<?php

namespace Wallabag\Helper;

use enshrined\svgSanitize\Sanitizer;
use GuzzleHttp\Psr7\Uri;
use GuzzleHttp\Psr7\UriResolver;
use Psr\Log\LoggerInterface;
use Symfony\Component\DomCrawler\Crawler;
use Symfony\Component\Finder\Finder;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Mime\MimeTypes;
use Symfony\Contracts\HttpClient\HttpClientInterface;
use Symfony\Contracts\HttpClient\ResponseInterface;

class DownloadImages
{
    public const REGENERATE_PICTURES_QUALITY = 80;

    private $client;
    private $baseFolder;
    private $logger;
    private $mimeTypes;
    private $wallabagUrl;

    public function __construct(HttpClientInterface $downloadImagesClient, $baseFolder, $wallabagUrl, LoggerInterface $logger)
    {
        $this->client = $downloadImagesClient;
        $this->baseFolder = $baseFolder;
        $this->wallabagUrl = rtrim($wallabagUrl, '/');
        $this->logger = $logger;
        $this->mimeTypes = new MimeTypes();

        $this->setFolder();
    }

    public function getBaseFolder()
    {
        return $this->baseFolder;
    }

    /**
     * Process the html and extract images URLs from it.
     *
     * @param string $html
     *
     * @return string[]
     */
    public static function extractImagesUrlsFromHtml($html)
    {
        $crawler = new Crawler($html);
        $imagesCrawler = $crawler->filterXpath('//img');
        $imagesUrls = $imagesCrawler->extract(['src']);
        $imagesSrcsetUrls = self::getSrcsetUrls($imagesCrawler);

        return array_unique(array_merge($imagesUrls, $imagesSrcsetUrls));
    }

    /**
     * Process the html and extract image from it, save them to local and return the updated html.
     *
     * @param int    $entryId ID of the entry
     * @param string $html
     * @param string $url     Used as a base path for relative image and folder
     *
     * @return string
     */
    public function processHtml($entryId, $html, $url)
    {
        $imagesUrls = self::extractImagesUrlsFromHtml($html);

        // ensure images aren't overlapping
        arsort($imagesUrls);

        $relativePath = $this->getRelativePath($entryId);

        // download and save the image to the folder
        foreach ($imagesUrls as $image) {
            $newImage = $this->processSingleImage($entryId, $image, $url, $relativePath);

            if (false === $newImage) {
                continue;
            }

            $html = str_replace($image, $newImage, $html);
            // if image contains "&" and we can't find it in the html it might be because it's encoded as &amp; or unicode
            if (false !== stripos($image, '&') && false === stripos($html, $image)) {
                $imageAmp = str_replace('&', '&amp;', $image);
                $html = str_replace($imageAmp, $newImage, $html);
                $imageUnicode = str_replace('&', '&#038;', $image);
                $html = str_replace($imageUnicode, $newImage, $html);
            }
        }

        return $html;
    }

    /**
     * Process a single image:
     *     - retrieve it
     *     - re-saved it (for security reason)
     *     - return the new local path.
     *
     * @param int    $entryId      ID of the entry
     * @param string $imagePath    Path to the image to retrieve
     * @param string $url          Url from where the image were found
     * @param string $relativePath Relative local path to saved the image
     *
     * @return string|false Relative url to access the image from the web
     */
    public function processSingleImage($entryId, $imagePath, $url, $relativePath = null)
    {
        if (null === $imagePath) {
            return false;
        }

        if (null === $relativePath) {
            $relativePath = $this->getRelativePath($entryId);
        }

        $this->logger->debug('DownloadImages: working on image: ' . $imagePath);

        $folderPath = $this->baseFolder . '/' . $relativePath;

