datafire/src/lib/response.js

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"use strict";

/**
 * @class
 * An HTTP response from ProjectServer
 *
 * @param {Object} [opts]
 * @param {number} [opts.statusCode]
 * @param {*} [opts.json] - JSON-serializable object to pass as body
 * @param {string} [opts.body] - body to send
 * @param {Object} [opts.headers]
 * @param {string} [opts.encoding]
 */
let Response = module.exports = function(opts={}) {
  this._isResponse = true;
  this.statusCode = opts.statusCode || 200;
  this.body = opts.body || '';
  this.encoding = opts.encoding || 'utf8';
  this.headers = opts.headers || {};
  if (opts.json !== undefined) {
    this.headers['Content-Type'] = 'application/json';
    this.body = JSON.stringify(opts.json, null, 2);
  }
}

/**
 * Check if the given object is a Response.
 * instanceof is too weak; in particular if the CLI and project versions
 * of DataFire are mismatched, it will return false.
 */
Response.isResponse = function(obj) {
  if (!obj || typeof obj !== 'object') return false;
  if (obj instanceof Response || obj._isResponse) return true;
  return false;
}

/**
 * Send the response to an express 'res'.
 */
Response.prototype.send = function(res) {
  res.status(this.statusCode);
  for (let header in this.headers) {
    res.set(header, this.headers[header]);
  }
  res.end(this.body, this.encoding);
}

Response.prototype.toString = function() {
  return "Status code " + this.statusCode + ":\n" + this.body
}

/**
 * Responses (particularly with statusCode >= 300) can be thrown.
 */
Response.prototype.toError = function() {
  return new Error(this.toString());
}

/**
 * Get the default response.
 * If 'body' is an Error, sends 500, otherwise 200.
 * @param {*|Error} body - what to send back
 */
Response.default = function(body) {
  let statusCode = 200;
  if (body instanceof Error) {
    statusCode = body.statusCode || 500;
    body = {error: body.message};
  }
  return new Response({
    statusCode,
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify(body, null, 2),
  })
}