<?php
namespace Vichan\Services\Embed;

use Vichan\Data\Driver\HttpDriver;
use Vichan\Data\Driver\LogDriver;


class EmbedService {
	private const TMP_FILE_PREFIX = 'oembed-thumb-';

	/**
	 * The input embed text isn't a valid URL.
	 */
	public const MATCH_EMBED_ERR_NOT_AN_URL = 0;
	/**
	 * The embed url doesn't match any supported url.
	 */
	public const MATCH_EMBED_ERR_NO_MATCH = 1;
	/**
	 * The embed url doesn't have a thumbnail.
	 */
	public const MATCH_EMBED_ERR_NO_THUMBNAIL = 2;

	private LogDriver $log;
	private OembedExtractor $oembed_extractor;
	private HttpDriver $http;
	private string $tmp_dir;
	private array $embed_entries;
	private int $thumb_download_timeout;


	public function __construct(LogDriver $log, OembedExtractor $oembed_extractor, array $embed_entries, int $thumb_download_timeout) {
		$this->log = $log;
		$this->oembed_extractor = $oembed_extractor;
		$this->embed_entries = $embed_entries;
		$this->thumb_download_timeout = $thumb_download_timeout;
	}

	private function make_tmp_file(): string {
		$ret = \tempnam($this->tmp_dir, self::TMP_FILE_PREFIX);
		if ($ret === false) {
			throw new \RuntimeException("Could not create temporary file in {$this->tmp_dir}");
		}
		\register_shutdown_function(fn() => @unlink($ret));
		return $ret;
	}

	/**
	 * Downloads the thumbnail into a temporary file.
	 *
	 * @return ?string The path to the temporary file, null if the file was too large.
	 */
	private function fetchThumbnail(string $thumbnail_url): ?string {
		$tmp_file = $this->make_tmp_file();
		$fd = \fopen($tmp_file, 'w+b');
		if ($fd === false) {
			throw new \RuntimeException("Could not open temporary file $tmp_file for read/write");
		}

		$ret = $this->http->requestGetInto($thumbnail_url, null, $fd, $this->thumb_download_timeout);
		return $ret ? $tmp_file : null;
	}

	/**
	 * Matches an alleged embed url and returns the path to the thumbnail, if any.
	 *
	 * @param string $rawText
	 * @return ?array Returns the url to the thumbnail and the path to the fallback if any embedding matches, null otherwise.
	 */
	private function matchAndExtract(string $rawText) {
		foreach ($this->embed_entries as $embed_entry) {
			$match_regex = $embed_entry['match_regex'];

			if (\preg_match($match_regex, $rawText, $matches)) {
				$type = $embed_entry['type'];

				if ($type === 'oembed') {
					$thumbnail_url_fallback = $embed_entry['thumbnail_url_fallback'] ?? null;
					$provider = $embed_entry['provider'];
					$oembed_resp = $this->oembed_extractor->fetch($provider, $rawText);

					return [ $oembed_resp->thumbnail_url, $thumbnail_url_fallback ];
				} elseif ($type === 'regex') {
					$thumbnail_url_regex = $embed_entry['thumbnail_url'];
					// Plz somebody review this.
					return [ \preg_replace($match_regex, $thumbnail_url_regex, $rawText), null ];
				} else {
					$this->log->log(LogDriver::ERROR, "Unknown embed type '$type', ignoring the embed entry");
				}
			}
		}

		return null;
	}

	/**
	 * @return array|int Returns the url to the thumbnail and if it should be moved if any embedding matches,
	 *                   otherwise it returns a MATCH_EMBED_ERR_* constant.
	 */
	public function matchEmbed(string $rawText) {
		$rawText = \trim($rawText);
		if (\filter_var($rawText, \FILTER_VALIDATE_URL) === false) {
			return self::MATCH_EMBED_ERR_NOT_AN_URL;
		}

		$ret = $this->matchAndExtract($rawText);
		if ($ret === null) {
			return self::MATCH_EMBED_ERR_NO_MATCH;
		}
		list($thumbnail_url, $thumbnail_url_fallback) = $ret;
		if (!isset($thumbnail_url, $thumbnail_url_fallback)) {
			return self::MATCH_EMBED_ERR_NO_THUMBNAIL;
		}

		if (\filter_var($thumbnail_url, \FILTER_VALIDATE_URL) === false) {
			$this->log->log(LogDriver::ERROR, "Thumbnail URL '$thumbnail_url' is not a valid URL, trying fallback");
		} else {
			$tmp_file = $this->fetchThumbnail($thumbnail_url);
			if ($tmp_file !== null) {
				return [ $tmp_file, true ];
			}
			$this->log->log(LogDriver::NOTICE, "Thumbnail at '$thumbnail_url' was too large, trying fallback");
		}

		if ($thumbnail_url_fallback === null) {
			return self::MATCH_EMBED_ERR_NO_THUMBNAIL;
		}
		return [ $thumbnail_url_fallback, false ];
	}
}