first solution

src/App.tsx

@@ -1,61 +1,122 @@
+import React, { useState } from 'react';
 import './App.scss';
 
-// import usersFromServer from './api/users';
-// import todosFromServer from './api/todos';
+import usersFromServer from './api/users';
+import todosFromServer from './api/todos';
+
+import { Todo } from './types/Todo';
+
+import { TodoList } from './components/TodoList';
+
+const findUserById = (id: number) => {
+  return usersFromServer.find(user => user.id === id) || null;
+};
+
+const todosWithUsers = todosFromServer.map(todo => ({
+  ...todo,
+  user: findUserById(todo.userId),
+}));
+
+export const App: React.FC = () => {
+  const [title, setTitle] = useState('');
+  const [userId, setUserId] = useState(0);
+
+  const [hasTitleError, setHasTitleError] = useState(false);
+  const [hasUserError, setHasUserError] = useState(false);
+
+  const [newTodos, setNewTodos] = useState<Todo[]>(todosWithUsers);
+
+  const handleTitleInput = ((e: React.ChangeEvent<HTMLInputElement>) => {
+    setTitle(e.target.value);
+    setHasTitleError(false);
+  });
+
+  const handleUserSelect = (e: React.ChangeEvent<HTMLSelectElement>) => {
+    setUserId(+e.target.value);
+    setHasUserError(false);
+  };
+
+  const resetForm = () => {
+    setTitle('');
+    setUserId(0);
+  };
+
+  const handleSubmit = ((e: React.ChangeEvent<HTMLFormElement>) => {
+    e.preventDefault();
+
+    if (!title && !userId) {
+      setHasTitleError(!hasTitleError);
+      setHasUserError(!hasUserError);
+
+      return;
+    }
+
+    if (!title) {
+      setHasTitleError(!hasTitleError);
+
+      return;
+    }
+
+    if (!userId) {
+      setHasUserError(!hasUserError);
+
+      return;
+    }
+
+    const newTodo = {
+      id: Math.max(...newTodos.map(todo => todo.id)) + 1,
+      title,
+      userId,
+      completed: false,
+      user: findUserById(userId),
+    };
+
+    setNewTodos(prevState => [...prevState, newTodo]);
+    resetForm();
+  });
 
-export const App = () => {
   return (
     <div className="App">
       <h1>Add todo form</h1>
 
-      <form action="/api/todos" method="POST">
+      <form
+        action="/api/todos"
+        method="POST"
+        onSubmit={handleSubmit}
+      >
         <div className="field">
-          <input type="text" data-cy="titleInput" />
-          <span className="error">Please enter a title</span>
+          <input
+            type="text"
+            data-cy="titleInput"
+            placeholder="Enter a Title"
+            value={title}
+            onChange={handleTitleInput}
+          />
+
+          {hasTitleError && <span className="error">Please enter a title</span>}
         </div>
 
         <div className="field">
-          <select data-cy="userSelect">
+          <select
+            data-cy="userSelect"
+            value={userId}
+            onChange={handleUserSelect}
+          >
             <option value="0" disabled>Choose a user</option>
+            {usersFromServer.map(user => (
+              <option value={user.id} key={user.id}>{user.name}</option>
+            ))}
           </select>
 
-          <span className="error">Please choose a user</span>
+          {hasUserError && <span className="error">Please choose a user</span>}
         </div>
 
         <button type="submit" data-cy="submitButton">
           Add
         </button>
       </form>
 
-      <section className="TodoList">
-        <article data-id="1" className="TodoInfo TodoInfo--completed">
-          <h2 className="TodoInfo__title">
-            delectus aut autem
-          </h2>
-
-          <a className="UserInfo" href="mailto:Sincere@april.biz">
-            Leanne Graham
-          </a>
-        </article>
-
-        <article data-id="15" className="TodoInfo TodoInfo--completed">
-          <h2 className="TodoInfo__title">delectus aut autem</h2>
-
-          <a className="UserInfo" href="mailto:Sincere@april.biz">
-            Leanne Graham
-          </a>
-        </article>
-
-        <article data-id="2" className="TodoInfo">
-          <h2 className="TodoInfo__title">
-            quis ut nam facilis et officia qui
-          </h2>
-
-          <a className="UserInfo" href="mailto:Julianne.OConner@kory.org">
-            Patricia Lebsack
-          </a>
-        </article>
-      </section>
+      <TodoList todos={newTodos} />
     </div>
   );
 };

src/components/TodoInfo/TodoInfo.tsx

@@ -1 +1,27 @@
-export const TodoInfo = () => {};
+import React from 'react';
+import cn from 'classnames';
+
+import { UserInfo } from '../UserInfo';
+import { Todo } from '../../types/Todo';
+
+interface Props {
+  todo: Todo,
+}
+
+export const TodoInfo: React.FC<Props> = ({ todo }) => {
+  const isCompleted = todo.completed && 'TodoInfo--completed';
+
+  return (
+    <article
+      data-id={todo.id}
+      className={cn('TodoInfo', isCompleted)}
+    >
+
+      <h2 className="TodoInfo__title">
+        {todo.title}
+      </h2>
+
+      {todo.user && <UserInfo user={todo.user} />}
+    </article>
+  );
+};

src/components/TodoList/TodoList.tsx

@@ -1 +1,16 @@
-export const TodoList = () => {};
+import React from 'react';
+
+import { TodoInfo } from '../TodoInfo/TodoInfo';
+import { Todo } from '../../types/Todo';
+
+type Props = {
+  todos: Todo[];
+};
+
+export const TodoList: React.FC<Props> = ({ todos }) => (
+  <section className="TodoList">
+    {todos.map(todo => (
+      <TodoInfo key={todo.id} todo={todo} />
+    ))}
+  </section>
+);

src/components/UserInfo/UserInfo.tsx

@@ -1 +1,12 @@
-export const UserInfo = () => {};
+import React from 'react';
+import { User } from '../../types/User';
+
+type Props = {
+  user: User;
+};
+
+export const UserInfo: React.FC<Props> = ({ user }) => (
+  <a className="UserInfo" href={`mailto:${user.email}`}>
+    {user.name}
+  </a>
+);

src/services/findUser.ts

@@ -0,0 +1,5 @@
+import usersFromServer from '../api/users';
+
+export const findUserById = (id: number) => {
+  return usersFromServer.find(user => user.id === id) || null;
+};

src/types/Todo.ts

@@ -0,0 +1,9 @@
+import { User } from './User';
+
+export interface Todo {
+  id: number,
+  title: string,
+  completed: boolean,
+  userId: number,
+  user: User | null,
+}

src/types/User.ts

@@ -0,0 +1,6 @@
+export interface User {
+  id: number,
+  name: string,
+  username: string,
+  email: string,
+}