<?php
class UrlHelper {
	const EXTRA_HREF_SCHEMES = [
		"magnet",
		"mailto",
		"tel"
	];

	const EXTRA_SCHEMES_BY_CONTENT_TYPE = [
		"application/x-bittorrent" => [ "magnet" ],
	];

	static string $fetch_last_error;
	static int $fetch_last_error_code;
	static string $fetch_last_error_content;
	static string $fetch_last_content_type;
	static string $fetch_last_modified;
	static string $fetch_effective_url;
	static string $fetch_effective_ip_addr;
	static bool $fetch_curl_used;

	/**
	 * @param array<string, string|int> $parts
	 */
	static function build_url(array $parts): string {
		$tmp = $parts['scheme'] . "://" . $parts['host'];

		if (isset($parts['path'])) $tmp .= $parts['path'];
		if (isset($parts['query'])) $tmp .= '?' . $parts['query'];
		if (isset($parts['fragment'])) $tmp .= '#' . $parts['fragment'];

		return $tmp;
	}

	/**
	 * Converts a (possibly) relative URL to a absolute one, using provided base URL.
	 * Provides some exceptions for additional schemes like data: if called with owning element/attribute.
	 *
	 * @param string $base_url     Base URL (i.e. from where the document is)
	 * @param string $rel_url Possibly relative URL in the document
	 * @param string $owner_element Owner element tag name (i.e. "a") (optional)
	 * @param string $owner_attribute Owner attribute (i.e. "href") (optional)
	 * @param string $content_type URL content type as specified by enclosures, etc.
	 *
	 * @return false|string Absolute URL or false on failure (either during URL parsing or validation)
	 */
	public static function rewrite_relative($base_url,
				$rel_url,
				string $owner_element = "",
				string $owner_attribute = "",
				string $content_type = "") {

		$rel_parts = parse_url($rel_url);

		if (!$rel_url) return $base_url;

		/**
		 * If parse_url failed to parse $rel_url return false to match the current "invalid thing" behavior
		 * of UrlHelper::validate().
		 *
		 * TODO: There are many places where a string return value is assumed.  We should either update those
		 * to account for the possibility of failure, or look into updating this function's return values.
		 */
		if ($rel_parts === false) {
			return false;
		}

		if (!empty($rel_parts['host']) && !empty($rel_parts['scheme'])) {
			return self::validate($rel_url);

		// protocol-relative URL (rare but they exist)
		} else if (strpos($rel_url, "//") === 0) {
			return self::validate("https:" . $rel_url);
		// allow some extra schemes for A href
		} else if (in_array($rel_parts["scheme"] ?? "", self::EXTRA_HREF_SCHEMES, true) &&
				$owner_element == "a" &&
				$owner_attribute == "href") {
			return $rel_url;
		// allow some extra schemes for links with feed-specified content type i.e. enclosures
		} else if ($content_type &&
				isset(self::EXTRA_SCHEMES_BY_CONTENT_TYPE[$content_type]) &&
				in_array($rel_parts["scheme"], self::EXTRA_SCHEMES_BY_CONTENT_TYPE[$content_type])) {
			return $rel_url;
		// allow limited subset of inline base64-encoded images for IMG elements
		} else if (($rel_parts["scheme"] ?? "") == "data" &&
				preg_match('%^image/(webp|gif|jpg|png|svg);base64,%', $rel_parts["path"]) &&
				$owner_element == "img" &&
				$owner_attribute == "src") {
			return $rel_url;
		} else {
			$base_parts = parse_url($base_url);

			$rel_parts['host'] = $base_parts['host'] ?? "";
			$rel_parts['scheme'] = $base_parts['scheme'] ?? "";

			if ($rel_parts['path'] ?? "") {

				// we append dirname() of base path to relative URL path as per RFC 3986 section 5.2.2
				$base_path = with_trailing_slash(dirname($base_parts['path'] ?? ""));

				// 1. absolute relative path (/test.html) = no-op, proceed as is

				// 2. dotslash relative URI (./test.html) - strip "./", append base path
				if (strpos($rel_parts['path'], './') === 0) {
					$rel_parts['path'] = $base_path . substr($rel_parts['path'], 2);
				// 3. anything else relative (test.html) - append dirname() of base path
				} else if (strpos($rel_parts['path'], '/') !== 0) {
					$rel_parts['path'] = $base_path . $rel_parts['path'];
				}

