<?php
/* vim: set expandtab sw=4 ts=4 sts=4: */
/**
 * function for the main export logic
 *
 * @package PhpMyAdmin
 */
namespace PhpMyAdmin;

use PhpMyAdmin\Core;
use PhpMyAdmin\Encoding;
use PhpMyAdmin\Message;
use PhpMyAdmin\Plugins;
use PhpMyAdmin\Plugins\ExportPlugin;
use PhpMyAdmin\Sanitize;
use PhpMyAdmin\Table;
use PhpMyAdmin\Url;
use PhpMyAdmin\Util;
use PhpMyAdmin\ZipExtension;

/**
 * PhpMyAdmin\Export class
 *
 * @package PhpMyAdmin
 */
class Export
{
    /**
     * Sets a session variable upon a possible fatal error during export
     *
     * @return void
     */
    public static function shutdown()
    {
        $error = error_get_last();
        if ($error != null && mb_strpos($error['message'], "execution time")) {
            //set session variable to check if there was error while exporting
            $_SESSION['pma_export_error'] = $error['message'];
        }
    }

    /**
     * Detect ob_gzhandler
     *
     * @return bool
     */
    public static function isGzHandlerEnabled()
    {
        return in_array('ob_gzhandler', ob_list_handlers());
    }

    /**
     * Detect whether gzencode is needed; it might not be needed if
     * the server is already compressing by itself
     *
     * @return bool Whether gzencode is needed
     */
    public static function gzencodeNeeded()
    {
        /*
         * We should gzencode only if the function exists
         * but we don't want to compress twice, therefore
         * gzencode only if transparent compression is not enabled
         * and gz compression was not asked via $cfg['OBGzip']
         * but transparent compression does not apply when saving to server
         */
        $chromeAndGreaterThan43 = PMA_USR_BROWSER_AGENT == 'CHROME'
            && PMA_USR_BROWSER_VER >= 43; // see bug #4942

        if (function_exists('gzencode')
            && ((! ini_get('zlib.output_compression')
            && ! self::isGzHandlerEnabled())
            || $GLOBALS['save_on_server']
            || $chromeAndGreaterThan43)
        ) {
            return true;
        }

        return false;
    }

    /**
     * Output handler for all exports, if needed buffering, it stores data into
     * $dump_buffer, otherwise it prints them out.
     *
     * @param string $line the insert statement
     *
     * @return bool Whether output succeeded
     */
    public static function outputHandler($line)
    {
        global $time_start, $dump_buffer, $dump_buffer_len, $save_filename;

        // Kanji encoding convert feature
        if ($GLOBALS['output_kanji_conversion']) {
            $line = Encoding::kanjiStrConv(
                $line,
                $GLOBALS['knjenc'],
                isset($GLOBALS['xkana']) ? $GLOBALS['xkana'] : ''
            );
        }

        // If we have to buffer data, we will perform everything at once at the end
        if ($GLOBALS['buffer_needed']) {

            $dump_buffer .= $line;
            if ($GLOBALS['onfly_compression']) {

                $dump_buffer_len += strlen($line);

                if ($dump_buffer_len > $GLOBALS['memory_limit']) {
                    if ($GLOBALS['output_charset_conversion']) {
                        $dump_buffer = Encoding::convertString(
                            'utf-8',
                            $GLOBALS['charset'],
                            $dump_buffer
                        );
                    }
                    if ($GLOBALS['compression'] == 'gzip'
                        && self::gzencodeNeeded()
                    ) {
                        // as a gzipped file
                        // without the optional parameter level because it bugs
                        $dump_buffer = gzencode($dump_buffer);
                    }
                    if ($GLOBALS['save_on_server']) {
                        $write_result = @fwrite($GLOBALS['file_handle'], $dump_buffer);
                        // Here, use strlen rather than mb_strlen to get the length
                        // in bytes to compare against the number of bytes written.
                        if ($write_result != strlen($dump_buffer)) {
                            $GLOBALS['message'] = Message::error(
                                __('Insufficient space to save the file %s.')
                            );
                            $GLOBALS['message']->addParam($save_filename);
                            return false;
                        }
                    } else {
                        echo $dump_buffer;
                    }
                    $dump_buffer = '';
                    $dump_buffer_len = 0;
                }
            } else {
                $time_now = time();
                if ($time_start >= $time_now + 30) {
                    $time_start = $time_now;
                    header('X-pmaPing: Pong');
                } // end if
            }
        } else {
            if ($GLOBALS['asfile']) {
                if ($GLOBALS['output_charset_conversion']) {
                    $line = Encoding::convertString(
                        'utf-8',
                        $GLOBALS['charset'],
                        $line
                    );
                }
                if ($GLOBALS['save_on_server'] && mb_strlen($line) > 0) {
                    $write_result = @fwrite($GLOBALS['file_handle'], $line);
                    // Here, use strlen rather than mb_strlen to get the length
                    // in bytes to compare against the number of bytes written.
                    if (! $write_result
                        || $write_result != strlen($line)
                    ) {
                        $GLOBALS['message'] = Message::error(
                            __('Insufficient space to save the file %s.')
                        );
                        $GLOBALS['message']->addParam($save_filename);
                        return false;
                    }
                    $time_now = time();
                    if ($time_start >= $time_now + 30) {
                        $time_start = $time_now;
                        header('X-pmaPing: Pong');
                    } // end if
                } else {
                    // We export as file - output normally
                    echo $line;
                }
            } else {
                // We export as html - replace special chars
                echo htmlspecialchars($line);
            }
        }
        return true;
    } // end of the 'self::outputHandler()' function

