<?php
/**
 * RSS 2.0 renderer.
 *
 * @package FeedWeaver
 */

namespace FeedWeaver\Render;

use FeedWeaver\Mapping\Mapping_Engine;

defined( 'ABSPATH' ) || exit;

/**
 * <rss version="2.0"><channel> ...channel elements... <item>...</item> </channel></rss>
 *
 * The channel's required elements (title, link, description) are always written. Items are
 * written exactly like custom XML items, in mapping order, so namespaces, attributes and
 * repeated elements work the same way.
 */
class Rss_Renderer extends Xml_Renderer {

	const ATOM_NS = 'http://www.w3.org/2005/Atom';

	/** @var array<string,string> Channel element => text. */
	private $channel;

	/** @var string Address written as <atom:link rel="self">, or '' for none. */
	private $self_url = '';

	/** @var string Prefix bound to the Atom namespace, or '' when no self link is written. */
	private $atom_prefix = '';

	/**
	 * @param array<string,string> $channel    Channel elements (see Rss_Profile::channel()).
	 * @param array<string,string> $namespaces Namespace declarations (prefix => URI).
	 * @param bool                 $pretty     Indent output.
	 * @param string               $self_url   The feed's own address for <atom:link rel="self">. It must never
	 *                                         carry a credential; pass '' to write no self link.
	 * @throws \InvalidArgumentException When a required channel element is missing.
	 */
	public function __construct( array $channel, array $namespaces = array(), bool $pretty = false, string $self_url = '' ) {
		foreach ( array( 'title', 'link', 'description' ) as $required ) {
			if ( ! isset( $channel[ $required ] ) || '' === trim( $channel[ $required ] ) ) {
				throw new \InvalidArgumentException( 'Missing RSS channel element.' );
			}
		}
		// The self link needs the Atom namespace. Reuse a prefix the administrator already bound to it;
		// otherwise declare "atom". If "atom" is bound to something else, write no self link rather than
		// guess another prefix or rebind it.
		if ( Rss_Profile::is_http_url( $self_url ) ) {
			$existing = array_search( self::ATOM_NS, $namespaces, true );
			if ( false !== $existing ) {
				$this->atom_prefix = (string) $existing;
				$this->self_url    = $self_url;
			} elseif ( ! isset( $namespaces['atom'] ) ) {
				$namespaces['atom'] = self::ATOM_NS;
				$this->atom_prefix  = 'atom';
				$this->self_url     = $self_url;
			}
		}
		parent::__construct( 'rss', 'item', $pretty, $namespaces );
		$this->channel = $channel;
	}

	/**
	 * {@inheritdoc}
	 */
	public function content_type(): string {
		return Rss_Profile::CONTENT_TYPE;
	}

	/**
	 * Renders the document.
	 *
	 * @param array<int,array<string,mixed>> $items Items, already checked by Rss_Profile::normalize_item().
	 * @return string
	 */
	public function render( array $items ): string {
		$writer = $this->open();
		$this->start_root( $writer, 'rss', array( 'version' => '2.0' ) );
		$writer->startElement( 'channel' );
		foreach ( $this->channel as $name => $text ) {
			$this->write_leaf( $writer, $name, $text );
		}
		if ( '' !== $this->self_url ) {
			$writer->startElement( $this->atom_prefix . ':link' );
			$writer->writeAttribute( 'href', $this->self_url );
			$writer->writeAttribute( 'rel', 'self' );
			$writer->writeAttribute( 'type', 'application/rss+xml' );
			$writer->endElement();
		}
		// The newest item's date, so the document only changes when the content does.
		if ( $items ) {
			$first = isset( $items[0]['pubDate'] ) ? $items[0]['pubDate'] : null;
			if ( is_array( $first ) && isset( $first[ Mapping_Engine::VALUE ] ) ) {
				$first = $first[ Mapping_Engine::VALUE ];
			}
			if ( is_string( $first ) && Rss_Profile::is_rss_date( $first ) ) {
				$this->write_leaf( $writer, 'lastBuildDate', $first );
			}
		}
		foreach ( $items as $item ) {
			$this->write_item( $writer, 'item', $item );
		}
		$writer->endElement();
		$writer->endElement();
		$writer->endDocument();
		return $writer->outputMemory();
	}
}