<?php
/**
 * Base class for displaying a list of items in an ajaxified HTML table.
 *
 * @since 3.1.0
 * @access private
 *
 * @package WordPress
 * @subpackage List_Table
 */
class WP_List_Table {

	/**
	 * The current list of items
	 *
	 * @since 3.1.0
	 * @var array
	 * @access public
	 */
	public $items;

	/**
	 * Various information about the current table
	 *
	 * @since 3.1.0
	 * @var array
	 * @access protected
	 */
	protected $_args;

	/**
	 * Various information needed for displaying the pagination
	 *
	 * @since 3.1.0
	 * @var array
	 */
	protected $_pagination_args = array();

	/**
	 * The current screen
	 *
	 * @since 3.1.0
	 * @var object
	 * @access protected
	 */
	protected $screen;

	/**
	 * Cached bulk actions
	 *
	 * @since 3.1.0
	 * @var array
	 * @access private
	 */
	private $_actions;

	/**
	 * Cached pagination output
	 *
	 * @since 3.1.0
	 * @var string
	 * @access private
	 */
	private $_pagination;

	/**
	 * The view switcher modes.
	 *
	 * @since 4.1.0
	 * @var array
	 * @access protected
	 */
	protected $modes = array();

	/**
	 * Stores the value returned by ->get_column_info()
	 *
	 * @var array
	 */
	protected $_column_headers;

	protected $compat_fields = array( '_args', '_pagination_args', 'screen', '_actions', '_pagination' );

	protected $compat_methods = array( 'set_pagination_args', 'get_views', 'get_bulk_actions', 'bulk_actions',
		'row_actions', 'months_dropdown', 'view_switcher', 'comments_bubble', 'get_items_per_page', 'pagination',
		'get_sortable_columns', 'get_column_info', 'get_table_classes', 'display_tablenav', 'extra_tablenav',
		'single_row_columns' );

	/**
	 * Constructor.
	 *
	 * The child class should call this constructor from its own constructor to override
	 * the default $args.
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @param array|string $args {
	 *     Array or string of arguments.
	 *
	 *     @type string $plural   Plural value used for labels and the objects being listed.
	 *                            This affects things such as CSS class-names and nonces used
	 *                            in the list table, e.g. 'posts'. Default empty.
	 *     @type string $singular Singular label for an object being listed, e.g. 'post'.
	 *                            Default empty
	 *     @type bool   $ajax     Whether the list table supports AJAX. This includes loading
	 *                            and sorting data, for example. If true, the class will call
	 *                            the {@see _js_vars()} method in the footer to provide variables
	 *                            to any scripts handling AJAX events. Default false.
	 *     @type string $screen   String containing the hook name used to determine the current
	 *                            screen. If left null, the current screen will be automatically set.
	 *                            Default null.
	 * }
	 */
	public function __construct( $args = array() ) {
		$args = wp_parse_args( $args, array(
			'plural' => '',
			'singular' => '',
			'ajax' => false,
			'screen' => null,
		) );

		$this->screen = convert_to_screen( $args['screen'] );

		add_filter( "manage_{$this->screen->id}_columns", array( $this, 'get_columns' ), 0 );

		if ( !$args['plural'] )
			$args['plural'] = $this->screen->base;

		$args['plural'] = sanitize_key( $args['plural'] );
		$args['singular'] = sanitize_key( $args['singular'] );

		$this->_args = $args;

		if ( $args['ajax'] ) {
			// wp_enqueue_script( 'list-table' );
			add_action( 'admin_footer', array( $this, '_js_vars' ) );
		}

		if ( empty( $this->modes ) ) {
			$this->modes = array(
				'list'    => __( 'List View' ),
				'excerpt' => __( 'Excerpt View' )
			);
		}
	}

	/**
	 * Make private properties readable for backwards compatibility.
	 *
	 * @since 4.0.0
	 * @access public
	 *
	 * @param string $name Property to get.
	 * @return mixed Property.
	 */
	public function __get( $name ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			return $this->$name;
		}
	}

	/**
	 * Make private properties settable for backwards compatibility.
	 *
	 * @since 4.0.0
	 * @access public
	 *
	 * @param string $name  Property to check if set.
	 * @param mixed  $value Property value.
	 * @return mixed Newly-set property.
	 */
	public function __set( $name, $value ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			return $this->$name = $value;
		}
	}