    /**
     * Returns HTML containing the footer for a displayed export
     *
     * @param string $back_button   the link for going Back
     * @param string $refreshButton the link for refreshing page
     *
     * @return string $html the HTML output
     */
    public static function getHtmlForDisplayedExportFooter($back_button, $refreshButton)
    {
        /**
         * Close the html tags and add the footers for on-screen export
         */
        $html = '</textarea>'
            . '    </form>'
            . '<br />'
            // bottom back button
            . $back_button
            . $refreshButton
            . '</div>'
            . '<script type="text/javascript">' . "\n"
            . '//<![CDATA[' . "\n"
            . 'var $body = $("body");' . "\n"
            . '$("#textSQLDUMP")' . "\n"
            . '.width($body.width() - 50)' . "\n"
            . '.height($body.height() - 100);' . "\n"
            . '//]]>' . "\n"
            . '</script>' . "\n";
        return $html;
    }

    /**
     * Computes the memory limit for export
     *
     * @return int $memory_limit the memory limit
     */
    public static function getMemoryLimit()
    {
        $memory_limit = trim(ini_get('memory_limit'));
        $memory_limit_num = (int)substr($memory_limit, 0, -1);
        $lowerLastChar = strtolower(substr($memory_limit, -1));
        // 2 MB as default
        if (empty($memory_limit) || '-1' == $memory_limit) {
            $memory_limit = 2 * 1024 * 1024;
        } elseif ($lowerLastChar == 'm') {
            $memory_limit = $memory_limit_num * 1024 * 1024;
        } elseif ($lowerLastChar == 'k') {
            $memory_limit = $memory_limit_num * 1024;
        } elseif ($lowerLastChar == 'g') {
            $memory_limit = $memory_limit_num * 1024 * 1024 * 1024;
        } else {
            $memory_limit = (int)$memory_limit;
        }

        // Some of memory is needed for other things and as threshold.
        // During export I had allocated (see memory_get_usage function)
        // approx 1.2MB so this comes from that.
        if ($memory_limit > 1500000) {
            $memory_limit -= 1500000;
        }

        // Some memory is needed for compression, assume 1/3
        $memory_limit /= 8;
        return $memory_limit;
    }

    /**
     * Return the filename and MIME type for export file
     *
     * @param string       $export_type       type of export
     * @param string       $remember_template whether to remember template
     * @param ExportPlugin $export_plugin     the export plugin
     * @param string       $compression       compression asked
     * @param string       $filename_template the filename template
     *
     * @return string[] the filename template and mime type
     */
    public static function getFilenameAndMimetype(
        $export_type, $remember_template, $export_plugin, $compression,
        $filename_template
    ) {
        if ($export_type == 'server') {
            if (! empty($remember_template)) {
                $GLOBALS['PMA_Config']->setUserValue(
                    'pma_server_filename_template',
                    'Export/file_template_server',
                    $filename_template
                );
            }
        } elseif ($export_type == 'database') {
            if (! empty($remember_template)) {
                $GLOBALS['PMA_Config']->setUserValue(
                    'pma_db_filename_template',
                    'Export/file_template_database',
                    $filename_template
                );
            }
        } else {
            if (! empty($remember_template)) {
                $GLOBALS['PMA_Config']->setUserValue(
                    'pma_table_filename_template',
                    'Export/file_template_table',
                    $filename_template
                );
            }
        }
        $filename = Util::expandUserString($filename_template);
        // remove dots in filename (coming from either the template or already
        // part of the filename) to avoid a remote code execution vulnerability
        $filename = Sanitize::sanitizeFilename($filename, $replaceDots = true);