        // build image path
        $absolutePath = $this->getAbsoluteLink($url, $imagePath);
        if (false === $absolutePath) {
            $this->logger->error('DownloadImages: Can not determine the absolute path for that image, skipping.');

            return false;
        }

        try {
            $res = $this->client->request(Request::METHOD_GET, $absolutePath);
        } catch (\Exception $e) {
            $this->logger->error('DownloadImages: Can not retrieve image, skipping.', ['exception' => $e]);

            return false;
        }

        $ext = $this->getExtensionFromResponse($res, $imagePath);
        if (false === $res) {
            return false;
        }

        $hashImage = hash('crc32', $absolutePath);
        $localPath = $folderPath . '/' . $hashImage . '.' . $ext;
        $urlPath = $this->wallabagUrl . '/assets/images/' . $relativePath . '/' . $hashImage . '.' . $ext;

        // custom case for SVG (because GD doesn't support SVG)
        if ('svg' === $ext) {
            try {
                $sanitizer = new Sanitizer();
                $sanitizer->minify(true);
                $sanitizer->removeRemoteReferences(true);
                $cleanSVG = $sanitizer->sanitize($res->getContent());

                // add an extra validation by checking about `<svg `
                if (false === $cleanSVG || !str_contains($cleanSVG, '<svg ')) {
                    $this->logger->error('DownloadImages: Bad SVG given', ['path' => $imagePath]);

                    return false;
                }

                file_put_contents($localPath, $cleanSVG);

                return $urlPath;
            } catch (\Exception $e) {
                $this->logger->error('DownloadImages: Error while sanitize SVG', ['path' => $imagePath, 'message' => $e->getMessage()]);

                return false;
            }
        }

        try {
            $im = imagecreatefromstring($res->getContent());
        } catch (\Exception $e) {
            $im = false;
        }

        if (false === $im) {
            $this->logger->error('DownloadImages: Error while regenerating image', ['path' => $localPath]);

            return false;
        }

        switch ($ext) {
            case 'gif':
                // use Imagick if available to keep GIF animation
                if (class_exists(\Imagick::class)) {
                    try {
                        $imagick = new \Imagick();
                        $imagick->readImageBlob($res->getContent());
                        $imagick->setImageFormat('gif');
                        $imagick->writeImages($localPath, true);
                    } catch (\Exception $e) {
                        // if Imagick fail, fallback to the default solution
                        imagegif($im, $localPath);
                    }
                } else {
                    imagegif($im, $localPath);
                }

                $this->logger->debug('DownloadImages: Re-creating gif');
                break;
            case 'jpeg':
            case 'jpg':
                imagejpeg($im, $localPath, self::REGENERATE_PICTURES_QUALITY);
                $this->logger->debug('DownloadImages: Re-creating jpg');
                break;
            case 'png':
                imagealphablending($im, false);
                imagesavealpha($im, true);
                imagepng($im, $localPath, ceil(self::REGENERATE_PICTURES_QUALITY / 100 * 9));
                $this->logger->debug('DownloadImages: Re-creating png');
                break;
            case 'webp':
                imagewebp($im, $localPath, self::REGENERATE_PICTURES_QUALITY);
                $this->logger->debug('DownloadImages: Re-creating webp');
        }

        imagedestroy($im);

        return $urlPath;
    }

    /**
     * Remove all images for the given entry id.
     *
     * @param int $entryId ID of the entry
     */
    public function removeImages($entryId)
    {
        $relativePath = $this->getRelativePath($entryId);
        $folderPath = $this->baseFolder . '/' . $relativePath;

        $finder = new Finder();
        $finder
            ->files()
            ->ignoreDotFiles(true)
            ->in($folderPath);

        foreach ($finder as $file) {
            @unlink($file->getRealPath());
        }

        @rmdir($folderPath);
    }

    /**
     * Generate the folder where we are going to save images based on the entry url.
     *
     * @param int  $entryId      ID of the entry
     * @param bool $createFolder Should we create the folder for the given id?
     *
     * @return string
     */
    public function getRelativePath($entryId, $createFolder = true)
    {
        $hashId = hash('crc32', $entryId);
        $relativePath = $hashId[0] . '/' . $hashId[1] . '/' . $hashId;
        $folderPath = $this->baseFolder . '/' . $relativePath;

        if (!file_exists($folderPath) && $createFolder) {
            mkdir($folderPath, 0777, true);
        }

