<?php
/**
 * The public-facing functionality of the plugin.
 *
 * @link       http://pixelative.co
 * @since      1.0.0
 *
 * @package    Amp_WP
 * @subpackage Amp_WP/public
 */

/**
 * The public-facing functionality of the plugin.
 *
 * Defines the plugin name, version, and two examples hooks for how to
 * enqueue the public-facing stylesheet and JavaScript.
 *
 * @package    Amp_WP
 * @subpackage Amp_WP/public
 * @author     Pixelative <mohsin@pixelative.co>
 */
class Amp_WP_Public {

	/**
	 * The ID of this plugin.
	 *
	 * @since    1.0.0
	 * @access   private
	 * @var      string    $plugin_name    The ID of this plugin.
	 */
	private $plugin_name;

	/**
	 * The version of this plugin.
	 *
	 * @since    1.0.0
	 * @access   private
	 * @var      string    $version    The current version of this plugin.
	 */
	private $version;
	
	/**
	 * Default endpoint for AMP URL of site.
	 * this cna can overridden by filter
	 *
	 * @since 1.0.4
	 */
	const SLUG = 'amp';

	/**
	 * Default Endpoint for AMP URL of Site.
	 * This cna Can Be Overridden by Filter
	 * 
	 * @var      string
	 * 
	 * @since   1.0.0
	 * 
	 */
	const AMP_WP_STARTPOINT = self::SLUG;

	/**
	 * pre_get_posts hook priority
	 *
	 * @var      int
	 * 
	 * @since   1.0.0
	 */
	const AMP_WP_ISOLATE_QUERY_HOOK_PRIORITY = 100;

	/**
	 * Store amp_wp_head action callbacks
	 *
	 * @see amp_wp_collect_and_remove_head_actions
	 * 
	 * @var     array
	 *
	 * @since   1.0.0
	 */
	private $head_actions;

	/**
	 * Store Array of Posts Id to Exlucde Transform Permalinks to Amp
	 *
	 * Array structure: array {
	 *      'post id' => dont care,
	 *      ...
	 * }
	 *
	 * @see amp_wp_transform_post_link_to_amp
	 *
	 * @var     array
	 * 
	 * @since   1.0.0
	 */
	public $excluded_posts_id = array();

	/**
	 * Initialize the class and set its properties.
	 *
	 * @param   string  $plugin_name    The name of the plugin.
	 * @param   string  $version        The version of this plugin.
	 * @since   1.0.0
	 * 
	 */
	public function __construct($plugin_name, $version) {

		$this->plugin_name = $plugin_name;
		$this->version = $version;

		// Registers the AMP Rewrite Rules
		add_filter('init', array($this, 'amp_wp_add_rewrite'));
		add_filter('init', array($this, 'amp_wp_append_index_rewrite_rule'));

		// Check Plugin Compatibility
		add_filter('template_redirect', array($this, 'amp_wp_plugins_compatibility'));

		// Initialize AMP Components
		add_filter('init', array($this, 'amp_wp_include_components'));

		// Changes Page Template File With AMP Template File
		add_action('template_include', array($this, 'amp_wp_include_template_file'), 9999);

		// Override Template File
		add_filter('comments_template', array($this, 'amp_wp_override_comments_template'), 9999);

		// Initialize AMP Theme and It’s Functionality
		add_action('after_setup_theme', array($this, 'amp_wp_template_functions'), 1);

		// Replace All Links Inside Contents to AMP Version.
		// Stops User to Go Outside of AMP Version.
		add_action('wp', array($this, 'amp_wp_replace_internal_links_with_amp_version'));

		// Registers All Components Scripts Into the Header Style and Scripts
		add_action('amp_wp_template_enqueue_scripts', array($this, 'amp_wp_enqueue_components_scripts'));

		// Let the Components to Do Their Functionality in Head
		add_action('amp_wp_template_head', array($this, 'amp_wp_trigger_component_head'), 0);

		// Collect All Output to Can Enqueue Only Needed Scripts and Styles in Pages.
		add_action('amp_wp_template_head', array($this, 'amp_wp_buffer_head_start'), 1);
		add_action('amp_wp_template_footer', array($this, 'amp_wp_buffer_head_end'), 999);

		// Collect and Rollback All Main Query Posts to Disable Thirdparty Codes to Change Main Query!
		// Action After 1000 Priority Can Work
		add_action( 'pre_get_posts', array( $this, 'amp_wp_isolate_pre_get_posts_start'), 1);
		add_action( 'pre_get_posts', array( $this, 'amp_wp_isolate_pre_get_posts_end'), self::AMP_WP_ISOLATE_QUERY_HOOK_PRIORITY);

		add_action('template_redirect', array($this, 'amp_wp_redirect_endpoint_url'));
		add_filter('redirect_canonical', array($this, 'amp_wp_fix_prevent_extra_redirect_single_pagination'));

		add_action('request', array($this, 'amp_wp_fix_search_page_queries'));
		add_filter('request', array($this, 'amp_wp_force_query_var_value'));
		add_action('parse_query', array($this, 'amp_wp_correct_query_when_is_front_page'));

