pdf-forms-for-woocommerce.php

<?php
/**
 * Plugin Name: PDF Forms Filler for WooCommerce
 * Plugin URI: https://pdfformsfiller.org/
 * Description: Automatically fill PDF forms with WooCommerce orders and attach generated PDFs to email notifications and order downloads.
 * Version: 1.1.0
 * Requires at least: 5.4
 * Requires PHP: 5.5
 * Requires Plugins: woocommerce
 * WC requires at least: 7.1.0
 * WC tested up to: 9.5
 * Author: Maximum.Software
 * Author URI: https://maximum.software/
 * Text Domain: pdf-forms-for-woocommerce
 * Domain Path: /languages
 * License: GPLv3
 * License URI: https://www.gnu.org/licenses/gpl-3.0.html
 */

if( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly

require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/tgm-config.php';
require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/wrapper.php';

if( ! class_exists( 'Pdf_Forms_For_WooCommerce', false ) )
{
	class Pdf_Forms_For_WooCommerce
	{
		const VERSION = '1.1.0';
		const MIN_WC_VERSION = '7.1.0';
		const MAX_WC_VERSION = '9.5.99';
		private static $BLACKLISTED_WC_VERSIONS = array();
		
		const META_KEY = '_pdf-forms-for-woocommerce-data';
		
		private static $instance = null;
		private $pdf_ninja_service = null;
		private $service = null;
		private $registered_services = false;
		private $tmp_storage = null;
		private $filled_pdfs = array();
		private $new_orders = array();
		private $delayed_saving_orders = array();
		private $do_not_save_orders = array();
		
		private function __construct()
		{
			add_action( 'admin_notices',  array( $this, 'admin_notices' ) );
			add_action( 'plugins_loaded', array( $this, 'plugin_init' ) );
			add_filter( 'plugin_action_links_' . plugin_basename( __FILE__ ), array( $this, 'action_links' ) );
		}
		
		/**
		 * Returns a global instance of this class
		 */
		public static function get_instance()
		{
			if( ! self::$instance )
				self::$instance = new self;
			
			return self::$instance;
		}
		
		/**
		 * Runs after all plugins have been loaded
		 */
		public function plugin_init()
		{
			add_action( 'init', array( $this, 'load_textdomain' ) );
			
			add_action( 'admin_enqueue_scripts', array( $this, 'admin_enqueue_scripts' ) );
			
			if( ! class_exists( 'WooCommerce' ) || ! defined( 'WC_VERSION' ) )
				return;
			
			add_action( 'wp_ajax_pdf_forms_for_woocommerce_get_attachment_data', array( $this, 'wp_ajax_get_attachment_data' ) );
			add_action( 'wp_ajax_pdf_forms_for_woocommerce_query_page_image', array( $this, 'wp_ajax_query_page_image' ) );
			add_action( 'wp_ajax_pdf_forms_for_woocommerce_generate_pdf_ninja_key', array( $this, 'wp_ajax_generate_pdf_ninja_key') );
			add_action( 'wp_ajax_pdf_forms_for_woocommerce_clear_messages', array( $this, 'wp_ajax_clear_messages') );
			add_action( 'wp_ajax_pdf_forms_for_woocommerce_reset_order_settings', array( $this, 'wp_ajax_reset_order_settings') );
			add_action( 'wp_ajax_pdf_forms_for_woocommerce_reset_order_pdfs', array( $this, 'wp_ajax_reset_order_pdfs') );
			
			add_action( 'init', array( $this, 'register_meta' ) );
			add_action( 'admin_menu', array( $this, 'register_services' ) );
			add_action( 'add_meta_boxes', array( $this, 'register_order_metabox' ) );
			
			add_action( 'before_woocommerce_init', array( $this, 'before_woocommerce_init' ) );
			add_action( 'woocommerce_new_order', array( $this, 'woocommerce_new_order' ), 10, 2 ); // since 2.7.0
			add_filter( 'woocommerce_before_order_object_save', array( $this, 'woocommerce_before_order_object_save' ), 10, 2 );
			add_filter( 'woocommerce_after_order_object_save', array( $this, 'woocommerce_after_order_object_save' ), 10, 2 );
			add_filter( 'woocommerce_email_attachments', array( $this, 'attach_pdfs' ), 10, 4 );
			add_action( 'woocommerce_email_sent', array( $this, 'remove_tmp_storage' ), 99, 0 ); // since WC 5.6.0
			add_filter( 'woocommerce_get_item_downloads', array( $this, 'woocommerce_get_item_downloads' ), 10, 3 );
			add_filter( 'woocommerce_customer_available_downloads', array( $this, 'woocommerce_customer_available_downloads' ), 10, 2 );
			
			add_action( 'before_delete_post', array( $this, 'before_delete_post' ), 10, 1 );
			add_action( 'woocommerce_before_delete_order', array( $this, 'woocommerce_before_delete_order' ), 10, 1 ); // since WC 7.1.0
			add_action( 'woocommerce_before_delete_order_item', array( $this, 'woocommerce_before_delete_order_item' ), 10, 1 ); // since WC 2.0.9
			
			add_filter( 'woocommerce_product_data_tabs', array( $this, 'add_product_data_tab' ) );
			add_action( 'woocommerce_product_data_panels', array( $this, 'print_product_data_tab_contents' ) );
			add_action( 'woocommerce_process_product_meta', array( $this, 'save_product_data' ), 99 );
			
			add_filter( 'woocommerce_get_settings_pages', array( $this, 'register_settings' ) );
			
			if( $service = $this->get_service() )
			{
				$service->plugin_init();
				if( $service != $this->pdf_ninja_service )
					$this->pdf_ninja_service->plugin_init();
			}
		}
		
		/*
		 * Loads plugin textdomain
		 */
		public function load_textdomain()
		{
			load_plugin_textdomain( 'pdf-forms-for-woocommerce', false, dirname( plugin_basename( __FILE__ ) ) . '/languages/' );
		}
		
		/*
		 * Declares WC compatibility
		 */
		public function before_woocommerce_init()
		{
			if( is_callable( array( '\Automattic\WooCommerce\Utilities\FeaturesUtil', 'declare_compatibility' ) ) )
				\Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility( 'custom_order_tables', __FILE__, true );
		}
		
		/*
		 * Checks if WC High-Performance Order Storage is enabled
		 */
		public static function is_wc_hpos_enabled()
		{
			return
				is_callable( array( '\Automattic\WooCommerce\Utilities\OrderUtil', 'custom_orders_table_usage_is_enabled' ) )
				&& \Automattic\WooCommerce\Utilities\OrderUtil::custom_orders_table_usage_is_enabled();
		}
		
		/*
		 * Registers the meta key for settings
		 */
		public function register_meta()
		{
			register_meta( 'post', self::META_KEY, array(
				'show_in_rest' => false,
				'single' => true,
				'type' => 'string',
				'auth_callback' => '__return_false',
			) );
		}
		
		/**
		 * Adds a metabox to edit order page
		 */
		// phpcs:disable WordPress.Security.NonceVerification.Recommended -- This function does not need nonce verification because it doesn't process any data, it only adds a meta box
		public function register_order_metabox()
		{
			// get current order
			$order = wc_get_order();
			if( ! is_a( $order, 'WC_Order' ) )
				return;
			
			// don't display meta box if the order doesn't have attachments and its item products don't have attachments
			$order_has_attachments = false;
			$order_item_product_has_attachments = false;
			
			// check order metadata for attachments
			$settings = $this->get_order_metadata( $order );
			if( is_array( $settings )
			&& isset( $settings['product-settings'] )
			&& is_array( $product_settings = $settings['product-settings'] ) )
			{
				foreach( $product_settings as $settings )
				{
					if( is_array( $settings )
					&& isset( $settings['attachments'] )
					&& is_array( $attachments = $settings['attachments'] )
					&& ! empty( $attachments ) )
					{
						$order_has_attachments = true;
						break;
					}
				}
			}
			
			if( ! $order_has_attachments )
			{
				// check order items for attachments
				$items = $order->get_items();
				foreach( $items as $item )
				{
					$product = $item->get_product();
					if( is_a( $product, 'WC_Product' ) )
					{
						$settings = self::get_metadata( $product->get_id(), 'product-settings' );
						if( is_array( $settings )
						&& isset( $settings['attachments'] )
						&& is_array( $attachments = $settings['attachments'] )
						&& ! empty( $attachments ) )
						{
							$order_item_product_has_attachments = true;
							break;
						}
					}
				}
			}
			
			if( ! $order_has_attachments && ! $order_item_product_has_attachments )
				return;
			
			add_meta_box(
				'pdf-forms-for-woocommerce-metabox', // ID
				__( 'PDF Forms Filler', 'pdf-forms-for-woocommerce' ), // title
				array( $this, 'display_order_metabox' ), // callback
				self::is_wc_hpos_enabled() ? wc_get_page_screen_id( 'shop-order' ) : 'shop_order',
				'side', // context
				'default' // priority
			);
		}
		// phpcs:enable WordPress.Security.NonceVerification.Recommended
		
		/**
		 * Add PDF Forms settings page to WooCommerce settings
		 */
		public function register_settings( $settings )
		{
			require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/integration/wc-settings-page.php';
			$settings[] = Pdf_Forms_For_WooCommerce_Settings_Page::get_instance();
			
			if( $service = $this->get_service() )
			{
				$service->register_settings();
				if( $service != $this->pdf_ninja_service )
					$this->pdf_ninja_service->register_settings();
			}
			
			return $settings;
		}
		
		/**
		 * Adds plugin action links
		 */
		public function action_links( $links )
		{
			$links[] = '<a target="_blank" href="https://wordpress.org/support/plugin/pdf-forms-for-woocommerce/">'.esc_html__( "Support", 'pdf-forms-for-woocommerce' ).'</a>';
			return $links;
		}
		
		/**
		 * Prints admin notices
		 */
		public function admin_notices()
		{
			if( ! class_exists( 'WooCommerce' ) || ! defined( 'WC_VERSION' ) )
			{
				if( current_user_can( 'activate_plugins' ) )
					echo Pdf_Forms_For_WooCommerce::render_error_notice( 'woocommerce-not-installed', array(
						'label'   => esc_html__( "PDF Forms Filler for WooCommerce Error", 'pdf-forms-for-woocommerce' ),
						'message' => esc_html__( "The required plugin 'WooCommerce' version is not installed!", 'pdf-forms-for-woocommerce' ),
					) );
				return;
			}
			
			if( ! $this->is_wc_version_supported( WC_VERSION ) )
				if( current_user_can( 'activate_plugins' ) )
					echo Pdf_Forms_For_WooCommerce::render_warning_notice( 'unsupported-woocommerce-version-'.WC_VERSION, array(
						'label'   => esc_html__( "PDF Forms Filler for WooCommerce Warning", 'pdf-forms-for-woocommerce' ),
						'message' =>
							self::replace_tags(
								esc_html__( "The currently installed version of 'WooCommerce' plugin ({current-woocommerce-version}) may not be supported by the current version of 'PDF Forms Filler for WooCommerce' plugin ({current-plugin-version}), please switch to 'WooCommerce' plugin version {supported-woocommerce-version} or below to ensure that 'PDF Forms Filler for WooCommerce' plugin would work correctly.", 'pdf-forms-for-woocommerce' ),
								array(
									'current-woocommerce-version' => esc_html( defined( 'WC_VERSION' ) ? WC_VERSION : __( "Unknown version", 'pdf-forms-for-woocommerce' ) ),
									'current-plugin-version' => esc_html( self::VERSION ),
									'supported-woocommerce-version' => esc_html( self::MAX_WC_VERSION ),
								)
							),
					) );
			
			if( $service = $this->get_service() )
			{
				$service->admin_notices();
				if( $service != $this->pdf_ninja_service )
					$this->pdf_ninja_service->admin_notices();
			}
			
			if( current_user_can( 'manage_woocommerce' ) )
			{
				// display previously logged admin messages
				$messages = self::get_admin_messages();
				if( count( $messages ) > 0 )
				{
					$messages = array_map( function( $message ) { return "<span class='".esc_attr($message['type'])."'>".esc_html($message['message'])."</span>"; }, $messages );
					$messageHtml = self::render(
						'admin-messages',
						array(
							'messages' => implode( '<br/>', $messages),
							'clear-all-messages' => esc_html__( "Clear All Messages", 'pdf-forms-for-woocommerce' )
							)
						);
					echo Pdf_Forms_For_WooCommerce::render_warning_notice( 'admin-messages-'.gmdate('Ymd'), array(
						'label'   => esc_html__( "PDF Forms Filler for WooCommerce Messages", 'pdf-forms-for-woocommerce' ),
						'message' => $messageHtml,
					) );
				}
			}
		}
		
