Serial Numbers for Transaction Receipts

class-llms-serial-number-generator.php

<?php // Do not copy this line

// copy from below this line

/**
 * Generates sequential serial numbers for a given post type
 */
class LLMS_Serial_Number_Generator {

	private $post_type = '';

	private $post_status = '';

	private $prefix = '';

	private $length = 7;
	
	public function __construct() {
		$this->hook();
	}

	/**
	 * Hooks into Purchase Receipt html
	 */
	public function hook() {
		add_filter( 'llms_notification_viewpurchase_receipt_get_email_html', array( $this, 'replace_merge_code' ), 10, 2 );
	}

	/**
	 * Initialises serial number generation.
	 * 
	 * @param string $post_type   Post Type to generate for
	 * @param string $post_status Generate when transitioning to this post status
	 * @param string $length      Desired length of the serial number including leading zeroes but excluding prefix
	 * @param string $prefix      Desired prefix
	 * 
	 * @return bool|null
	 */
	public function init ( $length = false, $prefix = false ) {

		$this->post_type = 'llms_transaction';

		$this->post_status = array( 'llms-txn-succeeded', 'llms-txn-refunded' );

		$this->length = ! empty( $length ) ? $length : $this->length;

		$this->prefix = ! empty( $prefix ) ? $prefix : $this->prefix;
	}

	/*
	 * Replace serial number merge code
	 * 
	 * @param string                                  $email_html        The email html
	 * @param LLMS_Notification_View_Purchase_Receipt $notification_view The view handler of purchase receipt notification
	 * 
	 * @return string
	 */
	public function replace_merge_code( $email_html, $notification_view ){

		// get the notification.
		$notification = new LLMS_Notification( $notification_view->id );

		// get the transaction post from the notification.
		$transaction = get_post( $notification->get( 'post_id' ) );

		// generate serial number.
		$serial_number = $this->maybe_generate( $transaction );

		// don't replace merge code on error.
		if( is_wp_error( $serial_number ) ){
			return $email_html;
		}

		// replace merge code
		$email_html = str_replace( '{{SERIAL_NUMBER}}', $serial_number, $email_html );

		return $email_html;
	}

	/**
	 * Generates and saves serial number for post.
	 * 
	 * @param string $old_status Earlier post status
	 * @param string $new_status New post status
	 * @param WP_Post $post The current post
	 */
	public function maybe_generate( $transaction ) {

		// initiliase.
		$this->init();

		// first check if the serial number is already in the meta.
		$existing_serial_number = get_post_meta( $transaction->ID, '_llms_serial_number', true );

		// if it's there, save further execution and bail.
		if( ! empty( $existing_serial_number ) ) {
			return $existing_serial_number;
		}

		// no serial number in meta, will need to generate.
		$serial_number = $this->generate( $transaction );

		return $serial_number;

	}

	/**
	 * Generates a serial number for support.
	 *
	 * @param WP_Post $post The post to generate serial number for
	 *
	 * @return string
	 */
	public function generate( $transaction ) {

		$is_test = ( 'live' !== get_post_meta( $transaction->ID, '_llms_api_mode', true ) ) ? true : false;

		$last_serial_number = $this->get_last_serial_number( $transaction, $is_test );
		// either this is the first post of its kind (last serial number is 0), or we have a definite existing last serial number.

		$current_serial_number = $this->increment_serial_number( $last_serial_number, $is_test );

		if ( ! $is_test ) {

			// save the serial number in meta, only for live transactions.
			update_post_meta( $transaction->ID, '_llms_serial_number', $current_serial_number );

		}

		return $current_serial_number;

	}

	/**
	 * Gets the last serial number value.
	 *
	 * @param WP_Post $post The post to generate serial number for
	 *
	 * @return string
	 */
	public function get_last_serial_number( $transaction, $is_test ) {
		$last_serial_number = 0;

		// get previous post.
		$previous_transaction = $this->get_previous_transaction( $transaction );

		// there is a previous transaction, attempt getting the previous serial number.
		if( ! empty ( $previous_transaction ) ) {	
			$last_serial_number = get_post_meta( $previous_transaction->ID, '_llms_serial_number', true );	
		}

		// there is a previous transaction but it doesn't have a serial number, this is probably the first run
		if( empty ( $last_serial_number ) && ! $is_test ) {
			$last_serial_number = $this->maybe_first_run( $previous_transaction );
		}

		// there is no previous transaction, serial number is 0
		return $last_serial_number;
	}

	/**
	 * Increments the last serial number.
	 *
	 * @param string $last_serial_number The post to generate serial number for
	 *
	 * @return string
	 */
	public function increment_serial_number( &$last_serial_number ) {

		// replace the prefix, if needed
		if( ! empty( $this->prefix ) ) {
			$last_serial_number =  str_replace( $this->prefix, '', $last_serial_number );
		} 

