kill-the-newsletter/index.ts

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