		/**
		 * Checks if WooCommerce version is supported
		 */
		public function is_wc_version_supported( $version )
		{
			if( version_compare( $version, self::MIN_WC_VERSION ) < 0
			||  version_compare( $version, self::MAX_WC_VERSION ) > 0 )
				return false;
			
			foreach( self::$BLACKLISTED_WC_VERSIONS as $blacklisted_version )
				if( version_compare( $version, $blacklisted_version ) == 0 )
					return false;
			
			return true;
		}
		
		/**
		 * Returns the service module instance
		 */
		public function get_service()
		{
			$this->register_services();
			
			if( ! $this->service )
				$this->set_service( $this->load_pdf_ninja_service() );
			
			return $this->service;
		}
		
		/**
		 * Sets the service module instance
		 */
		public function set_service( $service )
		{
			return $this->service = $service;
		}
		
		/**
		 * Loads and returns the storage module
		 */
		private static function get_storage()
		{
			require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/filesystem/storage.php';
			return Pdf_Forms_For_WooCommerce_Storage::get_instance();
		}
		
		/**
		 * Registers PDF.Ninja service
		 */
		public function register_services()
		{
			if( $this->registered_services )
				return;
			
			require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/services/service.php';
			
			$this->registered_services = true;
			$this->load_pdf_ninja_service();
		}
		
		/**
		 * Loads the Pdf.Ninja service module
		 */
		private function load_pdf_ninja_service()
		{
			if( ! $this->pdf_ninja_service )
			{
				require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/services/pdf-ninja.php';
				$this->pdf_ninja_service = Pdf_Forms_For_WooCommerce_Pdf_Ninja::get_instance();
			}
			
			return $this->pdf_ninja_service;
		}
		
		/**
		 * Creates a new instance of the placeholder processor
		 */
		public function get_placeholder_processor()
		{
			require_once untrailingslashit( dirname( __FILE__ ) ) . '/src/integration/wc-placeholder-processor.php';
			return new Pdf_Forms_For_WooCommerce_Placeholder_Processor();
		}
		
		/**
		 * Function for decoding metadata
		 */
		private static function decode_metadata( $data, $key = null )
		{
			if( ! empty( $data ) )
				$data = json_decode( $data, true );
			if( ! is_array( $data ) )
				return null;
			
			if( $key === null )
				return $data;
			
			if( isset( $data[$key] ) )
				return $data[$key];
			else
				return null;
		}
		
		/**
		 * Function for retrieving metadata
		 */
		public static function get_metadata( $post_id, $key = null )
		{
			return self::decode_metadata( get_post_meta( $post_id, self::META_KEY, $single=true ), $key );
		}
		
		/**
		 * Function for retrieving order metadata
		 * $order can be either an instance of WC_Order, an instance of WP_Post or a numeric order/post ID
		 * $key is the metadata key for a specific metadata element
		 * If $key is null, the whole metadata store is returned
		 */
		public function get_order_metadata( $order, $key = null )
		{
			if( ! is_a( $order, 'WC_Order' ) )
			{
				$order = wc_get_order( $order );
				if( ! is_a( $order, 'WC_Order' ) )
					return null;
			}
			
			if( ! self::is_wc_hpos_enabled() )
				return self::get_metadata( $order->get_id(), $key );
			
			return self::decode_metadata( $order->get_meta( self::META_KEY, $single=true ), $key );
		}
		
		/**
		 * Function for updating metadata
		 */
		private static function update_metadata_array( $data, $key = null, $value = null )
		{
			if( $key === null )
				$data = null;
			else
			{
				if( $value === null )
				{
					if( isset( $data[$key] ) )
						unset( $data[$key] );
				}
				else
					$data[$key] = $value;
				
				if( empty( $data ) )
					$data = null;
				else
					$data['version'] = self::VERSION; // keep track of schema version
			}
			
			return $data;
		}
		
		/**
		 * Function for encoding metadata
		 */
		private static function encode_metadata( $data, $hpos = false )
		{
			$data = Pdf_Forms_For_WooCommerce_Wrapper::json_encode( $data );
			
			if( !$hpos )
			{
				// wp bug workaround
				// https://developer.wordpress.org/reference/functions/update_post_meta/#workaround
				$data = wp_slash( $data );
			}
			
			return $data;
		}
		
		/**
		 * Function for setting metadata
		 * If $key is null, the whole metadata store is removed
		 * If $value is null, the metadata element with the given key is removed
		 */
		public static function set_metadata( $post_id, $key = null, $value = null )
		{
			// TODO: fix race condition
			$data = self::get_metadata( $post_id );
			$data = self::update_metadata_array( $data, $key, $value );
			
			if( $data === null)
				delete_post_meta( $post_id, self::META_KEY );
			else
				update_post_meta( $post_id, self::META_KEY, self::encode_metadata( $data ) );
			
			return $value;
		}
		
		/**
		 * Function for setting order metadata
		 * $order can be either an instance of WC_Order, an instance of WP_Post or a numeric order/post ID
		 * If $key is null, the whole metadata store is removed
		 * If $value is null, the metadata element with the given key is removed
		 */
		public function set_order_metadata( $order, $key = null, $value = null )
		{
			$by_id = is_numeric( $order );
			
			if( ! is_a( $order, 'WC_Order' ) )
			{
				// $order is probably order ID or post
				$order = wc_get_order( $order );
				if( ! is_a( $order, 'WC_Order' ) )
					throw new Exception( __( "Invalid order", 'pdf-forms-for-woocommerce' ) );
			}
			
			if( ! self::is_wc_hpos_enabled() )
				return self::set_metadata( $order->get_id(), $key, $value );
			
			$data = $this->get_order_metadata( $order );
			$new_data = self::update_metadata_array( $data, $key, $value );
			
			// if metadata has changed, update it
			if( $data != $new_data )
			{
				$data = $new_data;
				
				if( $data === null)
					$order->delete_meta_data( self::META_KEY );
				else
					$order->update_meta_data( self::META_KEY, self::encode_metadata( $data, true ) );
				
				$order_id = $order->get_id();
				if( ! isset( $this->do_not_save_orders[$order_id] ) )
				{
					if( $by_id )
						$order->save();
					else
					{
						// save after all changes have been made
						if( $order_id )
						{
							if( count( $this->delayed_saving_orders ) == 0 )
								add_action( 'shutdown', array( $this, 'save_delayed_orders' ) );
							$this->delayed_saving_orders[$order_id] = $order;
						}
					}
				}
			}
			
			return $value;
		}
		
		/**
		 * Function for delay-saving orders
		 * Used to avoid multiple unnecessary saves and other issues
		 */
		public function save_delayed_orders()
		{
			foreach( $this->delayed_saving_orders as $order )
				$order->save();
			$this->delayed_saving_orders = array();
		}
		
		/**
		 * Function for removing metadata
		 */
		public static function unset_metadata( $post_id, $key = null )
		{
			return self::set_metadata( $post_id, $key, null );
		}
		
		/**
		 * Function for removing order metadata
		 * $order can be either an instance of WC_Order, an instance of WP_Post or a numeric order/post ID
		 * If $key is null, the whole metadata store is removed
		 */
		public function unset_order_metadata( $order, $key = null )
		{
			return $this->set_order_metadata( $order, $key, null );
		}
		
		/**
		 * Hook that runs on user click 'Get New key' button and gets new pdf-ninja key
		 */
		public function wp_ajax_generate_pdf_ninja_key()
		{
			try
			{
				if( ! check_ajax_referer( 'pdf-forms-for-woocommerce-ajax-nonce', 'nonce', false ) )
					throw new Exception( __( "Nonce mismatch", 'pdf-forms-for-woocommerce' ) );
				
				if( ! current_user_can( 'manage_woocommerce' ) )
					throw new Exception( __( "Permission denied", 'pdf-forms-for-woocommerce' ) );
				
				$email = isset( $_POST['email'] ) ? sanitize_email( wp_unslash( $_POST['email'] ) ) : null;
				
				if( ! $email )
					throw new Exception( __( "Invalid email", 'pdf-forms-for-woocommerce' ) );
				
				$service = $this->get_service();
				$service->set_key( $key = $service->generate_key( $email ) );
			}
			catch ( Exception $e )
			{
				return wp_send_json( array (
					'success' => false,
					'error_message' => $e->getMessage()
				) );
			}
		
			wp_send_json_success();
		}
		
		/**
		 * Used for clearing notice messages in wp-admin interface
		 */
		public function wp_ajax_clear_messages()
		{
			try
			{
				if( ! check_ajax_referer( 'pdf-forms-for-woocommerce-ajax-nonce', 'nonce', false ) )
					throw new Exception( __( "Nonce mismatch", 'pdf-forms-for-woocommerce' ) );
				
				if( ! current_user_can( 'manage_woocommerce' ) )
					throw new Exception( __( "Permission denied", 'pdf-forms-for-woocommerce' ) );
				
				self::clear_admin_messages();
			}
			catch ( Exception $e )
			{
				return wp_send_json( array (
					'success' => false,
					'error_message' => $e->getMessage()
				) );
			}
			
			wp_send_json_success();
		}
		
		const DEFAULT_PDF_OPTIONS = array(
			'skip_empty' => false,
			'flatten' => false,
			'email_templates' => array( 'customer_processing_order', 'customer_completed_order' ),
			'filename' => "",
			'save_directory'=> "",
			'download_id' => "",
		);
		
		/**
		 * Returns MIME type of the file
		 */
		public static function get_mime_type( $filepath )
		{
			if( ! is_file( $filepath ) )
				return null;
			
			$mimetype = null;
			
			if( function_exists( 'finfo_open' ) )
			{
				if( version_compare( phpversion(), "5.3" ) < 0 )
				{
					$finfo = finfo_open( FILEINFO_MIME );
					if( $finfo )
					{
						$mimetype = finfo_file( $finfo, $filepath );
						$mimetype = explode( ";", $mimetype );
						$mimetype = reset( $mimetype );
						finfo_close( $finfo );
					}
				}
				else
				{
					$finfo = finfo_open( FILEINFO_MIME_TYPE );
					if( $finfo )
					{
						$mimetype = finfo_file( $finfo, $filepath );
						finfo_close( $finfo );
					}
				}
			}
			
			if( ! $mimetype && function_exists( 'mime_content_type' ) )
				$mimetype = mime_content_type( $filepath );
			
			// fallback
			if( ! $mimetype )
			{
				$type = wp_check_filetype( $filepath );
				if( isset( $type['type'] ) )
					$mimetype = $type['type'];
			}
			
			if( ! $mimetype )
				return 'application/octet-stream';
			
			return $mimetype;
		}
		
		/**
		 * Downloads a file from the given URL and saves the contents to the given filepath, returns mime type via argument
		 */
		private static function download_file( $url, $filepath, &$mimetype = null )
		{
			// if this url points to the site, copy the file directly
			$site_url = trailingslashit( get_site_url() );
			if( substr( $url, 0, strlen( $site_url ) ) == $site_url )
			{
				$path = substr( $url, strlen( $site_url ) );
				$home_path = trailingslashit( realpath( dirname(__FILE__) . '/../../../' ) );
				$sourcepath = realpath( $home_path . $path );
				if( $home_path && $sourcepath && substr( $sourcepath, 0, strlen( $home_path ) ) == $home_path )
					if( is_file( $sourcepath ) )
						if( copy($sourcepath, $filepath) )
						{
							$mimetype = self::get_mime_type( $sourcepath );
							return;
						}
			}
			
			$args = array(
				'compress'    => true,
				'decompress'  => true,
				'timeout'     => 100,
				'redirection' => 5,
				'user-agent'  => 'pdf-forms-for-woocommerce/' . self::VERSION,
			);
			
			$response = wp_remote_get( $url, $args );
			
			if( is_wp_error( $response ) )
				throw new Exception(
					self::replace_tags(
							__( "Failed to download file: {error-message}", 'pdf-forms-for-woocommerce' ),
							array( 'error-message' => $response->get_error_message() )
						)
				);
			
			$mimetype = wp_remote_retrieve_header( $response, 'content-type' );
			
			$body = wp_remote_retrieve_body( $response );
			
			if( file_put_contents( $filepath, $body ) === false || ! is_file( $filepath ) )
				throw new Exception( __( "Failed to create file", 'pdf-forms-for-woocommerce' ) );
		}
		
		/**
		 * Provides temporary file storage
		 */
		public function get_tmp_storage()
		{
			if( ! $this->tmp_storage )
			{
				// set up shutdown handler to clean up tmp dir on exit
				add_action( 'shutdown', array( $this, 'remove_tmp_storage' ), 99, 0 );
				
				$tmp_storage = self::get_storage();
				$tmp_storage->set_subpath( 'pdf-forms-for-woocommerce/tmp/' . sanitize_file_name( wp_hash( wp_rand() . microtime() ) ) );
				$this->tmp_storage = $tmp_storage;
				$this->tmp_storage->initialize_path();
			}
			
			return $this->tmp_storage;
		}
		
		/**
		 * Removes temporary file storage
		 */
		public function remove_tmp_storage()
		{
			if( ! $this->tmp_storage )
				return;
			
