<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/zf2 for the canonical source repository
 * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 */

namespace Zend\Feed\Reader;

use ArrayObject;
use DOMNodeList;
use Zend\Feed\Uri;

class FeedSet extends ArrayObject
{
    public $rss = null;

    public $rdf = null;

    public $atom = null;

    /**
     * Import a DOMNodeList from any document containing a set of links
     * for alternate versions of a document, which will normally refer to
     * RSS/RDF/Atom feeds for the current document.
     *
     * All such links are stored internally, however the first instance of
     * each RSS, RDF or Atom type has its URI stored as a public property
     * as a shortcut where the use case is simply to get a quick feed ref.
     *
     * Note that feeds are not loaded at this point, but will be lazy
     * loaded automatically when each links 'feed' array key is accessed.
     *
     * @param DOMNodeList $links
     * @param string $uri
     * @return void
     */
    public function addLinks(DOMNodeList $links, $uri)
    {
        foreach ($links as $link) {
            if (strtolower($link->getAttribute('rel')) !== 'alternate'
                || ! $link->getAttribute('type') || ! $link->getAttribute('href')) {
                continue;
            }
            if (! isset($this->rss) && $link->getAttribute('type') == 'application/rss+xml') {
                $this->rss = $this->absolutiseUri(trim($link->getAttribute('href')), $uri);
            } elseif (! isset($this->atom) && $link->getAttribute('type') == 'application/atom+xml') {
                $this->atom = $this->absolutiseUri(trim($link->getAttribute('href')), $uri);
            } elseif (! isset($this->rdf) && $link->getAttribute('type') == 'application/rdf+xml') {
                $this->rdf = $this->absolutiseUri(trim($link->getAttribute('href')), $uri);
            }
            $this[] = new static([
                'rel' => 'alternate',
                'type' => $link->getAttribute('type'),
                'href' => $this->absolutiseUri(trim($link->getAttribute('href')), $uri),
                'title' => $link->getAttribute('title'),
            ]);
        }
    }

    /**
     *  Attempt to turn a relative URI into an absolute URI
     *
     *  @param string $link
     *  @param string $uri OPTIONAL
     *  @return string|null absolutised link or null if invalid
     */
    protected function absolutiseUri($link, $uri = null)
    {
        $linkUri = Uri::factory($link);
        if ($linkUri->isAbsolute()) {
            // invalid absolute link can not be recovered
            return $linkUri->isValid() ? $link : null;
        }

        $scheme = 'http';
        if ($uri !== null) {
            $uri = Uri::factory($uri);
            $scheme = $uri->getScheme() ?: $scheme;
        }

        if ($linkUri->getHost()) {
            $link = $this->resolveSchemeRelativeUri($link, $scheme);
        } elseif ($uri !== null) {
            $link = $this->resolveRelativeUri($link, $scheme, $uri->getHost(), $uri->getPath());
        }

        if (! Uri::factory($link)->isValid()) {
            return null;
        }

        return $link;
    }

    /**
     * Resolves scheme relative link to absolute
     *
     * @param string $link
     * @param string $scheme
     * @return string
     */
    private function resolveSchemeRelativeUri($link, $scheme)
    {
        $link = ltrim($link, '/');
        return sprintf('%s://%s', $scheme, $link);
    }

    /**
     *  Resolves relative link to absolute
     *
     *  @param string $link
     *  @param string $scheme
     *  @param string $host
     *  @param string $uriPath
     *  @return string
     */
    private function resolveRelativeUri($link, $scheme, $host, $uriPath)
    {
        if ($link[0] !== '/') {
            $link = $uriPath . '/' . $link;
        }
        return sprintf(
            '%s://%s/%s',
            $scheme,
            $host,
            $this->canonicalizePath($link)
        );
    }

    /**
     *  Canonicalize relative path
     *
     * @param string $path
     * @return string
     */
    protected function canonicalizePath($path)
    {
        $parts = array_filter(explode('/', $path));
        $absolutes = [];
        foreach ($parts as $part) {
            if ('.' == $part) {
                continue;
            }
            if ('..' == $part) {
                array_pop($absolutes);
            } else {
                $absolutes[] = $part;
            }
        }
        return implode('/', $absolutes);
    }

    /**
     * Supports lazy loading of feeds using Reader::import() but
     * delegates any other operations to the parent class.
     *
     * @param string $offset
     * @return mixed
     */
    public function offsetGet($offset)
    {
        if ($offset == 'feed' && ! $this->offsetExists('feed')) {
            if (! $this->offsetExists('href')) {
                return;
            }
            $feed = Reader::import($this->offsetGet('href'));
            $this->offsetSet('feed', $feed);
            return $feed;
        }
        return parent::offsetGet($offset);
    }
}
