Adding ActivityPub to your static site

import type { VercelRequest, VercelResponse } from '@vercel/node';

export default function (req: VercelRequest, res: VercelResponse) {
  res.statusCode = 200;
  res.setHeader("Content-Type", `application/jrd+json`);
  res.end(`{  
    "subject": "acct:paul@paul.kinlan.me",
    "aliases": [
      "https://status.kinlan.me/@paul"
    ],
    "links": [
      {
        "rel": "self",
        "type": "application/activity+json",
        "href": "https://paul.kinlan.me/paul"
      }
    ]
  }`);
}

import type { VercelRequest, VercelResponse } from '@vercel/node';

export default function (req: VercelRequest, res: VercelResponse) {
  res.statusCode = 200;
  res.setHeader("Content-Type", `application/activity+json`);
  res.json({
    "@context": ["https://www.w3.org/ns/activitystreams", { "@language": "en- GB" }],
    "type": "Person",
    "id": "https://paul.kinlan.me/paul",
    "outbox": "https://paul.kinlan.me/outbox",
    "following": "https://paul.kinlan.me/following",
    "followers": "https://paul.kinlan.me/followers",
    "inbox": "https://paul.kinlan.me/inbox",
    "preferredUsername": "paul",
    "name": "Paul Kinlan - Modern Web Development with Chrome",
    "summary": "Paul is a Developer Advocate for Chrome and the Open Web at Google and loves to help make web development easier.",
    "icon": [
      "https://paul.kinlan.me/images/me.png"
    ],
    "publicKey": {
      "@context": "https://w3id.org/security/v1",
      "@type": "Key",
      "id": "https://paul.kinlan.me/paul#main-key",
      "owner": "https://paul.kinlan.me/paul",
      "publicKeyPem": process.env.ACTIVITYPUB_PUBLIC_KEY
    }
  });
}

import type { VercelRequest, VercelResponse } from '@vercel/node';
import { AP } from 'activitypub-core-types';
import type { Readable } from 'node:stream';
import * as admin from 'firebase-admin';
import { v4 as uuid } from 'uuid';
import { CoreObject, Entity } from 'activitypub-core-types/lib/activitypub/index';
import { sendSignedRequest } from '../../lib/activitypub/sendSignedRequest';
import { parseSignature } from '../../lib/activitypub/utils/parseSignature';
import { fetchActorInformation } from '../../lib/activitypub/utils/fetchActorInformation';

process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0';

if (!admin.apps.length) {
  admin.initializeApp({
    credential: admin.credential.cert({
      projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
      clientEmail: process.env.FIREBASE_CLIENT_EMAIL,
      privateKey: process.env.FIREBASE_PRIVATE_KEY.replace(/\\n/g, '\n')
    })
  });
}

const db = admin.firestore();

export const config = {
  api: {
    bodyParser: false,
  },
};

async function buffer(readable: Readable) {
  const chunks = [];
  for await (const chunk of readable) {
    chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : chunk);
  }
  return Buffer.concat(chunks);
}

function verifySignature(signature, publicKeyJson) {
  let signatureValid;

  try {
    // Verify the signature
    signatureValid = signature.verify(
      publicKeyJson.publicKeyPem,	// The PEM string from the public key object
    );
  } catch (error) {
    console.log("Signature Verification error", error)
  }

  return signatureValid;
}

export default async function (req: VercelRequest, res: VercelResponse) {
  const { body, query, method, url, headers } = req;

  res.statusCode = 200;
  res.setHeader("Content-Type", `application/activity+json`);

  // Verify the message some how.
  const buf = await buffer(req);
  const rawBody = buf.toString('utf8');

  const message = <AP.Activity>JSON.parse(rawBody);

  console.log(message);

  const signature = parseSignature(req);
  const actorInformation = await fetchActorInformation(signature.keyId);
  const signatureValid = verifySignature(signature, actorInformation.publicKey);

  if (signatureValid == null || signatureValid == false) {
    res.end('invalid signature');
    return;
  }

  // We should check the digest.
  if (message.type == "Follow") {
    // We are following.
    const followMessage: AP.Follow = <AP.Follow>message;
    if (followMessage.id == null) return;

    const collection = db.collection('followers');

    const actorID = (<URL>followMessage.actor).toString();
    const followDocRef = collection.doc(actorID.replace(/\//g, "_"));
    const followDoc = await followDocRef.get();

    if (followDoc.exists) {
      console.log("Already Following")
      return res.end('already following');
    }

    // Create the follow;
    await followDocRef.set(followMessage);

    const guid = uuid();
    const domain = 'paul.kinlan.me';

    const acceptRequest: AP.Accept = <AP.Accept>{
      "@context": "https://www.w3.org/ns/activitystreams",
      'id': new URL(`https://${domain}/${guid}`),
      'type': 'Accept',
      'actor': "https://paul.kinlan.me/paul",
      'object': followMessage
    };

    const actorInbox = new URL(actorInformation.inbox);

    const response = await sendSignedRequest(actorInbox, acceptRequest);

    console.log("Following result", response.status, response.statusText, await response.text());

    return res.end("ok")
  }

  if (message.type == "Undo") {
    // Undo a follow.
    const undoObject: AP.Undo = <AP.Undo>message;
    if (undoObject == null || undoObject.id == null) return;
    if (undoObject.object == null) return;
    if ("actor" in undoObject.object == false && (<CoreObject>undoObject.object).type != "Follow") return;

    const docId = undoObject.actor.toString().replace(/\//g, "_");
    const res = await db.collection('followers').doc(docId).delete();

    console.log("Deleted", res)
  }

  res.end();
};