			$this->tmp_storage->delete_subpath_recursively();
			$this->tmp_storage = null;
			
			remove_action( 'shutdown', array( $this, 'remove_tmp_storage' ), 99 );
		}
		
		/**
		 * Creates a temporary file path (but not the file itself)
		 */
		private function create_tmp_filepath( $subpath, $filename )
		{
			$uploads_dir = trailingslashit( $this->get_tmp_storage()->get_full_path() ) . $subpath;
			wp_mkdir_p( $uploads_dir );
			$filename = sanitize_file_name( $filename );
			$filename = wp_unique_filename( $uploads_dir, $filename );
			return trailingslashit( $uploads_dir ) . $filename;
		}
		
		/**
		 * Checks if the image MIME type is supported for embedding
		 */
		private function is_embed_image_format_supported( $mimetype )
		{
			$supported_mime_types = array(
					"image/jpeg",
					"image/png",
					"image/gif",
					"image/tiff",
					"image/bmp",
					"image/x-ms-bmp",
					"image/svg+xml",
					"image/webp",
				);
			
			if( $mimetype )
				foreach( $supported_mime_types as $smt )
					if( $mimetype === $smt )
						return true;
			
			return false;
		}
		
		/**
		 * Outputs order metabox
		 */
		public function display_order_metabox( $post_or_order_object = null )
		{
			print(
				self::render( 'spinner' ) .
				self::render(
					'order-metabox',
					array(
						'reset-settings-instructions' => esc_html__( "Product settings are stored in orders when they are created. Resetting settings is necessary when new product settings need to be applied to an old order.", 'pdf-forms-for-woocommerce' ),
						'reset-settings' => esc_html__( "Reset Settings", 'pdf-forms-for-woocommerce' ),
						'reset-pdfs-instructions' => esc_html__( "PDFs are refilled when orders status changes. Sometimes you may want to manually trigger PDFs to be refilled after changing some aspect of the order, such as the billing address.", 'pdf-forms-for-woocommerce' ),
						'reset-pdfs' => esc_html__( "Reset PDFs", 'pdf-forms-for-woocommerce' ),
					)
				)
			);
		}
		
		/**
		 * Used for resetting order settings in wp-admin edit order interface
		 */
		public function wp_ajax_reset_order_settings()
		{
			try
			{
				if( ! check_ajax_referer( 'pdf-forms-for-woocommerce-ajax-nonce', 'nonce', false ) )
					throw new Exception( __( "Nonce mismatch", 'pdf-forms-for-woocommerce' ) );
				
				if( ! current_user_can( 'manage_woocommerce' ) )
					throw new Exception( __( "Permission denied", 'pdf-forms-for-woocommerce' ) );
				
				$order_id = isset( $_POST['order_id'] ) ? intval( $_POST['order_id'] ) : null;
				if( ! $order_id )
					throw new Exception( __( "Invalid order ID", 'pdf-forms-for-woocommerce' ) );
				
				$order = wc_get_order( $order_id );
				if( ! is_a( $order, 'WC_Order' ) )
					throw new Exception( __( "Invalid order", 'pdf-forms-for-woocommerce' ) );
				
				$this->reset_order_settings( $order );
			}
			catch ( Exception $e )
			{
				return wp_send_json( array (
					'success' => false,
					'error_message' => $e->getMessage()
				) );
			}
			
			wp_send_json_success();
		}
		
		/**
		 * Used for resetting order pdfs in wp-admin edit order interface
		 */
		public function wp_ajax_reset_order_pdfs()
		{
			try
			{
				if( ! check_ajax_referer( 'pdf-forms-for-woocommerce-ajax-nonce', 'nonce', false ) )
					throw new Exception( __( "Nonce mismatch", 'pdf-forms-for-woocommerce' ) );
				
				if( ! current_user_can( 'manage_woocommerce' ) )
					throw new Exception( __( "Permission denied", 'pdf-forms-for-woocommerce' ) );
				
				$order_id = isset( $_POST['order_id'] ) ? intval( $_POST['order_id'] ) : null;
				if( ! $order_id )
					throw new Exception( __( "Invalid order ID", 'pdf-forms-for-woocommerce' ) );
				
				$order = wc_get_order( $order_id );
				if( ! is_a( $order, 'WC_Order' ) )
					throw new Exception( __( "Invalid order", 'pdf-forms-for-woocommerce' ) );
				
				// remove downloadable files
				$this->unset_downloadable_files( $order );
				
				// refilling is necessary only if PDFs are being saved in wp-uploads
				$product_settings = $this->get_order_metadata( $order, 'product-settings' );
				if( is_array( $product_settings ) && ! empty( $product_settings ) )
				{
					$placeholder_processor = $this->get_placeholder_processor();
					$placeholder_processor->set_order( $order );
					
					$items = $order->get_items();
					foreach( $items as $item )
					{
						$order_item_id = $item->get_id();
						$placeholder_processor->set_order_item( $item );
						
						$product_id = $item->get_product_id();
						
						$placeholder_processor->set_product_id( $product_id );
						
						if( ! isset( $product_settings[$product_id] ) )
							continue;
						
						$settings = $product_settings[$product_id];
						
						if( ! is_array( $settings )
						|| ! isset( $settings['attachments'] )
						|| ! is_array( $attachments = $settings['attachments'] ) )
							continue;
						
						foreach( $attachments as $attachment )
						{
							if( isset( $attachment['options'] )
							&& is_array( $options = $attachment['options'] )
							&& isset( $options['save_directory'] )
							&& $options['save_directory'] !== "" )
							{
								$files = $this->fill_pdfs( $settings, $placeholder_processor );
								break;
							}
						}
						
						// clear temporary files
						self::remove_tmp_storage();
					}
				}
			}
			catch ( Exception $e )
			{
				return wp_send_json( array (
					'success' => false,
					'error_message' => $e->getMessage()
				) );
			}
			
			wp_send_json_success();
		}
		
		/**
		 * Keeps track of new orders
		 */
		public function woocommerce_new_order( $order_id, $order )
		{
			$this->new_orders[$order_id] = $order_id;
		}
		
		/**
		 * Remove outdated order files
		 */
		public function woocommerce_before_order_object_save( $order, $data_store )
		{
			// certain events cause downloadable files to become stale, such as when order status changes
			// we need to delete the stale PDF files and recreate them
			// however, we probalby don't want to keep redoing it over and over
			// so, we should delete the old PDF files and recreate them later when needed
			
			if( is_a( $order, 'WC_Order' ) )
			{
				// check if this order is in the database
				$order_id = $order->get_id();
				if( $order_id )
				{
					$new_status = $order->get_status();
					$old_order = wc_get_order( $order_id );
					$old_status = $old_order->get_status();
					if( $old_status != $new_status )
					{
						// remove stale downloadable files
						$this->unset_downloadable_files( $order );
					}
				}
			}
		}
		
		/*
		 * Resets product settings for an order
		 * $order must be an instance of WC_Order
		 */
		private function reset_order_settings( $order )
		{
			// TODO: save copies of source PDF files in pdf-forms-for-woocommerce/pdf-cache directory in case they are deleted from media library and use the cached copy for this order
			
			$product_settings = array();
			
			$items = $order->get_items();
			foreach( $items as $item )
			{
				$product_id = $item->get_product_id();
				$settings = self::get_metadata( $product_id, 'product-settings' );
				if( ! is_array( $settings ) || empty( $settings ) )
					continue;
				$product_settings[$product_id] = $settings;
			}
			
			if( empty( $product_settings ) )
				$this->unset_order_metadata( $order, 'product-settings' );
			else
				$this->set_order_metadata( $order, 'product-settings', $product_settings );
		}
		
		/**
		 * Saves product settings in order metadata
		 */
		public function woocommerce_after_order_object_save( $order, $data_store )
		{
			if( ! is_a( $order, 'WC_Order' ) )
				return;
			
			$order_id = $order->get_id();
			
			// don't do anything if this order is not new
			if( ! isset( $this->new_orders[$order_id] ) )
				return;
			
			unset( $this->new_orders[$order_id] );
			
			$this->reset_order_settings( $order );
		}
		
		/**
		 * Fills PDFs and attaches them to email notifications
		 */
		public function attach_pdfs( $email_attachments, $email_id, $order, $email )
		{
			if( $email_id !== null && is_a( $order, 'WC_Order' ) && is_a( $email, 'WC_Email' ) )
			{
				$order_id = $order->get_id();
				$product_settings = $this->get_order_metadata( $order, 'product-settings' );
				if( is_array( $product_settings ) && ! empty( $product_settings ) )
				{
					$placeholder_processor = $this->get_placeholder_processor();
					$placeholder_processor->set_email( $email );
					$placeholder_processor->set_order( $order );
					
					$items = $order->get_items();
					foreach( $items as $item )
					{
						$order_item_id = $item->get_id();
						$placeholder_processor->set_order_item( $item );
						
						$product_id = $item->get_product_id();
						
						$placeholder_processor->set_product_id( $product_id );
						
						if( ! isset( $product_settings[$product_id] ) )
							continue;
						
						$settings = $product_settings[$product_id];
						
						if( ! is_array( $settings )
						|| ! isset( $settings['attachments'] )
						|| ! is_array( $attachments = $settings['attachments'] ) )
							continue;
						
						foreach( $attachments as $attachment )
						{
							if( isset( $attachment['options'] )
							&& is_array( $options = $attachment['options'] )
							&& isset( $options['email_templates'] )
							&& is_array( $email_templates = $options['email_templates'] )
							&& in_array( $email_id, $email_templates ) )
							{
								if( isset( $this->filled_pdfs[$order_id] ) && isset( $this->filled_pdfs[$order_id][$order_item_id] ) )
									$email_attachments = array_merge( $email_attachments, $this->filled_pdfs[$order_id][$order_item_id] );
								else
								{
									$files = $this->fill_pdfs( $settings, $placeholder_processor );
									$email_attachments = array_merge( $email_attachments, $files );
									$this->filled_pdfs[$order_id][$order_item_id] = $files;
								}
								
								break;
							}
						}
					}
				}
			}
			
			return $email_attachments;
		}
		
		/**
		 * Returns the storage instance for the order
		 * $order can be either an instance of WC_Order, an instance of WP_Post or a numeric order/post ID
		 */
		public function get_order_storage( $order )
		{
			// TODO: fix race condition
			$storage = self::get_storage();
			
			$storage_directory = $this->get_order_metadata( $order, 'storage-dir' );
			$order_directory = $this->get_order_metadata( $order, 'order-dir' );
			if( $storage_directory && $order_directory )
			{
				$storage->set_site_root_relative_storage_path( $storage_directory );
				$storage->set_subpath( $order_directory );
			}
			else
			{
				$storage_directory = $storage->get_site_root_relative_storage_path();
				$order_id = $order;
				if( is_a( $order, 'WC_Order' ) )
					$order_id = $order->get_id();
				else if( is_a( $order, 'WP_Post' ) )
					$order_id = $order->ID;
				$order_directory = 'pdf-forms-for-woocommerce/order-files/' . sanitize_file_name( $order_id . '-' . wp_hash( wp_rand() . microtime() ) );
				$storage->set_subpath( $order_directory );
				$this->set_order_metadata( $order, 'storage-dir', $storage_directory );
				$this->set_order_metadata( $order, 'order-dir', $order_directory );
			}
			
			return $storage;
		}
		
		/**
		 * Deletes the storage directory for the order
		 * $order can be either an instance of WC_Order, an instance of WP_Post or a numeric order/post ID
		 */
		public function delete_order_storage( $order )
		{
			// TODO: fix race condition
			$storage_directory = $this->get_order_metadata( $order, 'storage-dir' );
			$order_directory = $this->get_order_metadata( $order, 'order-dir' );
			if( $storage_directory && $order_directory )
			{
				$storage = self::get_storage();
				$storage->set_site_root_relative_storage_path( $storage_directory );
				$storage->set_subpath( $order_directory );
				$storage->delete_subpath_recursively();
				$this->unset_order_metadata( $order, 'storage-dir' );
				$this->unset_order_metadata( $order, 'order-dir' );
			}
		}
		
		public function get_downloadable_files( $order, $order_item_id = null )
		{
			$downloadable_files = $this->get_order_metadata( $order, 'downloadable-files' );
			if( is_array( $downloadable_files ) )
			{
				if( $order_item_id === null )
					return $downloadable_files;
				
				if( isset( $downloadable_files[$order_item_id] ) )
				{
					$order_item_files = $downloadable_files[$order_item_id];
					if( is_array( $order_item_files ) )
						return $order_item_files;
				}
			}
			
			return array();
		}
		
		/**
		 * Sets downloadable files for the order
		 * $order can be either an instance of WC_Order, an instance of WP_Post or a numeric order/post ID
		 */
		public function set_downloadable_files( $order, $order_item_id = null, $order_item_files = null )
		{
			// TODO: fix race condition
			$downloadable_files = $this->get_order_metadata( $order, 'downloadable-files' );
			if( ! is_array( $downloadable_files ) )
				$downloadable_files = array();
			
			if( $order_item_files === null )
			{
				if( $order_item_id === null )
					$downloadable_files = array();
				else
				{
					// TODO: delete old files
					unset( $downloadable_files[$order_item_id] );
				}
			}
			else if( $order_item_id !== null )
			{
				// TODO: delete old files
				$downloadable_files[$order_item_id] = $order_item_files;
			}
			
			if( count( $downloadable_files ) == 0 )
				$downloadable_files = null;
			