        // Grab basic dump extension and mime type
        // Check if the user already added extension;
        // get the substring where the extension would be if it was included
        $extension_start_pos = mb_strlen($filename) - mb_strlen(
            $export_plugin->getProperties()->getExtension()
        ) - 1;
        $user_extension = mb_substr(
            $filename, $extension_start_pos, mb_strlen($filename)
        );
        $required_extension = "." . $export_plugin->getProperties()->getExtension();
        if (mb_strtolower($user_extension) != $required_extension) {
            $filename  .= $required_extension;
        }
        $mime_type  = $export_plugin->getProperties()->getMimeType();

        // If dump is going to be compressed, set correct mime_type and add
        // compression to extension
        if ($compression == 'gzip') {
            $filename  .= '.gz';
            $mime_type = 'application/x-gzip';
        } elseif ($compression == 'zip') {
            $filename  .= '.zip';
            $mime_type = 'application/zip';
        }
        return array($filename, $mime_type);
    }

    /**
     * Open the export file
     *
     * @param string  $filename     the export filename
     * @param boolean $quick_export whether it's a quick export or not
     *
     * @return array the full save filename, possible message and the file handle
     */
    public static function openFile($filename, $quick_export)
    {
        $file_handle = null;
        $message = '';
        $doNotSaveItOver = true;

        if(isset($_POST['quick_export_onserver_overwrite'])) {
            $doNotSaveItOver = $_POST['quick_export_onserver_overwrite'] != 'saveitover';
        }

        $save_filename = Util::userDir($GLOBALS['cfg']['SaveDir'])
            . preg_replace('@[/\\\\]@', '_', $filename);

        if (@file_exists($save_filename)
            && ((! $quick_export && empty($_POST['onserver_overwrite']))
            || ($quick_export
            && $doNotSaveItOver))
        ) {
            $message = Message::error(
                __(
                    'File %s already exists on server, '
                    . 'change filename or check overwrite option.'
                )
            );
            $message->addParam($save_filename);
        } elseif (@is_file($save_filename) && ! @is_writable($save_filename)) {
            $message = Message::error(
                __(
                    'The web server does not have permission '
                    . 'to save the file %s.'
                )
            );
            $message->addParam($save_filename);
        } elseif (! $file_handle = @fopen($save_filename, 'w')) {
            $message = Message::error(
                __(
                    'The web server does not have permission '
                    . 'to save the file %s.'
                )
            );
            $message->addParam($save_filename);
        }
        return array($save_filename, $message, $file_handle);
    }

    /**
     * Close the export file
     *
     * @param resource $file_handle   the export file handle
     * @param string   $dump_buffer   the current dump buffer
     * @param string   $save_filename the export filename
     *
     * @return Message $message a message object (or empty string)
     */
    public static function closeFile($file_handle, $dump_buffer, $save_filename)
    {
        $write_result = @fwrite($file_handle, $dump_buffer);
        fclose($file_handle);
        // Here, use strlen rather than mb_strlen to get the length
        // in bytes to compare against the number of bytes written.
        if (strlen($dump_buffer) > 0
            && (! $write_result || $write_result != strlen($dump_buffer))
        ) {
            $message = new Message(
                __('Insufficient space to save the file %s.'),
                Message::ERROR,
                array($save_filename)
            );
        } else {
            $message = new Message(
                __('Dump has been saved to file %s.'),
                Message::SUCCESS,
                array($save_filename)
            );
        }
        return $message;
    }

    /**
     * Compress the export buffer
     *
     * @param array|string $dump_buffer the current dump buffer
     * @param string       $compression the compression mode
     * @param string       $filename    the filename
     *
     * @return object $message a message object (or empty string)
     */
    public static function compress($dump_buffer, $compression, $filename)
    {
        if ($compression == 'zip' && function_exists('gzcompress')) {
            $zipExtension = new ZipExtension();
            $filename = substr($filename, 0, -4); // remove extension (.zip)
            $dump_buffer = $zipExtension->createFile($dump_buffer, $filename);
        } elseif ($compression == 'gzip' && self::gzencodeNeeded()) {
            // without the optional parameter level because it bugs
            $dump_buffer = gzencode($dump_buffer);
        }
        return $dump_buffer;
    }