				//$rel_parts['path'] = str_replace("/./", "/", $rel_parts['path']);
				//$rel_parts['path'] = str_replace("//", "/", $rel_parts['path']);
			}

			return self::validate(self::build_url($rel_parts));
		}
	}

	/** extended filtering involves validation for safe ports and loopback
	 * @return false|string false if something went wrong, otherwise the URL string
	 */
	static function validate(string $url, bool $extended_filtering = false) {

		$url = clean($url);

		# fix protocol-relative URLs
		if (strpos($url, "//") === 0)
			$url = "https:" . $url;

		$tokens = parse_url($url);

		// this isn't really necessary because filter_var(... FILTER_VALIDATE_URL) requires host and scheme
		// as per https://php.watch/versions/7.3/filter-var-flag-deprecation but it might save time
		if (empty($tokens['host']))
			return false;

		if (!in_array(strtolower($tokens['scheme']), ['http', 'https']))
			return false;

		//convert IDNA hostname to punycode if possible
		if (function_exists("idn_to_ascii")) {
			if (mb_detect_encoding($tokens['host']) != 'ASCII') {
				if (defined('IDNA_NONTRANSITIONAL_TO_ASCII') && defined('INTL_IDNA_VARIANT_UTS46')) {
					$tokens['host'] = idn_to_ascii($tokens['host'], IDNA_NONTRANSITIONAL_TO_ASCII, INTL_IDNA_VARIANT_UTS46);
				} else {
					$tokens['host'] = idn_to_ascii($tokens['host']);
				}

				// if `idn_to_ascii` failed
				if ($tokens['host'] === false) {
					return false;
				}
			}
		}

		// separate set of tokens with urlencoded 'path' because filter_var() rightfully fails on non-latin characters
		// (used for validation only, we actually request the original URL, in case of urlencode breaking it)
		$tokens_filter_var = $tokens;

		if ($tokens['path'] ?? false) {
			$tokens_filter_var['path'] = implode("/",
										array_map("rawurlencode",
											array_map("rawurldecode",
												explode("/", $tokens['path']))));
		}

		$url = self::build_url($tokens);
		$url_filter_var = self::build_url($tokens_filter_var);

		if (filter_var($url_filter_var, FILTER_VALIDATE_URL) === false)
			return false;

		if ($extended_filtering) {
			if (!in_array($tokens['port'] ?? '', [80, 443, '']))
				return false;

			if (strtolower($tokens['host']) == 'localhost' || $tokens['host'] == '::1' || strpos($tokens['host'], '127.') === 0)
				return false;
		}

		return $url;
	}

	/**
	 * @return false|string
	 */
	static function resolve_redirects(string $url, int $timeout, int $nest = 0) {
		$scope = Tracer::start(__METHOD__, ['url' => $url]);

		// too many redirects
		if ($nest > 10) {
			$scope->getSpan()->setTag('error', 'too many redirects');
			$scope->close();
			return false;
		}

		$context_options = array(
			'http' => array(
					'header' => array(
						'Connection: close'
					),
					'method' => 'HEAD',
					'timeout' => $timeout,
					'protocol_version'=> 1.1)
			);

		if (Config::get(Config::HTTP_PROXY)) {
			$context_options['http']['request_fulluri'] = true;
			$context_options['http']['proxy'] = Config::get(Config::HTTP_PROXY);
		}

		$context = stream_context_create($context_options);

		// PHP 8 changed the second param from int to bool, but we still support PHP >= 7.4.0
		// @phpstan-ignore-next-line
		$headers = get_headers($url, 0, $context);

		if (is_array($headers)) {
			$headers = array_reverse($headers); // last one is the correct one

			foreach($headers as $header) {
				if (stripos($header, 'Location:') === 0) {
					$url = self::rewrite_relative($url, trim(substr($header, strlen('Location:'))));

					return self::resolve_redirects($url, $timeout, $nest + 1);
				}
			}

			$scope->close();
			return $url;
		}

		$scope->getSpan()->setTag('error', 'request failed');
		$scope->close();
		// request failed?
		return false;
	}

