Adapt Automattic/syndication to just use WP_RSS and make life easier for users

gistfile1.php

<?php

/**
 *
 *
 * @package
 **/
class GlowSyndication {

	/**
	 * Singleton stuff.
	 *
	 * @access @static
	 *
	 * @return  object
	 */
	static public function init() {
		static $instance = false;

		if ( ! $instance )
			$instance = new GlowSyndication();

		return $instance;

	}

	/**
	 * Class constructor
	 *
	 */
	public function __construct() {
		add_action( 'admin_head',              array( $this, 'action_admin_head' ) );
		add_action( 'save_post',               array( $this, 'action_save_post' ) );
		add_action( 'syn_after_site_form',     array( $this, 'action_syn_after_site_form' ) );
		add_action( 'syn_post_pull_edit_post', array( $this, 'action_syn_post_pull_edit_post' ), 10, 4 );
		add_action( 'syn_post_pull_new_post',  array( $this, 'action_syn_post_pull_new_post' ), 10, 4 );
		add_action( 'template_redirect',       array( $this, 'action_template_redirect' ) );

		add_filter( 'author_link',              array( $this, 'filter_author_link' ) );
		add_filter( 'post_link',                array( $this, 'filter_post_link' ), 10, 2 );
		add_filter( 'the_author',               array( $this, 'filter_the_author' ) );
		add_filter( 'syn_rss_pull_filter_post', array( $this, 'filter_syn_rss_pull_filter_post' ), 10, 4 );
		add_filter( 'syn_transports',           array( $this, 'filter_syn_transports' ) );
	}

	// HOOKS
	// =====

	/**
	 * Hooks the admin_head action
	 */
	public function action_admin_head() {
		if ( 'settings_page_push-syndicate-settings' == get_current_screen()->base ) {
			$this->settings_css();
		}
	}

	public function filter_syn_transports( $transports ) {
		foreach ( $transports as $transport => $details ) {
			if ( 'WP_RSS' != $transport ) {
				unset( $transports[ $transport ] );
			}
		}
		return $transports;
	}

	/**
	 * Hooks the save_post action to save some post meta for
	 * the syndication site (i.e. feed) post.
	 *
	 * @param int $post_id The ID of the post being saved
	 */
	public function action_save_post( $post_id ) {
		if ( 'syn_site' != get_post( $post_id )->post_type ) {
			return;
		}
		if ( isset( $_POST[ 'glow_rss_syndication' ] ) && $_POST[ 'glow_rss_syndication' ] ) {
			$convert_cats_to_tags = (bool) $_POST[ 'convert_cats_to_tags' ];
			update_post_meta( $post_id, 'convert_cats_to_tags', $convert_cats_to_tags );

			$redirect_to_origin = (bool) $_POST[ 'redirect_to_origin' ];
			update_post_meta( $post_id, 'redirect_to_origin', $redirect_to_origin );

			update_post_meta( $post_id, 'additional_tags', $_POST[ 'additional_tags' ] );
			update_post_meta( $post_id, 'additional_cats', $_POST[ 'additional_cats' ] );
			update_post_meta( $post_id, 'author_name',     $_POST[ 'author_name' ] );
			update_post_meta( $post_id, 'author_link',     $_POST[ 'author_link' ] );
		}
		if ( 'auto-draft' == get_post( $post_id )->post_status ) {
			update_post_meta( $post_id, 'syn_transport_type', 'WP_RSS' );
		}
	}

	/**
	 * Hooks the syn_after_site_form Syndication plugin action to add some additional
	 * fields to the form.
	 *
	 * @param WP_Post $site A WP_Post object in the syn_site CPT which represents this site (feed)
	 */
	public function action_syn_after_site_form( WP_Post $site ) {
		if ( 'WP_RSS' != get_post_meta( $site->ID, 'syn_transport_type', true ) ) {
			return;
		}

