<?php

namespace TablePress\PhpOffice\PhpSpreadsheet\Reader\Security;

use TablePress\PhpOffice\PhpSpreadsheet\Reader;

class XmlScanner
{
	private const ENCODING_PATTERN = '/encoding\s*=\s*(["\'])(.+?)\1/s';
	private const ENCODING_UTF7 = '/encoding\s*=\s*(["\'])UTF-7\1/si';

	/**
	 * String used to identify risky xml elements.
	 *
	 * @var string
	 */
	private $pattern;

	/** @var ?callable */
	private $callback;

	/** @var ?bool */
	private static $libxmlDisableEntityLoaderValue;

	/**
	 * @var bool
	 */
	private static $shutdownRegistered = false;

	public function __construct(string $pattern = '<!DOCTYPE')
	{
		$this->pattern = $pattern;

		$this->disableEntityLoaderCheck();

		// A fatal error will bypass the destructor, so we register a shutdown here
		if (!self::$shutdownRegistered) {
			self::$shutdownRegistered = true;
			register_shutdown_function([__CLASS__, 'shutdown']);
		}
	}

	public static function getInstance(Reader\IReader $reader): self
	{
		$pattern = ($reader instanceof Reader\Html) ? '<!ENTITY' : '<!DOCTYPE';

		return new self($pattern);
	}

	/**
	 * @codeCoverageIgnore
	 */
	public static function threadSafeLibxmlDisableEntityLoaderAvailability(): bool
	{
		if (PHP_MAJOR_VERSION === 7) {
			return true;
		}

		return false;
	}

	/**
	 * @codeCoverageIgnore
	 */
	private function disableEntityLoaderCheck(): void
	{
		if (\PHP_VERSION_ID < 80000) {
			$libxmlDisableEntityLoaderValue = libxml_disable_entity_loader(true);

			if (self::$libxmlDisableEntityLoaderValue === null) {
				self::$libxmlDisableEntityLoaderValue = $libxmlDisableEntityLoaderValue;
			}
		}
	}

	/**
	 * @codeCoverageIgnore
	 */
	public static function shutdown(): void
	{
		if (self::$libxmlDisableEntityLoaderValue !== null && \PHP_VERSION_ID < 80000) {
			libxml_disable_entity_loader(self::$libxmlDisableEntityLoaderValue);
			self::$libxmlDisableEntityLoaderValue = null;
		}
	}

	public function __destruct()
	{
		self::shutdown();
	}

	public function setAdditionalCallback(callable $callback): void
	{
		$this->callback = $callback;
	}

	/** @param mixed $arg */
	private static function forceString($arg): string
	{
		return is_string($arg) ? $arg : '';
	}

	/**
	 * @param string $xml
	 *
	 * @return string
	 */
	private function toUtf8($xml)
	{
		$charset = $this->findCharSet($xml);
		$foundUtf7 = $charset === 'UTF-7';
		if ($charset !== 'UTF-8') {
			$testStart = '/^.{0,4}\s*<?xml/s';
			$startWithXml1 = preg_match($testStart, $xml);
			$xml = self::forceString(mb_convert_encoding($xml, 'UTF-8', $charset));
			if ($startWithXml1 === 1 && preg_match($testStart, $xml) !== 1) {
				throw new Reader\Exception('Double encoding not permitted');
			}
			$foundUtf7 = $foundUtf7 || (preg_match(self::ENCODING_UTF7, $xml) === 1);
			$xml = preg_replace(self::ENCODING_PATTERN, '', $xml) ?? $xml;
		} else {
			$foundUtf7 = $foundUtf7 || (preg_match(self::ENCODING_UTF7, $xml) === 1);
		}
		if ($foundUtf7) {
			throw new Reader\Exception('UTF-7 encoding not permitted');
		}
		if (substr($xml, 0, Reader\Csv::UTF8_BOM_LEN) === Reader\Csv::UTF8_BOM) {
			$xml = (string) substr($xml, Reader\Csv::UTF8_BOM_LEN);
		}

		return $xml;
	}

	private function findCharSet(string $xml): string
	{
		if (str_starts_with($xml, "\x4c\x6f\xa7\x94")) {
			throw new Reader\Exception('EBCDIC encoding not permitted');
		}
		$encoding = Reader\Csv::guessEncodingBom('', $xml);
		if ($encoding !== '') {
			return $encoding;
		}
		$xml = str_replace("\0", '', $xml);
		if (preg_match(self::ENCODING_PATTERN, $xml, $matches)) {
			return strtoupper($matches[2]);
		}

		return 'UTF-8';
	}

	/**
	 * Scan the XML for use of <!ENTITY to prevent XXE/XEE attacks.
	 *
	 * @param false|string $xml
	 *
	 * @return string
	 */
	public function scan($xml)
	{
		// Don't rely purely on libxml_disable_entity_loader()
		$pattern = '/\0*' . implode('\0*', mb_str_split($this->pattern, 1, 'UTF-8')) . '\0*/';

		$xml = "$xml";
		if (preg_match($pattern, $xml)) {
			throw new Reader\Exception('Detected use of ENTITY in XML, spreadsheet file load() aborted to prevent XXE/XEE attacks');
		}

		$xml = $this->toUtf8($xml);
		if (preg_match($pattern, $xml)) {
			throw new Reader\Exception('Detected use of ENTITY in XML, spreadsheet file load() aborted to prevent XXE/XEE attacks');
		}

		if ($this->callback !== null) {
			$xml = call_user_func($this->callback, $xml);
		}
		/** @var string $xml */

		return $xml;
	}

	/**
	 * Scan the XML for use of <!ENTITY to prevent XXE/XEE attacks.
	 *
	 * @param string $filestream
	 *
	 * @return string
	 */
	public function scanFile($filestream)
	{
		return $this->scan(file_get_contents($filestream));
	}
}