			$this->set_order_metadata( $order, 'downloadable-files', $downloadable_files );
		}
		
		public function get_downloadable_file( $order, $order_item_id, $attachment_id )
		{
			$downloadable_files = $this->get_downloadable_files( $order, $order_item_id );
			if( isset( $downloadable_files[$attachment_id] ) )
				return $downloadable_files[$attachment_id];
			return null;
		}
		
		public function set_downloadable_file( $order, $order_item_id, $attachment_id, $fileurl, $filename )
		{
			// TODO: fix race condition
			$downloadable_files = $this->get_downloadable_files( $order, $order_item_id );
			$downloadable_files[$attachment_id] = array(
				'attachment_id' => $attachment_id,
				'file' => $fileurl,
				'filename' => $filename,
			);
			$this->set_downloadable_files( $order, $order_item_id, $downloadable_files );
		}
		
		public function unset_downloadable_files( $order, $order_item_id = null )
		{
			// TODO: fix race condition
			
			$downloadable_files = $this->get_downloadable_files( $order, $order_item_id );
			
			if( $order_item_id !== null )
				$downloadable_files = array( $downloadable_files );
			
			// delete files
			foreach( $downloadable_files as $downloadable_file_set )
				foreach( $downloadable_file_set as $downloadable_file )
					if( isset( $downloadable_file['file'] ) )
						@unlink( trailingslashit( ABSPATH ) . $downloadable_file['file'] );
			
			// TODO: delete order directories if they are empty
			
			$this->set_downloadable_files( $order, $order_item_id, null );
		}
		
		public function unset_downloadable_file( $order, $order_item_id, $attachment_id )
		{
			// TODO: fix race condition
			
			$downloadable_files = $this->get_downloadable_files( $order, $order_item_id );
			if( is_array( $downloadable_files ) && isset( $downloadable_files[$attachment_id] ) )
			{
				// delete file
				if( isset( $downloadable_files[$attachment_id] )
				&& is_array( $downloadable_file = $downloadable_files[$attachment_id] )
				&& isset( $downloadable_file['file'] ) )
					@unlink( $downloadable_file['file'] );
				
				unset( $downloadable_files[$attachment_id] );
				
				$this->set_downloadable_files( $order, $order_item_id, $downloadable_files );
			}
		}
		
		public function woocommerce_get_item_downloads( $files, $order_item, $order )
		{
			if( is_array( $files ) && is_a( $order_item, 'WC_Order_Item' ) && is_a( $order, 'WC_Order' ) )
			{
				$order_id = $order->get_id();
				$order_item_id = $order_item->get_id();
				$product_id = $order_item->get_product_id();
				$product_settings = $this->get_order_metadata( $order, 'product-settings' );
				
				if( is_array( $product_settings )
				&& isset( $product_settings[$product_id] )
				&& is_array( $settings = $product_settings[$product_id] )
				&& isset( $settings['attachments'] )
				&& is_array( $attachments = $settings['attachments'] ) )
				{
					// TODO: optimize
					foreach( $files as $download_id => &$file )
					{
						foreach( $attachments as $attachment )
						{
							$attachment_id = $attachment['attachment_id'];
							
							if( isset( $attachment['options'] )
							&& is_array( $options = $attachment['options'] )
							&& isset( $options['download_id'] )
							&& $options['download_id'] == $download_id )
							{
								$downloadable_file = $this->get_downloadable_file( $order, $order_item_id, $attachment_id );
								
								if( ! is_array( $downloadable_file ) || ! isset( $downloadable_file['file'] ) )
								{
									// if the PDF hasn't been filled yet then we need to fill it
									$placeholder_processor = $this->get_placeholder_processor();
									$placeholder_processor->set_order( $order );
									$placeholder_processor->set_order_item( $order_item );
									$placeholder_processor->set_product_id( $product_id );
									
									// fill PDFs so that they are also saved to the order directory
									// save a list of filled pdfs so that we don't need to fill them again when attaching them to emails
									$this->filled_pdfs[$order_id][$order_item_id] = $this->fill_pdfs( $settings, $placeholder_processor );
									
									$downloadable_file = $this->get_downloadable_file( $order, $order_item_id, $attachment_id );
								}
								
								if( is_array( $downloadable_file ) && isset( $downloadable_file['file'] ) )
								{
									$full_url = trailingslashit( get_site_url() ) . $downloadable_file['file'];
									$file['file'] = $full_url;
									// TODO: use 'secure' download URL
									$file['download_url'] = $full_url;
								}
								else
								{
									// if the PDF is not available for some reason, remove the download
									unset( $files[$download_id] );
								}
							}
						}
					}
				}
			}
			
			return $files;
		}
		
		/*
		 * Hook used on account downloads page to replace downloads URLs
		 */
		public function woocommerce_customer_available_downloads( $downloads, $customer_id )
		{
			// we don't have access to order_item_id, so, we need to match downloads to the order items and replace the download URLs when needed
			
			// TODO: optimize this code
			
			// group downloads by order id and product id
			$order_product_downloads = array();
			foreach( $downloads as $download_index => $download )
			{
				$order_id = $download['order_id'];
				$product_id = $download['product_id'];
				
				$order_product_downloads[$order_id][$product_id][] = $download_index;
			}
			
			// match order item id to product download
			$downloads_items = array();
			$downloads_product_settings = array();
			$downloads_attachment = array();
			$downloads_orders = array();
			// handle each order separately
			foreach( $order_product_downloads as $order_id => $order_products )
			{
				// load order items for this order
				$order = wc_get_order( $order_id );
				if( is_a( $order, 'WC_Order' ) )
				{
					$product_settings = $this->get_order_metadata( $order, 'product-settings' );
					if( ! is_array( $product_settings ) )
						$product_settings = array();
					
					$items = $order->get_items();
					
					// handle each product separately
					foreach( $order_products as $product_id => $product_downloads )
					{
						// load current product's settings
						if( ! isset( $product_settings[$product_id] ) )
							continue;
						
						$settings = $product_settings[$product_id];
						
						if( ! is_array( $settings )
						|| empty( $settings )
						|| ! isset( $settings['attachments'] )
						|| ! is_array( $attachments = $settings['attachments'] ) )
							continue;
						
						// handle each attachment separately
						foreach( $attachments as $attachment )
						{
							$attachment_id = $attachment['attachment_id'];
							
							if( isset( $attachment['options'] )
							&& is_array( $options = $attachment['options'] )
							&& isset( $options['download_id'] ) )
							{
								$attachment_download_id = $options['download_id'];
								
								foreach( $product_downloads as $download_index )
								{
									// if download id matches then that means that this download is for this attachment
									$download = $downloads[$download_index];
									if( $download['download_id'] == $attachment_download_id )
									{
										// now we need to find the order item id for this download
										foreach( $items as $iid => $item )
										{
											if( $item->get_product_id() == $product_id ) // if product matches
											{
												// save the mapping
												$downloads_items[$download_index] = $item;
												
												// cache information for later use
												$downloads_product_settings[$download_index] = $settings;
												$downloads_attachment[$download_index] = $attachment;
												$downloads_orders[$download_index] = $order;
												
												// remove item from the list so that we don't match it again to another download
												unset($items[$iid]);
												
												break;
											}
										}
									}
								}
							}
						}
					}
				}
			}
			
			// replace download urls with our own
			foreach( $downloads as $download_index => &$download )
			{
				if( isset( $downloads_items[$download_index] ) )
				{
					$settings = $downloads_product_settings[$download_index];
					$attachment = $downloads_attachment[$download_index];
					$attachment_id = $attachment['attachment_id'];
					$order = $downloads_orders[$download_index];
					$order_id = $download['order_id'];
					$order_item = $downloads_items[$download_index];
					$order_item_id = $order_item->get_id();
					
					$downloadable_file = $this->get_downloadable_file( $order_id, $order_item_id, $attachment_id );
					
					if( ! is_array( $downloadable_file ) || ! isset( $downloadable_file['file'] ) )
					{
						// if the PDF hasn't been filled yet then we need to fill it
						$placeholder_processor = $this->get_placeholder_processor();
						$placeholder_processor->set_order( $order );
						$placeholder_processor->set_order_item( $order_item );
						$placeholder_processor->set_product_id( $product_id );
						
						// fill PDFs so that they are also saved to the order directory
						$this->filled_pdfs[$order_id][$order_item_id] = $this->fill_pdfs( $settings, $placeholder_processor );
						
						$downloadable_file = $this->get_downloadable_file( $order_id, $order_item_id, $attachment_id );
					}
					
					if( is_array( $downloadable_file ) && isset( $downloadable_file['file'] ) )
					{
						$full_url = trailingslashit( get_site_url() ) . $downloadable_file['file'];
						$download['file']['file'] = $full_url;
						// TODO: use 'secure' download URL
						$download['download_url'] = $full_url;
					}
					else
					{
						// if the PDF is not available for some reason, remove the download
						unset( $downloads[$download_index] );
					}
				}
			}
			
			return $downloads;
		}
		
		/*
		 * Runs when post is deleted to clean up files
		 * The legacy / custom post type (CPT) order storage requires this hook
		 */
		public function before_delete_post( $post_id )
		{
			if( self::is_wc_hpos_enabled() )
				return;
			
			$type = get_post_type( $post_id );
			
			// delete the order directory
			if($type == 'shop_order')
				$this->woocommerce_before_delete_order( $post_id );
			// delete the order item's downloadable files
			else if($type == 'line_item')
				$this->woocommerce_before_delete_order_item( $post_id );
		}
		
		/*
		 * Runs when order is deleted to clean up order's items' downloadable files
		 */
		public function woocommerce_before_delete_order( $order_id )
		{
			// don't save the order because it is being deleted anyway
			$this->do_not_save_orders[$order_id] = $order_id;
			
			// remove downloadable files
			$this->unset_downloadable_files( $order_id );
			
			// delete order directory
			$this->delete_order_storage( $order_id );
		}
		
		/*
		 * Runs when order item is deleted to clean up order item's downloadable files
		 */
		public function woocommerce_before_delete_order_item( $order_item_id )
		{
			$order_id = wc_get_order_id_by_order_item_id( $order_item_id );
			if( ! $order_id )
				return;
			
			// remove order item downloadable files
			$this->unset_downloadable_files( $order_id, $order_item_id );
		}
		
		/**
		 * Saves messages to be shown to admin / store owner later
		 */
		private static function log_admin_message( $type, $message )
		{
			$messages = get_option( 'pdf-forms-for-woocommerce-messages', array() );
			
			if( ! is_array( $messages ) )
				$messages = array();
			
			// remove old messages to prevent the option from growing too large
			if( count( $messages ) > 999 )
				$messages = array_slice( $messages, -999 );
			
			$messages[] = array( 'type' => $type, 'message' => $message );
			
			update_option( 'pdf-forms-for-woocommerce-messages', $messages );
		}
		
		/**
		 * Retrieves admin messages
		 */
		private static function get_admin_messages()
		{
			$messages = get_option( 'pdf-forms-for-woocommerce-messages', array() );
			if( ! is_array( $messages ) )
				$messages = array();
			return $messages;
		}
		
		/**
		 * Clear admin messages
		 */
		private static function clear_admin_messages()
		{
			update_option( 'pdf-forms-for-woocommerce-messages', array() );
		}
		
		/**
		 * Fills PDFs
		 */
		private function fill_pdfs( $settings, $placeholder_processor )
		{
			try
			{
				$fill_id = wp_hash( wp_rand() . microtime() );
				
				$output_files = array();
				
				$attachments = array();
				$mappings = array();
				$embeds = array();
				$value_mappings = array();
				
				if( isset( $settings['attachments'] ) && is_array( $settings['attachments'] ) )
					$attachments = $settings['attachments'];
				if( isset( $settings['mappings'] ) && is_array( $settings['mappings'] ) )
					$mappings = $settings['mappings'];
				if( isset( $settings['embeds'] ) && is_array( $settings['embeds'] ) )
					$embeds = $settings['embeds'];
				if( isset( $settings['value_mappings'] ) && is_array( $settings['value_mappings'] ))
					$value_mappings = $settings['value_mappings'];
				
				$files = array();
				
				$service = $this->get_service();
				
				// preprocess embedded images
				$embed_files = array();
				foreach( $embeds as $id => $embed )
				{
					$filepath = null;
					$filename = null;
					$url_mimetype = null;
					
					$url = null;
					
					if( isset( $embed['placeholders'] ) ) 
						$url = $placeholder_processor->process( $embed["placeholders"] );
					
					if( $url != null )
					{
						if( filter_var( $url, FILTER_VALIDATE_URL ) !== FALSE )
						if( substr( $url, 0, 5 ) === 'http:' || substr( $url, 0, 6 ) === 'https:' )
						{
							$filepath = $this->create_tmp_filepath( $fill_id, 'img_download_'.count($embed_files).'.tmp' );
							self::download_file( $url, $filepath, $url_mimetype ); // can throw an exception
							$filename = $url;
						}
						
						if( substr( $url, 0, 5 ) === 'data:' )
						{
							$filepath = $this->create_tmp_filepath( $fill_id, 'img_data_'.count($embed_files).'.tmp' );
							$filename = $url;
							
