<?php
namespace Vichan\Service\Embed;

use Vichan\Data\Driver\{CacheDriver, HttpDriver};
use Vichan\Data\OembedResponse;


class OembedExtractor {
	private const DEFAULT_CACHE_TIMEOUT = 3600; // 1 hour.
	private const MIN_CACHE_TIMEOUT = 900; // 15 minutes.

	private CacheDriver $cache;
	private HttpDriver $http;
	private int $provider_timeout;


	public function __construct(CacheDriver $cache, HttpDriver $http, int $provider_timeout) {
		$this->cache = $cache;
		$this->http = $http;
		$this->provider_timeout = $provider_timeout;
	}

	/**
	 * Fetch the oembed data from the given provider with the given url.
	 *
	 * @param string $identifier Opaque identifier for caching, must be unique for each $url-$provider combination.
	 * @return OembedResponse The serialized remove response. May be cached.
	 */
	public function fetch(string $provider_url, string $url): OembedResponse {
		$ret = $this->cache->get("oembed_embedder_$provider_url$url");
		if ($ret === null) {
			$body = $this->http->requestGet(
				$provider_url,
				[
					'url' => $url,
					'format' => 'json'
				],
				[
					'Content-Type: application/json'
				],
				$this->provider_timeout
			);
			$json = \json_decode($body, true, 512, \JSON_THROW_ON_ERROR);

			$ret = [
				'title' => $json['title'] ?? null,
				'thumbnail_url' => $json['thumbnail_url'] ?? null,
			];

			$cache_timeout = self::DEFAULT_CACHE_TIMEOUT;
			if (isset($json['cache_age'])) {
				$cache_age = \intval($json['cache_age']);
				if ($cache_age > 0) {
					$cache_age = \max($cache_age, self::MIN_CACHE_TIMEOUT);
				}
			}

			$this->cache->set("oembed_embedder_$provider_url$url", $ret, $cache_timeout);
		}

		$resp = new OembedResponse();
		$resp->title = $ret['title'];
		$resp->thumbnail_url = $ret['thumbnail_url'];
		return $resp;
	}
}