        $this->logger->debug('DownloadImages: Folder used for that Entry id', ['folder' => $folderPath, 'entryId' => $entryId]);

        return $relativePath;
    }

    /**
     * Get images urls from the srcset image attribute.
     *
     * @return array An array of urls
     */
    private static function getSrcsetUrls(Crawler $imagesCrawler)
    {
        $urls = [];
        $iterator = $imagesCrawler->getIterator();

        while ($iterator->valid()) {
            $node = $iterator->current();
            \assert($node instanceof \DOMElement);

            $srcsetAttribute = $node->getAttribute('srcset');

            if ('' !== $srcsetAttribute) {
                // Couldn't start with " OR ' OR a white space
                // Could be one or more white space
                // Must be one or more digits followed by w OR x
                $pattern = "/(?:[^\"'\s]+\s*(?:\d+[wx])+)/";
                preg_match_all($pattern, $srcsetAttribute, $matches);

                $srcset = \call_user_func_array('array_merge', $matches);
                $srcsetUrls = array_map(function ($src) {
                    return trim(explode(' ', $src, 2)[0]);
                }, $srcset);
                $urls = array_merge($srcsetUrls, $urls);
            }

            $iterator->next();
        }

        return $urls;
    }

    /**
     * Setup base folder where all images are going to be saved.
     */
    private function setFolder()
    {
        // if folder doesn't exist, attempt to create one and store the folder name in property $folder
        if (!file_exists($this->baseFolder)) {
            mkdir($this->baseFolder, 0755, true);
        }
    }

    /**
     * Make an $url absolute based on the $base.
     *
     * @see Graby->makeAbsoluteStr
     *
     * @param string $base Base url
     * @param string $url  Url to make it absolute
     *
     * @return false|string
     */
    private function getAbsoluteLink($base, $url)
    {
        if (preg_match('!^https?://!i', $url)) {
            // already absolute
            return $url;
        }

        $base = new Uri($base);

        // in case the url has no scheme & host
        if ('' === $base->getAuthority() || '' === $base->getScheme()) {
            $this->logger->error('DownloadImages: Can not make an absolute link', ['base' => $base, 'url' => $url]);

            return false;
        }

        return (string) UriResolver::resolve($base, new Uri($url));
    }

    /**
     * Retrieve and validate the extension from the response of the url of the image.
     *
     * @param ResponseInterface $res       Http Response
     * @param string            $imagePath Path from the src image from the content (used for log only)
     *
     * @return string|false Extension name or false if validation failed
     */
    private function getExtensionFromResponse(ResponseInterface $res, $imagePath)
    {
        if (200 !== $res->getStatusCode()) {
            return false;
        }

        $ext = current($this->mimeTypes->getExtensions(current($res->getHeaders()['content-type'] ?? [])));
        $this->logger->debug('DownloadImages: Checking extension', ['ext' => $ext, 'header' => $res->getHeaders()['content-type'] ?? []]);

        // ok header doesn't have the extension, try a different way
        if (empty($ext)) {
            $types = [
                'jpeg' => "\xFF\xD8\xFF",
                'gif' => 'GIF',
                'png' => "\x89\x50\x4e\x47\x0d\x0a",
                'webp' => "\x52\x49\x46\x46",
            ];
            $bytes = substr($res->getContent(), 0, 8);

            foreach ($types as $type => $header) {
                if (str_starts_with($bytes, $header)) {
                    $ext = $type;
                    break;
                }
            }

            $this->logger->debug('DownloadImages: Checking extension (alternative)', ['ext' => $ext]);
        }

        if (!\in_array($ext, ['jpeg', 'jpg', 'gif', 'png', 'webp', 'svg'], true)) {
            $this->logger->error('DownloadImages: Processed image with not allowed extension. Skipping: ' . $imagePath);

            return false;
        }

        return $ext;
    }
}