	/**
	 * Make private properties checkable for backwards compatibility.
	 *
	 * @since 4.0.0
	 * @access public
	 *
	 * @param string $name Property to check if set.
	 * @return bool Whether the property is set.
	 */
	public function __isset( $name ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			return isset( $this->$name );
		}
	}

	/**
	 * Make private properties un-settable for backwards compatibility.
	 *
	 * @since 4.0.0
	 * @access public
	 *
	 * @param string $name Property to unset.
	 */
	public function __unset( $name ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			unset( $this->$name );
		}
	}

	/**
	 * Make private/protected methods readable for backwards compatibility.
	 *
	 * @since 4.0.0
	 * @access public
	 *
	 * @param callable $name      Method to call.
	 * @param array    $arguments Arguments to pass when calling.
	 * @return mixed|bool Return value of the callback, false otherwise.
	 */
	public function __call( $name, $arguments ) {
		if ( in_array( $name, $this->compat_methods ) ) {
			return call_user_func_array( array( $this, $name ), $arguments );
		}
		return false;
	}

	/**
	 * Checks the current user's permissions
	 *
	 * @since 3.1.0
	 * @access public
	 * @abstract
	 */
	public function ajax_user_can() {
		die( 'function WP_List_Table::ajax_user_can() must be over-ridden in a sub-class.' );
	}

	/**
	 * Prepares the list of items for displaying.
	 * @uses WP_List_Table::set_pagination_args()
	 *
	 * @since 3.1.0
	 * @access public
	 * @abstract
	 */
	public function prepare_items() {
		die( 'function WP_List_Table::prepare_items() must be over-ridden in a sub-class.' );
	}

	/**
	 * An internal method that sets all the necessary pagination arguments
	 *
	 * @param array $args An associative array with information about the pagination
	 * @access protected
	 */
	protected function set_pagination_args( $args ) {
		$args = wp_parse_args( $args, array(
			'total_items' => 0,
			'total_pages' => 0,
			'per_page' => 0,
		) );

		if ( !$args['total_pages'] && $args['per_page'] > 0 )
			$args['total_pages'] = ceil( $args['total_items'] / $args['per_page'] );

		// Redirect if page number is invalid and headers are not already sent.
		if ( ! headers_sent() && ( ! defined( 'DOING_AJAX' ) || ! DOING_AJAX ) && $args['total_pages'] > 0 && $this->get_pagenum() > $args['total_pages'] ) {
			wp_redirect( add_query_arg( 'paged', $args['total_pages'] ) );
			exit;
		}

		$this->_pagination_args = $args;
	}

	/**
	 * Access the pagination args.
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @param string $key Pagination argument to retrieve. Common values include 'total_items',
	 *                    'total_pages', 'per_page', or 'infinite_scroll'.
	 * @return int Number of items that correspond to the given pagination argument.
	 */
	public function get_pagination_arg( $key ) {
		if ( 'page' == $key )
			return $this->get_pagenum();

		if ( isset( $this->_pagination_args[$key] ) )
			return $this->_pagination_args[$key];
	}

	/**
	 * Whether the table has items to display or not
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @return bool
	 */
	public function has_items() {
		return !empty( $this->items );
	}

	/**
	 * Message to be displayed when there are no items
	 *
	 * @since 3.1.0
	 * @access public
	 */
	public function no_items() {
		_e( 'No items found.' );
	}

	/**
	 * Display the search box.
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @param string $text The search button text
	 * @param string $input_id The search input id
	 */
	public function search_box( $text, $input_id ) {
		if ( empty( $_REQUEST['s'] ) && !$this->has_items() )
			return;

