text: import { Meteor } from 'meteor/meteor';
  import { Random } from 'meteor/random';
  import _ from 'underscore';
  
  let timed = false;
  
  if (Meteor.isClient) {
  	const { getConfig } = require('../../ui-utils/client/config');
  	timed = [getConfig('debug'), getConfig('timed-callbacks')].includes('true');
  }
  /*
  * Callback hooks provide an easy way to add extra steps to common operations.
  * @namespace RocketChat.callbacks
  */
  
  export const callbacks = {};
  
  const wrapCallback = (callback) => (...args) => {
  	const time = Date.now();
  	const result = callback(...args);
  	const currentTime = Date.now() - time;
  	let stack = callback.stack
  		&& typeof callback.stack.split === 'function'
  		&& callback.stack.split('\n');
  	stack = stack && stack[2] && (stack[2].match(/\(.+\)/) || [])[0];
  	console.log(String(currentTime), callback.hook, callback.id, stack);
  	return result;
  };
  
  const wrapRun = (hook, fn) => (...args) => {
  	const time = Date.now();
  	const ret = fn(...args);
  	const totalTime = Date.now() - time;
  	console.log(`${ hook }:`, totalTime);
  	return ret;
  };
  
  const handleResult = (fn) => (result, constant) => {
  	const callbackResult = callbacks.runItem({ hook: fn.hook, callback: fn, result, constant });
  	return typeof callbackResult === 'undefined' ? result : callbackResult;
  };
  
  
  const identity = (e) => e;
  const pipe = (f, g) => (e, ...constants) => g(f(e, ...constants), ...constants);
  const createCallback = (hook, callbacks) => callbacks.map(handleResult).reduce(pipe, identity);
  
  const createCallbackTimed = (hook, callbacks) =>
  	wrapRun(hook,
  		callbacks
  			.map(wrapCallback)
  			.map(handleResult)
  			.reduce(pipe, identity),
  	);
  
  const create = (hook, cbs) =>
  	(timed ? createCallbackTimed(hook, cbs) : createCallback(hook, cbs));
  const combinedCallbacks = new Map();
  
  /*
  * Callback priorities
  * @enum {CallbackPriority}
  */
  callbacks.priority = {
  	HIGH: -1000,
  	MEDIUM: 0,
  	LOW: 1000,
  };
  
  const getHooks = (hookName) => callbacks[hookName] || [];
  
  /*
  * Add a callback function to a hook
  * @param {String} hook - The name of the hook
  * @param {Function} callback - The callback function
  * @param {CallbackPriority} priority - The callback run priority (order)
  * @param {String} id - Human friendly name for this callback
  */
  callbacks.add = function(
  	hook,
  	callback,
  	priority = callbacks.priority.MEDIUM,
  	id = Random.id(),
  ) {
  	callbacks[hook] = getHooks(hook);
  	if (callbacks[hook].find((cb) => cb.id === id)) {
  		return;
  	}
  	callback.hook = hook;
  	callback.priority = priority;
  	callback.id = id;
  	callback.stack = new Error().stack;
  
  	callbacks[hook].push(callback);
  	callbacks[hook] = _.sortBy(callbacks[hook], (callback) => callback.priority || callbacks.priority.MEDIUM);
  	combinedCallbacks.set(hook, create(hook, callbacks[hook]));
  };
  
  
  /*
  * Remove a callback from a hook
  * @param {string} hook - The name of the hook
  * @param {string} id - The callback's id
  */
  
  callbacks.remove = function(hook, id) {
  	callbacks[hook] = getHooks(hook).filter((callback) => callback.id !== id);
  	combinedCallbacks.set(hook, create(hook, callbacks[hook]));
  };
  
  callbacks.runItem = ({ callback, result, constant /* , hook */ }) => callback(result, constant);
  
  /*
  * Successively run all of a hook's callbacks on an item
  * @param {String} hook - The name of the hook
  * @param {Object} item - The post, comment, modifier, etc. on which to run the callbacks
  * @param {Object} [constant] - An optional constant that will be passed along to each callback
  * @returns {Object} Returns the item after it's been through all the callbacks for this hook
  */
  
  callbacks.run = function(hook, item, constant) {
  	const runner = combinedCallbacks.get(hook);
  	if (!runner) {
  		return item;
  	}
  
  	return runner(item, constant);
  
  	// return callbackItems.reduce(function(result, callback) {
  	// 	const callbackResult = callbacks.runItem({ hook, callback, result, constant });
  
  	// 	return typeof callbackResult === 'undefined' ? result : callbackResult;
  	// }, item);
  };
  
  
  /*
  * Successively run all of a hook's callbacks on an item, in async mode (only works on server)
  * @param {String} hook - The name of the hook
  * @param {Object} item - The post, comment, modifier, etc. on which to run the callbacks
  * @param {Object} [constant] - An optional constant that will be passed along to each callback
  */
  
  callbacks.runAsync = Meteor.isServer ? function(hook, item, constant) {
  	const callbackItems = callbacks[hook];
  	if (callbackItems && callbackItems.length) {
  		callbackItems.forEach((callback) => Meteor.defer(function() { callback(item, constant); }));
  	}
  	return item;
  } : () => { throw new Error('callbacks.runAsync on client server not allowed'); };
  