    /**
     * Saves the dump_buffer for a particular table in an array
     * Used in separate files export
     *
     * @param string  $object_name the name of current object to be stored
     * @param boolean $append      optional boolean to append to an existing index or not
     *
     * @return void
     */
    public static function saveObjectInBuffer($object_name, $append = false)
    {

        global $dump_buffer_objects, $dump_buffer, $dump_buffer_len;

        if (! empty($dump_buffer)) {
            if ($append && isset($dump_buffer_objects[$object_name])) {
                $dump_buffer_objects[$object_name] .= $dump_buffer;
            } else {
                $dump_buffer_objects[$object_name] = $dump_buffer;
            }
        }

        // Re - initialize
        $dump_buffer = '';
        $dump_buffer_len = 0;

    }

    /**
     * Returns HTML containing the header for a displayed export
     *
     * @param string $export_type the export type
     * @param string $db          the database name
     * @param string $table       the table name
     *
     * @return string[] the generated HTML and back button
     */
    public static function getHtmlForDisplayedExportHeader($export_type, $db, $table)
    {
        $html = '<div>';

        /**
         * Displays a back button with all the $_POST data in the URL
         * (store in a variable to also display after the textarea)
         */
        $back_button = '<p id="export_back_button">[ <a href="';
        if ($export_type == 'server') {
            $back_button .= 'server_export.php" data-post="' . Url::getCommon([], '', false);
        } elseif ($export_type == 'database') {
            $back_button .= 'db_export.php" data-post="' . Url::getCommon(array('db' => $db), '', false);
        } else {
            $back_button .= 'tbl_export.php" data-post="' . Url::getCommon(
                array(
                    'db' => $db, 'table' => $table
                ), '', false
            );
        }

        // Convert the multiple select elements from an array to a string
        if ($export_type == 'database') {
            $structOrDataForced = empty($_POST['structure_or_data_forced']);
            if ($structOrDataForced && ! isset($_POST['table_structure'])) {
                $_POST['table_structure'] = [];
            }
            if ($structOrDataForced && ! isset($_POST['table_data'])) {
                $_POST['table_data'] = [];
            }
        }

        foreach ($_POST as $name => $value) {
            if (!is_array($value)) {
                $back_button .= '&amp;' . urlencode($name) . '=' . urlencode($value);
            }
        }
        $back_button .= '&amp;repopulate=1">' . __('Back') . '</a> ]</p>';
        $html .= '<br />';
        $html .= $back_button;
        $refreshButton = '<form id="export_refresh_form" method="POST" action="export.php" class="disableAjax">';
        $refreshButton .= '[ <a class="disableAjax" onclick="$(this).parent().submit()">'. __('Refresh') .'</a> ]';
        foreach($_POST as $name => $value) {
            if (is_array($value)) {
                foreach($value as $val) {
                    $refreshButton .= '<input type="hidden" name="' . htmlentities((string) $name) . '[]" value="' . htmlentities((string) $val) . '">';
                }
            }
            else {
                $refreshButton .= '<input type="hidden" name="' . htmlentities((string) $name) . '" value="' . htmlentities((string) $value) . '">';
            }
        }
        $refreshButton .= '</form>';
        $html .= $refreshButton
            . '<br />'
            . '<form name="nofunction">'
            . '<textarea name="sqldump" cols="50" rows="30" '
            . 'id="textSQLDUMP" wrap="OFF">';