							$parsed = self::parse_data_uri( $url );
							if( $parsed !== false )
							{
								$url_mimetype = $parsed['mime'];
								if( file_put_contents( $filepath, $parsed['data'] ) === false || ! is_file( $filepath ) )
									throw new Exception( __( "Failed to create file", 'pdf-forms-for-woocommerce' ) );
							}
						}
					}
					
					if( ! $filepath )
						continue;
					
					$file_mimetype = self::get_mime_type( $filepath );
					
					$mimetype_supported = false;
					$mimetype = 'unknown';
					
					if( $file_mimetype )
					{
						$mimetype = $file_mimetype;
						
						// check if MIME type is supported based on file contents
						$mimetype_supported = $this->is_embed_image_format_supported( $file_mimetype );
					}
					
					// if we were not able to determine MIME type based on file contents
					// then fall back to URL MIME type (if we are dealing with a URL)
					// (maybe fileinfo functions are not functional and WP fallback failed due to the ".tmp" extension)
					if( !$mimetype_supported && $url_mimetype )
					{
						$mimetype = $url_mimetype;
						$mimetype_supported = $this->is_embed_image_format_supported( $url_mimetype );
					}
					
					if( !$mimetype_supported )
						throw new Exception(
							self::replace_tags(
								__( "File type {mime-type} of {file} is unsupported for {purpose}", 'pdf-forms-for-woocommerce' ),
								array( 'mime-type' => $mimetype, 'file' => $filename, 'purpose' => __( "image embedding", 'pdf-forms-for-woocommerce' ) )
							)
						);
					
					$embed_files[$id] = $filepath;
				}
				
				foreach( $attachments as $attachment )
				{
					$attachment_id = $attachment["attachment_id"];
					
					$fields = $this->get_fields( $attachment_id );
					$data = array();
					
					// process mappings
					foreach( $mappings as $mapping )
					{
						$i = strpos( $mapping["pdf_field"], '-');
						if( $i === FALSE )
							continue;
						
						$aid = substr( $mapping["pdf_field"], 0, $i );
						if( $aid != $attachment_id && $aid != 'all' )
							continue;
						
						$field = substr( $mapping["pdf_field"], $i+1);
						$field = self::base64url_decode( $field );
						
						if( !isset( $fields[$field] ) )
							continue;
						
						$multiple = isset( $fields[$field]['flags'] ) && in_array( 'MultiSelect', $fields[$field]['flags'] );
						
						if( isset( $mapping["placeholders"] ) )
						{
							$data[$field] = $placeholder_processor->process( $mapping["placeholders"] );
							
							if( $multiple )
							{
								$data[$field] = explode( "\n" , $data[$field] );
								foreach( $data[$field] as &$value )
									$value = trim( $value );
								unset( $value );
							}
						}
					}
					
					if( count( $value_mappings ) > 0 )
					{
						// process value mappings
						$processed_value_mappings = array();
						$value_mapping_data = array();
						$existing_data_fields = array_fill_keys( array_keys( $data ), true );
						foreach( $value_mappings as $value_mapping )
						{
							$i = strpos( $value_mapping["pdf_field"], '-' );
							if( $i === FALSE )
								continue;
							
							$aid = substr( $value_mapping["pdf_field"], 0, $i );
							if( $aid != $attachment_id && $aid != 'all' )
								continue;
							
							$field = substr( $value_mapping["pdf_field"], $i+1 );
							$field = self::base64url_decode( $field );
							
							if( !isset( $existing_data_fields[$field] ) )
								continue;
							
							if( !isset( $value_mapping_data[$field] ) )
								$value_mapping_data[$field] = $data[$field];
							
							$woo_value = strval( $value_mapping['woo_value'] );
							if( ! isset( $processed_value_mappings[$field] ) )
								$processed_value_mappings[$field] = array();
							if( ! isset( $processed_value_mappings[$field][$woo_value] ) )
								$processed_value_mappings[$field][$woo_value] = array();
							$processed_value_mappings[$field][$woo_value][] = $value_mapping;
						}
						
						// convert plain text values to arrays for processing
						foreach( $value_mapping_data as $field => &$value )
							if( ! is_array( $value ) )
								$value = array( $value );
						unset( $value );
						
						// determine old and new values
						$add_data = array();
						$remove_data = array();
						foreach($processed_value_mappings as $field => $woo_mappings_list)
							foreach($woo_mappings_list as $woo_value => $list)
							{
								foreach( $value_mapping_data[$field] as $key => $value )
									if( Pdf_Forms_For_WooCommerce_Wrapper::mb_strtolower( $value ) === Pdf_Forms_For_WooCommerce_Wrapper::mb_strtolower( $woo_value ) )
									{
										if( ! isset( $remove_data[$field] ) )
											$remove_data[$field] = array();
										$remove_data[$field][] = $value;
										
										if( ! isset( $add_data[$field] ) )
											$add_data[$field] = array();
										foreach( $list as $item )
											$add_data[$field][] = $item['pdf_value'];
									}
							}
						
						// remove old values
						foreach( $value_mapping_data as $field => &$value )
							if( isset( $remove_data[$field] ) )
								$value = array_diff( $value, $remove_data[$field] );
						unset( $value );
						
						// add new values
						foreach( $value_mapping_data as $field => &$value )
							if( isset( $add_data[$field] ) )
								$value = array_unique( array_merge( $value, $add_data[$field] ) );
						unset( $value );
						
						// convert arrays back to plain text where needed
						foreach( $value_mapping_data as $field => &$value )
							if( count( $value ) < 2 )
							{
								if( count( $value ) > 0 )
									$value = reset( $value );
								else
									$value = null;
							}
						unset( $value );
						
						// update data
						foreach( $value_mapping_data as $field => &$value )
							$data[$field] = $value;
						unset( $value );
					}
					
					// filter out anything that the pdf field can't accept
					foreach( $data as $field => &$value )
					{
						$type = $fields[$field]['type'];
						
						if( $type == 'radio' || $type == 'select' || $type == 'checkbox' )
						{
							// compile a list of field options
							$pdf_field_options = null;
							if( isset( $fields[$field]['options'] ) && is_array( $fields[$field]['options'] ) )
							{
								$pdf_field_options = $fields[$field]['options'];
								
								// if options are have more information than value, extract only the value
								foreach( $pdf_field_options as &$option )
									if( is_array( $option ) && isset( $option['value'] ) )
										$option = $option['value'];
								unset( $option );
							}
							
							// if a list of options are available then filter $value
							if( $pdf_field_options !== null )
							{
								if( is_array( $value ) )
									$value = array_intersect( $value, $pdf_field_options );
								else
									$value = in_array( $value, $pdf_field_options ) ? $value : null;
							}
						}
						
						// if pdf field is not a multiselect field but value is an array then use the first element only
						$pdf_field_multiselectable = isset( $fields[$field]['flags'] ) && in_array( 'MultiSelect', $fields[$field]['flags'] );
						if( !$pdf_field_multiselectable && is_array( $value ) )
						{
							if( count( $value ) > 0 )
								$value = reset( $value );
							else
								$value = null;
						}
					}
					unset( $value );
					
					// process image embeds
					$embeds_data = array();
					foreach( $embeds as $id => $embed )
						if( $embed['attachment_id'] == $attachment_id || $embed['attachment_id'] == 'all' )
						{
							if( isset( $embed_files[$id] ) )
							{
								$embed_data = array(
									'image' => $embed_files[$id],
									'page' => $embed['page'],
								);
								
								if($embed['page'] > 0)
								{
									$embed_data['left'] = $embed['left'];
									$embed_data['top'] = $embed['top'];
									$embed_data['width'] = $embed['width'];
									$embed_data['height'] = $embed['height'];
								};
								
								$embeds_data[] = $embed_data;
							}
						}
					
					// skip file if 'skip when empty' option is enabled and form data is blank
					if($attachment['options']['skip_empty'] )
					{
						$empty_data = true;
						foreach( $data as $field => $value )
							if( !( is_null( $value ) || $value === array() || trim( $value ) === "" ) )
							{
								$empty_data = false;
								break;
							}
						
						if( $empty_data && count( $embeds_data ) == 0 )
							continue;
					}
					
					// skip file if it is not used anywhere
					$attaching_to_notification = count( $attachment['options']['email_templates'] ) > 0;
					$saving_in_directory = strval( $attachment['options']['save_directory'] ) !== "";
					$creating_download = ! empty( $attachment['options']['download_id'] );
					if( ! $attaching_to_notification
					&& ! $saving_in_directory
					&& ! $creating_download )
						continue;
					
					$options = array();
					
					$options['flatten'] =
						isset($attachment['options']) &&
						isset($attachment['options']['flatten']) &&
						$attachment['options']['flatten'] == true;
					
					// determine if the attachment would be changed
					$filling_data = false;
					foreach( $data as $field => $value )
					{
						if( $value === null || $value === '' )
							$value = array();
						else if( ! is_array( $value ) )
							$value = array( $value );
						
						$pdf_value = null;
						if( isset( $fields[$field]['value'] ) )
							$pdf_value = $fields[$field]['value'];
						if( $pdf_value === null || $pdf_value === '' )
							$pdf_value = array();
						else if( ! is_array( $pdf_value ) )
							$pdf_value = array( $pdf_value );
						
						// check if values don't match
						if( ! ( array_diff( $value, $pdf_value ) == array() && array_diff( $pdf_value, $value ) == array() ) )
						{
							$filling_data = true;
							break;
						}
					}
					$attachment_affected = $filling_data || count( $embeds_data ) > 0 || $options['flatten'];
					
					$destfilename = strval( $attachment['options']['filename'] );
					if( $destfilename != "" )
						$destfilename = strval( $placeholder_processor->process( $destfilename ) );
					if( $destfilename == "" )
						$destfilename = sanitize_file_name( get_the_title( $attachment_id ) );
					
					$destfile = $this->create_tmp_filepath( $fill_id, $destfilename . '.pdf' );
					
					$filled = false;
					
					if( $service )
						// we only want to use the API when something needs to be done to the file
						if( $attachment_affected )
							$filled = $service->api_fill_embed( $destfile, $attachment_id, $data, $embeds_data, $options );
					
					if( ! $filled )
					{
						$filepath = get_attached_file( $attachment_id );
						if( empty( $filepath ) )
						{
							$fileurl = wp_get_attachment_url( $attachment_id );
							if( empty( $fileurl ) )
								throw new Exception( __( "Attachment file is not accessible", 'pdf-forms-for-woocommerce' ) );
							self::download_file( $fileurl, $destfile );
						}
						else
							copy( $filepath, $destfile );
					}
					$files[] = array( 'attachment_id' => $attachment_id, 'file' => $destfile, 'filename' => $destfilename . '.pdf', 'options' => $attachment['options'] );
				}
				
				if( count( $files ) > 0 )
				{
					$storage = self::get_storage();
					
					$order = $placeholder_processor->get_order();
					if( ! is_a( $order, 'WC_Order' ) )
						$order = null;
					$order_item_id = null;
					$order_item = $placeholder_processor->get_order_item();
					if( is_a( $order_item, 'WC_Order_Item' ) )
						$order_item_id = $order_item->get_id();
					$saved_files = $this->get_order_metadata( $order, 'saved-files' );
					if( ! is_array( $saved_files ) )
						$saved_files = array();
					
					foreach( $files as $id => $filedata )
					{
						$output_files[] = $filedata['file'];
						
						$save_directory = strval( $filedata['options']['save_directory'] );
						if( $save_directory !== "" )
						{
							// standardize directory separator
							$save_directory = str_replace( '\\', '/', $save_directory );
							
							// remove preceding slashes and dots and space characters
							$trim_characters = "/\\. \t\n\r\0\x0B";
							$save_directory = trim( $save_directory, $trim_characters );
							
							// replace placeholders in path elements
							$path_elements = explode( "/", $save_directory );
							$tag_replaced_path_elements = array();
							foreach ( $path_elements as $key => $value )
								$tag_replaced_path_elements[$key] = $placeholder_processor->process( $value );
							
							foreach( $tag_replaced_path_elements as $elmid => &$new_element )
							{
								// sanitize
								$new_element = trim( sanitize_file_name( $new_element ), $trim_characters );
								
								// if replaced and sanitized filename is blank then attempt to use the non-tag-replaced version
								if( $new_element === "" )
									$new_element = trim( sanitize_file_name( $path_elements[$elmid] ), $trim_characters );
							}
							unset($new_element);
							
							$save_directory = implode( "/", $tag_replaced_path_elements );
							$save_directory = preg_replace( '|/+|', '/', $save_directory ); // remove double slashes
							
							$storage->set_subpath( $save_directory );
							