		$convert_cats_to_tags = (bool) get_post_meta( $site->ID, 'convert_cats_to_tags', true );
		$redirect_to_origin = (bool) get_post_meta( $site->ID, 'redirect_to_origin', true );
		$additional_tags = get_post_meta( $site->ID, 'additional_tags', true );
		$additional_cats = get_post_meta( $site->ID, 'additional_cats', true );
		$author_name = get_post_meta( $site->ID, 'author_name', true );
		$author_link = get_post_meta( $site->ID, 'author_link', true );
		?>
		<input type="hidden" name="glow_rss_syndication" value="1" />
		<p>
			<input name="convert_cats_to_tags" id="convert_cats_to_tags" type="checkbox" <?php checked( $convert_cats_to_tags ); ?> />
			<label for="convert_cats_to_tags"><?php echo esc_html__( 'Convert categories to tags?', 'glow-multi-function' ); ?></label>
		</p>
		<p>
			<label for="additional_tags"><?php echo esc_html__( 'Additional tags added to posts in this feed', 'glow-multi-function' ); ?></label><br />
			<span class="description"><?php _e( 'Separate tags with commas: e.g. "Tag 1, Another tag, The third tag in the list"', 'glow-multi-function' ) ?></span>
		</p>
		<p>
			<input type="text" class="widefat" name="additional_tags" id="additional_tags" size="100" value="<?php echo esc_attr( $additional_tags ); ?>" />
		</p>
		<p>
			<label for="additional_cats"><?php echo esc_html__( 'Additional categories added to posts in this feed', 'glow-multi-function' ); ?></label><br />
			<span class="description"><?php _e( 'Separate categories with commas as per tags above', 'glow-multi-function' ) ?></span>
		</p>
		<p>
			<input type="text" class="widefat" name="additional_cats" id="additional_cats" size="100" value="<?php echo esc_attr( $additional_cats ); ?>" />
		</p>
		<p>
			<input name="redirect_to_origin" id="redirect_to_origin" type="checkbox" <?php checked( $redirect_to_origin ); ?> />
			<label for="redirect_to_origin"><?php echo esc_html__( 'Redirect syndicated posts to the origin blog?', 'glow-multi-function' ); ?></label>
		</p>
		<p>
			<label for="author_name"><?php echo esc_html__( 'Attribute posts to this author name:', 'glow-multi-function' ); ?></label>
		</p>
		<p>
			<input type="text" class="widefat" name="author_name" id="author_name" size="100" value="<?php echo esc_attr( $author_name ); ?>" />
		</p>
		<p>
			<label for="author_link"><?php echo esc_html__( 'Link post attribution (i.e. the author name link) to this URL:', 'glow-multi-function' ); ?></label>
		</p>
		<p>
			<input type="text" class="widefat" name="author_link" id="author_link" size="100" value="<?php echo esc_url( $author_link ); ?>" />
		</p>
		<?php
	}

	/**
	 * Hooks the syn_rss_pull_filter_post Syndication plugin filter during the assembly of the post_data
	 * array which will be passed to wp_insert_post.
	 *
	 * @param array          $post_data The post data, as would be passed to wp_insert_post
	 * @param array          $args
	 * @param SimplePie_Item $item A Simplepie item object
	 * @param int            $site_id The ID of the post holding the data describing this feed
	 *
	 * @return array Returns an array of post data suitable for wp_insert_post
	 */
	public function filter_syn_rss_pull_filter_post( $post_data, $args, $item, $site_id ) {
		$convert_cats_to_tags = (bool) get_post_meta( $site_id, 'convert_cats_to_tags', true );
		$additional_tags = get_post_meta( $site_id, 'additional_tags', true );
		$additional_cats = get_post_meta( $site_id, 'additional_cats', true );

		if ( $convert_cats_to_tags ) {
			$post_data = $this->convert_cats_to_tags( $post_data );
		}

		$post_data = $this->add_terms( $post_data, $additional_tags, 'post_tag' );
		$post_data = $this->add_terms( $post_data, $additional_cats, 'category' );