		// Auto Redirect Mobile Users
		add_action('template_redirect', array($this, 'amp_wp_auto_redirect_to_amp'), 1);

		// Init AMP WP JSON-LD
		add_action('template_redirect', 'Amp_WP_Public::amp_wp_init_json_ld', 1);

		$this->amp_wp_fix_front_page_display_options();
	}

	/**
	 * Register the stylesheets for the admin area.
	 *
	 * @since    1.0.0
	 */
	public function enqueue_styles() {
		
	}

	/**
	 * Register the JavaScript for the admin area.
	 *
	 * @since    1.0.0
	 */
	public function enqueue_scripts() {
		
	}

	/**
	 * Callback: Add rewrite rules
	 * Action: init
	 *
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_add_rewrite() {
		amp_wp_add_rewrite_startpoint(self::AMP_WP_STARTPOINT, EP_ALL);

		/**
		 * "Automattic AMP" Plugin Compatibility
		 */
		$amp_qv = defined('AMP_WP_QUERY_VAR') ? AMP_WP_QUERY_VAR : 'amp';
		add_rewrite_endpoint($amp_qv, EP_PERMALINK);
	}

	/**
	 * Add a Rewrite Rule to Detect site.com/amp/ Requests
	 *
	 * @version 1.0.0
	 * @since   1.0.0
	 *
	 * @return  array
	 */
	public function amp_wp_append_index_rewrite_rule() {
		add_rewrite_rule(self::AMP_WP_STARTPOINT . '/?$', "index.php?amp=index", 'top');
	}

	/**
	 * Change most popular cache plugins in amp version to compatible with it
	 *
	 * @since 1.0.0
	 */
	public function amp_wp_plugins_compatibility() {
		if (!is_amp_wp()) {
			return;
		}

		/**
		 * W3 total cache
		 */
		add_filter('w3tc_minify_js_enable', '__return_false');
		add_filter('w3tc_minify_css_enable', '__return_false');

		/**
		 * WP Rocket
		 */
		if (defined('WP_ROCKET_VERSION')) {
			if (!defined('DONOTMINIFYCSS')) {
				define('DONOTMINIFYCSS', true);
			}

			if (!defined('DONOTMINIFYJS')) {
				define('DONOTMINIFYJS', true);
			}

			// Disable WP Rocket lazy load
			add_filter('do_rocket_lazyload', '__return_false', PHP_INT_MAX);
			add_filter('do_rocket_lazyload_iframes', '__return_false', PHP_INT_MAX);

			// Disable HTTP protocol removing on script, link, img, srcset and form tags.
			remove_filter('rocket_buffer', '__rocket_protocol_rewrite', PHP_INT_MAX);
			remove_filter('wp_calculate_image_srcset', '__rocket_protocol_rewrite_srcset', PHP_INT_MAX);

			// Disable Concatenate Google Fonts
			add_filter('get_rocket_option_minify_google_fonts', '__return_false', PHP_INT_MAX);

			// Disable CSS & JS magnification
			add_filter('get_rocket_option_minify_js', '__return_false', PHP_INT_MAX);
			add_filter('get_rocket_option_minify_css', '__return_false', PHP_INT_MAX);
		}

		/**
		 * WP Speed of Light
		 *
		 * https://wordpress.org/plugins-wp/wp-speed-of-light/
		 */
		if (defined('WPSOL_VERSION')) {
			add_filter('wpsol_filter_js_noptimize', '__return_true', PHP_INT_MAX);
			add_filter('wpsol_filter_css_noptimize', '__return_true', PHP_INT_MAX);
		}

		/**
		 * Lazy Load
		 * https://wordpress.org/plugins/lazy-load/
		 */
		if (class_exists('LazyLoad_Images')) {
			add_filter('lazyload_is_enabled', '__return_false', PHP_INT_MAX);
		}

		/**
		 * Lazy Load XT
		 * https://wordpress.org/plugins/lazy-load-xt/
		 */
		if (class_exists('Image_Lazy_Load')) {
			global $lazyloadxt;
			if (is_object($lazyloadxt)) {
				remove_filter('the_content', array($lazyloadxt, 'filter_html'));
				remove_filter('widget_text', array($lazyloadxt, 'filter_html'));
				remove_filter('post_thumbnail_html', array($lazyloadxt, 'filter_html'));
				remove_filter('get_avatar', array($lazyloadxt, 'filter_html'));
			}
		}

		/*		 * *
		 * Facebook Comments Plugin
		 * https://wordpress.org/plugins/facebook-comments-plugin/
		 */
		if (function_exists('fbcommentshortcode')) {
			remove_action('wp_footer', 'fbmlsetup', 100);
			remove_filter('the_content', 'fbcommentbox', 100);
			remove_filter('widget_text', 'do_shortcode');
		}