							// determine if we need to overwrite an existing file or create a new one
							$overwrite = true; // by default, overwrite existing files to prevent a huge number of files from accumulating from the same order item / attachment
							$filename = $filedata['filename'];
							if( $order )
							{
								$filename_id = $order_item_id . '-' . $filedata['attachment_id'];
								if( isset( $saved_files[$filename_id] ) )
								{
									$overwrite = true;
									$filename = $saved_files[$filename_id];
								}
								else
									$overwrite = false; // don't overwrite if it is truly a new file, instead come up with a new filename and save it in the order metadata
							}
							
							$filename = $storage->save( $filedata['file'], $filename, $overwrite );
							
							if( $order && ! $overwrite )
							{
								// store filename in order metadata
								$saved_files[$filename_id] = $filename;
								$this->set_order_metadata( $order, 'saved-files', $saved_files);
							}
						}
						
						$save_order_file = $filedata['options']['download_id'];
						if ( ! empty( $save_order_file ) )
						{
							if( $order && $order_item_id )
							{
								$order_storage = $this->get_order_storage( $order );
								$order_storage->set_subpath( trailingslashit( $order_storage->get_subpath() ) . sanitize_file_name( $order_item_id ) );
								$dstfilename = $order_storage->save( $filedata['file'], $filedata['filename'] , $overwrite = true );
								
								// record file data in order meta
								$this->set_downloadable_file(
									$order,
									$order_item_id,
									$attachment_id,
									trailingslashit( $order_storage->get_site_root_relative_path() ) . $dstfilename,
									$filedata['filename']
								);
							}
						}
					}
				}
				
				return $output_files;
			}
			catch( Exception $e )
			{
				$product_id = $placeholder_processor->get_product_id();
				$order = $placeholder_processor->get_order();
				$order_id = is_a( $order, 'WC_Order' ) ? $order->get_id() : null;
				if( $product_id && $order_id)
					$caption = __( "[{timestamp}] (order:{order}, product:{product}) Error filling PDFs: {error-message} at {error-file}:{error-line}", 'pdf-forms-for-woocommerce' );
				else if( $order_id )
					$caption = __( "[{timestamp}] (order:{order}) Error filling PDFs for order {order}: {error-message} at {error-file}:{error-line}", 'pdf-forms-for-woocommerce' );
				else
					$caption = __( "[{timestamp}] Error filling PDFs: {error-message} at {error-file}:{error-line}", 'pdf-forms-for-woocommerce' );
				$error_message = self::replace_tags(
					$caption,
					array(
						'timestamp' => gmdate( 'Y-m-d H:i:s e' ),
						'product' => $product_id,
						'order' => $order_id,
						'error-message' => $e->getMessage(),
						'error-file' => wp_basename( $e->getFile() ),
						'error-line' => $e->getLine()
					)
				);
				
				// log error in woocommerce error logging facility
				wc_get_logger()->error( $error_message, array( 'source' => 'pdf-forms-for-woocommerce' ) );
				
				// notify store owner of error
				self::log_admin_message( 'error', $error_message );
				
				return array();
			}
		}
		
		/**
		 * Takes html template from the html folder and renders it with the given attributes
		 */
		public static function render( $template, $attributes = array() )
		{
			return self::render_file( plugin_dir_path(__FILE__) . 'html/' . $template . '.html', $attributes );
		}
		
		/**
		 * Renders a notice with the given attributes
		 */
		public static function render_notice( $notice_id, $type, $attributes = array() )
		{
			if( ! isset( $attributes['classes'] ) )
				$attributes['classes'] = "";
			$attributes['classes'] = trim( $attributes['classes'] . " notice-$type" );
			
			if( !isset( $attributes['label'] ) )
				$attributes['label'] = __( "PDF Forms Filler for WooCommerce", 'pdf-forms-for-woocommerce' );
			
			if( $notice_id )
			{
				$attributes['attributes'] = 'data-notice-id="'.esc_attr( $notice_id ).'"';
				$attributes['classes'] .= ' is-dismissible';
			}
			
			return self::render( "notice", $attributes );
		}
		
		/**
		 * Renders a success notice with the given attributes
		 */
		public static function render_success_notice( $notice_id, $attributes = array() )
		{
			return self::render_notice( $notice_id, 'success', $attributes );
		}
		
		/**
		 * Renders a warning notice with the given attributes
		 */
		public static function render_warning_notice( $notice_id, $attributes = array() )
		{
			return self::render_notice( $notice_id, 'warning', $attributes );
		}
		
		/**
		 * Renders an error notice with the given attributes
		 */
		public static function render_error_notice( $notice_id, $attributes = array() )
		{
			return self::render_notice( $notice_id, 'error', $attributes );
		}
		
		/**
		 * Helper for replace_tags function
		 */
		private static function add_curly_braces($str)
		{
			return '{'.$str.'}';
		}
		
		/**
		 * Takes a string with tags and replaces tags in the string with the given values in $tags array
		 */
		public static function replace_tags( $string, $tags = array() )
		{
			return str_replace(
				array_map( array( get_class(), 'add_curly_braces' ), array_keys( $tags ) ),
				array_values( $tags ),
				$string
			);
		}
		
		/**
		 * Takes html template file and renders it with the given attributes
		 */
		public static function render_file( $template_filepath, $attributes = array() )
		{
			// phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents -- $template_filepath is a local filesystem path and can't be used with wp_remote_get()
			return self::replace_tags( file_get_contents( $template_filepath ) , $attributes );
		}
		
		/**
		 * Adds the 'PDF Forms' tab on WooCommerce product page
		 */
		public function add_product_data_tab( $tabs )
		{
			$tabs['pdf-forms-for-woocommerce'] = array(
				'label'    => __( 'PDF Forms', 'pdf-forms-for-woocommerce' ),
				'target'   => 'pdf-forms-for-woocommerce-product-settings',
				'class'    => array()
			);
			
			return $tabs;
		}
		
		/**
		 * Prints 'PDF Forms' tab HTML contents
		 */
		public function print_product_data_tab_contents()
		{
			global $post;
			$product_id = $post->ID;
			
			$attachments = array();
			$email_templates = array();
			$woocommerce_placeholders = array();
			
			$service = $this->get_service();
			
			$settings = self::get_metadata( $product_id, 'product-settings' );
			if( ! is_array( $settings ) )
				$settings = array();
			
			// get attachments
			if( isset( $settings['attachments'] ) && is_array( $settings['attachments'] ) )
			foreach( $settings['attachments'] as $attachment )
			{
				$attachment_id = $attachment['attachment_id'];
				try
				{
					$info = $this->get_info( $attachment_id );
					$info['fields'] = $this->query_pdf_fields( $attachment_id );
				}
				catch( Exception $e ) { $info = null; }
				
				$attachments[] = array(
					'attachment_id' => $attachment_id,
					'filename' => get_the_title( $attachment_id ),
					'info' => $info,
				);
			}
			
			// get email templates
			$email_classes = WC()->mailer()->get_emails();
			$non_order_templates = array( 'customer_new_account', 'customer_reset_password' );
			foreach( $email_classes as $email_class )
				if( ! in_array( $email_class->id, $non_order_templates ) )
					$email_templates[] = array(
						'id' => $email_class->id,
						'alias' => $email_class->id,
						'text' => $email_class->title,
						'lowerText' => Pdf_Forms_For_WooCommerce_Wrapper::mb_strtolower( $email_class->title ),
					);
			
			// prepare woocommerce placeholders for select2
			foreach( $this->get_placeholder_processor()->get_placeholders() as $placeholder )
			{
				$tag = '{'.$placeholder['key'].'}';
				$woocommerce_placeholders[] = array(
					'id' => count( $woocommerce_placeholders ),
					'text' => $tag,
					'lowerText' => Pdf_Forms_For_WooCommerce_Wrapper::mb_strtolower( $tag ),
				);
			}
			
			// get product's downloads
			$downloads = array(
				array( 'id' => '', 'text' => __( "None", 'pdf-forms-for-woocommerce' ) ),
				array( 'id' => 'create-new-download', 'text' => __( "Create a new downloadable file", 'pdf-forms-for-woocommerce') ),
			);
			$product = wc_get_product( $product_id );
			if( $product )
			{
				$list = $product->get_downloads();
				if( is_array( $list ) )
					foreach( $list as $download )
						$downloads[] = array(
							'id' => $download->get_id(),
							'text' => $download->get_name(),
						);
			}
			
			$preload_data = array(
				'default_pdf_options' => self::DEFAULT_PDF_OPTIONS,
				'attachments' => $attachments,
				'email_templates' => $email_templates,
				'woocommerce_placeholders' => $woocommerce_placeholders,
				'downloads' => $downloads,
			);
			
			echo self::render( 'spinner' ) .
				self::render( 'product-settings', array(
					'messages' => call_user_func( function() use ( $service ) {
						ob_start();
						if( isset( $service ) ) $service->settings_notices();
						return ob_get_clean(); // no escaping needed
					} ),
					'data-field' => call_user_func( function() use ( $settings ) {
						ob_start();
						woocommerce_wp_hidden_input( array(
							'id'    => 'pdf-forms-for-woocommerce-data',
							'class' => 'pdf-forms-for-woocommerce-data',
							'value' => Pdf_Forms_For_WooCommerce_Wrapper::json_encode( $settings ),
						) );
						return ob_get_clean(); // no escaping needed
					} ),
					'preload-data' => esc_html( Pdf_Forms_For_WooCommerce_Wrapper::json_encode( $preload_data ) ),
					'instructions' => esc_html__( "You can use this section to attach a PDF file to your product and link WooCommerce placeholders to fields in the PDF file. You can also embed images from a URL into the PDF file. Changes here are applied when the product is saved.", 'pdf-forms-for-woocommerce' ),
					'attach-pdf' => esc_html__( "Attach a PDF File", 'pdf-forms-for-woocommerce' ),
					'delete' => esc_html__( 'Delete', 'pdf-forms-for-woocommerce' ),
					'map-value' => esc_html__( 'Map Value', 'pdf-forms-for-woocommerce' ),
					'options' => esc_html__( 'Options', 'pdf-forms-for-woocommerce' ),
					'skip-when-empty' => esc_html__( 'Skip when empty', 'pdf-forms-for-woocommerce' ),
					'email-templates' => esc_html__( 'Attach the filled PDF file to the following emails:', 'pdf-forms-for-woocommerce' ),
					'flatten' => esc_html__( 'Flatten', 'pdf-forms-for-woocommerce' ),
					'filename' => esc_html__( 'New filled PDF file name (placeholders allowed):', 'pdf-forms-for-woocommerce' ),
					'save-directory'=> esc_html__( 'Path for saving filled PDF file (placeholders allowed):', 'pdf-forms-for-woocommerce' ),
					'download-link' => esc_html__( "Provide a download link to the filled PDF file via the product's downloadable file:", 'pdf-forms-for-woocommerce' ),
					'leave-blank-to-disable'=> esc_html__( '(leave blank to disable this option)', 'pdf-forms-for-woocommerce' ),
					'field-mapping' => esc_html__( 'Field Mapper Tool', 'pdf-forms-for-woocommerce' ),
					'field-mapping-help' => esc_html__( 'This tool can be used to link WooCommerce placeholders to fields in the attached PDF files. When an order email notification is sent or downloadable file is requested, text with placeholder data will be inserted into the corresponding fields in the PDF file and the filled PDF will be made available.', 'pdf-forms-for-woocommerce' ),
					'pdf-field' => esc_html__( 'PDF field', 'pdf-forms-for-woocommerce' ),
					'woo-placeholder' => esc_html__( 'WooCommerce placeholders', 'pdf-forms-for-woocommerce' ),
					'add-mapping' => esc_html__( 'Add Mapping', 'pdf-forms-for-woocommerce' ),
					'delete-all' => esc_html__( 'Delete All', 'pdf-forms-for-woocommerce' ),
					'new-field' => esc_html__( 'New Field:', 'pdf-forms-for-woocommerce' ),
					'image-embedding' => esc_html__( 'Image Embedding Tool', 'pdf-forms-for-woocommerce' ),
					'image-embedding-help'=> esc_html__( 'This tool allows embedding of images into PDF files. Images are taken from the provided URLs that may contain placeholders. You can select a PDF file page and draw a bounding box for image insertion. Alternatively, you can insert your image in the center of every page.', 'pdf-forms-for-woocommerce' ),
					'add-woo-placeholder-embed' => esc_html__( 'Embed Image', 'pdf-forms-for-woocommerce' ),
					'delete-woo-placeholder-embed' => esc_html__( 'Delete', 'pdf-forms-for-woocommerce' ),
					'pdf-file' => esc_html__( 'PDF file', 'pdf-forms-for-woocommerce' ),
					'page' => esc_html__( 'Page', 'pdf-forms-for-woocommerce' ),
					'image-region-selection-hint' => esc_html__( 'Select a region where the image needs to be embeded.', 'pdf-forms-for-woocommerce' ),
					'top' => esc_html__( 'Top', 'pdf-forms-for-woocommerce' ),
					'left' => esc_html__( 'Left', 'pdf-forms-for-woocommerce' ),
					'width' => esc_html__( 'Width', 'pdf-forms-for-woocommerce' ),
					'height' => esc_html__( 'Height', 'pdf-forms-for-woocommerce' ),
					'pts' => esc_html__( 'pts', 'pdf-forms-for-woocommerce' ),
					'help-message' => self::replace_tags(
						esc_html__( "Have a question/comment/problem? Feel free to use {a-href-forum}the support forum{/a}.", 'pdf-forms-for-woocommerce' ),
						array(
							'a-href-forum' => '<a href="https://wordpress.org/support/plugin/pdf-forms-for-woocommerce/" target="_blank">',
							'/a' => '</a>',
						)
					),
					'show-help' => esc_html__( 'Show Help', 'pdf-forms-for-woocommerce' ),
					'hide-help' => esc_html__( 'Hide Help', 'pdf-forms-for-woocommerce' ),
				) );
		}
		