		$post_data['syn_origin_post_link'] = $item->get_link();

		return $post_data;
	}

	/**
	 * Hooks the syn_post_pull_new_post Syndication plugin action to save some values as post meta.
	 *
	 * @param int $post_id The ID of the post which has been created from a feed item
	 * @param array $post_data The array of post data that was passed to wp_insert_post
	 * @param WP_Post $site The WP_Post object in the syn_site CPT representing this site (feed)
	 * @param string $transport_type The transport type used to syndicate this post
	 */
	public function action_syn_post_pull_new_post( $post_id, $post_data, WP_Post $site, $transport_type ) {
		if ( 'WP_RSS' != $transport_type ) {
			return;
		}
		$this->save_origin_url_meta( $post_id, $post_data );
	}

	/**
	 * Hooks the syn_post_pull_edit_post Syndication plugin action to save some values as post meta.
	 *
	 * @param int $post_id The ID of the post which has been created from a feed item
	 * @param array $post_data The array of post data that was passed to wp_update_post
	 * @param WP_Post $site The WP_Post object in the syn_site CPT representing this site (feed)
	 * @param string $transport_type The transport type used to syndicate this post
	 */
	public function action_syn_post_pull_edit_post( $post_id, $post_data, $site, $transport_type ) {
		if ( 'WP_RSS' != $transport_type ) {
			return;
		}
		$this->save_origin_url_meta( $post_id, $post_data );
	}

	/**
	 * Hooks the post_link filter to change the permalink to link to the origin post
	 * where appropriate.
	 *
	 * @param string $permalink The permalink URL
	 * @param WP_Post $post The WP_Post object the permalink is for
	 *
	 * @return string The permalink URL
	 */
	public function filter_post_link( $permalink, WP_Post $post ) {
		$origin_url = $this->get_post_redirect_location( $post->ID );
		if ( $origin_url ) {
			return esc_url( $origin_url );
		}
		return $permalink;
	}

	/**
	 * Hooks the template_redirect action to send an HTTP redirect back to the
	 * origin post where appropriate.
	 */
	public function action_template_redirect() {
		if ( is_singular() ) {
			$origin_url = $this->get_post_redirect_location();
			if ( $origin_url ) {
				wp_redirect( esc_url( $origin_url ), 301 );
				exit;
			}
		}
	}

	/**
	 * Hooks the author_link filter to link back to the author URL which is (optionally)
	 * specified on the site (feed) syn_site CPT post.
	 *
	 * @param string $permalink The author permalink
	 *
	 * @return string The author permalink URL
	 */
	public function filter_author_link( $permalink ) {
		$syn_site_id = $this->get_post_syndication_site_id();
		if ( ! $syn_site_id ) {
			return $permalink;
		}

		$author_link = get_post_meta( $syn_site_id, 'author_link', true );
		if ( $author_link ) {
			return esc_url( $author_link );
		}

		return $permalink;
	}

	/**
	 * Hooks the the_author filter to change the author name
	 * to display.
	 *
	 * @param string $author_name The author name to display
	 *
	 * @return string The author name to display
	 */
	public function filter_the_author( $author_name ) {
		$syn_site_id = $this->get_post_syndication_site_id();
		if ( ! $syn_site_id ) {
			return $author_name;
		}

		$author_name = get_post_meta( $syn_site_id, 'author_name', true );
		if ( $author_name ) {
			return esc_html( $author_name );
		}

		return $author_name;
	}

	// METHODS
	// =======

	/**
	 * Some CSS to output on the settings screen, to hide things we
	 * don't want to see (because they're irrelevant).
	 */
	public function settings_css() {
		?>
			<style type="text/css">
				div.syn-push-syndicate-post-types,
				div.syn-delete-pushed-posts,
				div.syn-api-token-config,
				div.syn-api-token {
					display: none;
				}
			</style>
		<?php
	}

	/**
	 * Save a value from the post data array to post meta.
	 *
	 * @param int $post_id The ID of the post to save the meta on
	 * @param array $post_data An array of post data similar to that passed to wp_insert_post
	 */
	protected function save_origin_url_meta( $post_id, $post_data ) {
		if ( isset( $post_data['syn_origin_post_link'] ) ) {
			$origin_post_url = $post_data['syn_origin_post_link'];
			update_post_meta( $post_id, 'syn_origin_post_url', $origin_post_url );
		}
	}