	/**
	 * @param array<string, bool|int|string>|string $options
	 * @return false|string false if something went wrong, otherwise string contents
	 */
	// TODO: max_size currently only works for CURL transfers
	// TODO: multiple-argument way is deprecated, first parameter is a hash now
	public static function fetch($options /* previously: 0: $url , 1: $type = false, 2: $login = false, 3: $pass = false,
				4: $post_query = false, 5: $timeout = false, 6: $timestamp = 0, 7: $useragent = false*/) {

		self::$fetch_last_error = "";
		self::$fetch_last_error_code = -1;
		self::$fetch_last_error_content = "";
		self::$fetch_last_content_type = "";
		self::$fetch_curl_used = false;
		self::$fetch_last_modified = "";
		self::$fetch_effective_url = "";
		self::$fetch_effective_ip_addr = "";

		if (!is_array($options)) {

			// falling back on compatibility shim
			$option_names = [ "url", "type", "login", "pass", "post_query", "timeout", "last_modified", "useragent" ];
			$tmp = [];

			for ($i = 0; $i < func_num_args(); $i++) {
				$tmp[$option_names[$i]] = func_get_arg($i);
			}

			$options = $tmp;

			/*$options = array(
					"url" => func_get_arg(0),
					"type" => @func_get_arg(1),
					"login" => @func_get_arg(2),
					"pass" => @func_get_arg(3),
					"post_query" => @func_get_arg(4),
					"timeout" => @func_get_arg(5),
					"timestamp" => @func_get_arg(6),
					"useragent" => @func_get_arg(7)
			); */
		}
		$url = $options["url"];

		$scope = Tracer::start(__METHOD__, ['url' => $url]);

		$type = isset($options["type"]) ? $options["type"] : false;
		$login = isset($options["login"]) ? $options["login"] : false;
		$pass = isset($options["pass"]) ? $options["pass"] : false;
		$post_query = isset($options["post_query"]) ? $options["post_query"] : false;
		$timeout = isset($options["timeout"]) ? $options["timeout"] : false;
		$last_modified = isset($options["last_modified"]) ? $options["last_modified"] : "";
		$useragent = isset($options["useragent"]) ? $options["useragent"] : false;
		$followlocation = isset($options["followlocation"]) ? $options["followlocation"] : true;
		$max_size = isset($options["max_size"]) ? $options["max_size"] : Config::get(Config::MAX_DOWNLOAD_FILE_SIZE); // in bytes
		$http_accept = isset($options["http_accept"]) ? $options["http_accept"] : false;
		$http_referrer = isset($options["http_referrer"]) ? $options["http_referrer"] : false;

		$url = ltrim($url, ' ');
		$url = str_replace(' ', '%20', $url);

		Debug::log("[UrlHelper] fetching: $url", Debug::LOG_EXTENDED);

		$url = self::validate($url, true);

		if (!$url) {
			self::$fetch_last_error = "Requested URL failed extended validation.";

			$scope->getSpan()->setTag('error', self::$fetch_last_error);
			$scope->close();
			return false;
		}

		$url_host = parse_url($url, PHP_URL_HOST);
		$ip_addr = gethostbyname($url_host);

		if (!$ip_addr || strpos($ip_addr, "127.") === 0) {
			self::$fetch_last_error = "URL hostname failed to resolve or resolved to a loopback address ($ip_addr)";

			$scope->getSpan()->setTag('error', self::$fetch_last_error);
			$scope->close();
			return false;
		}

		if (function_exists('curl_init') && !ini_get("open_basedir")) {

			self::$fetch_curl_used = true;

			$ch = curl_init($url);

			if (!$ch) {
				self::$fetch_last_error = "curl_init() failed";
				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			$curl_http_headers = [];

			if ($last_modified && !$post_query)
				array_push($curl_http_headers, "If-Modified-Since: $last_modified");

			if ($http_accept)
				array_push($curl_http_headers, "Accept: " . $http_accept);

			if (count($curl_http_headers) > 0)
				curl_setopt($ch, CURLOPT_HTTPHEADER, $curl_http_headers);

			curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout ? $timeout : Config::get(Config::FILE_FETCH_CONNECT_TIMEOUT));
			curl_setopt($ch, CURLOPT_TIMEOUT, $timeout ? $timeout : Config::get(Config::FILE_FETCH_TIMEOUT));
			curl_setopt($ch, CURLOPT_FOLLOWLOCATION, $followlocation);
			curl_setopt($ch, CURLOPT_MAXREDIRS, 20);
			curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
			curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
			curl_setopt($ch, CURLOPT_HEADER, true);
			curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
			curl_setopt($ch, CURLOPT_USERAGENT, $useragent ? $useragent : Config::get_user_agent());
			curl_setopt($ch, CURLOPT_ENCODING, "");
			curl_setopt($ch, CURLOPT_COOKIEJAR, "/dev/null");

			if  ($http_referrer)
				curl_setopt($ch, CURLOPT_REFERER, $http_referrer);

			if ($max_size) {
				curl_setopt($ch, CURLOPT_NOPROGRESS, false);
				curl_setopt($ch, CURLOPT_BUFFERSIZE, 16384); // needed to get 5 arguments in progress function?