		$input_id = $input_id . '-search-input';

		if ( ! empty( $_REQUEST['orderby'] ) )
			echo '<input type="hidden" name="orderby" value="' . esc_attr( $_REQUEST['orderby'] ) . '" />';
		if ( ! empty( $_REQUEST['order'] ) )
			echo '<input type="hidden" name="order" value="' . esc_attr( $_REQUEST['order'] ) . '" />';
		if ( ! empty( $_REQUEST['post_mime_type'] ) )
			echo '<input type="hidden" name="post_mime_type" value="' . esc_attr( $_REQUEST['post_mime_type'] ) . '" />';
		if ( ! empty( $_REQUEST['detached'] ) )
			echo '<input type="hidden" name="detached" value="' . esc_attr( $_REQUEST['detached'] ) . '" />';
?>
<p class="search-box">
	<label class="screen-reader-text" for="<?php echo $input_id ?>"><?php echo $text; ?>:</label>
	<input type="search" id="<?php echo $input_id ?>" name="s" value="<?php _admin_search_query(); ?>" />
	<?php submit_button( $text, 'button', '', false, array('id' => 'search-submit') ); ?>
</p>
<?php
	}

	/**
	 * Get an associative array ( id => link ) with the list
	 * of views available on this table.
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @return array
	 */
	protected function get_views() {
		return array();
	}

	/**
	 * Display the list of views available on this table.
	 *
	 * @since 3.1.0
	 * @access public
	 */
	public function views() {
		$views = $this->get_views();
		/**
		 * Filter the list of available list table views.
		 *
		 * The dynamic portion of the hook name, `$this->screen->id`, refers
		 * to the ID of the current screen, usually a string.
		 *
		 * @since 3.5.0
		 *
		 * @param array $views An array of available list table views.
		 */
		$views = apply_filters( "views_{$this->screen->id}", $views );

		if ( empty( $views ) )
			return;

		echo "<ul class='subsubsub'>\n";
		foreach ( $views as $class => $view ) {
			$views[ $class ] = "\t<li class='$class'>$view";
		}
		echo implode( " |</li>\n", $views ) . "</li>\n";
		echo "</ul>";
	}

	/**
	 * Get an associative array ( option_name => option_title ) with the list
	 * of bulk actions available on this table.
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @return array
	 */
	protected function get_bulk_actions() {
		return array();
	}

	/**
	 * Display the bulk actions dropdown.
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param string $which The location of the bulk actions: 'top' or 'bottom'.
	 *                      This is designated as optional for backwards-compatibility.
	 */
	protected function bulk_actions( $which = '' ) {
		if ( is_null( $this->_actions ) ) {
			$no_new_actions = $this->_actions = $this->get_bulk_actions();
			/**
			 * Filter the list table Bulk Actions drop-down.
			 *
			 * The dynamic portion of the hook name, `$this->screen->id`, refers
			 * to the ID of the current screen, usually a string.
			 *
			 * This filter can currently only be used to remove bulk actions.
			 *
			 * @since 3.5.0
			 *
			 * @param array $actions An array of the available bulk actions.
			 */
			$this->_actions = apply_filters( "bulk_actions-{$this->screen->id}", $this->_actions );
			$this->_actions = array_intersect_assoc( $this->_actions, $no_new_actions );
			$two = '';
		} else {
			$two = '2';
		}

		if ( empty( $this->_actions ) )
			return;

		echo "<label for='bulk-action-selector-" . esc_attr( $which ) . "' class='screen-reader-text'>" . __( 'Select bulk action' ) . "</label>";
		echo "<select name='action$two' id='bulk-action-selector-" . esc_attr( $which ) . "'>\n";
		echo "<option value='-1' selected='selected'>" . __( 'Bulk Actions' ) . "</option>\n";

		foreach ( $this->_actions as $name => $title ) {
			$class = 'edit' == $name ? ' class="hide-if-no-js"' : '';

			echo "\t<option value='$name'$class>$title</option>\n";
		}

		echo "</select>\n";

		submit_button( __( 'Apply' ), 'action', '', false, array( 'id' => "doaction$two" ) );
		echo "\n";
	}

	/**
	 * Get the current action selected from the bulk actions dropdown.
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @return string|bool The action name or False if no action was selected
	 */
	public function current_action() {
		if ( isset( $_REQUEST['filter_action'] ) && ! empty( $_REQUEST['filter_action'] ) )
			return false;

		if ( isset( $_REQUEST['action'] ) && -1 != $_REQUEST['action'] )
			return $_REQUEST['action'];

		if ( isset( $_REQUEST['action2'] ) && -1 != $_REQUEST['action2'] )
			return $_REQUEST['action2'];

		return false;
	}

	/**
	 * Generate row actions div
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param array $actions The list of actions
	 * @param bool $always_visible Whether the actions should be always visible
	 * @return string
	 */
	protected function row_actions( $actions, $always_visible = false ) {
		$action_count = count( $actions );
		$i = 0;

		if ( !$action_count )
			return '';

