An express app that redirects to largest SoundCloud artwork URL that doesn't 404.

FixSoundCloudArtworkUrl.js

'use strict';

var express = require('express'),
    app = express();

require('./config/development')(app, express);
require('./config/production')(app, express);

var redis = require('redis'),
    request = require('request'),
    Promise = require('bluebird');

Promise.promisifyAll(redis.RedisClient.prototype);

var redisSettings = app.set('redis'),
    redisClient = redis.createClient(redisSettings.port, redisSettings.host, redisSettings.options);

app.configure(function () {
  app.use(express.bodyParser());
  app.use(app.router);
});

function sendError(res, status, error) {
  if (!(error instanceof Error)) {
    error = new Error(JSON.stringify(error));
  }

  return res
    .status(status || 500)
    .end(error && error.message || 'Internal Server Error');
}

function generateCacheHeaders() {
  var maxAge = 3600 * 24 * 365;

  return {
    'Cache-Control': 'public,max-age=' + maxAge,
    'Expires': new Date(Date.now() + (maxAge * 1000)).toUTCString()
  };
}

function getCacheKey(url) {
  return 'soundcloud-thumbnail-proxy:' + url;
}

app.get('/*', function (req, res) {
  var originalUrl = req.params[0],
      cacheKey = getCacheKey(originalUrl),
      urls;

  // https://developers.soundcloud.com/docs/api/reference#artwork_url
  // This is a ridiculous naming scheme, by the way.

  urls = [
    originalUrl,
    originalUrl.replace('-large', '-t500x500'),
    originalUrl.replace('-large', '-crop'), // 400x400
    originalUrl.replace('-large', '-t300x300'),
    originalUrl.replace('-large', '-large') // 100x100
  ];

  return redisClient.getAsync(cacheKey).then(function (cachedUrl) {
    if (cachedUrl) {
      return cachedUrl;
    }

    return Promise.reduce(urls, function (resolvedUrl, url) {
      if (resolvedUrl) {
        return resolvedUrl;
      }

      return new Promise(function (resolve) {
        request.head(url, function (err, response) {
          if (!err && response.statusCode === 200) {
            resolve(url);
          } else {
            resolve(null);
          }
        });
      });
    }, null);
  }).then(function (url) {
    if (!url) {
      throw new Error('File not found');
    }

    var headers = generateCacheHeaders();
    for (var key in headers) {
      if (headers.hasOwnProperty(key)) {
        res.setHeader(key, headers[key]);
      }
    }

    res.redirect(url);
    redisClient.set(cacheKey, url);
    redisClient.expire(cacheKey, 60 * 60 * 24 * 30);

  }).catch(function (err) {
    sendError(res, 404, err);
  });

});

app.get('/crossdomain.xml', function (req, res) {
  req.setEncoding('utf8');
  res.writeHead(200, { 'Content-Type': 'text/xml' });
  res.end('<?xml version="1.0" ?><cross-domain-policy><allow-access-from domain="*" /></cross-domain-policy>');
});

redisClient.on('ready', function () {
  app.listen(app.set('port'));
});

redisClient.on('error', function () {
  throw new Error('Could not connect to Redis');
});

module.exports = app;

Heya,

Silly question - Where do i add the url for the soundcloud link?

Also is it possible for the output to be the a string which is the url of the artwork image.

example url:

url: https://soundcloud.com/jens-records/jens012-a1-funkig/s-ueATsI77OHU?in=jens-records/sets/jens112-the-ristorante-ep//s-9lt1WDfSCtf

url for artwork:

https://i1.sndcdn.com/artworks-1TKywvsYSljt2vXR-KSOtfQ-t500x500.jpg