		/*		 * *
		 * Yoast SEO
		 * https://wordpress.org/plugins/wordpress-seo/
		 */
		if (defined('WPSEO_VERSION')) {
			if (class_exists('WPSEO_OpenGraph')) {
				add_action('amp_wp_template_head', array($this, 'amp_wp_yoast_seo_metatags_compatibility'));
			}

			if (is_home() && !amp_wp_is_static_home_page() && self::amp_wp_get_option('show_on_front') === 'page') {
				add_filter('pre_get_document_title', 'Amp_WP_Public::amp_wp_yoast_seo_homepage_title', 99);
			}

			if (is_home()) {
				add_filter('amp_wp_json_ld_website', 'Amp_WP_Public::amp_wp_yoast_seo_homepage_json_ld');
			}
		}

		/*		 * *
		 * Ultimate Tweaker
		 * https://ultimate-tweaker.com/
		 */
		if (class_exists('ultimate_tweaker_Plugin_File') && defined('UT_VERSION')) {
			amp_wp_remove_class_filter('post_thumbnail_html', 'OT_media_image_no_width_height_Tweak', '_do', 10);
			amp_wp_remove_class_filter('image_send_to_editor', 'OT_media_image_no_width_height_Tweak', '_do', 10);
		}

		/**
		 * WPO Tweaks
		 *
		 * https://servicios.ayudawp.com/
		 */
		if (function_exists('wpo_tweaks_init')) {
			remove_filter('script_loader_tag', 'wpo_defer_parsing_of_js');
		}
	}

	/**
	 * Include Active Template functions.php File If Exits
	 *
	 * Callback: include
	 * action: after_setup_theme
	 *
	 * @since   1.0.0
	 */
	public function amp_wp_template_functions() {
		if (file_exists(AMPWP_TEMPLATE_DIR_PATH . 'includes/functions/amp-wp-template-functions.php')) {
			require_once AMPWP_TEMPLATE_DIR_PATH . 'includes/functions/amp-wp-template-functions.php';
		}
	}

	/**
	 * Callback: Include registered AMP components
	 * Action: init
	 *
	 * @since 1.0.0
	 */
	public function amp_wp_include_components() {
		include AMPWP_TEMPLATE_DIR_PATH . 'includes/components/class-amp-wp-img-component.php';
		include AMPWP_TEMPLATE_DIR_PATH . 'includes/components/class-amp-wp-iframe-component.php';
		include AMPWP_TEMPLATE_DIR_PATH . 'includes/components/class-amp-wp-carousel-component.php';
	}

	/**
	 * Callback: Include AMP template file in AMP pages
	 * Action: template_include
	 *
	 * @param   string $template_file_path Original Template File Path
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 *
	 * @return  string
	 */
	public function amp_wp_include_template_file($template_file_path) {
		if( !is_amp_wp() ) {
			return $template_file_path;
		}

		$include = $this->amp_wp_template_loader();
		if ($include) {
			return $include;
		}
	}

	/**
	 * Load a Template
	 *
	 * Handles Template Usage so That We Can Use Our Own Templates Instead of the Themes
	 *
	 * Templates are in the 'templates' folder. amp-wp looks for theme.
	 * overrides in /yourtheme/amp-wp/ by default.
	 *
	 * @see Template Hierarchy Reference https://developer.wordpress.org/files/2014/10/wp-hierarchy.png
	 * @param   mixed   $template
	 * @return  string
	 */
	public function amp_wp_template_loader() {
		if (amp_wp_is_static_home_page()) {
			$template = amp_wp_static_home_page_template();
			$this->amp_wp_set_page_query(apply_filters('amp_wp_template_page_on_front', 0));
		} elseif (is_home()) {
			$template = amp_wp_home_template();
		} elseif (is_post_type_archive()) {
			$template = amp_wp_archive_post_type_template();
		} elseif (is_archive()) {
			$template = amp_wp_archive_template();
		} elseif (is_attachment()) {
			$template = amp_wp_attachment_template();
			remove_filter('the_content', 'prepend_attachment');
		} elseif (is_single()) {
			$template = amp_wp_single_template();
		} elseif (is_page()) {
			$template = amp_wp_page_template();
		} elseif (is_404()) {
			$template = amp_wp_404_template();
		} elseif (is_search()) {
			$template = amp_wp_search_template();
		} elseif (is_embed()) {
			return $template;
		} else {
			$template = amp_wp_index_template();
		}
		return $template;
	}

	/**
	 * Replace amp comment file with theme file
	 *
	 * @param string $file
	 *
	 * @since 1.0.0
	 * @return string
	 */
	public function amp_wp_override_comments_template($file) {
		if (is_amp_wp()) {
			if ($path = amp_wp_locate_template(basename($file))) {
				return $path;
			}
		}
		return $file;
	}