		$out = '<div class="' . ( $always_visible ? 'row-actions visible' : 'row-actions' ) . '">';
		foreach ( $actions as $action => $link ) {
			++$i;
			( $i == $action_count ) ? $sep = '' : $sep = ' | ';
			$out .= "<span class='$action'>$link$sep</span>";
		}
		$out .= '</div>';

		return $out;
	}

	/**
	 * Display a monthly dropdown for filtering items
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @global wpdb      $wpdb
	 * @global WP_Locale $wp_locale
	 *
	 * @param string $post_type
	 */
	protected function months_dropdown( $post_type ) {
		global $wpdb, $wp_locale;

		/**
		 * Filter whether to remove the 'Months' drop-down from the post list table.
		 *
		 * @since 4.2.0
		 *
		 * @param bool   $disable   Whether to disable the drop-down. Default false.
		 * @param string $post_type The post type.
		 */
		if ( apply_filters( 'disable_months_dropdown', false, $post_type ) ) {
			return;
		}

		$months = $wpdb->get_results( $wpdb->prepare( "
			SELECT DISTINCT YEAR( post_date ) AS year, MONTH( post_date ) AS month
			FROM $wpdb->posts
			WHERE post_type = %s
			ORDER BY post_date DESC
		", $post_type ) );

		/**
		 * Filter the 'Months' drop-down results.
		 *
		 * @since 3.7.0
		 *
		 * @param object $months    The months drop-down query results.
		 * @param string $post_type The post type.
		 */
		$months = apply_filters( 'months_dropdown_results', $months, $post_type );

		$month_count = count( $months );

		if ( !$month_count || ( 1 == $month_count && 0 == $months[0]->month ) )
			return;

		$m = isset( $_GET['m'] ) ? (int) $_GET['m'] : 0;
?>
		<label for="filter-by-date" class="screen-reader-text"><?php _e( 'Filter by date' ); ?></label>
		<select name="m" id="filter-by-date">
			<option<?php selected( $m, 0 ); ?> value="0"><?php _e( 'All dates' ); ?></option>
<?php
		foreach ( $months as $arc_row ) {
			if ( 0 == $arc_row->year )
				continue;

			$month = zeroise( $arc_row->month, 2 );
			$year = $arc_row->year;

			printf( "<option %s value='%s'>%s</option>\n",
				selected( $m, $year . $month, false ),
				esc_attr( $arc_row->year . $month ),
				/* translators: 1: month name, 2: 4-digit year */
				sprintf( __( '%1$s %2$d' ), $wp_locale->get_month( $month ), $year )
			);
		}
?>
		</select>
<?php
	}

	/**
	 * Display a view switcher
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param string $current_mode
	 */
	protected function view_switcher( $current_mode ) {
?>
		<input type="hidden" name="mode" value="<?php echo esc_attr( $current_mode ); ?>" />
		<div class="view-switch">
<?php
			foreach ( $this->modes as $mode => $title ) {
				$classes = array( 'view-' . $mode );
				if ( $current_mode == $mode )
					$classes[] = 'current';
				printf(
					"<a href='%s' class='%s' id='view-switch-$mode'><span class='screen-reader-text'>%s</span></a>\n",
					esc_url( add_query_arg( 'mode', $mode ) ),
					implode( ' ', $classes ),
					$title
				);
			}
		?>
		</div>
<?php
	}

