Client: async resources, make store reusable, move plugins and add getTaskFor getter (#8575)

Add library to manage async resource
Make Store reusable for easier testing
Move plugin to libs
Add getTaskFor getter with tests

website/client/libs/asyncResource.js

@@ -0,0 +1,45 @@
+import get from 'lodash/get';
+import axios from 'axios';
+
+// Return an object used to describe, in the app state, an
+// async resource loaded from the server with its data and status.
+export function asyncResourceFactory () {
+  return {
+    loadingStatus: 'NOT_LOADED', // NOT_LOADED, LOADING, LOADED
+    data: null,
+  };
+}
+
+export function loadAsyncResource ({store, path, url, deserialize, forceLoad = false}) {
+  if (!store) throw new Error('"store" is required and must be the application store.');
+  if (!path) throw new Error('The path to the resource in the application state is required.');
+  if (!url) throw new Error('The resource\'s url on the server is required.');
+  if (!deserialize) throw new Error('A response deserialization function named must be passed as "deserialize".');
+
+  const resource = get(store.state, path);
+  if (!resource) throw new Error(`No resouce found at path "${path}".`);
+  const loadingStatus = resource.loadingStatus;
+
+  if (loadingStatus === 'LOADED' && !forceLoad) {
+    return Promise.resolve(resource);
+  } else if (loadingStatus === 'LOADING') {
+    return new Promise((resolve, reject) => {
+      const resourceWatcher = store.watch(state => get(state, `${path}.loadingStatus`), (newLoadingStatus) => {
+        resourceWatcher(); // remove the watcher
+        if (newLoadingStatus === 'LOADED') {
+          return resolve(resource);
+        } else {
+          return reject(); // TODO add reason?
+        }
+      });
+    });
+  } else if (loadingStatus === 'NOT_LOADED' || loadingStatus === 'LOADED' && forceLoad) {
+    return axios.get(url).then(response => { // TODO support more params
+      resource.loadingStatus = 'LOADED';
+      resource.data = deserialize(response);
+      return resource;
+    });
+  } else {
+    return Promise.reject(new Error(`Invalid loading status "${loadingStatus} for resource at "${path}".`));
+  }
+}