@annoto/ims-lti/src/extensions/content.js

Module for building an LTI Tool Provider and accept LTI launch requests

/*
 * decaffeinate suggestions:
 * DS102: Remove unnecessary code created because of implicit returns
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
const url = require('url');

const errors = require('../errors');

const FILE_RETURN_TYPE = 'file';
const IFRAME_RETURN_TYPE = 'iframe';
const IMAGE_URL_RETURN_TYPE = 'image_url';
const LTI_LAUNCH_URL_RETURN_TYPE = 'lti_launch_url';
const OEMBED_RETURN_TYPE = 'oembed';
const URL_RETURN_TYPE = 'url';

const parse_url = function(raw_url) {
  const return_url = url.parse(raw_url, true);
  delete return_url.path;
  return return_url;
};

const optional_url_property_setter = return_url =>
  function(property, value) {
    if (typeof value !== 'undefined') {
      return (return_url.query[property] = value);
    }
  };
class ContentExtension {
  constructor(params) {
    this.return_types = params.ext_content_return_types.split(',');
    // According to the spec if the ext_content_return_url is not present launch_presentation_return_url is the fallback.
    this.return_url =
      params.ext_content_return_url || params.launch_presentation_return_url;
    this.file_extensions =
      (params.ext_content_file_extensions &&
        params.ext_content_file_extensions.split(',')) ||
      [];
  }

  has_return_type(return_type) {
    return this.return_types.indexOf(return_type) !== -1;
  }

  has_file_extension(extension) {
    return this.file_extensions.indexOf(extension) !== -1;
  }

  send_file(res, file_url, text, content_type) {
    this._validate_return_type(FILE_RETURN_TYPE);

    const return_url = parse_url(this.return_url, true);
    const set_if_exists = optional_url_property_setter(return_url);

    return_url.query.return_type = FILE_RETURN_TYPE;
    return_url.query.url = file_url;
    return_url.query.text = text;

    set_if_exists('content_type', content_type);

    return exports.redirector(res, url.format(return_url));
  }

  send_iframe(res, iframe_url, title, width, height) {
    this._validate_return_type(IFRAME_RETURN_TYPE);

    const return_url = parse_url(this.return_url, true);
    const set_if_exists = optional_url_property_setter(return_url);

    return_url.query.return_type = IFRAME_RETURN_TYPE;
    return_url.query.url = iframe_url;

    set_if_exists('title', title);
    set_if_exists('width', width);
    set_if_exists('height', height);

    return exports.redirector(res, url.format(return_url));
  }

  send_image_url(res, image_url, text, width, height) {
    this._validate_return_type(IMAGE_URL_RETURN_TYPE);

    const return_url = parse_url(this.return_url, true);
    const set_if_exists = optional_url_property_setter(return_url);

    return_url.query.return_type = IMAGE_URL_RETURN_TYPE;
    return_url.query.url = image_url;

    set_if_exists('text', text);
    set_if_exists('width', width);
    set_if_exists('height', height);

    return exports.redirector(res, url.format(return_url));
  }

  send_lti_launch_url(res, launch_url, title, text) {
    this._validate_return_type(LTI_LAUNCH_URL_RETURN_TYPE);

    const return_url = parse_url(this.return_url, true);
    const set_if_exists = optional_url_property_setter(return_url);

    return_url.query.return_type = LTI_LAUNCH_URL_RETURN_TYPE;
    return_url.query.url = launch_url;

    set_if_exists('title', title);
    set_if_exists('text', text);

    return exports.redirector(res, url.format(return_url));
  }

  send_oembed(res, oembed_url, endpoint) {
    this._validate_return_type(OEMBED_RETURN_TYPE);

    const return_url = parse_url(this.return_url, true);
    const set_if_exists = optional_url_property_setter(return_url);

    return_url.query.return_type = OEMBED_RETURN_TYPE;
    return_url.query.url = oembed_url;

    set_if_exists('endpoint', endpoint);

    return exports.redirector(res, url.format(return_url));
  }

  send_url(res, hyperlink, text, title, target) {
    this._validate_return_type(URL_RETURN_TYPE);

    const return_url = parse_url(this.return_url, true);
    const set_if_exists = optional_url_property_setter(return_url);

    return_url.query.return_type = URL_RETURN_TYPE;
    return_url.query.url = hyperlink;

    set_if_exists('text', text);
    set_if_exists('title', title);
    set_if_exists('target', target);

    return exports.redirector(res, url.format(return_url));
  }

  _validate_return_type(return_type) {
    if (this.has_return_type(return_type) === false) {
      throw new errors.ExtensionError(
        `Invalid return type, valid options are ${this.return_types.join(', ')}`
      );
    }
  }
}

exports.init = function(provider) {
  // The extension is defined to exist if the ext_content_return_types parameter is present.
  if (provider.body.ext_content_return_types) {
    return (provider.ext_content = new ContentExtension(provider.body));
  } else {
    return (provider.ext_content = false);
  }
};

// The default redirector is set to be compatible with Express and can be easily overridden by accessing the ims-lti
// module and setting lti.Extensions.Content.redirector to a custom function.
exports.redirector = (res, url) => res.redirect(303, url);