	/**
	 * Display a comment count bubble
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param int $post_id          The post ID.
	 * @param int $pending_comments Number of pending comments.
	 */
	protected function comments_bubble( $post_id, $pending_comments ) {
		$pending_phrase = sprintf( __( '%s pending' ), number_format( $pending_comments ) );

		if ( $pending_comments )
			echo '<strong>';

		echo "<a href='" . esc_url( add_query_arg( 'p', $post_id, admin_url( 'edit-comments.php' ) ) ) . "' title='" . esc_attr( $pending_phrase ) . "' class='post-com-count'><span class='comment-count'>" . number_format_i18n( get_comments_number() ) . "</span></a>";

		if ( $pending_comments )
			echo '</strong>';
	}

	/**
	 * Get the current page number
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @return int
	 */
	public function get_pagenum() {
		$pagenum = isset( $_REQUEST['paged'] ) ? absint( $_REQUEST['paged'] ) : 0;

		if( isset( $this->_pagination_args['total_pages'] ) && $pagenum > $this->_pagination_args['total_pages'] )
			$pagenum = $this->_pagination_args['total_pages'];

		return max( 1, $pagenum );
	}

	/**
	 * Get number of items to display on a single page
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param string $option
	 * @param int    $default
	 * @return int
	 */
	protected function get_items_per_page( $option, $default = 20 ) {
		$per_page = (int) get_user_option( $option );
		if ( empty( $per_page ) || $per_page < 1 )
			$per_page = $default;

		/**
		 * Filter the number of items to be displayed on each page of the list table.
		 *
		 * The dynamic hook name, $option, refers to the `per_page` option depending
		 * on the type of list table in use. Possible values include: 'edit_comments_per_page',
		 * 'sites_network_per_page', 'site_themes_network_per_page', 'themes_network_per_page',
		 * 'users_network_per_page', 'edit_post_per_page', 'edit_page_per_page',
		 * 'edit_{$post_type}_per_page', etc.
		 *
		 * @since 2.9.0
		 *
		 * @param int $per_page Number of items to be displayed. Default 20.
		 */
		return (int) apply_filters( $option, $per_page );
	}

	/**
	 * Display the pagination.
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param string $which
	 */
	protected function pagination( $which ) {
		if ( empty( $this->_pagination_args ) ) {
			return;
		}

		$total_items = $this->_pagination_args['total_items'];
		$total_pages = $this->_pagination_args['total_pages'];
		$infinite_scroll = false;
		if ( isset( $this->_pagination_args['infinite_scroll'] ) ) {
			$infinite_scroll = $this->_pagination_args['infinite_scroll'];
		}

		$output = '<span class="displaying-num">' . sprintf( _n( '%s item', '%s items', $total_items ), number_format_i18n( $total_items ) ) . '</span>';

		$current = $this->get_pagenum();

		$current_url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] );

		$current_url = remove_query_arg( array( 'hotkeys_highlight_last', 'hotkeys_highlight_first' ), $current_url );

		$page_links = array();

		$disable_first = $disable_last = '';
		if ( $current == 1 ) {
			$disable_first = ' disabled';
		}
		if ( $current == $total_pages ) {
			$disable_last = ' disabled';
		}
		$page_links[] = sprintf( "<a class='%s' title='%s' href='%s'>%s</a>",
			'first-page' . $disable_first,
			esc_attr__( 'Go to the first page' ),
			esc_url( remove_query_arg( 'paged', $current_url ) ),
			'&laquo;'
		);

		$page_links[] = sprintf( "<a class='%s' title='%s' href='%s'>%s</a>",
			'prev-page' . $disable_first,
			esc_attr__( 'Go to the previous page' ),
			esc_url( add_query_arg( 'paged', max( 1, $current-1 ), $current_url ) ),
			'&lsaquo;'
		);

		if ( 'bottom' == $which ) {
			$html_current_page = $current;
		} else {
			$html_current_page = sprintf( "%s<input class='current-page' id='current-page-selector' title='%s' type='text' name='paged' value='%s' size='%d' />",
				'<label for="current-page-selector" class="screen-reader-text">' . __( 'Select Page' ) . '</label>',
				esc_attr__( 'Current page' ),
				$current,
				strlen( $total_pages )
			);
		}
		$html_total_pages = sprintf( "<span class='total-pages'>%s</span>", number_format_i18n( $total_pages ) );
		$page_links[] = '<span class="paging-input">' . sprintf( _x( '%1$s of %2$s', 'paging' ), $html_current_page, $html_total_pages ) . '</span>';

