<?php
/**
 * The new contextual help API helper.
 *
 * Example usage:
 * <code>
 * $help = new WpmuDev_ContextualHelper();
 * $help->add_page(
 *		'dashboard',
 *		array(
 *			array(
 *				'id' => 'myid',
 *				'title' => __('My title', 'textdomain'),
 *				'content' => '<p>' . __('My content lalala', 'textdomain') . '</p>',
 *			),
 *		),
 * 		'<p>My awesome sidebar!</p>',
 *		false // Don't clear existing items.
 *	);
 * $help->initialize();
 * </code>
 */

if ( ! class_exists( 'WpmuDev_ContextualHelp' ) ) {

	class WpmuDev_ContextualHelp {

		private $_pages = array();

		private $_auto_clear_wp_help = false;

		public function __construct() {}

		/**
		 * Add an array of tabs to a certain page.
		 *
		 * @param string $screen_id Screen ID to which to bind the help. Can be obtained by something like <code>$screen = get_current_screen(); $screen_id = @$screen->id;</code>
		 * @param array $tabs (optional) Array of tabs to add. Each tab is an associative array, with these keys: id, title, content.
		 * @param string $sidebar (optional) HTML string to be displayed as contextual help sidebar.
		 * @param bool $clear (optional) Clear the existing contextual help content for this page before the new tabs.
		 */
		public function add_page( $screen_id, $tabs = array(), $sidebar = '', $clear = false ) {
			if ( ! is_array( $tabs ) ) { return false; }
			$this->_pages[ $screen_id ] = array(
				'tabs' => $tabs,
				'sidebar' => $sidebar,
				'clear' => $clear,
			);
		}

		/**
		 * Removes a page from instance queue.
		 *
		 * @param string $screen_id Screen ID to clear.
		 */
		public function remove_page( $screen_id ) {
			@$this->_pages[ $screen_id ] = array();
		}

		/**
		 * Adds a contextual tab to be displayed on a page.
		 *
		 * @param string $screen_id Screen ID to which to bind the tab.
		 * @param array $tab An associative array representing a tab.
		 */
		public function add_tab( $screen_id, $tab = array() ) {
			if ( ! is_array( $tab ) ) { return false; }
			$this->_pages[] = isset( $this->_pages[ $screen_id ] ) ? $this->_pages[ $screen_id ] : array();
			@$this->_pages[ $screen_id ]['tabs'][] = $tab;
		}

		/**
		 * Removes a tab from instance queue.
		 *
		 * @param string $screen_id Screen ID to which to bind the tab.
		 * @param string $tab_id The value of "id" key of tab to be removed.
		 */
		public function remove_tab( $screen_id, $tab_id ) {
			if ( ! $tab_id ) { return false; }

			$tabs = @$this->_pages[ $screen_id ]['tabs'];
			if ( ! $tabs ) { return false; }

			$tmp = array();
			foreach ( $tabs as $tab ) {
				if ( @$tab['id'] == $tmp_id ) { continue; }
				$tmp[] = $tab;
			}
			$this->_pages[ $screen_id ]['tabs'] = $tmp;
		}

		/**
		 * Set up automatic clearing of existing help
		 * prior to adding queued help content.
		 */
		public function clear_wp_help() {
			$this->_auto_clear_wp_help = true;
		}

		/**
		 * Sets up queued items as contextual help.
		 */
		public function initialize() {
			$this->_add_hooks();
		}


		private function _add_hooks() {
			global $wp_version;
			$version = preg_replace( '/-.*$/', '', $wp_version );

			if ( version_compare( $version, '3.3', '>=' ) ) {
				add_action( 'admin_head', array( $this, 'add_contextual_help' ), 999 );
			} else {
				add_filter( 'contextual_help', array( $this, 'add_compatibility_contextual_help' ), 1, 1 );
			}
		}

		/**
		 * Hook hander.
		 * No need to be called manually.
		 */
		public function add_contextual_help() {
			$screen = get_current_screen();
			if ( ! is_object( $screen ) ) { return false; }

			if ( ! isset( $this->_pages['_global_'] ) ) {
				$screen_id = @$screen->id;
				if ( ! @$this->_pages[ $screen_id ] || ! @$this->_pages[ $screen_id ]['tabs'] ) { return false; }
				$info = $this->_pages[ $screen_id ];
			} else {
				$info = $this->_pages['_global_'];
			}

			$clear = (@$info['clear'] || $this->_auto_clear_wp_help);
			if ( $clear ) { $screen->remove_help_tabs(); }

			$screen->set_help_sidebar( @$info['sidebar'] );

			foreach ( $info['tabs'] as $tab ) {
				$screen->add_help_tab( $tab );
			}
		}

		/**
		 * Compatibility layer for pre-3.3 installs.
		 */
		public function add_compatibility_contextual_help( $help ) {
			if ( ! isset( $this->_pages['_global_'] ) ) {
				$screen = get_current_screen();
				if ( ! is_object( $screen ) ) { return $help; }

				$screen_id = @$screen->id;
				if ( ! @$this->_pages[ $screen_id ] || ! @$this->_pages[ $screen_id ]['tabs'] ) { return $help; }
				$info = $this->_pages[ $screen_id ];
			} else {
				$info = $this->_pages['_global_'];
			}

			$clear = (@$info['clear'] || $this->_auto_clear_wp_help);
			if ( $clear ) { $help = ''; }

			foreach ( $info['tabs'] as $tab ) {
				$help .= '<h3>' . $tab['title'] . '</h3>' . $tab['content'];
			}

			return $help;
		}
	}

}