<?php
class FeedParser {
	private $doc;
	private $error;
	private $libxml_errors = array();
	private $items = array();
	private $link;
	private $title;
	private $type;
	private $xpath;
	private $jsonobj;

	const FEED_RDF = 0;
	const FEED_RSS = 1;
	const FEED_ATOM = 2;
	const FEED_JSON = 3;

	function normalize_encoding($data) {
		if (preg_match('/^(<\?xml[\t\n\r ].*?encoding[\t\n\r ]*=[\t\n\r ]*["\'])(.+?)(["\'].*?\?>)/s', $data, $matches) === 1) {

			$encoding = strtolower($matches[2]);

			if (in_array($encoding, array_map('strtolower', mb_list_encodings())))
				$data = mb_convert_encoding($data, 'UTF-8', $encoding);

			$data = preg_replace('/^<\?xml[\t\n\r ].*?\?>/s', $matches[1] . "UTF-8" . $matches[3] , $data);
		}

		return $data;
	}

	function __construct($data) {
		$this->jsonobj = @json_decode($data, false);

		// not sure of a better solution to report parsing errors for both kinds of (potentially broken) content

		if ($this->jsonobj) {
			return;
		} else if (!preg_match("/<(\\?xml|feed|channel|rdf|rss)/m", mb_substr($data, 0, 512))) {
			$this->error = 'JSON error: ' . json_last_error_msg();
			return;
		}

		libxml_use_internal_errors(true);
		libxml_clear_errors();
		$this->doc = new DOMDocument();
		$this->doc->loadXML($data);

		mb_substitute_character("none");

		$error = libxml_get_last_error();

		// libxml compiled without iconv?
		if ($error && $error->code == 32) {
			$data = $this->normalize_encoding($data);

			if ($data) {
				libxml_clear_errors();

				$this->doc = new DOMDocument();
				$this->doc->loadXML($data);

				$error = libxml_get_last_error();
			}
		}

		// some terrible invalid unicode entity?
		if ($error) {
			foreach (libxml_get_errors() as $err) {
				if ($err->code == 9) {
					// if the source feed is not in utf8, next conversion will fail
					$data = $this->normalize_encoding($data);

					// remove dangling bytes
					$data = mb_convert_encoding($data, 'UTF-8', 'UTF-8');

					// apparently not all UTF-8 characters are valid for XML
					$data = preg_replace('/[^\x{0009}\x{000a}\x{000d}\x{0020}-\x{D7FF}\x{E000}-\x{FFFD}]+/u', ' ', $data);

					if ($data) {
						libxml_clear_errors();

						$this->doc = new DOMDocument();
						$this->doc->loadXML($data);

						$error = libxml_get_last_error();
					}
					break;
				}
			}
		}

		if ($error) {
			foreach (libxml_get_errors() as $error) {
				if ($error->level == LIBXML_ERR_FATAL) {
					if(!isset($this->error)) //currently only the first error is reported
						$this->error = $this->format_error($error);
					$this->libxml_errors [] = $this->format_error($error);
				}
			}
		}
		libxml_clear_errors();
	}

	function init() {

		if ($this->jsonobj) {
			$this->type = $this::FEED_JSON;

			$this->title = $this->jsonobj->title;
			$this->link = $this->jsonobj->feed_url;

			foreach ($this->jsonobj->items as $item) {
				array_push($this->items, new FeedItem_Json($item, $this->jsonobj, false));
			}

		} else if ($this->doc) {

			$xpath = new DOMXPath($this->doc);
			$xpath->registerNamespace('atom', 'http://www.w3.org/2005/Atom');
			$xpath->registerNamespace('atom03', 'http://purl.org/atom/ns#');
			$xpath->registerNamespace('media', 'http://search.yahoo.com/mrss/');
			$xpath->registerNamespace('rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#');
			$xpath->registerNamespace('slash', 'http://purl.org/rss/1.0/modules/slash/');
			$xpath->registerNamespace('dc', 'http://purl.org/dc/elements/1.1/');
			$xpath->registerNamespace('content', 'http://purl.org/rss/1.0/modules/content/');
			$xpath->registerNamespace('thread', 'http://purl.org/syndication/thread/1.0');

			$this->xpath = $xpath;