		$page_links[] = sprintf( "<a class='%s' title='%s' href='%s'>%s</a>",
			'next-page' . $disable_last,
			esc_attr__( 'Go to the next page' ),
			esc_url( add_query_arg( 'paged', min( $total_pages, $current+1 ), $current_url ) ),
			'&rsaquo;'
		);

		$page_links[] = sprintf( "<a class='%s' title='%s' href='%s'>%s</a>",
			'last-page' . $disable_last,
			esc_attr__( 'Go to the last page' ),
			esc_url( add_query_arg( 'paged', $total_pages, $current_url ) ),
			'&raquo;'
		);

		$pagination_links_class = 'pagination-links';
		if ( ! empty( $infinite_scroll ) ) {
			$pagination_links_class = ' hide-if-js';
		}
		$output .= "\n<span class='$pagination_links_class'>" . join( "\n", $page_links ) . '</span>';

		if ( $total_pages ) {
			$page_class = $total_pages < 2 ? ' one-page' : '';
		} else {
			$page_class = ' no-pages';
		}
		$this->_pagination = "<div class='tablenav-pages{$page_class}'>$output</div>";

		echo $this->_pagination;
	}

	/**
	 * Get a list of columns. The format is:
	 * 'internal-name' => 'Title'
	 *
	 * @since 3.1.0
	 * @access public
	 * @abstract
	 *
	 * @return array
	 */
	public function get_columns() {
		die( 'function WP_List_Table::get_columns() must be over-ridden in a sub-class.' );
	}

	/**
	 * Get a list of sortable columns. The format is:
	 * 'internal-name' => 'orderby'
	 * or
	 * 'internal-name' => array( 'orderby', true )
	 *
	 * The second format will make the initial sorting order be descending
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @return array
	 */
	protected function get_sortable_columns() {
		return array();
	}

	/**
	 * Get name of default primary column
	 *
	 * @since 4.3.0
	 * @access protected
	 *
	 * @return string
	 */
	protected function get_default_primary_column_name() {
		return '';
	}

	/**
	 * Get name of primary column.
	 *
	 * @since 4.3.0
	 * @access protected
	 *
	 * @return string Filtered name of primary column
	 */
	protected function get_primary_column_name() {
		$columns = $this->get_columns();
		$default = $this->get_default_primary_column_name();
		/**
		 * Filter the name of the primary column for the current list table, with context as argument (eg: 'plugins').
		 *
		 * @since 4.3.0
		 *
		 * @param string $default Column name default for the specific list table (eg: 'name')
		 * @param string $context Screen ID for specific list table (eg: 'plugins')
		 */
		$column  = apply_filters( 'list_table_primary_column', $default, $this->screen->id );

		if ( empty( $column ) || ! isset( $columns[ $column ] ) ) {
			$column = $default;
		}

		return $column;
	}

	/**
	 * Get a list of all, hidden and sortable columns, with filter applied
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @return array
	 */
	protected function get_column_info() {
		if ( isset( $this->_column_headers ) )
			return $this->_column_headers;

		$columns = get_column_headers( $this->screen );
		$hidden = get_hidden_columns( $this->screen );

		$sortable_columns = $this->get_sortable_columns();
		/**
		 * Filter the list table sortable columns for a specific screen.
		 *
		 * The dynamic portion of the hook name, `$this->screen->id`, refers
		 * to the ID of the current screen, usually a string.
		 *
		 * @since 3.5.0
		 *
		 * @param array $sortable_columns An array of sortable columns.
		 */
		$_sortable = apply_filters( "manage_{$this->screen->id}_sortable_columns", $sortable_columns );

		$sortable = array();
		foreach ( $_sortable as $id => $data ) {
			if ( empty( $data ) )
				continue;

			$data = (array) $data;
			if ( !isset( $data[1] ) )
				$data[1] = false;

			$sortable[$id] = $data;
		}

		$primary = $this->get_primary_column_name();
		$this->_column_headers = array( $columns, $hidden, $sortable, $primary );

		return $this->_column_headers;
	}

	/**
	 * Return number of visible columns
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @return int
	 */
	public function get_column_count() {
		list ( $columns, $hidden ) = $this->get_column_info();
		$hidden = array_intersect( array_keys( $columns ), array_filter( $hidden ) );
		return count( $columns ) - count( $hidden );
	}