        return array($html, $back_button, $refreshButton);
    }

    /**
     * Export at the server level
     *
     * @param string       $db_select       the selected databases to export
     * @param string       $whatStrucOrData structure or data or both
     * @param ExportPlugin $export_plugin   the selected export plugin
     * @param string       $crlf            end of line character(s)
     * @param string       $err_url         the URL in case of error
     * @param string       $export_type     the export type
     * @param bool         $do_relation     whether to export relation info
     * @param bool         $do_comments     whether to add comments
     * @param bool         $do_mime         whether to add MIME info
     * @param bool         $do_dates        whether to add dates
     * @param array        $aliases         alias information for db/table/column
     * @param string       $separate_files  whether it is a separate-files export
     *
     * @return void
     */
    public static function exportServer(
        $db_select, $whatStrucOrData, $export_plugin, $crlf, $err_url,
        $export_type, $do_relation, $do_comments, $do_mime, $do_dates,
        array $aliases, $separate_files
    ) {
        if (! empty($db_select)) {
            $tmp_select = implode($db_select, '|');
            $tmp_select = '|' . $tmp_select . '|';
        }
        // Walk over databases
        foreach ($GLOBALS['dblist']->databases as $current_db) {
            if (isset($tmp_select)
                && mb_strpos(' ' . $tmp_select, '|' . $current_db . '|')
            ) {
                $tables = $GLOBALS['dbi']->getTables($current_db);
                self::exportDatabase(
                    $current_db, $tables, $whatStrucOrData, $tables, $tables,
                    $export_plugin, $crlf, $err_url, $export_type, $do_relation,
                    $do_comments, $do_mime, $do_dates, $aliases,
                    $separate_files == 'database' ? $separate_files : ''
                );
                if ($separate_files == 'server') {
                    self::saveObjectInBuffer($current_db);
                }
            }
        } // end foreach database
    }

    /**
     * Export at the database level
     *
     * @param string       $db              the database to export
     * @param array        $tables          the tables to export
     * @param string       $whatStrucOrData structure or data or both
     * @param array        $table_structure whether to export structure for each table
     * @param array        $table_data      whether to export data for each table
     * @param ExportPlugin $export_plugin   the selected export plugin
     * @param string       $crlf            end of line character(s)
     * @param string       $err_url         the URL in case of error
     * @param string       $export_type     the export type
     * @param bool         $do_relation     whether to export relation info
     * @param bool         $do_comments     whether to add comments
     * @param bool         $do_mime         whether to add MIME info
     * @param bool         $do_dates        whether to add dates
     * @param array        $aliases         Alias information for db/table/column
     * @param string       $separate_files  whether it is a separate-files export
     *
     * @return void
     */
    public static function exportDatabase(
        $db, array $tables, $whatStrucOrData, array $table_structure, array $table_data,
        $export_plugin, $crlf, $err_url, $export_type, $do_relation,
        $do_comments, $do_mime, $do_dates, array $aliases, $separate_files
    ) {
        $db_alias = !empty($aliases[$db]['alias'])
            ? $aliases[$db]['alias'] : '';

        if (! $export_plugin->exportDBHeader($db, $db_alias)) {
            return;
        }
        if (! $export_plugin->exportDBCreate($db, $export_type, $db_alias)) {
            return;
        }
        if ($separate_files == 'database') {
            self::saveObjectInBuffer('database', true);
        }

        if (($GLOBALS['sql_structure_or_data'] == 'structure'
            || $GLOBALS['sql_structure_or_data'] == 'structure_and_data')
            && isset($GLOBALS['sql_procedure_function'])
        ) {
            $export_plugin->exportRoutines($db, $aliases);

            if ($separate_files == 'database') {
                self::saveObjectInBuffer('routines');
            }
        }

        $views = array();

        foreach ($tables as $table) {
            $_table = new Table($table, $db);
            // if this is a view, collect it for later;
            // views must be exported after the tables
            $is_view = $_table->isView();
            if ($is_view) {
                $views[] = $table;
            }
            if (($whatStrucOrData == 'structure'
                || $whatStrucOrData == 'structure_and_data')
                && in_array($table, $table_structure)
            ) {
                // for a view, export a stand-in definition of the table
                // to resolve view dependencies (only when it's a single-file export)
                if ($is_view) {
                    if ($separate_files == ''
                        && isset($GLOBALS['sql_create_view'])
                        && ! $export_plugin->exportStructure(
                            $db, $table, $crlf, $err_url, 'stand_in',
                            $export_type, $do_relation, $do_comments,
                            $do_mime, $do_dates, $aliases
                        )
                    ) {
                        break;
                    }
                } elseif (isset($GLOBALS['sql_create_table'])) {

                    $table_size = $GLOBALS['maxsize'];
                    // Checking if the maximum table size constrain has been set
                    // And if that constrain is a valid number or not
                    if ($table_size !== '' && is_numeric($table_size)) {
                        // This obtains the current table's size
                        $query = 'SELECT data_length + index_length
                              from information_schema.TABLES
                              WHERE table_schema = "' . $GLOBALS['dbi']->escapeString($db) . '"
                              AND table_name = "' . $GLOBALS['dbi']->escapeString($table) . '"';

