misskey/packages/backend/src/server/web/url-preview.ts

import * as Koa from 'koa';
import summaly from 'summaly';
import { fetchMeta } from '@/misc/fetch-meta';
import Logger from '@/services/logger';
import config from '@/config/index';
import { query } from '@/prelude/url';
import { getJson } from '@/misc/fetch';

const logger = new Logger('url-preview');

module.exports = async (ctx: Koa.Context) => {
	const meta = await fetchMeta();

	logger.info(meta.summalyProxy
		? `(Proxy) Getting preview of ${ctx.query.url}@${ctx.query.lang} ...`
		: `Getting preview of ${ctx.query.url}@${ctx.query.lang} ...`);

	try {
		const summary = meta.summalyProxy ? await getJson(`${meta.summalyProxy}?${query({
			url: ctx.query.url,
			lang: ctx.query.lang || 'ja-JP',
		})}`) : await summaly(ctx.query.url, {
			followRedirects: false,
			lang: ctx.query.lang || 'ja-JP',
		});

		logger.succ(`Got preview of ${ctx.query.url}: ${summary.title}`);

		summary.icon = wrap(summary.icon);
		summary.thumbnail = wrap(summary.thumbnail);

		// Cache 7days
		ctx.set('Cache-Control', 'max-age=604800, immutable');

		ctx.body = summary;
	} catch (e) {
		logger.warn(`Failed to get preview of ${ctx.query.url}: ${e}`);
		ctx.status = 200;
		ctx.set('Cache-Control', 'max-age=86400, immutable');
		ctx.body = '{}';
	}
};

function wrap(url?: string): string | null {
	return url != null
		? url.match(/^https?:\/\//)
			? `${config.url}/proxy/preview.jpg?${query({
				url,
				preview: '1',
			})}`
			: url
		: null;
}