	/**
	 * Take an array of post data, such as might be passed to wp_insert_post,
	 * and convert all the cats to tags, creating the tags where they
	 * don't exist.
	 *
	 * @param array $post_data An array of post data similar to that passed to wp_insert_post
	 *
	 * @return array An array of post data similar to that passed to wp_insert_post
	 */
	protected function convert_cats_to_tags( $post_data ) {
		foreach ( $post_data['post_category'] as $cat_id ) {
			$cat = get_category( $cat_id );

			$tag = get_term_by( 'name', $cat->name, 'post_tag' );
			// Create tag if it doesn't exist
			if ( ! $tag ) {
				$tag = wp_insert_term( $cat->name, 'post_tag' );
			}

			$post_data['tags_input'][] = (int) $tag->term_id;
		}
		// Substitute an empty array for the cats
		$post_data['post_category'] = array();
		return $post_data;
	}

	/**
	 * @param array $post_data An array of post data similar to that passed to wp_insert_post
	 * @param string $terms_string A comma separated string of term names
	 * @param string $tax_name The name of a taxonomy: either post_tag or category
	 *
	 * @return array An array of post data similar to that passed to wp_insert_post
	 */
	protected function add_terms( $post_data, $terms_string, $tax_name ) {
		$term_names = explode( ',', $terms_string );
		foreach ( $term_names as $term_name ) {
			$term_name = trim( $term_name );
			$term = get_term_by( 'name', $term_name, $tax_name );
			// Create tag if it doesn't exist
			if ( ! $term ) {
				$term = wp_insert_term( $term_name, $tax_name );
			}

			if ( 'post_tag' == $tax_name ) {
				if ( ! is_array( $post_data['tags_input'] ) ) {
					$post_data['tags_input'] = array();
				}
				$post_data['tags_input'][] = (int) $term->term_id;
			}

			if ( 'category' == $tax_name ) {
				if ( ! is_array( $post_data['post_category'] ) ) {
					$post_data['post_category'] = array();
				}
				$post_data['post_category'][] = (int) $term->term_id;
			}
		}
		return $post_data;
	}

	/**
	 * Return the URL for the remote (origin) post which was syndicated to
	 * create this post, or false if none.
	 *
	 * @param int|bool $post_id The ID of a post (optional, "current" global post is used if false)
	 *
	 * @return bool|string The URL for the originally syndicated post, or false if none
	 */
	protected function get_post_redirect_location( $post_id = false ) {
		if ( false === $post_id ) {
			$post_id = get_post()->ID;
		}
		$origin_url = get_post_meta( $post_id, 'syn_origin_post_url', true );
		// Check for an origin URL saved on the post (no DB queries required)
		if ( $origin_url ) {
			// Only get the syndication site meta if we need to as this requires a DB query
			$syn_site_id = $this->get_post_syndication_site_id();
			$redirect_to_origin = (bool) get_post_meta( $syn_site_id, 'redirect_to_origin', true );
			if ( $redirect_to_origin ) {
				return $origin_url;
			}
		}
		return false;
	}

	/**
	 * Returns the ID of the WP post in the syn_site CPT which represents the site (feed)
	 * this post was syndicated from.
	 *
	 * @param int|bool $post_id The ID of a post (optional, "current" global post is used if false)
	 *
	 * @return bool|int the ID of a WP post in the syn_site CPT
	 */
	protected function get_post_syndication_site_id( $post_id = false ) {
		if ( false === $post_id ) {
			$post_id = get_post()->ID;
		}
		$origin_url = get_post_meta( $post_id, 'syn_origin_post_url', true );
		// Check for an origin URL saved on the post (no DB queries required)
		if ( $origin_url ) {
			// Only get the syndication site meta if we need to as this requires a DB query
			$syn_site_id = (int) get_post_meta( $post_id, 'syn_source_site_id', true );
			return $syn_site_id;
		}
		return false;
	}

}

// Initiate the singleton
GlowSyndication::init();