                        $size = $GLOBALS['dbi']->fetchValue($query);
                        //Converting the size to MB
                        $size = ($size / 1024) / 1024;
                        if ($size > $table_size) {
                            continue;
                        }
                    }

                    if (! $export_plugin->exportStructure(
                        $db, $table, $crlf, $err_url, 'create_table',
                        $export_type, $do_relation, $do_comments,
                        $do_mime, $do_dates, $aliases
                    )) {
                        break;
                    }

                }

            }
            // if this is a view or a merge table, don't export data
            if (($whatStrucOrData == 'data' || $whatStrucOrData == 'structure_and_data')
                && in_array($table, $table_data)
                && ! ($is_view)
            ) {
                $tableObj = new Table($table, $db);
                $nonGeneratedCols = $tableObj->getNonGeneratedColumns(true);

                $local_query  = 'SELECT ' . implode(', ', $nonGeneratedCols)
                    .  ' FROM ' . Util::backquote($db)
                    . '.' . Util::backquote($table);

                if (! $export_plugin->exportData(
                    $db, $table, $crlf, $err_url, $local_query, $aliases
                )) {
                    break;
                }
            }

            // this buffer was filled, we save it and go to the next one
            if ($separate_files == 'database') {
                self::saveObjectInBuffer('table_' . $table);
            }

            // now export the triggers (needs to be done after the data because
            // triggers can modify already imported tables)
            if (isset($GLOBALS['sql_create_trigger']) && ($whatStrucOrData == 'structure'
                || $whatStrucOrData == 'structure_and_data')
                && in_array($table, $table_structure)
            ) {
                if (! $export_plugin->exportStructure(
                    $db, $table, $crlf, $err_url, 'triggers',
                    $export_type, $do_relation, $do_comments,
                    $do_mime, $do_dates, $aliases
                )) {
                    break;
                }

                if ($separate_files == 'database') {
                    self::saveObjectInBuffer('table_' . $table, true);
                }
            }

        }

        if (isset($GLOBALS['sql_create_view'])) {

            foreach ($views as $view) {
                // no data export for a view
                if ($whatStrucOrData == 'structure'
                    || $whatStrucOrData == 'structure_and_data'
                ) {
                    if (! $export_plugin->exportStructure(
                        $db, $view, $crlf, $err_url, 'create_view',
                        $export_type, $do_relation, $do_comments,
                        $do_mime, $do_dates, $aliases
                    )) {
                        break;
                    }

                    if ($separate_files == 'database') {
                        self::saveObjectInBuffer('view_' . $view);
                    }
                }
            }

        }

        if (! $export_plugin->exportDBFooter($db)) {
            return;
        }

        // export metadata related to this db
        if (isset($GLOBALS['sql_metadata'])) {
            // Types of metadata to export.
            // In the future these can be allowed to be selected by the user
            $metadataTypes = self::getMetadataTypes();
            $export_plugin->exportMetadata($db, $tables, $metadataTypes);

            if ($separate_files == 'database') {
                self::saveObjectInBuffer('metadata');
            }
        }

        if ($separate_files == 'database') {
            self::saveObjectInBuffer('extra');
        }

        if (($GLOBALS['sql_structure_or_data'] == 'structure'
            || $GLOBALS['sql_structure_or_data'] == 'structure_and_data')
            && isset($GLOBALS['sql_procedure_function'])
        ) {
            $export_plugin->exportEvents($db);

            if ($separate_files == 'database') {
                self::saveObjectInBuffer('events');
            }
        }
    }