	/**
	 * Replaces All Website Internal Links With AMP Version
	 *
	 * @hooked wp
	 *
	 * @param WP $wp
	 *
	 * @since  1.0.0
	 * @return string
	 */
	public function amp_wp_replace_internal_links_with_amp_version($wp) {
		if (empty($wp->query_vars['amp'])) {
			return;
		}

		add_filter('nav_menu_link_attributes', array('Amp_WP_Content_Sanitizer', 'replace_href_with_amp'));
		add_filter('the_content', array('Amp_WP_Content_Sanitizer', 'transform_all_links_to_amp'));

		add_filter('author_link', array('Amp_WP_Content_Sanitizer', 'transform_to_amp_url'));
		add_filter('term_link', array('Amp_WP_Content_Sanitizer', 'transform_to_amp_url'));

		add_filter('post_link', array($this, 'amp_wp_transform_post_link_to_amp'), 20, 2);
		add_filter('page_link', array($this, 'amp_wp_transform_post_link_to_amp'), 20, 2);
		add_filter('attachment_link', array('Amp_WP_Content_Sanitizer', 'transform_to_amp_url'));
		add_filter('post_type_link', array('Amp_WP_Content_Sanitizer', 'transform_to_amp_url'));
	}

	/**
	 * Transform allowed posts URL to AMP
	 *
	 * @param   string      $url  The Post’s Permalink
	 * @param   WP_Post|int $post The post object/id  of the post.
	 *
	 * @since   1.0.0
	 * @return  string
	 */
	public function amp_wp_transform_post_link_to_amp($url, $post) {
		$post_id = isset($post->ID) ? $post->ID : $post;

		if (isset($this->excluded_posts_id[$post_id])) {
			return $url;
		}
		return Amp_WP_Content_Sanitizer::transform_to_amp_url($url);
	}

	/**
	 * Append AMP Components JavaScript If AMP Version Requested
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_enqueue_components_scripts() {
		$deps = array('ampproject');
		amp_wp_enqueue_script($deps[0], 'https://cdn.ampproject.org/v0.js');

		// Enqueues all needed scripts of components with 'ampproject' dependency
		$this->amp_wp_call_components_method('enqueue_amp_scripts', $deps);

		if (current_theme_supports('amp-wp-navigation') && current_theme_supports('amp-wp-has-nav-child')) {
			amp_wp_enqueue_script('amp-accordion', 'https://cdn.ampproject.org/v0/amp-accordion-0.1.js');
		}
		if (current_theme_supports('amp-wp-form')) {
			amp_wp_enqueue_script('amp-form', 'https://cdn.ampproject.org/v0/amp-form-0.1.js');
		}
	}

	/**
	 * Callback: Fire head method of component for following purpose:
	 * 1) Component able to add_filter or add_action if needed
	 * 2) Create fresh instance of each component and cache
	 *
	 * Action:  amp_wp_template_head
	 *
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_trigger_component_head() {
		$this->amp_wp_call_components_method('head');
	}

	/**
	 * Callback: Starts the Collecting Output to Enable Components to Add Style Into Head
	 * Print Theme Completely Then Fire amp_wp_head() Callbacks and Append It Before </head>
	 *
	 * Action:  amp_wp_template_head
	 *
	 * @see     amp_wp_buffer_head_end
	 *
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_buffer_head_start() {
		remove_action(current_action(), array($this, __FUNCTION__), 1);
		$this->amp_wp_collect_and_remove_head_actions();
		ob_start();
	}

	/**
	 * Collect amp_wp_head actions and remove those actions
	 *
	 * @see   amp_wp_head
	 *
	 * @since 1.0.0
	 */
	public function amp_wp_collect_and_remove_head_actions() {
		$actions = &$GLOBALS['wp_filter']['amp_wp_template_head'];
		$this->head_actions = $actions;
		$actions = array();
	}

	/**
	 * Callback: Fire amp_wp_head() and print buffered output
	 * Action:  amp_wp_template_head
	 *
	 * @see amp_wp_buffer_head_start
	 *
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_buffer_head_end() {

		$content = ob_get_clean();
		$prepend = '';

		if (!amp_wp_is_customize_preview()) {
			$prepend .= '</head>';

			/**
			 * Convert Output to Valid AMP HTML
			 */
			$instance = new Amp_WP_Html_Util();
			$instance->loadHTML('<!DOCTYPE html><html><head><meta http-equiv="content-type" content="text/html; charset=utf-8">' . $content . '</body></html>', null, false);

			preg_match('#(<\s*body[^>]*>)#isx', $content, $match);
			$prepend .= isset($match[1]) ? $match[1] : '<body>'; // open body tag

			$this->amp_wp_render_content($instance, true); // Convert HTML top amp html
			// @see Amp_WP_Component::enqueue_amp_tags_script
			$this->amp_wp_call_components_method('enqueue_amp_tags_script', $instance);

			$content = $instance->get_content(true);
			// End convert output to valid amp html
		}