		/**
		 * Hook that runs on product save action to validate plugin data
		 */
		// phpcs:disable WordPress.Security.NonceVerification.Missing -- Nonce verification is supposedly already done by WooCommerce prior to calling this function in WC_Admin_Meta_Boxes::save_meta_boxes()
		public function save_product_data( $product_id )
		{
			if( ! isset( $_POST['pdf-forms-for-woocommerce-data'] ) )
				return;
			
			try
			{
				$data = json_decode( wp_unslash( $_POST['pdf-forms-for-woocommerce-data'] ), true );
				
				if( ! is_array( $data ) )
					throw new Exception(
							__( "Failed to decode data", 'pdf-forms-for-woocommerce' ),
						);
				
				// check attachments
				$attachments = array();
				if( isset( $data['attachments'] ) && is_array( $data['attachments'] ) )
				{
					// get email templates
					$email_classes = WC()->mailer()->get_emails();
					$email_templates = array();
					foreach( $email_classes as $email_class )
						$email_templates[] = $email_class->id;
					
					foreach( $data['attachments'] as $attachment )
					{
						$attachment_id = $attachment['attachment_id'];
						
						// check permissions
						if( ! current_user_can( 'edit_post', $attachment_id ) )
							continue;
						
						// check options
						if( !isset( $attachment['options'] ) || !is_array( $attachment['options'] ) )
							$attachment['options'] = self::DEFAULT_PDF_OPTIONS;
						else
						{
							// add missing options
							foreach( self::DEFAULT_PDF_OPTIONS as $option_name => $option_value )
								if( ! isset( $attachment['options'][$option_name] ) )
									$attachment['options'][$option_name] = $option_value;
							
							// remove non-existing options
							$allowed_options = array_keys( self::DEFAULT_PDF_OPTIONS );
							foreach( $attachment['options'] as $option_name => $option_value )
								if( ! in_array( $option_name, $allowed_options ) )
									unset( $attachment['options'][$option_name] );
							
							// check skip_empty to make sure it is a boolean value
							if( isset( $attachment['options']['skip_empty'] ) && ! is_bool( $attachment['options']['skip_empty'] ) )
								$attachment['options']['skip_empty'] = boolval( $attachment['options']['skip_empty'] );
							
							// check flatten to make sure it is a boolean value
							if( isset( $attachment['options']['flatten'] ) && ! is_bool( $attachment['options']['flatten'] ) )
								$attachment['options']['flatten'] = boolval( $attachment['options']['flatten'] );
							
							// check email templates
							if( isset( $attachment['options']['email_templates'] ) )
							{
								$option_value = $attachment['options']['email_templates'];
								if( ! is_array( $option_value ) )
									$option_value = array();
								if( count( $option_value ) > 0 )
									foreach( $option_value as $etid => $email_template )
										// check to make sure this notification is valid
										if( ! in_array( $email_template, $email_templates ) )
											unset( $attachment['options']['email_templates'][$etid] );
							}
							
							// create a new downloadable file if necessary
							if( ! empty( $attachment['options']['download_id'] ) )
							{
								$product = wc_get_product( $product_id );
								
								// make sure product is downloadable
								if( ! $product->get_downloadable() )
									$product->set_downloadable( true );
								
								$downloads = $product->get_downloads();
								
								if( $attachment['options']['download_id'] == 'create-new-download' )
								{
									$attachment['options']['download_id'] = '';
									
									// create the product's downloadable file entry
									$download_id = '';
									$attachment_url = wp_get_attachment_url( $attachment_id );
									
									// check if download already exists
									foreach( $downloads as $download )
										if( $download->get_file() == $attachment_url )
											$download_id = $download->get_id();
									
									// don't create a new download if one already exists
									if( $download_id == '' && $product)
									{
										if( ! empty( $attachment['options']['filename'] ) )
											$name = strval( $attachment['options']['filename'] );
										else
											$name = get_the_title( $attachment_id );
										
										$downloads[] = array(
											'name' => $name,
											'file' => $attachment_url,
										);
										$product->set_downloads( $downloads );
										$product->save();
										
										$downloads = $product->get_downloads();
										
										// get download id
										$download_id = '';
										foreach( $downloads as $download )
											if( $download->get_file() == $attachment_url )
												$download_id = $download->get_id();
									}
									
									// update download id in options
									$attachment['options']['download_id'] = $download_id;
								}
								
								// make sure download id is valid
								if( ! empty( $attachment['options']['download_id'] ) )
								{
									$download_id = $attachment['options']['download_id'];
									$download_exists = false;
									foreach( $downloads as $download )
										if( $download->get_id() == $download_id )
										{
											$download_exists = true;
											break;
										}
									if( ! $download_exists )
										$attachment['options']['download_id'] = '';
								}
							}
						}
						
						$attachments[$attachment_id] = $attachment;
					}
				}
				$data['attachments'] = $attachments;
				
				// process mappings
				$mappings = array();
				if( isset( $data['mappings'] ) && is_array( $data['mappings'] ) )
				{
					foreach( $data['mappings'] as $mapping )
					{
						if( isset( $mapping['placeholders'] ) && isset( $mapping['pdf_field'] ) )
							$mappings[] = array( 'placeholders' => $mapping['placeholders'], 'pdf_field' => $mapping['pdf_field'] );
						
						// TODO: make sure pdf field exists
					}
				}
				$data['mappings'] = $mappings;
				
				// process embeds
				$embeds = array();
				if( isset( $data['embeds'] ) && is_array( $data['embeds'] ) )
				{
					foreach( $data['embeds'] as $embed )
					{
						if( ! isset( $embed['attachment_id'] ) )
							continue;
						
						if( ! isset( $embed['placeholders'] ) )
							continue;
						
						// make sure attachment exists
						if( ! isset( $data['attachments'][ $embed['attachment_id'] ] ) && $embed['attachment_id'] !== 'all' )
							continue;
						
						// TODO: make sure pdf page exists
						// TODO: check insertion position and size
						
						if( isset( $embed['placeholders'] ) )
							$embed['placeholders'] = strval( $embed['placeholders'] );
						
						// TODO: don't reuse user input but create a new array with checked data
						$embeds[] = $embed;
					}
				}
				$data['embeds'] = $embeds;
				
				// process value mappings
				if( !isset( $data['value_mappings'] ) || !is_array( $data['value_mappings'] ) )
					$data['value_mappings'] = array();
				else
				{
					$value_mappings = array();
					foreach( $data['value_mappings'] as $value_mapping )
						if( isset( $value_mapping['pdf_field'] ) && isset( $value_mapping['woo_value'] ) && isset( $value_mapping['pdf_value'] ) )
							$value_mappings[] = array( 'pdf_field' => $value_mapping['pdf_field'], 'woo_value' => $value_mapping['woo_value'], 'pdf_value' => $value_mapping['pdf_value'] );
					$data['value_mappings'] = $value_mappings;
				}
				
				self::set_metadata( $product_id, 'product-settings', $data );
			}
			catch( Exception $e )
			{
				$error_message = self::replace_tags(
					__( "Error saving PDF form data: {error-message} at {error-file}:{error-line}", 'pdf-forms-for-woocommerce' ),
					array( 'error-message' => $e->getMessage(), 'error-file' => wp_basename( $e->getFile() ), 'error-line' => $e->getLine() )
				);
				
				// log error in woocommerce error logging facility
				wc_get_logger()->error( $error_message, array( 'source' => 'pdf-forms-for-woocommerce' ) );
				
				// show error message in to the user
				WC_Admin_Meta_Boxes::add_error( $error_message );
			}
		}
		// phpcs:enable WordPress.Security.NonceVerification.Missing
		
		/**
		 * Adds necessary admin scripts and styles
		 */
		public function admin_enqueue_scripts( $hook )
		{
			wp_register_script( 'pdf_forms_for_woocommerce_notices_script', plugins_url( 'js/notices.js', __FILE__ ), array( 'jquery' ), self::VERSION );
			wp_register_style( 'pdf_forms_for_woocommerce_notices_style', plugin_dir_url( __FILE__ ) . 'css/notices.css', array( ), self::VERSION );
			
			wp_localize_script( 'pdf_forms_for_woocommerce_notices_script', 'pdf_forms_for_woocommerce', array(
				'ajax_url' => admin_url( 'admin-ajax.php' ),
				'ajax_nonce' => wp_create_nonce( 'pdf-forms-for-woocommerce-ajax-nonce' ),
			) );
			
			wp_enqueue_script( 'pdf_forms_for_woocommerce_notices_script' );
			wp_enqueue_style( 'pdf_forms_for_woocommerce_notices_style' );
			
			if( ! class_exists( 'WooCommerce' ) || ! defined( 'WC_VERSION' ) )
				return;
			
			wp_register_script( 'pdf_forms_filler_spinner_script', plugins_url( 'js/spinner.js', __FILE__ ), array('jquery'), '1.0.0' );
			wp_register_style( 'pdf_forms_filler_spinner_style', plugins_url( 'css/spinner.css', __FILE__ ), array(), '1.0.0' );
			
			$post_type = get_post_type();
			
			// if we are on the product edit page then load the admin scripts
			if( ( 'post.php' == $hook || 'post-new.php' == $hook ) && 'product' == $post_type )
			{
				wp_register_style( 'select2', plugin_dir_url( __FILE__ ) . 'css/select2.min.css', array(), '4.0.13' );
				wp_register_script( 'select2', plugin_dir_url(  __FILE__ ) . 'js/select2/select2.min.js', array( 'jquery' ), '4.0.13' );
				
				wp_register_script( 'pdf_forms_for_woocommerce_admin_product_script', plugin_dir_url( __FILE__ ) . 'js/admin-product.js', array( 'jquery', 'jcrop', 'select2' ), self::VERSION );
				wp_register_style( 'pdf_forms_for_woocommerce_admin_product_style', plugin_dir_url( __FILE__ ) . 'css/admin-product.css', array( 'jcrop', 'select2' ), self::VERSION );
				
				wp_localize_script( 'pdf_forms_for_woocommerce_admin_product_script', 'pdf_forms_for_woocommerce', array(
					'ajax_url' => admin_url( 'admin-ajax.php' ),
					'ajax_nonce' => wp_create_nonce( 'pdf-forms-for-woocommerce-ajax-nonce' ),
					'__No_Post_ID' => __( "Failed to determine post ID", 'pdf-forms-for-woocommerce' ),
					'__No_Preload_Data' => __( 'Failed to load PDF form data', 'pdf-forms-for-woocommerce' ),
					'__Unknown_error' => __( 'Unknown error', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Delete_Attachment' => __( 'Are you sure you want to delete this file?  This will delete field mappings and image embeds associated with this file.', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Delete_Mapping' => __( 'Are you sure you want to delete this mapping?', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Delete_All_Mappings' => __( 'Are you sure you want to delete all mappings?', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Delete_All_Value_Mappings' => __( 'Are you sure you want to delete all value mappings?', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Attach_Empty_Pdf' => __( 'Are you sure you want to attach a PDF file without any form fields?', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Delete_Embed' => __( 'Are you sure you want to delete this embeded image?', 'pdf-forms-for-woocommerce' ),
					'__Show_Help' => __( 'Show Help', 'pdf-forms-for-woocommerce' ),
					'__Hide_Help' => __( 'Hide Help', 'pdf-forms-for-woocommerce' ),
					'__PDF_Frame_Title' => __( 'Select a PDF file', 'pdf-forms-for-woocommerce'),
					'__PDF_Frame_Button' => __( 'Select', 'pdf-forms-for-woocommerce'),
					'__All_PDFs' => __( 'All PDFs', 'pdf-forms-for-woocommerce' ),
					'__All_Pages' => __( 'All', 'pdf-forms-for-woocommerce' ),
					'__Null_Value_Mapping' => __( '--- EMPTY ---', 'pdf-forms-for-woocommerce' ),
				) );
				
				wp_enqueue_media();
				
				wp_enqueue_script( 'pdf_forms_for_woocommerce_admin_product_script' );
				wp_enqueue_style( 'pdf_forms_for_woocommerce_admin_product_style' );
				
				wp_enqueue_script( 'pdf_forms_filler_spinner_script' );
				wp_enqueue_style( 'pdf_forms_filler_spinner_style' );
			}
			