    /**
     * Export at the table level
     *
     * @param string       $db              the database to export
     * @param string       $table           the table to export
     * @param string       $whatStrucOrData structure or data or both
     * @param ExportPlugin $export_plugin   the selected export plugin
     * @param string       $crlf            end of line character(s)
     * @param string       $err_url         the URL in case of error
     * @param string       $export_type     the export type
     * @param bool         $do_relation     whether to export relation info
     * @param bool         $do_comments     whether to add comments
     * @param bool         $do_mime         whether to add MIME info
     * @param bool         $do_dates        whether to add dates
     * @param string       $allrows         whether "dump all rows" was ticked
     * @param string       $limit_to        upper limit
     * @param string       $limit_from      starting limit
     * @param string       $sql_query       query for which exporting is requested
     * @param array        $aliases         Alias information for db/table/column
     *
     * @return void
     */
    public static function exportTable(
        $db, $table, $whatStrucOrData, $export_plugin, $crlf, $err_url,
        $export_type, $do_relation, $do_comments, $do_mime, $do_dates,
        $allrows, $limit_to, $limit_from, $sql_query, array $aliases
    ) {
        $db_alias = !empty($aliases[$db]['alias'])
            ? $aliases[$db]['alias'] : '';
        if (! $export_plugin->exportDBHeader($db, $db_alias)) {
            return;
        }
        if (isset($allrows)
            && $allrows == '0'
            && $limit_to > 0
            && $limit_from >= 0
        ) {
            $add_query  = ' LIMIT '
                        . (($limit_from > 0) ? $limit_from . ', ' : '')
                        . $limit_to;
        } else {
            $add_query  = '';
        }

        $_table = new Table($table, $db);
        $is_view = $_table->isView();
        if ($whatStrucOrData == 'structure'
            || $whatStrucOrData == 'structure_and_data'
        ) {

            if ($is_view) {

                if (isset($GLOBALS['sql_create_view'])) {
                    if (! $export_plugin->exportStructure(
                        $db, $table, $crlf, $err_url, 'create_view',
                        $export_type, $do_relation, $do_comments,
                        $do_mime, $do_dates, $aliases
                    )) {
                        return;
                    }
                }

            } elseif (isset($GLOBALS['sql_create_table'])) {

                if (! $export_plugin->exportStructure(
                    $db, $table, $crlf, $err_url, 'create_table',
                    $export_type, $do_relation, $do_comments,
                    $do_mime, $do_dates, $aliases
                )) {
                    return;
                }

            }

        }
        // If this is an export of a single view, we have to export data;
        // for example, a PDF report
        // if it is a merge table, no data is exported
        if ($whatStrucOrData == 'data'
            || $whatStrucOrData == 'structure_and_data'
        ) {
            if (! empty($sql_query)) {
                // only preg_replace if needed
                if (! empty($add_query)) {
                    // remove trailing semicolon before adding a LIMIT
                    $sql_query = preg_replace('%;\s*$%', '', $sql_query);
                }
                $local_query = $sql_query . $add_query;
                $GLOBALS['dbi']->selectDb($db);
            } else {
                // Data is exported only for Non-generated columns
                $tableObj = new Table($table, $db);
                $nonGeneratedCols = $tableObj->getNonGeneratedColumns(true);

                $local_query  = 'SELECT ' . implode(', ', $nonGeneratedCols)
                    .  ' FROM ' . Util::backquote($db)
                    . '.' . Util::backquote($table) . $add_query;
            }
            if (! $export_plugin->exportData(
                $db, $table, $crlf, $err_url, $local_query, $aliases
            )) {
                return;
            }
        }
        // now export the triggers (needs to be done after the data because
        // triggers can modify already imported tables)
        if (isset($GLOBALS['sql_create_trigger']) && ($whatStrucOrData == 'structure'
            || $whatStrucOrData == 'structure_and_data')
        ) {
            if (! $export_plugin->exportStructure(
                $db, $table, $crlf, $err_url, 'triggers',
                $export_type, $do_relation, $do_comments,
                $do_mime, $do_dates, $aliases
            )) {
                return;
            }
        }
        if (! $export_plugin->exportDBFooter($db)) {
            return;
        }

        if (isset($GLOBALS['sql_metadata'])) {
            // Types of metadata to export.
            // In the future these can be allowed to be selected by the user
            $metadataTypes = self::getMetadataTypes();
            $export_plugin->exportMetadata($db, $table, $metadataTypes);
        }
    }

    /**
     * Loads correct page after doing export
     *
     * @param string $db          the database name
     * @param string $table       the table name
     * @param string $export_type Export type
     *
     * @return void
     */
    public static function showPage($db, $table, $export_type)
    {
        global $cfg;
        if ($export_type == 'server') {
            $active_page = 'server_export.php';
            include_once 'server_export.php';
        } elseif ($export_type == 'database') {
            $active_page = 'db_export.php';
            include_once 'db_export.php';
        } else {
            $active_page = 'tbl_export.php';
            include_once 'tbl_export.php';
        }
        exit();
    }

