<?php

namespace CleantalkSP\SpbctWP\Scanner;

use CleantalkSP\SpbctWP\Helpers\Helper;
use CleantalkSP\SpbctWP\Scanner\Frontend\ModuleResult;

/**
 * Class FrontendScan
 *
 * Scan any content for frontend malware (HTML, JS)
 *
 * @version       2.0.0
 * @package       Security by Cleantalk
 * @category      ScannerFrontend
 * @author        Cleantalk team (welcome@cleantalk.org)
 * @copyright (C) 2014 CleanTalk team (http://cleantalk.org)
 * @license       GNU/GPL: http://www.gnu.org/copyleft/gpl.html
 * @link          https://github.com/CleanTalk/php-antispam
 */
class FrontendScan
{
    /**
     * Given conten to check
     * @var string
     */
    private $content;
    /**
     * DOMDocument created from content
     * @var \DOMDocument
     */
    private $dom;
    /**
     * @var \DOMXPath Contains JS tags from content
     */
    private $js_tags = null;
    /**
     * URL that consider as home URL. All links with this host consider as harmful
     * @var string
     */
    private $home_url;
    /**
     * URL that consider as harmful
     * @var array|string
     */
    private $except_urls = array();


    /**
     * Signatures with HTML code
     * @var array
     */
    private $signatures_html;
    /**
     * Signatures with JS code
     * @var array
     */
    private $signatures_js;

    /*
     * Flags for scan type
     */
    private $scan_for_redirect = false;
    private $scan_for_dbd = false;
    private $scan_for_signatures_js = false;
    private $scan_for_signatures_html = false;
    private $scan_for_csrf = false;

    /**
     * Results of a scan
     * @var array
     */
    private $result = array();

    /**
     * Constructor
     *
     * @param array $check_list
     */
    public function __construct($check_list = array('redirects', 'dbd', 'signatures_js', 'signatures_html'))
    {
        $this->scan_for_redirect        = in_array('redirects', $check_list);
        $this->scan_for_dbd             = in_array('dbd', $check_list);
        $this->scan_for_signatures_js   = in_array('signatures_js', $check_list);
        $this->scan_for_signatures_html = in_array('signatures_html', $check_list);
        $this->scan_for_csrf            = in_array('csrf', $check_list);
    }

    /**
     * Method which gathering all check types
     *
     * Liquid interface
     *
     * @return FrontendScan
     */
    public function check()
    {
        $this->scan_for_redirect        = $this->scan_for_redirect && $this->home_url;
        $this->scan_for_dbd             = $this->scan_for_dbd && $this->home_url;
        $this->scan_for_signatures_js   = $this->scan_for_signatures_js && $this->signatures_js;
        $this->scan_for_signatures_html = $this->scan_for_signatures_html && $this->signatures_html;

        $this->result = array_merge(
            $this->scan_for_redirect ? $this->checkForRedirects() : array(),
            $this->scan_for_dbd ? $this->checkForDriveByDownload() : array(),
            $this->scan_for_signatures_js ? $this->checkForSignaturesJs() : array(),
            $this->scan_for_signatures_html ? $this->checkForSignaturesHtml() : array(),
            $this->scan_for_csrf ? $this->checkForCsrf() : array()
        );

        return $this;
    }

    /**
     * Check given DOMDocument for redirects
     *
     * @return array
     */
    private function checkForRedirects()
    {
        if ( ! $this->js_tags ) {
            // Getting JS tags to check
            $xpath         = new \DOMXPath($this->dom);
            $this->js_tags = $xpath->evaluate("/html//script");
        }

        $url_exceptions = $this->except_urls
            ? $this->home_url . '|' . implode('|', $this->except_urls)
            : $this->home_url;

        $results = $this->checkForAnything(
            $this->js_tags,
            '/location(?:\s*\.\s*href\s*)?\s*=\s*["\'](?:http[s]?:\/\/)(?:www\.)?(?!' . $url_exceptions . ').*/',
            'regexp'
        );

        return $this->compileResults($results, 'redirects');
    }

    /**
     * Check given DOMDocument for drive by download attack
     *
     * @return array
     */
    private function checkForDriveByDownload()
    {
        // Getting JS tags to check
        $xpath   = new \DOMXPath($this->dom);
        $iframes = $xpath->evaluate("/html//iframe");

