221 lines
7.7 KiB
TypeScript
221 lines
7.7 KiB
TypeScript
import express from "express";
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import { SMTPServer } from "smtp-server";
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import mailparser from "mailparser";
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import { promises as fs } from "fs";
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import * as entities from "entities";
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import { JSDOM } from "jsdom";
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import * as sanitizeXMLString from "sanitize-xml-string";
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import writeFileAtomic from "write-file-atomic";
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import cryptoRandomString from "crypto-random-string";
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export const WEB_PORT = process.env.WEB_PORT ?? 8000;
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export const EMAIL_PORT = process.env.EMAIL_PORT ?? 2525;
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export const BASE_URL = process.env.BASE_URL ?? "http://localhost:8000";
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export const EMAIL_DOMAIN = process.env.EMAIL_DOMAIN ?? "localhost";
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export const ISSUE_REPORT =
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process.env.ISSUE_REPORT ?? "mailto:kill-the-newsletter@leafac.com";
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export const webServer = express()
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.use(express.static("static"))
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.use(express.urlencoded({ extended: true }))
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.get("/", (req, res) =>
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res.send(
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layout(`
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<form method="POST" action="/">
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<p>
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<input type="text" name="name" placeholder="Newsletter Name…" maxlength="500" size="30" required>
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<button>Create Inbox</button>
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</p>
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</form>
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`)
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)
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)
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.post("/", async (req, res, next) => {
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try {
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const { name } = req.body;
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const identifier = createIdentifier();
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await writeFileAtomic(feedPath(identifier), feed(X(name), identifier));
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res.send(
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layout(`
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<p><strong>“${H(name)}” Inbox Created</strong></p>
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${created(identifier)}
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`)
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);
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} catch (error) {
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console.error(error);
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next(error);
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}
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})
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.get("/alternate", (req, res) =>
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res.send(
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layout(`
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<p>Typically each entry in a feed includes a link<br>to an online version of the same content,<br>but the content from the entries in a <strong>Kill the Newsletter!</strong><br>feed come from emails—an online version may not even exist—<br>so you’re reading this instead.</p>
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<p><a href="${BASE_URL}"><strong>Create an Inbox</strong></a></p>
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`)
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)
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)
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.listen(WEB_PORT);
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export const emailServer = new SMTPServer({
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disabledCommands: ["AUTH", "STARTTLS"],
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async onData(stream, session, callback) {
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try {
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const email = await mailparser.simpleParser(stream);
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const newEntry = entry(
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X(email.subject ?? ""),
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X(email.from?.text ?? ""),
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X(typeof email.html === "string" ? email.html : email.textAsHtml ?? "")
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);
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for (const { address } of session.envelope.rcptTo) {
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const match = address.match(
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new RegExp(`^(?<identifier>\\w+)@${EMAIL_DOMAIN}$`)
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);
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if (match?.groups === undefined) continue;
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const path = feedPath(match.groups.identifier);
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const xmlText = await fs.readFile(path, "utf8").catch(() => null);
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if (xmlText === null) continue;
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const xml = new JSDOM(xmlText, { contentType: "text/xml" });
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const document = xml.window.document;
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const updated = document.querySelector("feed > updated");
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if (updated === null)
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throw new Error(`Can’t find ‘updated’ field in feed at ‘${path}’.`);
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updated.textContent = now();
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const firstEntry = document.querySelector("feed > entry:first-of-type");
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if (firstEntry !== null)
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firstEntry.insertAdjacentHTML("beforebegin", newEntry);
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else
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document
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.querySelector("feed")!
