<?php
/**
 * Plugin Name: Metadata
 * Description: Parses metadata (AKA custom fields)
 * Version: 1.0
 * Author: Janis Elsts
 * ModuleID: metadata
 * ModuleCategory: parser
 * ModuleClassName: blcMetadataParser
 * ModuleContext: on-demand
 * ModuleLazyInit: true
 * ModuleAlwaysActive: true
 * ModuleHidden: true
*/

class blcMetadataParser extends blcParser {
	var $supported_formats    = array( 'metadata' );
	var $supported_containers = array();

	/**
	 * Parse a metadata value.
	 *
	 * @param string|array $content Metadata value(s).
	 * @param string $base_url The base URL to use for normalizing relative URLs. If ommitted, the blog's root URL will be used.
	 * @param string $default_link_text
	 * @return array An array of new blcLinkInstance objects.
	 */
	function parse( $content, $base_url = '', $default_link_text = '' ) {
		$instances = array();

		if ( ! is_array( $content ) ) {
			$content = array( $content );
		}

		foreach ( $content as $value ) {
			//parse all values of a seralized custom field
			if ( is_array( $value ) ) {
				foreach ( $value as $singular_value ) {
					//only get urls
					//todo: filter relative urls
					if ( filter_var( $singular_value, FILTER_VALIDATE_URL ) ) {
						$instances[] = $this->parse_metafield( $singular_value, $base_url, $default_link_text );
					}
				}
			} else {
				$instances[] = $this->parse_metafield( $value, $base_url, $default_link_text );
			}
		}

		return array_values( array_filter( $instances ) );
	}

	/**
	 * Metadata url parser helper.
	 *
	 * @param string $metaurl The url on the meta data
	 * @param string $default_link_text
	 * @return array An array of new blcLinkInstance objects.
	 */
	function parse_metafield( $metaurl = '', $base_url, $default_link_text = '' ) {
		//The complete contents of the meta field are stored in raw_url.
		//This is useful for editing/unlinking, when one may need to
		//distinguish between multiple fields with the same name.
		$raw_url = $metaurl;

		//If this is a multiline metadata field take only the first line (workaround for the 'enclosure' field).
		$lines = explode( "\n", $metaurl );
		$url   = trim( reset( $lines ) );

		//Attempt to parse the URL
		$parts = @parse_url( $url );

		if ( ! $parts ) {
			return ''; //Ignore invalid URLs
		}

		if ( ! isset( $parts['scheme'] ) ) {
			//No scheme - likely a relative URL. Turn it into an absolute one.
			$url = $this->relative2absolute( $url, $base_url );

			//Skip invalid URLs (again)
			if ( ! $url || ( strlen( $url ) < 6 ) ) {
				return '';
			}
		}

		//The URL is okay, create and populate a new link instance.
		$instance = new blcLinkInstance();

		$instance->set_parser( $this );
		$instance->raw_url   = $raw_url;
		$instance->link_text = $default_link_text;

		$link_obj = new blcLink( $url ); //Creates or loads the link
		$instance->set_link( $link_obj );

		return $instance;
	}

	/**
	 * Change the URL in a metadata field to another one.
	 *
	 * This is tricky because there can be multiple metadata fields with the same name
	 * but different values. So we ignore $content (which might be an array of multiple
	 * metadata values) and use the old raw_url that we stored when parsing the field(s)
	 * instead.
	 *
	 * @see blcMetadataParser::parse()
	 *
	 * @param string $content Ignored.
	 * @param string $new_url The new URL.
	 * @param string $old_url Ignored.
	 * @param string $old_raw_url The current meta value.
	 *
	 * @return array|WP_Error
	 */
	function edit( $content, $new_url, $old_url, $old_raw_url ) {
		//For multiline fields (like 'enclosure') we only want to change the first line.
		$lines = explode( "\n", $old_raw_url );
		array_shift( $lines ); //Discard the old first line
		array_unshift( $lines, $new_url ); //Insert the new URL in its place.
		$content = implode( "\n", $lines );

		return array(
			'content' => $content,
			'raw_url' => $new_url,
		);
	}

	/**
	 * Get the link text for printing in the "Broken Links" table.
	 *
	 * @param blcLinkInstance $instance
	 * @param string $context
	 * @return string HTML
	 */
	function ui_get_link_text( $instance, $context = 'display' ) {
		$image_html = sprintf(
			'<img src="%s" class="blc-small-image" title="%2$s" alt="%2$s"> ',
			esc_attr( plugins_url( '/images/font-awesome/font-awesome-code.png', BLC_PLUGIN_FILE ) ),
			__( 'Custom field', 'broken-link-checker' )
		);

		$field_html = sprintf(
			'<code>%s</code>',
			$instance->container_field
		);

		if ( 'email' !== $context ) {
			$field_html = $image_html . $field_html;
		}

		return $field_html;
	}
}