        $url_exceptions = $this->except_urls
            ? $this->home_url . '|' . implode('|', $this->except_urls)
            : $this->home_url;

        $results = array();
        foreach ( $iframes as $iframe ) {
            $results = array_merge(
                $results,
                $this->checkForAnything(
                    $iframe,
                    '#^http[s]?://(?!([a-zA-Z0-9-]*\.)*(' . $url_exceptions . ')).*#',
                    'regexp'
                )
            );
        }

        return $this->compileResults($results, 'dbd');
    }

    /**
     * Check given DOMDocument for JS signatures
     *
     * @return ModuleResult[]
     */
    private function checkForSignaturesJs()
    {
        if ( ! $this->js_tags ) {
            // Getting JS tags to check
            $xpath         = new \DOMXPath($this->dom);
            $this->js_tags = $xpath->evaluate("/html//script");
        }

        $results = $this->checkForAnything(
            $this->js_tags,
            $this->signatures_js
        );

        return $this->compileResults($results, 'signatures');
    }

    /**
     * * Check given content for HTML signatures
     *
     * @return ModuleResult[]
     */
    private function checkForSignaturesHtml()
    {
        /* @ToDo We need to check the Dom Node instead the string to get line number
         * $xpath = new \DOMXPath($this->dom);
         * $html_hode = $xpath->evaluate( "/html" );
         */

        $results = $this->checkForAnything(
            $this->content,
            $this->signatures_html
        );

        return $this->compileResults($results, 'signatures');
    }

    /**
     * Check given content for CSRF implementation signatures
     *
     * @return ModuleResult[]
     */
    private function checkForCsrf()
    {
        $params_parts = array('cid', 'uid', 'account', 'user');
        $attributes   = array('src', 'href');

        $needles        = '@(?<!' . $this->home_url . ')\?.*?(' . implode('|', $params_parts) . ').*?=@';
        $xpath          = new \DOMXPath($this->dom);
        $attributes_DOM = $xpath->evaluate('//@' . implode('|//@', $attributes));

        $results = $this->checkForAnything(
            $attributes_DOM,
            $needles,
            'regexp'
        );

        return $this->compileResults($results, 'csrf');
    }

    /**
     * Universal method to check any type of threat
     *
     * @param array|string|\DOMElement $haystacks
     * @param array|string $needles
     * @param string $search_type
     *
     * @return array
     * @psalm-suppress UndefinedMethod
     */
    private function checkForAnything($haystacks, $needles, $search_type = 'string')
    {
        $haystacks = is_string($haystacks) ? array($haystacks) : $haystacks;
        $needles   = is_string($needles) ? array($needles) : $needles;

        if ( $haystacks instanceof \DOMElement && $haystacks->tagName === 'iframe' ) {
            $iframe    = $haystacks;
            $haystacks = array(
                $iframe->getAttribute('src'),
                $iframe->getAttribute('data-src'),
                $iframe->getAttribute('data-frame-src'),
            );
        }

        foreach ( $haystacks as $key => $haystack ) {
            // Getting text value for haystack
            $haystack = $haystack instanceof \DOMElement || $haystack instanceof \DOMAttr
                ? $haystack->nodeValue
                : $haystack;

            foreach ( $needles as $needle ) {
                $signature = null;
                // If $needle is a signature
                if ( is_array($needle) ) {
                    $signature = $needle;

                    // Getting type of search needle

                    $search_type = Helper::isRegexp($needle['body'])
                        ? 'regexp'
                        : 'string';

                    // Gettin the body
                    $needle = $needle['body'];
                }


                switch ( $search_type ) {
                    // Check with strings
                    case 'string':
                        $pos = strpos($haystack, $needle);
                        if ( $pos !== false ) {
                            $out[] = array(
                                'haystack_original' => isset($iframe) ? $iframe : $haystacks[$key],
                                'haystack'          => $haystack,
                                'found'             => substr($haystack, $pos, strlen($needle)),
                                'needle'            => $signature,
                            );
                        }
                        break;

