refactor(agent): refactor agentService to es6 (#4091)

app/agent/services/agentService.js

@@ -1,21 +1,17 @@
+import angular from 'angular';
+
 import { AgentViewModel } from '../models/agent';
 
-angular.module('portainer.agent').factory('AgentService', [
-  '$q',
-  'Agent',
-  'AgentVersion1',
-  'HttpRequestHelper',
-  'Host',
-  'StateManager',
-  function AgentServiceFactory($q, Agent, AgentVersion1, HttpRequestHelper, Host, StateManager) {
-    'use strict';
-    var service = {};
+angular.module('portainer.agent').factory('AgentService', AgentServiceFactory);
 
-    service.agents = agents;
-    service.hostInfo = hostInfo;
+function AgentServiceFactory(Agent, AgentVersion1, HttpRequestHelper, Host, StateManager) {
+  return {
+    agents,
+    hostInfo,
+  };
 
   function getAgentApiVersion() {
-      var state = StateManager.getState();
+    const state = StateManager.getState();
     return state.endpoint.agentApiVersion;
   }
 
@@ -24,27 +20,16 @@ angular.module('portainer.agent').factory('AgentService', [
     return Host.info().$promise;
   }
 
-    function agents() {
-      var deferred = $q.defer();
-
-      var agentVersion = getAgentApiVersion();
-      var service = agentVersion > 1 ? Agent : AgentVersion1;
-
-      service
-        .query({ version: agentVersion })
-        .$promise.then(function success(data) {
-          var agents = data.map(function (item) {
+  async function agents() {
+    const agentVersion = getAgentApiVersion();
+    const service = agentVersion > 1 ? Agent : AgentVersion1;
+    try {
+      const agents = await service.query({ version: agentVersion }).$promise;
+      return agents.map(function (item) {
         return new AgentViewModel(item);
       });
-          deferred.resolve(agents);
-        })
-        .catch(function error(err) {
-          deferred.reject({ msg: 'Unable to retrieve agents', err: err });
-        });
-
-      return deferred.promise;
+    } catch (err) {
+      throw { msg: 'Unable to retrieve agents', err };
     }
-
-    return service;
-  },
-]);
+  }
+}