'use strict';

var utils = require('./../utils');
var transformData = require('./transformData');

/**
 * Dispatch a request to the server using whichever adapter
 * is supported by the current environment.
 *
 * @param {object} config The config that is to be used for the request
 * @returns {Promise} The Promise to be fulfilled
 */
module.exports = function dispatchRequest(config) {
  // Ensure headers exist
  config.headers = config.headers || {};

  // Transform request data
  config.data = transformData(
    config.data,
    config.headers,
    config.transformRequest
  );

  // Flatten headers
  config.headers = utils.merge(
    config.headers.common || {},
    config.headers[config.method] || {},
    config.headers || {}
  );

  utils.forEach(
    ['delete', 'get', 'head', 'post', 'put', 'patch', 'common'],
    function cleanHeaderConfig(method) {
      delete config.headers[method];
    }
  );

  return new Promise(function executor(resolve, reject) {
    try {
      var adapter;

      if (typeof config.adapter === 'function') {
        // For custom adapter support
        adapter = config.adapter;
      } else if (typeof XMLHttpRequest !== 'undefined') {
        // For browsers use XHR adapter
        adapter = require('../adapters/xhr');
      } else if (typeof process !== 'undefined') {
        // For node use HTTP adapter
        adapter = require('../adapters/http');
      }

      if (typeof adapter === 'function') {
        adapter(resolve, reject, config);
      }
    } catch (e) {
      reject(e);
    }
  }).then(function onFulfilled(response) {
    // Transform response data
    response.data = transformData(
      response.data,
      response.headers,
      config.transformResponse
    );

    return response;
  });
};