    return FALSE;
}

// --------------------------------------------------------------------

/**
 * Set client character set
 *
 * @param   string  $charset
 * @return  bool
 */
protected function _db_set_charset($charset)
{
    return $this->conn_id->set_charset($charset);
}

// --------------------------------------------------------------------

/**
 * Database version number
 *
 * @return  string
 */
public function version()
{
    if (isset($this->data_cache['version']))
    {
        return $this->data_cache['version'];
    }

    return $this->data_cache['version'] = $this->conn_id->server_info;
}

// --------------------------------------------------------------------

/**
 * Execute the query
 *
 * @param   string  $sql    an SQL query
 * @return  mixed
 */
protected function _execute($sql)
{
    return $this->conn_id->query($this->_prep_query($sql));
}

// --------------------------------------------------------------------

/**
 * Prep the query
 *
 * If needed, each database adapter can prep the query string
 *
 * @param   string  $sql    an SQL query
 * @return  string
 */
protected function _prep_query($sql)
{
    // mysqli_affected_rows() returns 0 for "DELETE FROM TABLE" queries. This hack
    // modifies the query so that it a proper number of affected rows is returned.
    if ($this->delete_hack === TRUE && preg_match('/^s*DELETEs+FROMs+(S+)s*$/i', $sql))
    {
        return trim($sql).' WHERE 1=1';
    }

    return $sql;
}

// --------------------------------------------------------------------

/**
 * Begin Transaction
 *
 * @return  bool
 */
protected function _trans_begin()
{
    $this->conn_id->autocommit(FALSE);
    return is_php('5.5')
        ? $this->conn_id->begin_transaction()
        : $this->simple_query('START TRANSACTION'); // can also be BEGIN or BEGIN WORK
}

// --------------------------------------------------------------------

/**
 * Commit Transaction
 *
 * @return  bool
 */
protected function _trans_commit()
{
    if ($this->conn_id->commit())
    {
        $this->conn_id->autocommit(TRUE);
        return TRUE;
    }

    return FALSE;
}

// --------------------------------------------------------------------

/**
 * Rollback Transaction
 *
 * @return  bool
 */
protected function _trans_rollback()
{
    if ($this->conn_id->rollback())
    {
        $this->conn_id->autocommit(TRUE);
        return TRUE;
    }

    return FALSE;
}

// --------------------------------------------------------------------

/**
 * Platform-dependent string escape
 *
 * @param   string
 * @return  string
 */
protected function _escape_str($str)
{
    return $this->conn_id->real_escape_string($str);
}

// --------------------------------------------------------------------

/**
 * Affected Rows
 *
 * @return  int
 */
public function affected_rows()
{
    return $this->conn_id->affected_rows;
}

// --------------------------------------------------------------------

/**
 * Insert ID
 *
 * @return  int
 */
public function insert_id()
{
    return $this->conn_id->insert_id;
}

// --------------------------------------------------------------------

/**
 * List table query
 *
 * Generates a platform-specific query string so that the table names can be fetched
 *
 * @param   bool    $prefix_limit
 * @return  string
 */
protected function _list_tables($prefix_limit = FALSE)
{
    $sql = 'SHOW TABLES FROM '.$this->escape_identifiers($this->database);

    if ($prefix_limit !== FALSE && $this->dbprefix !== '')
    {
        return $sql." LIKE '".$this->escape_like_str($this->dbprefix)."%'";
    }

    return $sql;
}

// --------------------------------------------------------------------

/**
 * Show column query
 *
 * Generates a platform-specific query string so that the column names can be fetched
 *
 * @param   string  $table
 * @return  string
 */
protected function _list_columns($table = '')
{
    return 'SHOW COLUMNS FROM '.$this->protect_identifiers($table, TRUE, NULL, FALSE);
}

// --------------------------------------------------------------------

/**
 * Returns an object with field data
 *
 * @param   string  $table
 * @return  array
 */
public function field_data($table)
{
    if (($query = $this->query('SHOW COLUMNS FROM '.$this->protect_identifiers($table, TRUE, NULL, FALSE))) === FALSE)
    {
        return FALSE;
    }
    $query = $query->result_object();

    $retval = array();
    for ($i = 0, $c = count($query); $i < $c; $i++)
    {
        $retval[$i]         = new stdClass();
        $retval[$i]->name       = $query[$i]->Field;

        sscanf($query[$i]->Type, '%[a-z](%d)',
            $retval[$i]->type,
            $retval[$i]->max_length
        );

        $retval[$i]->default        = $query[$i]->Default;
        $retval[$i]->primary_key    = (int) ($query[$i]->Key === 'PRI');
    }

    return $retval;
}

// --------------------------------------------------------------------

/**
 * Error
 *
 * Returns an array containing code and message of the last
 * database error that has occurred.
 *
 * @return  array
 */
public function error()
{
    if ( ! empty($this->_mysqli->connect_errno))
    {
        return array(
            'code'    => $this->_mysqli->connect_errno,
            'message' => $this->_mysqli->connect_error
        );
    }

    return array('code' => $this->conn_id->errno, 'message' => $this->conn_id->error);
}

// --------------------------------------------------------------------

/**
 * FROM tables
 *
 * Groups tables in FROM clauses if needed, so there is no confusion
 * about operator precedence.
 *
 * @return  string
 */
protected function _from_tables()
{
    if ( ! empty($this->qb_join) && count($this->qb_from) > 1)
    {
        return '('.implode(', ', $this->qb_from).')';
    }

    return implode(', ', $this->qb_from);
}

// --------------------------------------------------------------------

/**
 * Close DB Connection
 *
 * @return  void
 */
protected function _close()
{
    $this->conn_id->close();
}