				// holy shit closures in php
				// download & upload are *expected* sizes respectively, could be zero
				curl_setopt($ch, CURLOPT_PROGRESSFUNCTION, function($curl_handle, $download_size, $downloaded, $upload_size, $uploaded) use(&$max_size, $url) {
					//Debug::log("[curl progressfunction] $downloaded $max_size", Debug::$LOG_EXTENDED);

					if ($downloaded > $max_size) {
						Debug::log("[UrlHelper] fetch error: curl reached max size of $max_size bytes downloading $url, aborting.", Debug::LOG_VERBOSE);
						return 1;
					}

					return 0;
				});

			}

			if (Config::get(Config::HTTP_PROXY)) {
				curl_setopt($ch, CURLOPT_PROXY, Config::get(Config::HTTP_PROXY));
			}

			if ($post_query) {
				curl_setopt($ch, CURLOPT_POST, true);
				curl_setopt($ch, CURLOPT_POSTFIELDS, $post_query);
			}

			if ($login && $pass)
				curl_setopt($ch, CURLOPT_USERPWD, "$login:$pass");

			$ret = @curl_exec($ch);
			$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);

			// CURLAUTH_BASIC didn't work, let's retry with CURLAUTH_ANY in case it's actually something
			// unusual like NTLM...
			if ($http_code == 403 && $login && $pass) {
				curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_ANY);

				$ret = @curl_exec($ch);
			}

			if (curl_errno($ch) === 23 || curl_errno($ch) === 61) {
				curl_setopt($ch, CURLOPT_ENCODING, 'none');
				$ret = @curl_exec($ch);
			}

			$headers_length = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
			$headers = explode("\r\n", substr($ret, 0, $headers_length));
			$contents = substr($ret, $headers_length);

			foreach ($headers as $header) {
				if (strstr($header, ": ") !== false) {
					list ($key, $value) = explode(": ", $header);

					if (strtolower($key) == "last-modified") {
						self::$fetch_last_modified = $value;
					}
				}

				if (substr(strtolower($header), 0, 7) == 'http/1.') {
					self::$fetch_last_error_code = (int) substr($header, 9, 3);
					self::$fetch_last_error = $header;
				}
			}

			$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
			self::$fetch_last_content_type = curl_getinfo($ch, CURLINFO_CONTENT_TYPE);

			self::$fetch_effective_url = curl_getinfo($ch, CURLINFO_EFFECTIVE_URL);

			if (!self::validate(self::$fetch_effective_url, true)) {
				self::$fetch_last_error = "URL received after redirection failed extended validation.";

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			self::$fetch_effective_ip_addr = gethostbyname(parse_url(self::$fetch_effective_url, PHP_URL_HOST));

			if (!self::$fetch_effective_ip_addr || strpos(self::$fetch_effective_ip_addr, "127.") === 0) {
				self::$fetch_last_error = "URL hostname received after redirection failed to resolve or resolved to a loopback address (".self::$fetch_effective_ip_addr.")";

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			self::$fetch_last_error_code = $http_code;

			if ($http_code != 200 || $type && strpos(self::$fetch_last_content_type, "$type") === false) {

				if (curl_errno($ch) != 0) {
					self::$fetch_last_error .=  "; " . curl_errno($ch) . " " . curl_error($ch);
				} else {
					self::$fetch_last_error = "HTTP Code: $http_code ";
				}

				self::$fetch_last_error_content = $contents;
				curl_close($ch);

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			if (!$contents) {
				if (curl_errno($ch) === 0) {
					self::$fetch_last_error = 'Successful response, but no content was received.';
				} else {
					self::$fetch_last_error = curl_errno($ch) . " " . curl_error($ch);
				}
				curl_close($ch);

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			curl_close($ch);

			$is_gzipped = RSSUtils::is_gzipped($contents);

			if ($is_gzipped && is_string($contents)) {
				$tmp = @gzdecode($contents);

				if ($tmp) $contents = $tmp;
			}

			$scope->close();

			return $contents;
		} else {

			self::$fetch_curl_used = false;

			if ($login && $pass){
				$url_parts = array();

				preg_match("/(^[^:]*):\/\/(.*)/", $url, $url_parts);