    /**
     * Merge two alias arrays, if array1 and array2 have
     * conflicting alias then array2 value is used if it
     * is non empty otherwise array1 value.
     *
     * @param array $aliases1 first array of aliases
     * @param array $aliases2 second array of aliases
     *
     * @return array resultant merged aliases info
     */
    public static function mergeAliases(array $aliases1, array $aliases2)
    {
        // First do a recursive array merge
        // on aliases arrays.
        $aliases = array_merge_recursive($aliases1, $aliases2);
        // Now, resolve conflicts in aliases, if any
        foreach ($aliases as $db_name => $db) {
            // If alias key is an array then
            // it is a merge conflict.
            if (isset($db['alias']) && is_array($db['alias'])) {
                $val1 = $db['alias'][0];
                $val2 = $db['alias'][1];
                // Use aliases2 alias if non empty
                $aliases[$db_name]['alias']
                    = empty($val2) ? $val1 : $val2;
            }
            if (!isset($db['tables'])) {
                continue;
            }
            foreach ($db['tables'] as $tbl_name => $tbl) {
                if (isset($tbl['alias']) && is_array($tbl['alias'])) {
                    $val1 = $tbl['alias'][0];
                    $val2 = $tbl['alias'][1];
                    // Use aliases2 alias if non empty
                    $aliases[$db_name]['tables'][$tbl_name]['alias']
                        = empty($val2) ? $val1 : $val2;
                }
                if (!isset($tbl['columns'])) {
                    continue;
                }
                foreach ($tbl['columns'] as  $col => $col_as) {
                    if (isset($col_as) && is_array($col_as)) {
                        $val1 = $col_as[0];
                        $val2 = $col_as[1];
                        // Use aliases2 alias if non empty
                        $aliases[$db_name]['tables'][$tbl_name]['columns'][$col]
                            = empty($val2) ? $val1 : $val2;
                    }
                };
            };
        }
        return $aliases;
    }

    /**
     * Locks tables
     *
     * @param string $db       database name
     * @param array  $tables   list of table names
     * @param string $lockType lock type; "[LOW_PRIORITY] WRITE" or "READ [LOCAL]"
     *
     * @return mixed result of the query
     */
    public static function lockTables($db, array $tables, $lockType = "WRITE")
    {
        $locks = array();
        foreach ($tables as $table) {
            $locks[] = Util::backquote($db) . "."
                . Util::backquote($table) . " " . $lockType;
        }

        $sql = "LOCK TABLES " . implode(", ", $locks);
        return $GLOBALS['dbi']->tryQuery($sql);
    }

    /**
     * Releases table locks
     *
     * @return mixed result of the query
     */
    public static function unlockTables()
    {
        return $GLOBALS['dbi']->tryQuery("UNLOCK TABLES");
    }

    /**
     * Returns all the metadata types that can be exported with a database or a table
     *
     * @return string[] metadata types.
     */
    public static function getMetadataTypes()
    {
        return array(
            'column_info',
            'table_uiprefs',
            'tracking',
            'bookmark',
            'relation',
            'table_coords',
            'pdf_pages',
            'savedsearches',
            'central_columns',
            'export_templates',
        );
    }

    /**
     * Returns the checked clause, depending on the presence of key in array
     *
     * @param string $key   the key to look for
     * @param array  $array array to verify
     *
     * @return string the checked clause
     */
    public static function getCheckedClause($key, array $array)
    {
        if (in_array($key, $array)) {
            return ' checked="checked"';
        }

        return '';
    }

    /**
     * get all the export options and verify
     * call and include the appropriate Schema Class depending on $export_type
     *
     * @param string $export_type format of the export
     *
     * @return void
     */
    public static function processExportSchema($export_type)
    {
        /**
         * default is PDF, otherwise validate it's only letters a-z
         */
        if (! isset($export_type) || ! preg_match('/^[a-zA-Z]+$/', $export_type)) {
            $export_type = 'pdf';
        }

        // sanitize this parameter which will be used below in a file inclusion
        $export_type = Core::securePath($export_type);

        // get the specific plugin
        /* @var $export_plugin SchemaPlugin */
        $export_plugin = Plugins::getPlugin(
            "schema",
            $export_type,
            'libraries/classes/Plugins/Schema/'
        );

        // Check schema export type
        if (! isset($export_plugin)) {
            Core::fatalError(__('Bad type!'));
        }

        $GLOBALS['dbi']->selectDb($_POST['db']);
        $export_plugin->exportSchema($_POST['db']);
    }
}