		$GLOBALS['wp_filter']['amp_wp_template_head'] = $this->head_actions;
		$this->head_actions = array();
		do_action('amp_wp_template_head');
		echo $prepend, $content;
	}

	/**
	 * Transforms HTML Content to AMP Content
	 *
	 * todo: Add File Caching
	 *
	 * @param   Amp_WP_Html_Util    $instance
	 * @param   boolean             $sanitize
	 *
	 * @since   1.0.0
	 */
	public function amp_wp_render_content(Amp_WP_Html_Util $instance, $sanitize = false) {
		$this->amp_wp_call_components_method('render', $instance);
		if ($sanitize) {
			$sanitizer = new Amp_WP_Content_Sanitizer($instance);
			$sanitizer->sanitize();
		}
	}

	/**
	 * Fire specific method of all components
	 *
	 * @param string $method_name component method
	 *
	 * @param mixed  $param
	 *
	 * @return mixed
	 * @since 1.0.0
	 *
	 */
	public function amp_wp_call_components_method($method_name, $param = null) {
		global $amp_wp_registered_components;

		if (!$amp_wp_registered_components) {
			return $param;
		}

		// collect and prepare method arguments
		$args = func_get_args();
		$args = array_slice($args, 1);
		if (!isset($args[0])) {
			$args[0] = null;
		}

		// iterate registered components and call method on them
		foreach ($amp_wp_registered_components as $component) {
			$instance = Amp_WP_Component::instance($component['component_class']);
			if ($this->_amp_wp_can_call_component_method($instance, $method_name, $args)) {
				$args[0] = call_user_func_array(array($instance, $method_name), $args);
			}
		}
		return $args[0];
	}

	/**
	 * Determines that method exists and is callable on object instance
	 *
	 * @param   Amp_WP_Component $instance    Live object of Amp_WP_Component
	 * @param   string               $method_name Method of object
	 * @param   array                $args
	 *
	 * @access  private
	 * @since   1.0.0
	 *
	 * @return bool
	 */
	private function _amp_wp_can_call_component_method(&$instance, &$method_name, &$args) {
		$return = is_callable(array($instance, $method_name));
		switch ($method_name) {
			case 'enqueue_amp_scripts':
				$return = $return && $instance->can_enqueue_scripts();
				break;
		}
		return $return;
	}

	/**
	 * Callback: Prevent Third Party Codes to Change the Main Query on AMP Version
	 *
	 * You Can Add Action To 'pre_get_posts' With Priority Grater Than 1000 to Change It.
	 *
	 * Action:  pre_get_posts
	 *
	 * @see     amp_wp_isolate_pre_get_posts_end
	 *
	 * @param   WP_Query    $wp_query
	 * 
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_isolate_pre_get_posts_start($wp_query) {
		global $amp_wp_isolate_pre_get_posts;
		if (is_amp_wp($wp_query) && !is_admin() && $wp_query->is_main_query()) {
			$amp_wp_isolate_pre_get_posts = $wp_query->query_vars;
		}
	}

	/**
	 * Rollback the Main Query Vars.
	 *
	 * @see 'amp_wp_isolate_pre_get_posts_end' for more documentation
	 *
	 * Action:  pre_get_posts
	 * @version 1.0.0
	 * @since   1.0.0
	 *
	 * @param WP_Query $wp_query
	 */
	public function amp_wp_isolate_pre_get_posts_end(&$wp_query) {
		global $amp_wp_isolate_pre_get_posts;
		if (is_amp_wp($wp_query) && !is_admin() && $wp_query->is_main_query()) {
			if ($amp_wp_isolate_pre_get_posts) {
				$wp_query->query_vars = $amp_wp_isolate_pre_get_posts;
				unset($amp_wp_isolate_pre_get_posts);
			}
		}
	}

	/**
	 * Handy fix for changing search query
	 *
	 * @param   mixed $q
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 * @return  mixed
	 */
	public function amp_wp_fix_search_page_queries($q) {
		if (!empty($q['amp']) && !empty($q['s'])) {
			$q['post_type'] = array('post');
		}
		return $q;
	}

	/**
	 * Make sure the `amp` query var has an explicit value.
	 * 
	 * @param   int     $query_vars
	 * @since   1.0.0
	 * 
	 * @return  int
	 */
	public function amp_wp_force_query_var_value($query_vars) {
		if (isset($query_vars[self::AMP_WP_STARTPOINT]) && '' === $query_vars[self::AMP_WP_STARTPOINT]) {
			$query_vars[self::AMP_WP_STARTPOINT] = 1;
		}
		return $query_vars;
	}

