<?php

if (!class_exists('swift_staff_page_templater')) {

    class swift_staff_page_templater {

        /**
         * A reference to an instance of this class.
         */
        private static $instance;

        /**
         * The array of templates that this plugin tracks.
         */
        protected $templates;

        /**
         * Returns an instance of this class.
         */
        public static function swift_staff_get_instance() {

            if (null == self::$instance) {
                self::$instance = new swift_staff_page_templater();
            }

            return self::$instance;
        }

        /**
         * Initializes the plugin by setting filters and administration functions.
         */
        private function __construct() {

            $this->templates = array();


            // Add a filter to the attributes metabox to inject template into the cache.
            if (version_compare(floatval(get_bloginfo('version')), '4.6', '<')) { // 4.6 and older
                add_filter(
                        'page_attributes_dropdown_pages_args', array($this, 'swift_staff_register_project_templates')
                );
            } else { // Add a filter to the wp 4.7 version attributes metabox
                add_filter(
                        'theme_page_templates', array($this, 'swift_staff_add_new_template')
                );
            }


            // Add a filter to the save post to inject out template into the page cache
            add_filter(
                    'wp_insert_post_data', array($this, 'swift_staff_register_project_templates')
            );


            // Add a filter to the template include to determine if the page has our
            // template assigned and return it's path
            add_filter(
                    'template_include', array($this, 'swift_staff_view_project_template')
            );


            // Add your templates to this array.
            $this->templates = array(
                'swift-job-template.php' => 'Swift Jobs',
                'rss-jobs-feed.php' => 'Jobs Feed',
            );
        }

        /**
         * Adds our template to the page dropdown for v4.7+
         *
         */
        public function swift_staff_add_new_template($posts_templates) {
            $posts_templates = array_merge($posts_templates, $this->templates);
            return $posts_templates;
        }

        /**
         * Adds our template to the pages cache in order to trick WordPress
         * into thinking the template file exists where it doens't really exist.
         *
         */
        public function swift_staff_register_project_templates($atts) {

            // Create the key used for the themes cache
            $cache_key = 'page_templates-' . md5(get_theme_root() . '/' . get_stylesheet());

            // Retrieve the cache list.
            // If it doesn't exist, or it's empty prepare an array
            $templates = wp_get_theme()->get_page_templates();
            if (empty($templates)) {
                $templates = array();
            }

            // New cache, therefore remove the old one
            wp_cache_delete($cache_key, 'themes');

            // Now add our template to the list of templates by merging our templates
            // with the existing templates array from the cache.
            $templates = array_merge($templates, $this->templates);

            // Add the modified cache to allow WordPress to pick it up for listing
            // available templates
            wp_cache_add($cache_key, $templates, 'themes', 1800);

            return $atts;
        }

        /**
         * Checks if the template is assigned to the page
         */
        public function swift_staff_view_project_template($template) {

            // Get global post
            global $post;

            // Return template if post is empty
            if (!$post) {
                return $template;
            }

            // Return default template if we don't have a custom one defined
            if (!isset($this->templates[get_post_meta($post->ID, '_wp_page_template', true)])) {
                return $template;
            }

            $file = plugin_dir_path(__FILE__) . get_post_meta($post->ID, '_wp_page_template', true);

            // Just to be safe, we check if the file exist first
            if (file_exists($file)) {
                return $file;
            } else {
                echo $file;
            }

            // Return template
            return $template;
        }

    }

}

add_action('plugins_loaded', array('swift_staff_page_templater', 'swift_staff_get_instance'));