solution

src/App.tsx

@@ -1,3 +1,4 @@
+import { useState, useEffect } from 'react';
 import classNames from 'classnames';
 
 import 'bulma/css/bulma.css';
@@ -8,53 +9,102 @@ import { PostsList } from './components/PostsList';
 import { PostDetails } from './components/PostDetails';
 import { UserSelector } from './components/UserSelector';
 import { Loader } from './components/Loader';
+import { User } from './types/User';
+import { Post } from './types/Post';
+import { getUserPosts } from './api/posts';
 
-export const App = () => (
-  <main className="section">
-    <div className="container">
-      <div className="tile is-ancestor">
-        <div className="tile is-parent">
-          <div className="tile is-child box is-success">
-            <div className="block">
-              <UserSelector />
-            </div>
+export const App = () => {
+  const [selectedUser, setSelectedUser] = useState<User | null>(null);
+  const [posts, setPosts] = useState<Post[]>([]);
+  const [postsIsLoading, setPostsIsLoading] = useState(false);
+  const [hasPostsError, setHasPostsError] = useState('');
 
-            <div className="block" data-cy="MainContent">
-              <p data-cy="NoSelectedUser">No user selected</p>
+  const [chosenPost, setChosenPost] = useState<Post | null>(null);
 
-              <Loader />
+  const hasNoPosts =
+    selectedUser && !postsIsLoading && !hasPostsError && !posts.length;
 
-              <div
-                className="notification is-danger"
-                data-cy="PostsLoadingError"
-              >
-                Something went wrong!
-              </div>
+  useEffect(() => {
+    if (!selectedUser) {
+      return;
+    }
+
+    setPostsIsLoading(true);
+    setHasPostsError('');
+    setPosts([]);
+    setChosenPost(null);
 
-              <div className="notification is-warning" data-cy="NoPostsYet">
-                No posts yet
+    getUserPosts(selectedUser.id)
+      .then(setPosts)
+      .catch(() => setHasPostsError('Something went wrong!'))
+      .finally(() => setPostsIsLoading(false));
+  }, [selectedUser]);
+
+  return (
+    <main className="section">
+      <div className="container">
+        <div className="tile is-ancestor">
+          <div className="tile is-parent">
+            <div className="tile is-child box is-success">
+              <div className="block">
+                <UserSelector
+                  selectedUser={selectedUser}
+                  onSelect={setSelectedUser}
+                  onPost={setChosenPost}
+                />
               </div>
 
-              <PostsList />
+              <div className="block" data-cy="MainContent">
+                {!selectedUser && (
+                  <p data-cy="NoSelectedUser">No user selected</p>
+                )}
+
+                {postsIsLoading && <Loader />}
+
+                {!postsIsLoading && hasPostsError && (
+                  <div
+                    className="notification is-danger"
+                    data-cy="PostsLoadingError"
+                  >
+                    {hasPostsError}
+                  </div>
+                )}
+
+                {hasNoPosts && (
+                  <div className="notification is-warning" data-cy="NoPostsYet">
+                    No posts yet
+                  </div>
+                )}
+
+                {!postsIsLoading && posts.length > 0 && (
+                  <PostsList
+                    posts={posts}
+                    chosenPost={chosenPost}
+                    onSelect={setChosenPost}
+                  />
+                )}
+              </div>
             </div>
           </div>
-        </div>
 
-        <div
-          data-cy="Sidebar"
-          className={classNames(
-            'tile',
-            'is-parent',
-            'is-8-desktop',
-            'Sidebar',
-            'Sidebar--open',
-          )}
-        >
-          <div className="tile is-child box is-success ">
-            <PostDetails />
+          <div
+            data-cy="Sidebar"
+            className={classNames(
+              'tile',
+              'is-parent',
+              'is-8-desktop',
+              'Sidebar',
+              {
+                'Sidebar--open': chosenPost,
+              },
+            )}
+          >
+            <div className="tile is-child box is-success ">
+              {chosenPost && <PostDetails post={chosenPost} />}
+            </div>
           </div>
         </div>
       </div>
-    </div>
-  </main>
-);
+    </main>
+  );
+};

src/api/comments.ts

@@ -0,0 +1,19 @@
+import { Comment } from '../types/Comment';
+import { client } from '../utils/fetchClient';
+
+export const getPostComments = (postId: number) => {
+  return client.get<Comment[]>(`/comments?postId=${postId}`);
+};
+
+export const postComment = ({
+  name,
+  email,
+  body,
+  postId,
+}: Omit<Comment, 'id'>) => {
+  return client.post<Comment>('/comments', { name, email, body, postId });
+};
+
+export const deleteComment = (commentId: number) => {
+  return client.delete(`/comments/${commentId}`);
+};

src/api/posts.ts

@@ -0,0 +1,6 @@
+import { Post } from '../types/Post';
+import { client } from '../utils/fetchClient';
+
+export const getUserPosts = (userId: number) => {
+  return client.get<Post[]>(`/posts?userId=${userId}`);
+};

src/api/users.ts

@@ -0,0 +1,6 @@
+import { User } from '../types/User';
+import { client } from '../utils/fetchClient';
+
+export const getUsers = () => {
+  return client.get<User[]>('/users');
+};