Post follow and updates notifications V1 (#111)

* It is now possible to follow a post in order to receive updates about it
* Notifications are now sent when updates are published
* Post status changes are now tracked
* Update sidebar now shows the post status history
* Mark a comment as a post update using the comment form
* ... more ...

app/javascript/actions/Follow/requestFollow.ts

@@ -0,0 +1,58 @@
+import { Action } from 'redux';
+import { ThunkAction } from 'redux-thunk';
+
+import IFollowJSON from '../../interfaces/json/IFollow';
+
+import { State } from '../../reducers/rootReducer';
+
+export const FOLLOW_REQUEST_START = 'FOLLOW_REQUEST_START';
+interface FollowRequestStartAction {
+  type: typeof FOLLOW_REQUEST_START;
+}
+
+export const FOLLOW_REQUEST_SUCCESS = 'FOLLOW_REQUEST_SUCCESS';
+interface FollowRequestSuccessAction {
+  type: typeof FOLLOW_REQUEST_SUCCESS;
+  follow: IFollowJSON;
+}
+
+export const FOLLOW_REQUEST_FAILURE = 'FOLLOW_REQUEST_FAILURE';
+interface FollowRequestFailureAction {
+  type: typeof FOLLOW_REQUEST_FAILURE;
+  error: string;
+}
+
+export type FollowRequestActionTypes =
+  FollowRequestStartAction |
+  FollowRequestSuccessAction |
+  FollowRequestFailureAction;
+
+const followRequestStart = (): FollowRequestActionTypes => ({
+  type: FOLLOW_REQUEST_START,
+});
+
+const followRequestSuccess = (
+  follow: IFollowJSON,
+): FollowRequestActionTypes => ({
+  type: FOLLOW_REQUEST_SUCCESS,
+  follow,
+});
+
+const followRequestFailure = (error: string): FollowRequestActionTypes => ({
+  type: FOLLOW_REQUEST_FAILURE,
+  error,
+});
+
+export const requestFollow = (
+  postId: number,
+): ThunkAction<void, State, null, Action<string>> => async (dispatch) => {
+  dispatch(followRequestStart());
+
+  try {
+    const response = await fetch(`/posts/${postId}/follows`);
+    const json = await response.json();
+    dispatch(followRequestSuccess(json));
+  } catch (e) {
+    dispatch(followRequestFailure(e));
+  }
+};

app/javascript/actions/Follow/submitFollow.ts

@@ -0,0 +1,47 @@
+import { Action } from "redux";
+import { ThunkAction } from "redux-thunk";
+
+import { State } from "../../reducers/rootReducer";
+import buildRequestHeaders from "../../helpers/buildRequestHeaders";
+import HttpStatus from "../../constants/http_status";
+import IFollowJSON from "../../interfaces/json/IFollow";
+
+export const FOLLOW_SUBMIT_SUCCESS = 'FOLLOW_SUBMIT_SUCCESS';
+interface FollowSubmitSuccessAction {
+  type: typeof FOLLOW_SUBMIT_SUCCESS,
+  postId: number;
+  isFollow: boolean;
+  follow: IFollowJSON;
+}
+
+export type FollowActionTypes = FollowSubmitSuccessAction;
+
+const followSubmitSuccess = (
+  postId: number,
+  isFollow: boolean,
+  follow: IFollowJSON,  
+): FollowSubmitSuccessAction => ({
+  type: FOLLOW_SUBMIT_SUCCESS,
+  postId,
+  isFollow,
+  follow,
+});
+
+export const submitFollow = (
+  postId: number,
+  isFollow: boolean,
+  authenticityToken: string,
+): ThunkAction<void, State, null, Action<string>> => async (dispatch) => {
+  try {
+    const res = await fetch(`/posts/${postId}/follows`, {
+      method: isFollow ? 'POST' : 'DELETE',
+      headers: buildRequestHeaders(authenticityToken),
+    });
+    const json = await res.json();
+
+    if (res.status === HttpStatus.Created || res.status === HttpStatus.Accepted)
+      dispatch(followSubmitSuccess(postId, isFollow, json));
+  } catch (e) {
+    console.log('An error occurred while following a post');
+  }
+}