	/**
	 * Fix up WP_Query for front page when amp query var is present.
	 *
	 * Normally the front page would not get served if a query var is present other than preview, page, paged, and cpage.
	 *
	 * @since 1.0.0
	 * @see WP_Query::parse_query()
	 * @link https://github.com/WordPress/wordpress-develop/blob/0baa8ae85c670d338e78e408f8d6e301c6410c86/src/wp-includes/class-wp-query.php#L951-L971
	 *
	 * @param WP_Query $query Query.
	 */
	public function amp_wp_correct_query_when_is_front_page(WP_Query $query) {
		$is_front_page_query = (
			$query->is_main_query() &&
			$query->is_home() &&
			// Is AMP endpoint.
			false !== $query->get(self::AMP_WP_STARTPOINT, false) &&
			// Is query not yet fixed uo up to be front page.
			!$query->is_front_page() &&
			// Is showing pages on front.
			'page' === get_option('show_on_front') &&
			// Has page on front set.
			get_option('page_on_front') &&
			// See line in WP_Query::parse_query() at <https://github.com/WordPress/wordpress-develop/blob/0baa8ae/src/wp-includes/class-wp-query.php#L961>.
			0 === count(array_diff(array_keys(wp_parse_args($query->query)), array(self::AMP_WP_STARTPOINT, 'preview', 'page', 'paged', 'cpage')))
		);
		if ($is_front_page_query) {
			$query->is_home = false;
			$query->is_page = true;
			$query->is_singular = true;
			$query->set('page_id', get_option('page_on_front'));
		}
	}

	/**
	 * "Automattic AMP" Plugin Compatibility
	 *
	 * Redirect AMP URLs With AMP Endpoint to New AMP URL
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_redirect_endpoint_url() {
		if( !amp_wp_get_permalink_structure() ) {
			return;
		}
		
		if( amp_wp_url_format() === 'start-point' ) {
			$this->redirect_to_start_point_amp();
		} else {
			$this->redirect_to_end_point_amp();
		}
	}
	
	/**
	 * Redirect end-point AMP URLs to start-point
	 *
	 * @since 1.0.4
	 */
	public function redirect_to_start_point_amp() {
		
		$amp_qv = defined('AMP_WP_QUERY_VAR') ? AMP_WP_QUERY_VAR : 'amp';
		if (get_query_var($amp_qv, false) === false) {
			if (!is_404()) { # /amp at the end of some urls cause 404 error
				return;
			}
		}
		
		$path = amp_wp_get_wp_installation_slug();
		$request_url = str_replace($path, '', $_SERVER['REQUEST_URI']);
		$url_prefix = preg_quote( amp_wp_permalink_prefix(), '#' );
		preg_match("#^/*$url_prefix(.*?)/$amp_qv/*$#", $request_url, $automattic_amp_match);
		
		if( !$this->amp_version_exists() ) {
			if( !empty( $automattic_amp_match[1] ) ) {
				$redirect_url = home_url( $automattic_amp_match[1] );
			} elseif (preg_match("#^/*$amp_qv/+(.*?)/*$#", $request_url, $matched)) {
				$redirect_url = home_url($matched[1]);
			} else {
				$redirect_url = amp_wp_get_canonical_url();
			}
			if( $redirect_url ) {
				wp_redirect($redirect_url);
				exit;
			}
		}
		
		if (!empty($automattic_amp_match[1])) {
			$new_amp_url = Amp_WP_Content_Sanitizer::transform_to_amp_url( site_url( $automattic_amp_match[1] ) );
			$new_amp_url = trailingslashit( $new_amp_url );

			if( $new_amp_url && trim( str_replace( site_url(), '', $new_amp_url), '/' ) !== trim($request_url, '/' ) ) {
				wp_redirect( $new_amp_url, 301 );
				exit;
			}
		}
	}
	
	/**
	 * Redirect end-point AMP URLs to end-point
	 *
	 * @since 1.0.4
	 */
	public function redirect_to_end_point_amp() {
		
		$request_url = str_replace( amp_wp_get_wp_installation_slug(), '', $_SERVER['REQUEST_URI'] );
		
		if( !preg_match( '#^/?([^/]+)(.+)#', $request_url, $match ) ) { return; }
		
		if( $match[1] !== Amp_WP_Public::SLUG ) { return; }

		$new_amp_url = trailingslashit( Amp_WP_Content_Sanitizer::transform_to_amp_url( home_url( $match[2] ) ) );
		if ( $new_amp_url && trim( $match[2], '/' ) !== '' ) {
			wp_redirect( $new_amp_url, 301 );
			exit;
		}
	}

	/**
	 * Prevent Redirect Pages Within Single Post
	 *
	 * @param   bool $redirect
	 *
	 * @access  public
	 * @since   1.0.0
	 * 
	 * @return  bool
	 */
	public function amp_wp_fix_prevent_extra_redirect_single_pagination($redirect) {
		if ($redirect && is_amp_wp() && get_query_var('page') > 1) {
			return false;
		}
		return $redirect;
	}