			$root = $xpath->query("(//atom03:feed|//atom:feed|//channel|//rdf:rdf|//rdf:RDF)");

			if ($root && $root->length > 0) {
				$root = $root->item(0);

				if ($root) {
					switch (mb_strtolower($root->tagName)) {
						case "rdf:rdf":
							$this->type = $this::FEED_RDF;
							break;
						case "channel":
							$this->type = $this::FEED_RSS;
							break;
						case "feed":
						case "atom:feed":
							$this->type = $this::FEED_ATOM;
							break;
						default:
							if( !isset($this->error) ){
								$this->error = "Unknown/unsupported feed type";
							}
							return;
					}
				}

				switch ($this->type) {
					case $this::FEED_ATOM:

						$title = $xpath->query("//atom:feed/atom:title")->item(0);

						if (!$title)
							$title = $xpath->query("//atom03:feed/atom03:title")->item(0);


						if ($title) {
							$this->title = $title->nodeValue;
						}

						$link = $xpath->query("//atom:feed/atom:link[not(@rel)]")->item(0);

						if (!$link)
							$link = $xpath->query("//atom:feed/atom:link[@rel='alternate']")->item(0);

						if (!$link)
							$link = $xpath->query("//atom03:feed/atom03:link[not(@rel)]")->item(0);

						if (!$link)
							$link = $xpath->query("//atom03:feed/atom03:link[@rel='alternate']")->item(0);

						if ($link && $link->hasAttributes()) {
							$this->link = $link->getAttribute("href");
						}

						$articles = $xpath->query("//atom:entry");

						if (!$articles || $articles->length == 0)
							$articles = $xpath->query("//atom03:entry");

						foreach ($articles as $article) {
							array_push($this->items, new FeedItem_Atom($article, $this->doc, $this->xpath));
						}

						break;
					case $this::FEED_RSS:
						$title = $xpath->query("//channel/title")->item(0);

						if ($title) {
							$this->title = $title->nodeValue;
						}

						$link = $xpath->query("//channel/link")->item(0);

						if ($link) {
							if ($link->getAttribute("href"))
								$this->link = $link->getAttribute("href");
							else if ($link->nodeValue)
								$this->link = $link->nodeValue;
						}

						$articles = $xpath->query("//channel/item");

						foreach ($articles as $article) {
							array_push($this->items, new FeedItem_RSS($article, $this->doc, $this->xpath));
						}

						break;
					case $this::FEED_RDF:
						$xpath->registerNamespace('rssfake', 'http://purl.org/rss/1.0/');

						$title = $xpath->query("//rssfake:channel/rssfake:title")->item(0);

						if ($title) {
							$this->title = $title->nodeValue;
						}

						$link = $xpath->query("//rssfake:channel/rssfake:link")->item(0);

						if ($link) {
							$this->link = $link->nodeValue;
						}

						$articles = $xpath->query("//rssfake:item");

						foreach ($articles as $article) {
							array_push($this->items, new FeedItem_RSS($article, $this->doc, $this->xpath));
						}

						break;

				}

				if ($this->title) $this->title = trim($this->title);
				if ($this->link) $this->link = trim($this->link);

			} else {
				if( !isset($this->error) ){
					$this->error = "Unknown/unsupported feed type";
				}
				return;
			}
		}

	}

	function format_error($error) {
		if ($error) {
			return sprintf("LibXML error %s at line %d (column %d): %s",
				$error->code, $error->line, $error->column,
				$error->message);
		} else {
			return "";
		}
	}

	function error() {
		return $this->error;
	}

	function errors() {
		return $this->libxml_errors;
	}

	function get_link() {
		return $this->link;
	}

	function get_title() {
		return $this->title;
	}

	function get_items() {
		return $this->items;
	}

	function get_links($rel) {
		$rv = array();

		switch ($this->type) {
		case $this::FEED_ATOM:
			$links = $this->xpath->query("//atom:feed/atom:link");

			foreach ($links as $link) {
				if (!$rel || $link->hasAttribute('rel') && $link->getAttribute('rel') == $rel) {
					array_push($rv, trim($link->getAttribute('href')));
				}
			}
			break;
		case $this::FEED_RSS:
			$links = $this->xpath->query("//atom:link");

			foreach ($links as $link) {
				if (!$rel || $link->hasAttribute('rel') && $link->getAttribute('rel') == $rel) {
					array_push($rv, trim($link->getAttribute('href')));
				}
			}
			break;
		}

		return $rv;
	}
}