			// if we are on the order edit page then load the order page admin scripts
			$is_order_page = self::is_wc_hpos_enabled() ?
				  ( ( 'woocommerce_page_wc-orders' == $hook ) && isset( $_GET['id'] ) )
				: ( ( 'post.php' == $hook ) && 'shop_order' == $post_type );
			if( $is_order_page )
			{
				wp_register_script( 'pdf_forms_for_woocommerce_admin_order_script', plugins_url( 'js/admin-order.js', __FILE__ ), array( 'jquery' ), self::VERSION );
				
				$order = wc_get_order();
				wp_localize_script( 'pdf_forms_for_woocommerce_admin_order_script', 'pdf_forms_for_woocommerce', array(
					'ajax_url' => admin_url( 'admin-ajax.php' ),
					'ajax_nonce' => wp_create_nonce( 'pdf-forms-for-woocommerce-ajax-nonce' ),
					'order_id' => is_a( $order, 'WC_Order' ) ? $order->get_id() : null,
					'__Confirm_Reset_Settings' => __( 'Are you sure you want to reset settings for this order?', 'pdf-forms-for-woocommerce' ),
					'__Confirm_Reset_PDFs' => __( 'Are you sure you want to reset PDFs for this order?', 'pdf-forms-for-woocommerce' ),
				) );
				
				wp_enqueue_script( 'pdf_forms_for_woocommerce_admin_order_script' );
				
				wp_enqueue_script( 'pdf_forms_filler_spinner_script' );
				wp_enqueue_style( 'pdf_forms_filler_spinner_style' );
			}
			
			if( $service = $this->get_service() )
			{
				$service->admin_enqueue_scripts( $hook );
				if( $service != $this->pdf_ninja_service )
					$this->pdf_ninja_service->admin_enqueue_scripts( $hook );
			}
		}
		
		/**
		 * Used for retreiving PDF file information in wp-admin interface
		 */
		public function wp_ajax_get_attachment_data()
		{
			try
			{
				if( ! check_ajax_referer( 'pdf-forms-for-woocommerce-ajax-nonce', 'nonce', false ) )
					throw new Exception( __( "Nonce mismatch", 'pdf-forms-for-woocommerce' ) );
				
				$attachment_id = isset( $_POST['file_id'] ) ? intval( $_POST['file_id'] ) : null;
				
				if( ! $attachment_id )
					throw new Exception( __( "Invalid attachment ID", 'pdf-forms-for-woocommerce' ) );
				
				if( ! current_user_can( 'edit_post', $attachment_id ) )
					throw new Exception( __( "Permission denied", 'pdf-forms-for-woocommerce' ) );
				
				if( ( $filepath = get_attached_file( $attachment_id ) ) !== false
				&& ( $mimetype = self::get_mime_type( $filepath ) ) != null
				&& $mimetype !== 'application/pdf' )
					throw new Exception(
						self::replace_tags(
							__( "File type {mime-type} of {file} is unsupported for {purpose}", 'pdf-forms-for-woocommerce' ),
							array( 'mime-type' => $mimetype, 'file' => wp_basename( $filepath ), 'purpose' => __( "PDF form filling", 'pdf-forms-for-woocommerce' ) )
						)
					);
				
				$info = $this->get_info( $attachment_id );
				$info['fields'] = $this->query_pdf_fields( $attachment_id );
				
				return wp_send_json( array(
					'success' => true,
					'attachment_id' => $attachment_id,
					'filename' => wp_basename( $filepath ),
					'info' => $info,
				) );
			}
			catch( Exception $e )
			{
				return wp_send_json( array(
					'success' => false,
					'error_message' => $e->getMessage(),
					'error_location' => wp_basename( $e->getFile() ) . ":" . $e->getLine(),
				) );
			}
		}
		
		/**
		 * Returns (and computes, if necessary) the md5 sum of the media file
		 */
		public static function get_attachment_md5sum( $attachment_id )
		{
			$md5sum = self::get_metadata( $attachment_id, 'md5sum' );
			if( ! $md5sum )
				return self::update_attachment_md5sum( $attachment_id );
			else
				return $md5sum;
		}
		
		/**
		 * Computes, saves and returns the md5 sum of the media file
		 */
		public static function update_attachment_md5sum( $attachment_id )
		{
			// clear info cache
			self::unset_metadata( $attachment_id, 'info' );
			
			// delete page snapshots
			$args = array(
				'post_parent' => $attachment_id,
				'meta_key' => self::META_KEY . '-page',
				'post_type' => 'attachment',
				'post_status' => 'any',
				'posts_per_page' => -1,
			);
			foreach( get_posts( $args ) as $post )
				wp_delete_post( $post->ID, $force_delete = true );
			
			$filepath = get_attached_file( $attachment_id );
			
			if( $filepath !== false && is_readable( $filepath ) !== false )
				$md5sum = @md5_file( $filepath );
			else
			{
				$fileurl = wp_get_attachment_url( $attachment_id );
				if( $fileurl === false )
					throw new Exception( __( "Attachment file is not accessible", 'pdf-forms-for-woocommerce' ) );
				
				try
				{
					$temp_filepath = wp_tempnam();
					self::download_file( $fileurl, $temp_filepath ); // can throw an exception
					$md5sum = @md5_file( $temp_filepath );
					@unlink( $temp_filepath );
				}
				catch(Exception $e)
				{
					@unlink( $temp_filepath );
					throw $e;
				}
			}
			
			if( $md5sum === false )
				throw new Exception( __( "Could not read attached file", 'pdf-forms-for-woocommerce' ) );
			
			return self::set_metadata( $attachment_id, 'md5sum', $md5sum );
		}
		
		/**
		 * Caching wrapper for $service->api_get_info()
		 */
		public function get_info( $attachment_id )
		{
			// cache
			$data = self::get_metadata( $attachment_id );
			if( isset( $data['info'] ) && isset( $data['md5sum'] ) )
			{
				$info = $data['info'];
				$old_md5sum = $data['md5sum'];
				
				// use cache only if file is locally accessible
				$filepath = get_attached_file( $attachment_id );
				if( $filepath !== false && is_readable( $filepath ) !== false )
				{
					$new_md5sum = md5_file( $filepath );
					if( $new_md5sum !== false && $new_md5sum === $old_md5sum )
						return $info;
					else
						self::update_attachment_md5sum( $attachment_id );
				}
			}
			
			$service = $this->get_service();
			if( !$service )
				throw new Exception( __( "No service", 'pdf-forms-for-woocommerce' ) );
			
			$info = $service->api_get_info( $attachment_id );
			
			// set up array keys so it is easier to search
			$fields = array();
			foreach( $info['fields'] as $field )
				if( isset( $field['name'] ) )
					$fields[ $field['name'] ] = $field;
			$info['fields'] = $fields;
			
			$pages = array();
			foreach( $info['pages'] as $page )
				$pages[$page['number']] = $page;
			$info['page'] = $pages;
			
			// set fields cache
			self::set_metadata( $attachment_id, 'info', $info );
			
			return $info;
		}
		
		/**
		 * Caches and returns fields for an attachment
		 */
		public function get_fields( $attachment_id )
		{
			$info = $this->get_info( $attachment_id );
			return $info['fields'];
		}
		
		/**
		 * Helper function used in wp-admin interface
		 */
		private function query_pdf_fields( $attachment_id )
		{
			$fields = $this->get_fields( $attachment_id );
			
			foreach( $fields as $id => &$field )
			{
				if( !isset( $field['name'] ) )
				{
					unset( $fields[$id] );
					continue;
				}
				
				$name = strval( $field['name'] );
				$field['id'] = self::base64url_encode( $name );
			}
			
			return $fields;
		}
		
		/**
		 * Downloads and caches PDF page images, returns image attachment id
		 */
		public function get_pdf_snapshot( $attachment_id, $page )
		{
			$args = array(
				'post_parent' => $attachment_id,
				'meta_key' => self::META_KEY . '-page',
				'meta_value' => strval( $page ),
				'post_type' => 'attachment',
				'post_status' => 'any',
				'posts_per_page' => 1,
			);
			$posts = get_posts( $args );
			
			if( count( $posts ) > 0 )
			{
				$old_attachment_id = reset( $posts )->ID;
				return $old_attachment_id;
			}
			
			$wp_upload_dir = wp_upload_dir();
			if( isset( $wp_upload_dir['error'] ) && false !== $wp_upload_dir['error'] )
				throw new Exception( $wp_upload_dir['error'] );
			if( ! isset( $wp_upload_dir['path'] ) || ! isset( $wp_upload_dir['url'] ) )
				throw new Exception( __( "Failed to determine upload path", 'pdf-forms-for-woocommerce' ) );
			
			$filename = wp_unique_filename( $wp_upload_dir['path'], sanitize_file_name( get_the_title( $attachment_id ) ) . '.page' . strval( intval( $page ) ) . '.jpg' );
			$filepath = trailingslashit( $wp_upload_dir['path'] ) . $filename;
			
			$service = $this->get_service();
			if( $service )
				$service->api_image( $filepath, $attachment_id, $page );
			
			$mimetype = self::get_mime_type( $filepath );
			
			$attachment = array(
				'guid'           => $wp_upload_dir['url'] . '/' . $filename,
				'post_mime_type' => $mimetype,
				'post_title'     => preg_replace( '/\.[^.]+$/', '', $filename ),
				'post_content'   => '',
				'post_status'    => 'inherit'
			);
			
			$new_attachment_id = wp_insert_attachment( $attachment, $filepath, $attachment_id );
			
			update_post_meta( $new_attachment_id, self::META_KEY . '-page', strval( $page ) );
			
			return $new_attachment_id;
		}
		
		/**
		 * Used for getting PDF page images in wp-admin interface
		 */
		public function wp_ajax_query_page_image()
		{
			try
			{
				if ( ! check_ajax_referer( 'pdf-forms-for-woocommerce-ajax-nonce', 'nonce', false ) )
					throw new Exception( __( "Nonce mismatch", 'pdf-forms-for-woocommerce' ) );
				
				$attachment_id = isset( $_POST['attachment_id'] ) ? intval( $_POST['attachment_id'] ) : null;
				$page = isset( $_POST['page'] ) ? intval( $_POST['page'] ) : null;
				
				if ( $page < 1 )
					throw new Exception( __( "Invalid page number", 'pdf-forms-for-woocommerce' ) );
				
				if( ! current_user_can( 'edit_post', $attachment_id ) )
					throw new Exception( __( "Permission denied", 'pdf-forms-for-woocommerce' ) );
				
				$attachment_id = $this->get_pdf_snapshot( $attachment_id, $page );
				$snapshot = wp_get_attachment_image_src( $attachment_id, array( 500, 500 ) );
				
				if( !$snapshot || !is_array( $snapshot ) )
					throw new Exception( __( "Failed to retrieve page snapshot", 'pdf-forms-for-woocommerce' ) );
				
				return wp_send_json( array(
					'success' => true,
					'snapshot' => reset( $snapshot ),
				) );
			}
			catch( Exception $e )
			{
				return wp_send_json( array(
					'success' => false,
					'error_message' => $e->getMessage(),
					'error_location' => wp_basename( $e->getFile() ) . ":". $e->getLine(),
				) );
			}
		}
		
		/**
		 * Helper functions for encoding/decoding field names
		 */
		public static function base64url_encode( $data )
		{
			// phpcs:ignore Generic.PHP.ForbiddenFunctions -- only used to encode field names to avoid DB/JSON encoding issues
			return rtrim( strtr( base64_encode( $data ), '+/', '._' ), '=' );
		}
		public static function base64url_decode( $data )
		{
			// phpcs:ignore Generic.PHP.ForbiddenFunctions -- only used to decode field names to avoid DB/JSON encoding issues
			return base64_decode( str_pad( strtr( $data, '._', '+/' ), strlen( $data ) % 4, '=', STR_PAD_RIGHT ) );
		}
		
		/*
		 * Parses data URI
		 */
		public static function parse_data_uri( $uri )
		{
			if( ! preg_match( '/data:([a-zA-Z-\/+.]*)((;[a-zA-Z0-9-_=.+]+)*),(.*)/', $uri, $matches ) )
				return false;
			
			$data = $matches[4];
			$mime = $matches[1] ? $matches[1] : null;
			
			$base64 = false;
			foreach( explode( ';', $matches[2] ) as $ext )
				if( $ext == "base64" )
				{
					$base64 = true; 
					if( ! ( $data = base64_decode( $data, $strict=true ) ) ) // phpcs:ignore Generic.PHP.ForbiddenFunctions -- only used to decode data URI that has base64-encoded content
						return false;
				}
			
			if( ! $base64 )
				$data = rawurldecode( $data );
			
			return array(
				'data' => $data,
				'mime' => $mime,
			);
		}
	}
	
	Pdf_Forms_For_WooCommerce::get_instance();
}