OEmbed.

jquery.oembed.js

(function ($) {
  var providers = {};

  /*
    Given a URL find a provider that can OEmbed the url given.
  */
  function find (url) {
    var site = url.match(/^https?:\/\/([^/]+)/)[1];
    for (var domain in providers)
      if (site.indexOf(domain) > -1)
        return providers[domain];
  }

  /*
    Register a provider.

    @example
      // Goliath JSONP gateway.
      $.oembed.provider('youtube', ['youtube.com', 'youtu.be'], window.document.location.host + '/oembed');
      $.oembed.provider('yfrog',   ['yfrog.com'],               window.document.location.host + '/oembed');
  */
  function provider (name, domains, endpoint) {
    $.each(domains, function () {
      providers[this] = {name: name, endpoint: endpoint};
    });
  }

  /*
    GET the OEmbed JSON for a given URL.

    @note There is no error callback yet.
    @example
      $.oembed.get('http://vimeo.com/7100569', function (json) {
        // oembed json.
      });
  */
  function get (url, success) {
    var provider = find(url);
    if (!provider) return;
    // TODO: Chrome blocks http endpoints on https.
    // TODO: Flickr uses non-standard jsoncallback instead of callback for JSONP.
    $.getJSON('http://' + provider.endpoint + '?callback=?&format=json', {url: url}, success);
  }

  provider('instagram', ['instagr.am'], 'api.instagram.com/oembed');
  provider('vimeo',     ['vimeo.com'],  'api/oembed.json');

  $.oembed = {get: get, provider: provider};
})(jQuery);

oembed.rb

require 'goliath'
require 'em-synchrony'
require 'em-synchrony/em-http'
require 'addressable/uri'

# Goliath API to wrap endpoints without jsonp so the JS the jquery lib may use them.
#
# Usually endpoints that don't provide jsonp do so because they have rate limiting and other restrictions. To make
# them usable client side this thin Goliath API wraps the responses in a jsonp callback.
#
# @note Some common domains are already registered.
#   * yfrog.com
#   * youtu.be
#   * youtube.com
#
# @example
#   Oembed.provider 'youtube', %w{youtu.be youtube.com}, 'http://www.youtube.com/oembed'
#   Oembed.provider 'yfrog',   %w{yfrog.com},            'http://www.yfrog.com/api/oembed'
class Oembed < Goliath::API
  # List all registered providers.
  def self.providers
    @providers ||= []
  end

  # Register a provider.
  #
  # @example
  #   Oembed.provider 'youtube', %w{youtu.be youtube.com}, 'http://www.youtube.com/oembed'
  #   Oembed.provider 'yfrog',   %w{yfrog.com},            'http://www.yfrog.com/api/oembed'
  #
  #--
  # TODO: Don't add providers more than once.
  def self.provider name, domains, endpoint
    [domains].flatten.each{|domain| providers << [name, domain, endpoint]}
  end

  provider 'youtube', %w{youtu.be youtube.com}, 'http://www.youtube.com/oembed'
  provider 'yfrog',   %w{yfrog.com},            'http://www.yfrog.com/api/oembed'

  use Goliath::Rack::Params
  use Goliath::Rack::JSONP

  def response env
    uri      = Addressable::URI.parse(params['url'])
    provider = self.class.providers.find{|provider| uri.host.include?(provider[1])}
    return [404, {}, ''] unless provider

    endpoint       = Addressable::URI.parse(provider[2])
    endpoint.query = env['QUERY_STRING']

    # TODO: Chunked response streaming?
    http = EventMachine::HttpRequest.new(endpoint).get(redirects: 4)
    [http.response_header.status, {}, http.response]
  end
end # Oembed