				$pass = urlencode($pass);

				if ($url_parts[1] && $url_parts[2]) {
					$url = $url_parts[1] . "://$login:$pass@" . $url_parts[2];
				}
			}

			// TODO: should this support POST requests or not? idk

			 $context_options = array(
				  'http' => array(
						'header' => array(
							'Connection: close'
						),
						'method' => 'GET',
						'ignore_errors' => true,
						'timeout' => $timeout ? $timeout : Config::get(Config::FILE_FETCH_TIMEOUT),
						'protocol_version'=> 1.1)
				  );

			if (!$post_query && $last_modified)
				array_push($context_options['http']['header'], "If-Modified-Since: $last_modified");

			if ($http_accept)
				array_push($context_options['http']['header'], "Accept: $http_accept");

			if ($http_referrer)
				array_push($context_options['http']['header'], "Referer: $http_referrer");

			if (Config::get(Config::HTTP_PROXY)) {
				$context_options['http']['request_fulluri'] = true;
				$context_options['http']['proxy'] = Config::get(Config::HTTP_PROXY);
			}

			$context = stream_context_create($context_options);

			$old_error = error_get_last();

			self::$fetch_effective_url = self::resolve_redirects($url, $timeout ? $timeout : Config::get(Config::FILE_FETCH_CONNECT_TIMEOUT));

			if (!self::validate(self::$fetch_effective_url, true)) {
				self::$fetch_last_error = "URL received after redirection failed extended validation.";

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			self::$fetch_effective_ip_addr = gethostbyname(parse_url(self::$fetch_effective_url, PHP_URL_HOST));

			if (!self::$fetch_effective_ip_addr || strpos(self::$fetch_effective_ip_addr, "127.") === 0) {
				self::$fetch_last_error = "URL hostname received after redirection failed to resolve or resolved to a loopback address (".self::$fetch_effective_ip_addr.")";

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			$data = @file_get_contents($url, false, $context);

			if ($data === false) {
				self::$fetch_last_error = "'file_get_contents' failed.";

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			foreach ($http_response_header as $header) {
				if (strstr($header, ": ") !== false) {
					list ($key, $value) = explode(": ", $header);

					$key = strtolower($key);

					if ($key == 'content-type') {
						self::$fetch_last_content_type = $value;
						// don't abort here b/c there might be more than one
						// e.g. if we were being redirected -- last one is the right one
					} else if ($key == 'last-modified') {
						self::$fetch_last_modified = $value;
					} else if ($key == 'location') {
						self::$fetch_effective_url = $value;
					}
				}

				if (substr(strtolower($header), 0, 7) == 'http/1.') {
					self::$fetch_last_error_code = (int) substr($header, 9, 3);
					self::$fetch_last_error = $header;
				}
			}

			if (self::$fetch_last_error_code != 200) {
				$error = error_get_last();

				if (($error['message'] ?? '') != ($old_error['message'] ?? '')) {
					self::$fetch_last_error .= "; " . $error["message"];
				}

				self::$fetch_last_error_content = $data;

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}

			if ($data) {
				$is_gzipped = RSSUtils::is_gzipped($data);

				if ($is_gzipped) {
					$tmp = @gzdecode($data);

					if ($tmp) $data = $tmp;
				}

				$scope->close();
				return $data;
			} else {
				self::$fetch_last_error = 'Successful response, but no content was received.';

				$scope->getSpan()->setTag('error', self::$fetch_last_error);
				$scope->close();
				return false;
			}
		}
	}

	/**
	 * @return false|string false if the provided URL didn't match expected patterns, otherwise the video ID string
	 */
	public static function url_to_youtube_vid(string $url) {
		$url = str_replace("youtube.com", "youtube-nocookie.com", $url);

		$regexps = [
			"/\/\/www\.youtube-nocookie\.com\/v\/([\w-]+)/",
			"/\/\/www\.youtube-nocookie\.com\/embed\/([\w-]+)/",
			"/\/\/www\.youtube-nocookie\.com\/watch?v=([\w-]+)/",
			"/\/\/youtu.be\/([\w-]+)/",
		];

		foreach ($regexps as $re) {
			$matches = [];

			if (preg_match($re, $url, $matches)) {
				return $matches[1];
			}
		}

		return false;
	}


}