rss-to-activitypub/updateFeeds.js

const Database = require('better-sqlite3');
const db = new Database('bot-node.db'),
      Parser = require('rss-parser'),
      request = require('request'),
      crypto = require('crypto'),
      parser = new Parser();

// get all feeds from DB
let feeds = db.prepare('select * from feeds').all();
for (var feed of feeds) {
  // fetch new RSS for each feed
  parser.parseURL(feed.feed, function(err, feedData) {
    if (err) {
      console.log('error fetching', feed.feed, err);
    }
    else {
      //console.log(feedData);
      // get the old feed data from the database
      let oldFeed = JSON.parse(feed.content);

      // compare the feed item contents. if there's one or more whole new items (aka a new item with a unique guid),
      // add the items to a list like
      // [ { items: [], username }, {}, ... ]

      let oldItems = oldFeed.items;
      let newItems = feedData.items;

      // find the difference of the sets of guids (fall back to title or
      // description since guid is not required by spec) in the old and new feeds

      let oldGuidSet = new Set(oldItems.map(el => el.guid || el.title || el.description));
      let newGuidSet = new Set(newItems.map(el => el.guid || el.title || el.description));
      // find things in the new set that aren't in the old set
      let difference = new Set( [...newGuidSet].filter(x => !oldGuidSet.has(x)));
      difference = [...difference];
      
      //console.log('diff', difference);

      if (difference.length > 0) {
        // get a list of new items in the diff
        let brandNewItems = newItems.filter(el => difference.includes(el.guid) || difference.includes(el.title) || difference.includes(el.description));
        let acct = feed.username;
        let domain = 'bots.tinysubversions.com';
        //console.log(acct, brandNewItems);

        // send the message to everyone for each item!
        for (var item of brandNewItems) {
          // FIX THIS
          item = transformContent(item);
          //console.log(item.urls);
          let message = `<p><a href="${item.link}">${item.title}</a></p><p>${item.content}</p>`;
          if (item.enclosure && item.enclosure.url && item.enclosure.url.includes('.mp3')) {
            message += `<p><a href="${item.enclosure.url}">${item.enclosure.url}</a></p>`;
          }
          sendCreateMessage(message, acct, domain, null, null, item);
        }

        // update the DB with new contents
        let content = JSON.stringify(feedData);
        db.prepare('insert or replace into feeds(feed, username, content) values(?, ?, ?)').run(feed.feed, acct, content);
      }
    }
  });
}

// TODO: update the display name of a feed if the feed title has changed

// This is a function with a bunch of custom rules for different kinds of content I've found in the wild in things like Reddit rss feeds
function transformContent(item) {
  let cheerio = require('cheerio');
  //console.log(item.content);
  if (item.content === undefined) {
    item.urls = [];
    return item;
  }
  let $ = cheerio.load(item.content);

  // look through all the links
  let links = $('a');
  let urls = [];
  //console.log('links', links.length);
  links.each((i,e) => {
    let url = $(e).attr('href');
    // if there's an image, add it as a media attachment
    if (url && url.match(/(http)?s?:?(\/\/[^"']*\.(?:png|jpg|jpeg|gif|png|svg))/)) {
      //console.log(url);
      urls.push(url);
    }
  });
  item.urls = urls;

  // remove multiple line breaks
  $('br+br+br').remove();
  $('p').each((i, el) => {
    if($(el).html().replace(/\s|&nbsp;/g, '').length === 0) {$(el).remove();}
  });

  // convert li items to bullet points
  $('li').each((i, el) => {
    //console.log($(el).html());
    $(el).replaceWith(`<span>- ${$(el).html()}</span><br>`);
  });

  item.content = $('body').html();
  return item;
}

// for each item in the list, get the account corresponding to the username
//    for each item in the ITEMS list, send a message to all followers

// TODO import these form a helper
function signAndSend(message, name, domain, req, res, targetDomain, inbox) {
  // get the private key
  console.log('sending to ', name, targetDomain, inbox);
  let inboxFragment = inbox.replace('https://'+targetDomain,'');
  let result = db.prepare('select privkey from accounts where name = ?').get(name);
  //console.log('got key', result === undefined, `${name}@${domain}`);
  if (result === undefined) {
    console.log(`No record found for ${name}.`);
  }
  else {
    let privkey = result.privkey;
    const signer = crypto.createSign('sha256');
    let d = new Date();
    let stringToSign = `(request-target): post ${inboxFragment}\nhost: ${targetDomain}\ndate: ${d.toUTCString()}`;
    signer.update(stringToSign);
    signer.end();
    const signature = signer.sign(privkey);
    const signature_b64 = signature.toString('base64');
    let header = `keyId="https://${domain}/u/${name}",headers="(request-target) host date",signature="${signature_b64}"`;
    //console.log('signature:',header);
    request({
      url: inbox,
      headers: {
        'Host': targetDomain,
        'Date': d.toUTCString(),
        'Signature': header
      },
      method: 'POST',
      json: true,
      body: message
    }, function (error, response, body){
    });
  }
}

function createMessage(text, name, domain, item) {
  const guid = crypto.randomBytes(16).toString('hex');
  let d = new Date();

  let out = {
    '@context': 'https://www.w3.org/ns/activitystreams',

    'id': `https://${domain}/${guid}`,
    'type': 'Create',
    'actor': `https://${domain}/u/${name}`,

    'object': {
      'id': `https://${domain}/${guid}`,
      'type': 'Note',
      'published': d.toISOString(),
      'attributedTo': `https://${domain}/u/${name}`,
      'content': text,
      'to': 'https://www.w3.org/ns/activitystreams#Public'
    }
  };

  // add image attachment
  let attachment;
  if (item.urls.length > 0) {
    //console.log('appending');
    attachment = {
      'type': 'Document',
      'mediaType': 'image/png', // TODO: update the mediaType to match jpeg,gif,etc
      'url': item.urls[0],
      'name': null
    };
    out.object.attachment = attachment;
  }

  return out;
}

function sendCreateMessage(text, name, domain, req, res, item) {
  let message = createMessage(text, name, domain, item);

  let result = db.prepare('select followers from accounts where name = ?').get(`${name}@${domain}`);
  let followers = JSON.parse(result.followers);
  //console.log(followers);
  if (!followers) {
    followers = [];
  }
  for (let follower of followers) {
    let inbox = follower+'/inbox';
    let myURL = new URL(follower);
    let targetDomain = myURL.hostname;
    signAndSend(message, name, domain, req, res, targetDomain, inbox);
  }
}