                    // Check with regular expression
                    case 'regexp':
                        if ( preg_match($needle, $haystack, $matches) ) {
                            $out[] = array(
                                'haystack_original' => isset($iframe) ? $iframe : $haystacks[$key],
                                'haystack'          => $haystack,
                                'found'             => $matches[0],
                                'needle'            => $signature,
                            );
                        }
                        break;
                }
            }
        }

        return isset($out) ? $out : array();
    }

    /**
     * Universal method construct weakspot arrays.
     *
     * @param string $weak_spot_inner contains dangerous code line that found in check__for_anything result.
     *
     * @return string Array of arrays of weakspot data or false if empty.
     */
    private function getStringContainsBadCode($weak_spot_inner)
    {
        if ( empty($weak_spot_inner) ) {
            return '';
        }
        $weak_spot_inner_start            = strpos($this->content, $weak_spot_inner);
        $content_length                   = strlen($this->content);
        $result_line_starts_with_position =
            strrpos(
                $this->content,
                "\n",
                -1 * ($content_length - $weak_spot_inner_start)
            ) + 1;
        $result_line_ends_with_position   = strpos($this->content, "\n", $weak_spot_inner_start);
        $result                           = substr(
            $this->content,
            $result_line_starts_with_position > 0
                ? $result_line_starts_with_position
                : 0,
            $result_line_ends_with_position - $result_line_starts_with_position
        );
        if ( ! $result ) {
            $result = '...' . $weak_spot_inner . '...';
        }

        return $result;
    }

    /**
     * Get $this->result
     *
     * @return array
     */
    public function getResult()
    {
        return $this->result;
    }

    /**
     * Set $this->content and it's derivatives
     *
     * @param string $content
     *
     * @return FrontendScan
     */
    public function setContent($content = '')
    {
        $this->content = $content;

        $this->dom = new \DOMDocument();

        try {
            @$this->dom->loadHTML($this->content);
        } catch (\Error $e) { // phpcs:ignore PHPCompatibility.Classes.NewClasses.errorFound
            error_log($e->getMessage());
        }

        return $this;
    }

    /**
     * @param string $home_url
     *
     * @return FrontendScan
     */
    public function setHomeUrl($home_url)
    {
        $this->home_url = parse_url($home_url, PHP_URL_HOST);

        return $this;
    }

    /**
     * @param $signatures
     *
     * @return FrontendScan
     */
    public function setSignatures($signatures)
    {
        // Spplit signatures in two groups
        foreach ( $signatures as $signature ) {
            if ( $signature['type'] === 'CODE_HTML' ) {
                $this->signatures_html[] = $signature;
            }

            if ( $signature['type'] === 'CODE_JS' ) {
                $this->signatures_js[] = $signature;
            }
        }

        return $this;
    }

    /**
     * @param array $except_urls
     *
     * @return FrontendScan
     */
    public function setExceptUrls($except_urls)
    {
        $except_urls = (array)$except_urls;

        foreach ( $except_urls as & $except_url ) {
            if ( preg_match('#https?://#', $except_url) ) {
                $except_url = parse_url($except_url, PHP_URL_HOST);
                $except_url = preg_replace('#.*?([a-zA-Z0-9-]+\.[a-zA-Z0-9-]+)$#', '$1', $except_url);
            }
        }
        unset($except_url);

        $this->except_urls = $except_urls;

        return $this;
    }

    /**
     * @param array[] $results
     * @param string $type
     *
     * @return ModuleResult[]
     */
    private function compileResults($results, $type)
    {
        $out = [];
        foreach ( $results as $result ) {
            $out[] = $this->compileResult($result, $type);
        }

        return $out ?: [];
    }

    /**
     * @param array $result Contains results of check__for_anything
     * @param string $type Type of check, in fact transfers the caller method
     *
     * @return ModuleResult
     */
    private function compileResult($result, $type)
    {
        return new ModuleResult([
            'type'         => $type,
            'line'         => $result['haystack_original'] instanceof \DOMElement
                ? $result['haystack_original']->getLineNo() - 1
                : 0,
            'found'        => substr(htmlentities($result['found']), 0, 1000),
            'surroundings' => substr(
                htmlentities(
                    $this->getStringContainsBadCode(
                        substr($result['found'], 0, 1000)
                    )
                ),
                0,
                1500
            ),
            'needle'       => $result['needle'],
        ]);
    }
}