		$last_serial_number = intval( $last_serial_number ) + 1;

		// increment and add leading zeroes.
		$new_serial_number = sprintf( "%0{$this->length}d",  $last_serial_number ) ;

		// prefix if needed.
		if( ! empty( $this->prefix ) ) {
			$new_serial_number = $this->prefix . $new_serial_number;
		}

		return $new_serial_number;
	}

	/**
	 * Fetches the previous post
	 * 
	 * @param WP_Post $post The current post
	 * 
	 * @return WP_Post
	 */
	private function get_previous_transaction( $transaction ){

		// bail, if no post is provided
		if ( ! $transaction ) {
			return null;
		}

		$post_status__in = "'" . implode( "','", $this->post_status ) . "'";

		global $wpdb;

		$where = $wpdb->prepare(
			"WHERE p.post_date < %s AND p.post_type = %s AND p.post_status IN ( $post_status__in ) AND m.meta_key = %s AND m.meta_value = %s",
			$transaction->post_date, $transaction->post_type , '_llms_api_mode', 'live' 
		);

		$sort = "ORDER BY p.post_date DESC LIMIT 1";

		$query = "SELECT p.ID FROM $wpdb->posts AS p LEFT JOIN $wpdb->postmeta as m ON p.ID = m.post_id $where $sort";

		$previous_transaction = $wpdb->get_var( $query );

		if ( null === $previous_transaction ) {
			$previous_transaction = '';
		}

		if ( $previous_transaction ) {
			$previous_transaction = get_post( $previous_transaction );
		}

		return $previous_transaction;
	}

	/**
	 * Creates all older serial numbers on first run.
	 * 
	 * @param WP_Post $previous_post The previous post.
	 * 
	 * @return WP_Post
	 */
	public function maybe_first_run( $previous_transaction ) {

		$older_transactions = $this->get_older();

		if( ! $older_transactions ) {
			return 0;
		}

		return $this->first_run( $older_transactions, $previous_transaction );
	}

	public function first_run( $older_transactions, $previous_transaction ) {

		$older_serial_numbers_generated = $this->generate_all_at_once( $older_transactions );

		// return the error if there was one.
		if( is_wp_error( $older_serial_numbers_generated ) ) {
			return $older_serial_numbers_generated;
		}

		/*
		 * bypass cache for last serial number by directly querying the database
		 * because it was just added and won't show up in get_post_meta untill a reload.
		 */

		if( empty ( $previous_transaction ) ) {
			return 0;
		}

		global $wpdb;

		$last_serial_number = $wpdb->get_var(
			$wpdb->prepare(
				"SELECT meta_value FROM $wpdb->postmeta WHERE meta_key=%s AND post_id=%d ",
				'_llms_serial_number', $previous_transaction->ID
			)
		);

		return $last_serial_number;
	}

	public function get_older() {
		// set up query args.
		$older_transactions_query_args = array(
			'post_type' => $this->post_type,
			'post_status' => $this->post_status,
			'posts_per_page' => -1, // we want all the posts at once
			'fields' => 'ids', // we just need the IDs
			'order' => 'ASC', 
			'orderby' => 'date',
			'meta_query' => array(
				array(
					'key' => '_llms_api_mode',
					'value' => 'live',
				),
			),
		);

		// get query results.
		$older_transactions = new WP_Query( $older_transactions_query_args );

		// no posts found. bail!
		if( empty( $older_transactions->found_posts ) ) {
			return false;
		}
		
		return $older_transactions;
	}

	/**
	 * Retroactively generates and saves serial numbers for all post
	 * 
	 * @return bool|WP_Error
	 */
	private function generate_all_at_once( $older_transactions ) {

		// get the post IDs.
		$older_transaction_ids = $older_transactions->posts;

		// generate as many serial numbers as needed.
		$serial_numbers = range( 1, intval( $older_transactions->found_posts ) );

		$meta_key = '_llms_serial_number';

		global $wpdb;

		// initialise db query
		$sql_query = "INSERT INTO $wpdb->postmeta ( post_id, meta_key, meta_value ) ";

		$counter = 0;

		foreach( $older_transaction_ids as $post_id ) {

			// use up one serial number from left in each iteration
			$meta_value = $this->increment_serial_number( $counter );

			// set up part of the database query
			$sql_query_sel[]= "SELECT $post_id, '$meta_key', '$meta_value'";

		}

		// setup complete
		$sql_query.= implode( " UNION ALL ", $sql_query_sel );

		$results = $wpdb->query( $sql_query );

		if( ! $results ){
			return new WP_Error( 'failed', __( 'Failed saving serial numbers for older transactions.', 'lifterlms' ) );
		}

		// this would be the last, ie, current serial number
		return true;

    }

}

new LLMS_Serial_Number_Generator();