	/**
	 * Get Requested Page URL
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 * @return  string
	 */
	public static function amp_wp_get_requested_page_url() {
		if (isset($_SERVER['HTTP_HOST'])) {
			$requested_url = is_ssl() ? 'https://' : 'http://';
			$requested_url .= $_SERVER['HTTP_HOST'];
			$requested_url .= $_SERVER['REQUEST_URI'];

			return $requested_url;
		}
		return '';
	}

	/**
	 * Redirect Users to AMP Version of the Page Automatically
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_auto_redirect_to_amp() {
		if (is_amp_wp()) {
			return;
		}
		if (!apply_filters('amp_wp_template_auto_redirect', false)) {
			return;
		}

		if (!empty($_GET['amp-wp-skip-redirect']) || !empty($_COOKIE['amp-wp-skip-redirect'])) {
			if (!isset($_COOKIE['amp-wp-skip-redirect'])) {
				setcookie('amp-wp-skip-redirect', true, time() + DAY_IN_SECONDS, '/');
			}
			return;
		} else {
			if (isset($_COOKIE['amp-wp-skip-redirect'])) {
				unset($_COOKIE['amp-wp-skip-redirect']);
			}
		}

		// if post have not AMP version
		if (!$this->amp_version_exists()) {
			return;
		}

		if (wp_is_mobile()) {
			$requested_url = self::amp_wp_get_requested_page_url();
			$amp_permalink = Amp_WP_Content_Sanitizer::transform_to_amp_url($requested_url);

			if ($requested_url && $amp_permalink && $amp_permalink !== $requested_url) {
				wp_redirect($amp_permalink);
				exit;
			}
		} elseif (Amp_WP_Public::amp_wp_have_cache_plugin()) {
			// Adds advanced javascript code to page to redirect page in front end!
			// Last and safest way to redirect but it will have a little delay!
			add_action('wp_print_scripts', array($this, 'amp_wp_print_mobile_redirect_script'));
		}
	}

	/**
	 * Is Any Caching Plugin Install on This WordPress Installation
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 * @return bool
	 */
	public function amp_wp_have_cache_plugin() {
		if (defined('WP_CACHE') && WP_CACHE) {
			return true;
		}

		// Fix for "WP Fastest Cache" plugin
		if( $plugins = array_flip( wp_get_active_and_valid_plugins() ) ) {
			return isset( $plugins[WP_PLUGIN_DIR . '/wp-fastest-cache/wpFastestCache.php'] );
		}

		return false;
	}

	/**
	 * Print Script to Redirect Mobile Devices to AMP Version
	 *
	 * @access	public
	 * @version	1.0.0
	 * @since		1.0.0
	 * @since		1.0.4		Fix: Mobile users force redirect.
	 */
	public function amp_wp_print_mobile_redirect_script() {
		$requested_url = self::amp_wp_get_requested_page_url();
		$amp_permalink = Amp_WP_Content_Sanitizer::transform_to_amp_url($requested_url);

		if (!$requested_url || !$amp_permalink || $amp_permalink === $requested_url) {
			return;
		}
		$script = file_get_contents( amp_wp_min_suffix( AMPWP_PATH . 'js/mobile_redirect', '.js' ) );
		$script = str_replace( '%%amp_permalink%%', $amp_permalink, $script );
		?>
		<script><?php echo $script; ?></script>
		<?php
	}

	/**
	 * Initialize AMP WP JSON-LD
	 */
	public static function amp_wp_init_json_ld() {
		if (!is_amp_wp()) {
			return;
		}

		if (!class_exists('Amp_WP_Json_Ld_Generator')) {
			include AMPWP_PATH . 'includes/class-amp-wp-json-ld-generator.php';
		}

		// Config AMP WP JSON-LD
		add_filter('amp_wp_json_ld_config', 'Amp_WP_Public::config_json_ld', 15);
	}

	/**
	 * Configurations of JSON-LD
	 *
	 * @param   $config
	 * @since   1.0.0
	 *
	 * @return  mixed
	 */
	public static function config_json_ld($config) {
		$branding = amp_wp_get_branding_info();
		if (!empty($branding['logo']['src'])) {
			$config['logo'] = $branding['logo']['src'];
		}
		return $config;
	}

	/**
	 * Fix Front Page Display Option to Detect Homepage
	 * 
	 * @access  1.0.0
	 * @version 1.0.0
	 * @since   1.0.0
	 */
	public function amp_wp_fix_front_page_display_options() {
		add_action('pre_option_page_on_front', array($this, 'amp_wp_return_zero_in_amp'));
		add_action('pre_option_show_on_front', array($this, 'amp_wp_fix_show_on_front'));
	}

	/**
	 * Just Return Zero in AMP Version
	 *
	 * @param mixed $current
	 *
	 * @access  1.0.0
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 * @return mixed
	 */
	public function amp_wp_return_zero_in_amp($current) {
		if (is_amp_wp() && empty($GLOBALS['_amp_bypass_option'])) {
			return 0;
		}
		return $current;
	}

