74 lines
2.3 KiB
JavaScript
74 lines
2.3 KiB
JavaScript
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const cheerio = require('cheerio');
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const errors = require('@tryghost/errors');
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module.exports = class MentionDiscoveryService {
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#externalRequest;
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constructor({externalRequest}) {
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this.#externalRequest = externalRequest;
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}
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/**
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* Fetches the given URL to identify the webmention endpoint
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* @param {URL} url
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* @returns {Promise<URL|null>}
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*/
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async getEndpoint(url) {
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try {
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const response = await this.#externalRequest(url.href, {
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throwHttpErrors: false,
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followRedirects: true,
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maxRedirects: 10
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});
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if (response.statusCode === 404) {
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throw new errors.BadRequestError({
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message: 'Webmention discovery service could not find target site',
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statusCode: response.statusCode
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});
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}
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return this.getEndpointFromResponse(response);
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} catch (error) {
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return null;
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}
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}
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/**
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* @private
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* Parses the given response for the first webmention endpoint
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* @param {Object} response
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* @returns {Promise<URL|null>}
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*/
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async getEndpointFromResponse(response) {
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let href;
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let endpoint;
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// Link: <uri-reference>; param1=value1; param2="value2"
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// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link
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const linkHeader = response.headers.link;
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if (linkHeader && linkHeader.includes('rel="webmention"')) {
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linkHeader.split(',').forEach((p) => {
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if (p.includes('rel="webmention"')) {
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href = p.substring(p.indexOf('<') + 1, p.indexOf('>'));
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endpoint = new URL(href);
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return;
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}
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});
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}
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if (endpoint) {
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return endpoint;
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}
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// must be html to find links/tags
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if (!response.headers['content-type'].includes('text/html')) {
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return null;
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}
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const $ = cheerio.load(response.body);
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// must be first <link> OR <a> element with rel=webmention
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href = $('a[rel="webmention"],link[rel="webmention"]').first().attr('href');
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endpoint = href ? new URL(href) : null;
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return endpoint;
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}
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};
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