Solution

src/App.scss

@@ -1,3 +1,7 @@
+iframe {
+  display: none;
+}
+
 .Sidebar {
   overflow: hidden;
   opacity: 0;

src/App.tsx

@@ -1,4 +1,4 @@
-import React from 'react';
+import React, { useEffect, useState } from 'react';
 import 'bulma/bulma.sass';
 import '@fortawesome/fontawesome-free/css/all.css';
 import './App.scss';
@@ -8,53 +8,182 @@ import { PostsList } from './components/PostsList';
 import { PostDetails } from './components/PostDetails';
 import { UserSelector } from './components/UserSelector';
 import { Loader } from './components/Loader';
+import { getUsers } from './services/user';
+import { getUserPosts } from './services/posts';
+import * as services from './services/comments';
+import { User } from './types/User';
+import { Post } from './types/Post';
+import { Comment, CommentData } from './types/Comment';
+import { ErrorType } from './types/ErrorType';
 
 export const App: React.FC = () => {
+  const [users, setUsers] = useState<User[]>([]);
+  const [selectedUser, setSelectedUser] = useState<User | null>(null);
+
+  const [posts, setPosts] = useState<Post[]>([]);
+  const [selectedPost, setSelectedPost] = useState<Post | null>(null);
+
+  const [comments, setComments] = useState<Comment[]>([]);
+
+  const [errorMessage, setErrorMessage] = useState('');
+
+  const [isLoading, setIsLoading] = useState(false);
+
+  const loadUsers = async () => {
+    setErrorMessage('');
+    setPosts([]);
+    setSelectedPost(null);
+    setComments([]);
+    setIsLoading(true);
+    try {
+      const loadedUser = await getUsers();
+
+      setUsers(loadedUser);
+    } catch {
+      setErrorMessage(ErrorType.USERS);
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    loadUsers();
+  }, [selectedUser]);
+
+  const loadPosts = async (id: number) => {
+    setErrorMessage('');
+    setIsLoading(true);
+    try {
+      const loadedPosts = await getUserPosts(id);
+
+      setPosts(loadedPosts);
+    } catch {
+      setErrorMessage(ErrorType.POSTS);
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    if (selectedUser) {
+      loadPosts(selectedUser?.id);
+    }
+  }, [selectedUser]);
+
+  const loadComments = async (id: number) => {
+    setErrorMessage('');
+    setIsLoading(true);
+    try {
+      const loadedComments = await services.getPostComments(id);
+
+      setComments(loadedComments);
+    } catch {
+      setErrorMessage(ErrorType.COMMENTS);
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    if (selectedPost) {
+      loadComments(selectedPost?.id);
+    }
+  }, [selectedPost]);
+
+  const deleteComment = async (commentId: number) => {
+    setErrorMessage('');
+    setComments(currentComments => currentComments
+      .filter(({ id }) => id !== commentId));
+    try {
+      await services.deleteComment(commentId);
+    } catch (error) {
+      setComments(comments);
+      setErrorMessage(ErrorType.COMM_DEL);
+      throw error;
+    }
+  };
+
+  const addComment = async (comment: CommentData) => {
+    setErrorMessage('');
+    try {
+      const addedComment = await services.postComment(comment);
+
+      setComments(currComments => [...currComments, addedComment]);
+    } catch {
+      setErrorMessage(ErrorType.COMM_ADD);
+    }
+  };
+
   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 />
+                <UserSelector
+                  users={users}
+                  selectedUser={selectedUser}
+                  setSelectedUser={setSelectedUser}
+                />
               </div>
 
               <div className="block" data-cy="MainContent">
-                <p data-cy="NoSelectedUser">
-                  No user selected
-                </p>
+                {!selectedUser && !isLoading && !errorMessage && (
+                  <p data-cy="NoSelectedUser">
+                    No user selected
+                  </p>
+                )}
 
-                <Loader />
+                {isLoading && posts.length === 0 && <Loader />}
 
-                <div
-                  className="notification is-danger"
-                  data-cy="PostsLoadingError"
-                >
-                  Something went wrong!
-                </div>
+                {errorMessage && (
+                  <div
+                    className="notification is-danger"
+                    data-cy="PostsLoadingError"
+                  >
+                    {errorMessage}
+                  </div>
+                )}
 
-                <div className="notification is-warning" data-cy="NoPostsYet">
-                  No posts yet
-                </div>
+                {selectedUser && !posts.length
+                && !isLoading && !errorMessage && (
+                  <div className="notification is-warning" data-cy="NoPostsYet">
+                    No posts yet
+                  </div>
+                )}
 
-                <PostsList />
+                {posts.length > 0 && (
+                  <PostsList
+                    posts={posts}
+                    selectedPost={selectedPost}
+                    setSelectedPost={setSelectedPost}
+                  />
+                )}
               </div>
             </div>
           </div>
-
           <div
             data-cy="Sidebar"
             className={classNames(
               'tile',
               'is-parent',
               'is-8-desktop',
               'Sidebar',
-              'Sidebar--open',
+              { 'Sidebar--open': selectedPost },
             )}
           >
             <div className="tile is-child box is-success ">
-              <PostDetails />
+              {selectedPost && (
+                <PostDetails
+                  comments={comments}
+                  isLoading={isLoading}
+                  errorMessage={errorMessage}
+                  selectedPost={selectedPost}
+                  onCommentDelete={deleteComment}
+                  onCommentAdd={addComment}
+                />
+              )}
             </div>
           </div>
         </div>