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.insertAdjacentHTML("beforeend", newEntry);
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while (
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document.querySelector("feed > entry") !== null &&
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xml.serialize().length > 500_000
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)
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document.querySelector("feed > entry:last-of-type")!.remove();
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await writeFileAtomic(
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path,
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`<?xml version="1.0" encoding="utf-8"?>${xml.serialize()}`
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);
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}
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callback();
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} catch (error) {
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console.error(
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`Error receiving email: ${JSON.stringify(session, null, 2)}`
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);
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console.error(error);
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stream.resume();
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callback(new Error("Failed to receive message. Please try again."));
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}
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},
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}).listen(EMAIL_PORT);
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function layout(content: string): string {
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return `<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Kill the Newsletter!</title>
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<meta name="author" content="Leandro Facchinetti">
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<meta name="description" content="Convert email newsletters into Atom feeds.">
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<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
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<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png">
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<link rel="icon" type="image/x-icon" href="/favicon.ico">
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<link rel="stylesheet" type="text/css" href="/styles.css">
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</head>
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<body>
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<header>
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<h1><a href="/">Kill the Newsletter!</a></h1>
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<p>Convert email newsletters into Atom feeds</p>
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<p><img alt="Convert email newsletters into Atom feeds" src="/logo.svg"></p>
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</header>
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<main>${content}</main>
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<footer><p>By <a href="https://www.leafac.com">Leandro Facchinetti</a> · <a href="https://github.com/leafac/www.kill-the-newsletter.com">Source</a> · <a href="${ISSUE_REPORT}">Report an Issue</a></p></footer>
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</body>
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</html>
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`;
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}
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function created(identifier: string): string {
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return `
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<p>Sign up for the newsletter with<br><code>${feedEmail(
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identifier
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)}</code></p>
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<p>Subscribe to the Atom feed at<br><code>${feedURL(identifier)}</code></p>
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<p>Don’t share these addresses.<br>They contain an identifier that other people could use<br>to send you spam and to control your newsletter subscriptions.</p>
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<p>Enjoy your readings!</p>
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<p><a href="${BASE_URL}"><strong>Create Another Inbox</strong></a></p>
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`.trim();
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}
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function feed(name: string, identifier: string): string {
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return `<?xml version="1.0" encoding="utf-8"?>
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<feed xmlns="http://www.w3.org/2005/Atom">
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<link rel="self" type="application/atom+xml" href="${feedURL(
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identifier
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)}"/>
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<link rel="alternate" type="text/html" href="${BASE_URL}/alternate"/>
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<id>${urn(identifier)}</id>
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<title>${name}</title>
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<subtitle>Kill the Newsletter! Inbox: ${feedEmail(
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identifier
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)} → ${feedURL(identifier)}</subtitle>
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<updated>${now()}</updated>
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<author><name>Kill the Newsletter!</name></author>
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${entry(
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`“${name}” Inbox Created`,
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"Kill the Newsletter!",
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X(created(identifier))
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)}
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</feed>
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`;
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}
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function entry(title: string, author: string, content: string): string {
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return `
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<entry>
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<id>${urn(createIdentifier())}</id>
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<title>${title}</title>
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<author><name>${author}</name></author>
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<updated>${now()}</updated>
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<link rel="alternate" type="text/html" href="${BASE_URL}/alternate"/>
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<content type="html">${content}</content>
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</entry>
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`.trim();
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}
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function createIdentifier(): string {
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return cryptoRandomString({
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length: 20,
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characters: "1234567890qwertyuiopasdfghjklzxcvbnm",
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});
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}
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function now(): string {
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return new Date().toISOString();
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}
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function feedPath(identifier: string): string {
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return `static/feeds/${identifier}.xml`;
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}
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function feedURL(identifier: string): string {
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return `${BASE_URL}/feeds/${identifier}.xml`;
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}
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function feedEmail(identifier: string): string {
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return `${identifier}@${EMAIL_DOMAIN}`;
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}
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function urn(identifier: string): string {
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return `urn:kill-the-newsletter:${identifier}`;
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}
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function X(string: string): string {
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return entities.encodeXML(sanitizeXMLString.sanitize(string));
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}
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function H(string: string): string {
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return entities.encodeHTML(sanitizeXMLString.sanitize(string));
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}
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