solution

src/App.scss

@@ -17,7 +17,3 @@
     }
   }
 }
-
-.message-body {
-  white-space: pre-line;
-}

src/App.tsx

@@ -1,60 +1,98 @@
-import classNames from 'classnames';
-
-import 'bulma/css/bulma.css';
-import '@fortawesome/fontawesome-free/css/all.css';
+import { useState } from 'react';
+import cn from 'classnames';
 import './App.scss';
 
+import { User, Post } from './types';
+import { getPosts } from './services';
+
 import { PostsList } from './components/PostsList';
 import { PostDetails } from './components/PostDetails';
 import { UserSelector } from './components/UserSelector';
 import { Loader } from './components/Loader';
 
-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 [hasPostsLoadingError, setHasPostsLoadingError] = useState(false);
+  const [isLoading, setIsLoading] = useState(false);
+  const [selectedPost, setSelectedPost] = useState<Post | null>(null);
 
-            <div className="block" data-cy="MainContent">
-              <p data-cy="NoSelectedUser">No user selected</p>
+  const showNoPostsYet =
+    !!selectedUser && !isLoading && !hasPostsLoadingError && !posts.length;
 
-              <Loader />
+  const showPostList =
+    !!selectedUser && !isLoading && !hasPostsLoadingError && !!posts.length;
 
-              <div
-                className="notification is-danger"
-                data-cy="PostsLoadingError"
-              >
-                Something went wrong!
-              </div>
+  const handleLoadPosts = (userId: User['id']) => {
+    setIsLoading(true);
+    setHasPostsLoadingError(false);
+    setSelectedPost(null);
+
+    getPosts(userId)
+      .then(setPosts)
+      .catch(() => setHasPostsLoadingError(true))
+      .finally(() => setIsLoading(false));
+  };
 
-              <div className="notification is-warning" data-cy="NoPostsYet">
-                No posts yet
+  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}
+                  onSelectedUser={setSelectedUser}
+                  onLoadPosts={handleLoadPosts}
+                />
               </div>
 
-              <PostsList />
+              <div className="block" data-cy="MainContent">
+                {!selectedUser && (
+                  <p data-cy="NoSelectedUser">No user selected</p>
+                )}
+
+                {isLoading && <Loader />}
+
+                {hasPostsLoadingError && (
+                  <div
+                    className="notification is-danger"
+                    data-cy="PostsLoadingError"
+                  >
+                    Something went wrong!
+                  </div>
+                )}
+
+                {showNoPostsYet && (
+                  <div className="notification is-warning" data-cy="NoPostsYet">
+                    No posts yet
+                  </div>
+                )}
+
+                {showPostList && (
+                  <PostsList
+                    posts={posts}
+                    selectedPost={selectedPost}
+                    onSelectedPost={setSelectedPost}
+                  />
+                )}
+              </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={cn('tile is-parent is-8-desktop Sidebar', {
+              'Sidebar--open': !!selectedPost,
+            })}
+          >
+            <div className="tile is-child box is-success ">
+              {!!selectedPost && <PostDetails post={selectedPost} />}
+            </div>
           </div>
         </div>
       </div>
-    </div>
-  </main>
-);
+    </main>
+  );
+};

src/components/CommentsList/CommentsList.tsx

@@ -0,0 +1,37 @@
+import { FC } from 'react';
+import { Comment } from '../../types';
+
+interface Props {
+  comments: Comment[];
+  onDeleteComment: (commentId: Comment['id']) => void;
+}
+
+export const CommentsList: FC<Props> = ({ comments, onDeleteComment }) => {
+  return (
+    <>
+      <p className="title is-4">Comments:</p>
+
+      {comments.map(({ id, email, name, body }) => (
+        <article key={id} className="message is-small" data-cy="Comment">
+          <div className="message-header">
+            <a href={`mailto:${email}`} data-cy="CommentAuthor">
+              {name}
+            </a>
+
+            <button
+              data-cy="CommentDelete"
+              type="button"
+              className="delete is-small"
+              aria-label="delete"
+              onClick={() => onDeleteComment(id)}
+            />
+          </div>
+
+          <div className="message-body" data-cy="CommentBody">
+            {body}
+          </div>
+        </article>
+      ))}
+    </>
+  );
+};

src/components/CommentsList/index.ts

@@ -0,0 +1 @@
+export * from './CommentsList';