	/**
	 * Just Return ‘Posts’ String in AMP Version
	 *
	 * @param mixed $current
	 * 
	 * @access  1.0.0
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 * @return mixed
	 */
	public function amp_wp_fix_show_on_front($current) {
		if (is_amp_wp() && empty($GLOBALS['_amp_bypass_option'])) {
			return 'posts';
		}
		return $current;
	}

	/**
	 * Setup page query
	 *
	 * @param $page_id
	 * 
	 * @access  1.0.0
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 */
	public function amp_wp_set_page_query($page_id) {
		query_posts('page_id=' . $page_id . '&amp=' . get_query_var('amp'));
	}

	/**
	 * Check AMP version of the posts exists
	 *
	 * @since 1.0.0
	 * @return bool of exists
	 */
	public static function amp_version_exists() {

		static $filters;

		if (!isset($filters)) {
			$filters = wp_parse_args(
				apply_filters(
					'amp_wp_filter_config_list',
					array()
				),
				array(
					'disabled_post_types' => array(),
					'disabled_taxonomies' => array(),
					'disabled_homepage' => false,
					'disabled_search' => false,
				)
			);
		}

		if (is_singular()) {
			$post_id = get_queried_object_id();
		} elseif (is_home() && amp_wp_is_static_home_page()) {
			$post_id = intval(apply_filters('amp_wp_template_page_on_front', 0));
		} else {
			$post_id = 0;
		}

		if ($post_id) {
			//if( get_post_meta( $post_id, 'disable-amp-wp', true ) || isset( $this->excluded_posts_id[$post_id] ) ) {
			if (get_post_meta($post_id, 'disable-amp-wp', true)) {
				return false;
			}
		}

		if( empty( $filters ) ) {
			return true;
		}
		if ( is_home() || is_front_page() ) {
			return !$filters['disabled_homepage'];
		}
		if (is_search()) {
			return !$filters['disabled_search'];
		}
		if (is_singular()) {
			return !in_array(get_queried_object()->post_type, $filters['disabled_post_types']);
		}
		if (is_post_type_archive()) {
			$queried_object = get_queried_object();
			if ($queried_object instanceof WP_Post_Type) { #  WP >= 4.6.0
				$post_type = $queried_object->name;
			} elseif ($queried_object instanceof WP_Post) { #  WP < 4.6.0
				$post_type = $queried_object->post_type;
			} else {
				return false;
			}
			return !in_array($post_type, $filters['disabled_post_types']);
		}
		if (is_tax() || is_category() || is_tag()) {
			return !in_array(get_queried_object()->taxonomy, $filters['disabled_taxonomies']);
		}
		return true;
	}

	/**
	 * Prints meta tags with using Yoast SEO Open Graph feature.
	 */
	public function amp_wp_yoast_seo_metatags_compatibility() {

		// Remove canonical from in Yoast to generate correct canonical
		amp_wp_remove_class_action('wpseo_head', 'WPSEO_Frontend', 'canonical', 20);

		do_action('wpseo_opengraph');
	}

	/**
	 * Sync non-amp Homepage Title With AMP Version
	 *
	 * @param   string  $title
	 *
	 * @access  public
	 * @version 1.0.0
	 * @since   1.0.0
	 * 
	 * @return string
	 */
	public static function amp_wp_yoast_seo_homepage_title($title) {
		if (( $post_id = self::amp_wp_get_option('page_on_front') ) && is_callable('WPSEO_Frontend::get_instance')) {
			$post = get_post($post_id);
			if ($post instanceof WP_Post) {
				$wp_seo = WPSEO_Frontend::get_instance();
				if ($new_title = $wp_seo->get_content_title($post)) {
					return $new_title;
				}
			}
		}
		return $title;
	}

	/**
	 * Sync json-ld Data With Yoast SEO Plugin
	 *
	 * @param array $data
	 *
	 * @since 1.0.0
	 * @return array
	 */
	public static function amp_wp_yoast_seo_homepage_json_ld($data) {
		if (is_callable('WPSEO_Options::get_options')) {
			$options = WPSEO_Options::get_options(array('wpseo', 'wpseo_social'));

			if (!empty($options['website_name'])) {
				$data['name'] = $options['website_name'];
			}
			if (!empty($options['alternate_website_name'])) {
				$data['alternateName'] = $options['alternate_website_name'];
				unset($data['description']);
			}
		}
		return $data;
	}

	/**
	 * Get WordPress option
	 *
	 * @param string $option
	 * @param mixed  $default
	 *
	 * @since 1.0.0
	 * @return mixed
	 */
	public static function amp_wp_get_option($option, $default = false) {
		$tmp = isset($GLOBALS['_amp_bypass_option']) ? $GLOBALS['_amp_bypass_option'] : false;
		$GLOBALS['_amp_bypass_option'] = true;
		$results = get_option($option, $default);
		$GLOBALS['_amp_bypass_option'] = $tmp;

		return $results;
	}
}