	/**
	 * Print column headers, accounting for hidden and sortable columns.
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @staticvar int $cb_counter
	 *
	 * @param bool $with_id Whether to set the id attribute or not
	 */
	public function print_column_headers( $with_id = true ) {
		list( $columns, $hidden, $sortable ) = $this->get_column_info();

		$current_url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] );
		$current_url = remove_query_arg( 'paged', $current_url );

		if ( isset( $_GET['orderby'] ) )
			$current_orderby = $_GET['orderby'];
		else
			$current_orderby = '';

		if ( isset( $_GET['order'] ) && 'desc' == $_GET['order'] )
			$current_order = 'desc';
		else
			$current_order = 'asc';

		if ( ! empty( $columns['cb'] ) ) {
			static $cb_counter = 1;
			$columns['cb'] = '<label class="screen-reader-text" for="cb-select-all-' . $cb_counter . '">' . __( 'Select All' ) . '</label>'
				. '<input id="cb-select-all-' . $cb_counter . '" type="checkbox" />';
			$cb_counter++;
		}

		foreach ( $columns as $column_key => $column_display_name ) {
			$class = array( 'manage-column', "column-$column_key" );

			$style = '';
			if ( in_array( $column_key, $hidden ) )
				$style = 'display:none;';

			$style = ' style="' . $style . '"';

			if ( 'cb' == $column_key )
				$class[] = 'check-column';
			elseif ( in_array( $column_key, array( 'posts', 'comments', 'links' ) ) )
				$class[] = 'num';

			if ( isset( $sortable[$column_key] ) ) {
				list( $orderby, $desc_first ) = $sortable[$column_key];

				if ( $current_orderby == $orderby ) {
					$order = 'asc' == $current_order ? 'desc' : 'asc';
					$class[] = 'sorted';
					$class[] = $current_order;
				} else {
					$order = $desc_first ? 'desc' : 'asc';
					$class[] = 'sortable';
					$class[] = $desc_first ? 'asc' : 'desc';
				}

				$column_display_name = '<a href="' . esc_url( add_query_arg( compact( 'orderby', 'order' ), $current_url ) ) . '"><span>' . $column_display_name . '</span><span class="sorting-indicator"></span></a>';
			}

			$id = $with_id ? "id='$column_key'" : '';

			if ( !empty( $class ) )
				$class = "class='" . join( ' ', $class ) . "'";

			echo "<th scope='col' $id $class $style>$column_display_name</th>";
		}
	}

	/**
	 * Display the table
	 *
	 * @since 3.1.0
	 * @access public
	 */
	public function display() {
		$singular = $this->_args['singular'];

		$this->display_tablenav( 'top' );

?>
<table class="wp-list-table <?php echo implode( ' ', $this->get_table_classes() ); ?>">
	<thead>
	<tr>
		<?php $this->print_column_headers(); ?>
	</tr>
	</thead>

	<tbody id="the-list"<?php
		if ( $singular ) {
			echo " data-wp-lists='list:$singular'";
		} ?>>
		<?php $this->display_rows_or_placeholder(); ?>
	</tbody>

	<tfoot>
	<tr>
		<?php $this->print_column_headers( false ); ?>
	</tr>
	</tfoot>

</table>
<?php
		$this->display_tablenav( 'bottom' );
	}

	/**
	 * Get a list of CSS classes for the list table table tag.
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @return array List of CSS classes for the table tag.
	 */
	protected function get_table_classes() {
		return array( 'widefat', 'fixed', 'striped', $this->_args['plural'] );
	}

	/**
	 * Generate the table navigation above or below the table
	 *
	 * @since 3.1.0
	 * @access protected
	 * @param string $which
	 */
	protected function display_tablenav( $which ) {
		if ( 'top' == $which )
			wp_nonce_field( 'bulk-' . $this->_args['plural'] );
?>
	<div class="tablenav <?php echo esc_attr( $which ); ?>">

		<div class="alignleft actions bulkactions">
			<?php $this->bulk_actions( $which ); ?>
		</div>
<?php
		$this->extra_tablenav( $which );
		$this->pagination( $which );
?>

		<br class="clear" />
	</div>
<?php
	}

	/**
	 * Extra controls to be displayed between bulk actions and pagination
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param string $which
	 */
	protected function extra_tablenav( $which ) {}

