<?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;
		}
	}

}