{{- $pctx := . -}}
{{- if .IsHome -}}{{ $pctx = .Site }}{{- end -}}
{{- $pages := slice -}}
{{- if or $.IsHome $.IsSection -}}
{{- $pages = $pctx.RegularPages -}}
{{- else -}}
{{- $pages = $pctx.Pages -}}
{{- end -}}
{{- $limit := .Site.Config.Services.RSS.Limit -}}
{{- if ge $limit 1 -}}
{{- $pages = $pages | first $limit -}}
{{- end -}}
{
  "@context": "https://www.w3.org/ns/activitystreams",
  "id": "{{ $.Site.BaseURL }}outbox",
  "summary": "{{$.Site.Author.name}} - {{$.Site.Title}}",
  "type": "OrderedCollection",
  {{ $notdrafts := where $pages ".Draft" "!=" true }}
  {{ $all :=  where $notdrafts "Type" "in" (slice "journal" "post" "page")}}
  "totalItems": {{(len $all)}},
  "orderedItems": [
  {{ range $index, $element := $all  }}
    {{- if ne $index 0 }}, {{ end }}
    {
      "@context": "https://www.w3.org/ns/activitystreams",
      "id": "{{.Permalink}}-create",
      "type": "Create",
      "actor": "https://paul.kinlan.me/paul",
      "object": {
        "id": "{{ .Permalink }}",
        "type": "Note",
        "content": "{{.Title}}<br>{{.Summary}}",
        "url": "{{.Permalink}}",
        "attributedTo": "https://paul.kinlan.me/paul",
        "to": "https://www.w3.org/ns/activitystreams#Public",
        "published": {{ dateFormat "2006-01-02T15:04:05-07:00" .Date | jsonify }}
      }
    }
  {{end}}
  ]
}

[mediaTypes]
[mediaTypes."application/activity+json"]
suffixes = ["ajson"]

[outputFormats]
[outputFormats.ACTIVITY_OUTBOX]
mediaType = "application/activity+json"
notAlternative = true
baseName = "outbox"

[outputs]
home = ["HTML", "RSS", "ACTIVITY_OUTBOX"]

import type { VercelRequest, VercelResponse } from '@vercel/node';
import { join } from 'path';
import { cwd } from 'process';
import { readFileSync } from 'fs';

/*
  This returns a list of posts for the single user 'Paul'.
  It's a GET request. This doesn't post it to anyone's timeline.
*/
export default function (req: VercelRequest, res: VercelResponse) {
  // All of the outbox data is generated at build time, so just return that static file.
  const file = join(cwd(), 'public', 'outbox.ajson');
  const stringified = readFileSync(file, 'utf8');

  res.statusCode = 200;
  res.setHeader("Content-Type", `application/activity+json`);

  return res.end(stringified);
};

import type { VercelRequest, VercelResponse } from '@vercel/node';
import { AP } from 'activitypub-core-types';
import * as admin from 'firebase-admin';
import { OrderedCollection } from 'activitypub-core-types/lib/activitypub/index';
import { sendSignedRequest } from '../../lib/activitypub/utils/sendSignedRequest';
import { fetchActorInformation } from '../../lib/activitypub/utils/fetchActorInformation';

process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0';

if (!admin.apps.length) {
  admin.initializeApp({
    credential: admin.credential.cert({
      projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
      clientEmail: process.env.FIREBASE_CLIENT_EMAIL,
      privateKey: process.env.FIREBASE_PRIVATE_KEY.replace(/\\n/g, '\n')
    })
  });
}

const db = admin.firestore();

export const config = {
  api: {
    bodyParser: false
  }
};

/*
  Sends the latest not that hasn't yet been sent.
*/
export default async function (req: VercelRequest, res: VercelResponse) {
  const { body, query, method, url, headers } = req;
  const { token } = query;

  if (method != "POST") {
    res.status(401).end("Invalid Method, must be POST");
    return;
  }

  if (token != process.env.ACTIVITYPUB_CREATE_TOKEN) {
    res.status(401).end("Invalid token");
    return;
  }

  const configCollection = db.collection('config');
  const configRef = configCollection.doc("config");
  const config = await configRef.get();

  if (config.exists == false) {
    // Config doesn't exist, make something
    configRef.set({
      "lastId": 0
    });
  }

  const configData = config.data();
  let lastId = 0;
  if (configData != undefined) {
    lastId = configData.lastId;
  }

  // Get my outbox because it contains all my notes.
  const outboxResponse = await fetch('https://paul.kinlan.me/outbox');
  const outbox = <OrderedCollection>(await outboxResponse.json());

  const followersCollection = db.collection('followers');
  const followersQuerySnapshot = await followersCollection.get();

  for (const followerDoc of followersQuerySnapshot.docs) {
    const follower = followerDoc.data();
    try {
      const actorInformation = await fetchActorInformation(follower.actor);
      const actorInbox = new URL(actorInformation.inbox);

      for (const iteIdx in (<AP.EntityReference[]>outbox.orderedItems)) {
        // We have to break somewhere... do it after the first.
        const item = (<AP.EntityReference[]>outbox.orderedItems)[iteIdx];

        if (item.object != undefined) {
          // We might not need this.
          item.object.published = (new Date()).toISOString();
        }

        console.log(`Sending to ${actorInbox}`, item);
        
        // Item will be an entity, i.e, { Create { Note } }
        const response = await sendSignedRequest(actorInbox, <AP.Activity> item);
        console.log("Send result: ", actorInbox, response.status, response.statusText, await response.text());

        break;
      }
    } catch (ex) {
      console.log("Error", ex, follower);
    }
  }

  res.status(200).end("ok");
};