	/**
	 * Generate the tbody element for the list table.
	 *
	 * @since 3.1.0
	 * @access public
	 */
	public function display_rows_or_placeholder() {
		if ( $this->has_items() ) {
			$this->display_rows();
		} else {
			echo '<tr class="no-items"><td class="colspanchange" colspan="' . $this->get_column_count() . '">';
			$this->no_items();
			echo '</td></tr>';
		}
	}

	/**
	 * Generate the table rows
	 *
	 * @since 3.1.0
	 * @access public
	 */
	public function display_rows() {
		foreach ( $this->items as $item )
			$this->single_row( $item );
	}

	/**
	 * Generates content for a single row of the table
	 *
	 * @since 3.1.0
	 * @access public
	 *
	 * @param object $item The current item
	 */
	public function single_row( $item ) {
		echo '<tr>';
		$this->single_row_columns( $item );
		echo '</tr>';
	}

	protected function column_default( $item, $column_name ) {}

	protected function column_cb( $item ) {}

	/**
	 * Generates the columns for a single row of the table
	 *
	 * @since 3.1.0
	 * @access protected
	 *
	 * @param object $item The current item
	 */
	protected function single_row_columns( $item ) {
		list( $columns, $hidden, $sortable, $primary ) = $this->get_column_info();

		foreach ( $columns as $column_name => $column_display_name ) {
			$classes = "$column_name column-$column_name";
			if ( $primary === $column_name ) {
				$classes .= ' has-row-actions column-primary';
			}

			$style = '';
			if ( in_array( $column_name, $hidden ) ) {
				$style = ' style="display:none;"';
			}

			$attributes = "class='$classes'$style";

			if ( 'cb' == $column_name ) {
				echo '<th scope="row" class="check-column">';
				echo $this->column_cb( $item );
				echo '</th>';
			}
			elseif ( method_exists( $this, 'column_' . $column_name ) ) {
				echo "<td $attributes>";
				echo call_user_func( array( $this, 'column_' . $column_name ), $item );
				echo $this->handle_row_actions( $item, $column_name, $primary );
				echo "</td>";
			}
			else {
				echo "<td $attributes>";
				echo $this->column_default( $item, $column_name );
				echo $this->handle_row_actions( $item, $column_name, $primary );
				echo "</td>";
			}
		}
	}

	/**
	 * Generate and display row actions links
	 *
	 * @since 4.3.0
	 * @access protected
	 *
	 * @param object $item Item being acted upon
	 * @param string $column_name Current column name
	 * @param string $primary Primary column name
	 *
	 * @return string
	 */
	protected function handle_row_actions( $item, $column_name, $primary ) {
		return '';
 	}

	/**
	 * Handle an incoming ajax request (called from admin-ajax.php)
	 *
	 * @since 3.1.0
	 * @access public
	 */
	public function ajax_response() {
		$this->prepare_items();

		ob_start();
		if ( ! empty( $_REQUEST['no_placeholder'] ) ) {
			$this->display_rows();
		} else {
			$this->display_rows_or_placeholder();
		}

		$rows = ob_get_clean();

		$response = array( 'rows' => $rows );

		if ( isset( $this->_pagination_args['total_items'] ) ) {
			$response['total_items_i18n'] = sprintf(
				_n( '%s item', '%s items', $this->_pagination_args['total_items'] ),
				number_format_i18n( $this->_pagination_args['total_items'] )
			);
		}
		if ( isset( $this->_pagination_args['total_pages'] ) ) {
			$response['total_pages'] = $this->_pagination_args['total_pages'];
			$response['total_pages_i18n'] = number_format_i18n( $this->_pagination_args['total_pages'] );
		}

		die( wp_json_encode( $response ) );
	}

	/**
	 * Send required variables to JavaScript land
	 *
	 * @access public
	 */
	public function _js_vars() {
		$args = array(
			'class'  => get_class( $this ),
			'screen' => array(
				'id'   => $this->screen->id,
				'base' => $this->screen->base,
			)
		);

		printf( "<script type='text/javascript'>list_args = %s;</script>\n", wp_json_encode( $args ) );
	}
}