From cdee00c277de03509df6948b7a9ed82cff56d596 Mon Sep 17 00:00:00 2001
From: Horoshko Vitaliy <horoshko29@gmail.com>
Date: Fri, 6 Mar 2026 23:00:08 +0200
Subject: [PATCH 1/2] task solution

---
 README.md                            |   2 +-
 src/App.tsx                          | 272 +++++++++++++++++++++++++--
 src/api/todos.ts                     |   8 +
 src/components/ErrorNotification.tsx |  32 ++++
 src/components/Footer.tsx            |  69 +++++++
 src/components/Header.tsx            |  55 ++++++
 src/components/TodoItem.tsx          | 123 ++++++++++++
 src/components/TodoList.tsx          |  86 +++++++++
 src/types/Todo.ts                    |   6 +
 src/utils/fetchClient.ts             |  46 +++++
 10 files changed, 684 insertions(+), 15 deletions(-)
 create mode 100644 src/api/todos.ts
 create mode 100644 src/components/ErrorNotification.tsx
 create mode 100644 src/components/Footer.tsx
 create mode 100644 src/components/Header.tsx
 create mode 100644 src/components/TodoItem.tsx
 create mode 100644 src/components/TodoList.tsx
 create mode 100644 src/types/Todo.ts
 create mode 100644 src/utils/fetchClient.ts

diff --git a/README.md b/README.md
index 47a1add059..95b5d340d8 100644
--- a/README.md
+++ b/README.md
@@ -47,4 +47,4 @@ Implement the ability to edit a todo title on double click:
 
 - Implement a solution following the [React task guideline](https://github.com/mate-academy/react_task-guideline#react-tasks-guideline).
 - Use the [React TypeScript cheat sheet](https://mate-academy.github.io/fe-program/js/extra/react-typescript).
-- Replace `<your_account>` with your Github username in the [DEMO LINK](https://<your_account>.github.io/react_todo-app-with-api/) and add it to the PR description.
+- Replace `<your_account>` with your Github username in the [DEMO LINK](https://VitaliyHoroshko.github.io/react_todo-app-with-api/) and add it to the PR description.
diff --git a/src/App.tsx b/src/App.tsx
index 81e011f432..d4ea2ca7b5 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,26 +1,270 @@
-/* eslint-disable max-len */
+/* eslint-disable jsx-a11y/label-has-associated-control */
 /* eslint-disable jsx-a11y/control-has-associated-label */
-import React from 'react';
+import React, { useEffect, useState } from 'react';
 import { UserWarning } from './UserWarning';
+import { getTodos, USER_ID } from './api/todos';
+import { Todo } from './types/Todo';
+import { client } from './utils/fetchClient';
 
-const USER_ID = 0;
+import Header from './components/Header';
+import TodoList from './components/TodoList';
+import Footer from './components/Footer';
+import ErrorNotification from './components/ErrorNotification';
 
 export const App: React.FC = () => {
+  const [todos, setTodos] = useState<Todo[]>([]);
+  const [error, setError] = useState('');
+  const [filter, setFilter] = useState<'all' | 'active' | 'completed'>('all');
+  const [loading, setLoading] = useState(false);
+  const [tempTodo, setTempTodo] = useState<Todo | null>(null);
+  const [updatingIds, setUpdatingIds] = useState<number[]>([]);
+  const [newTitle, setNewTitle] = useState('');
+  const [editingId, setEditingId] = useState<number | null>(null);
+
+  const newTodoRef = React.useRef<HTMLInputElement>(null);
+
+  useEffect(() => {
+    if (!USER_ID) {
+      return;
+    }
+
+    setError('');
+    setLoading(true);
+    getTodos()
+      .then(todosFromServer => {
+        setTimeout(() => setTodos(todosFromServer), 150);
+      })
+      .catch(() => setError('Unable to load todos'))
+      .finally(() => setLoading(false));
+  }, []);
+
+  useEffect(() => {
+    if (!loading) {
+      newTodoRef.current?.focus();
+    }
+  }, [loading]);
+
+  useEffect(() => {
+    if (error) {
+      const timer = setTimeout(() => setError(''), 3000);
+
+      return () => clearTimeout(timer);
+    }
+  }, [error]);
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    const trimmed = newTitle.trim();
+
+    if (!trimmed) {
+      setError('Title should not be empty');
+
+      return;
+    }
+
+    const optimisticTodo: Todo = {
+      id: 0,
+      title: trimmed,
+      completed: false,
+      userId: USER_ID,
+    };
+
+    setTempTodo(optimisticTodo);
+    setLoading(true);
+
+    try {
+      const addedTodo = await client.post<Todo>('/todos', {
+        title: trimmed,
+        userId: USER_ID,
+        completed: false,
+      });
+
+      setTodos(prev => [...prev, addedTodo]);
+      setTempTodo(null);
+      setNewTitle('');
+      newTodoRef.current?.focus();
+    } catch {
+      setError('Unable to add a todo');
+      setTempTodo(null);
+      newTodoRef.current?.focus();
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  const deleteTodo = async (id: number) => {
+    setUpdatingIds(prev => [...prev, id]);
+    try {
+      await client.delete(`/todos/${id}`);
+      setTodos(prev => prev.filter(t => t.id !== id));
+
+      newTodoRef.current?.focus();
+    } catch {
+      setError('Unable to delete a todo');
+    } finally {
+      setUpdatingIds(prev => prev.filter(i => i !== id));
+    }
+  };
+
+  const toggleTodo = async (id: number) => {
+    const activeTodo = todos.find(todo => todo.id === id);
+
+    if (!activeTodo) {
+      return;
+    }
+
+    const newStatus = !activeTodo.completed;
+
+    setUpdatingIds(prev => [...prev, id]);
+
+    try {
+      const updatedTodo = await client.patch<Todo>(`/todos/${id}`, {
+        completed: newStatus,
+      });
+
+      setTodos(prevTodos =>
+        prevTodos.map(todo => {
+          return todo.id === id ? updatedTodo : todo;
+        }),
+      );
+    } catch {
+      setError('Unable to update a todo');
+    } finally {
+      setUpdatingIds(prev => prev.filter(i => i !== id));
+    }
+  };
+
+  const updateTodo = async (id: number, title: string) => {
+    setUpdatingIds(prev => [...prev, id]);
+
+    try {
+      const updatedTodo = await client.patch<Todo>(`/todos/${id}`, { title });
+
+      setTodos(prev => prev.map(todo => (todo.id === id ? updatedTodo : todo)));
+      setEditingId(null);
+    } catch {
+      setError('Unable to update a todo');
+    } finally {
+      setUpdatingIds(prev => prev.filter(i => i !== id));
+    }
+  };
+
+  const toggleAll = async () => {
+    const newCompleted = !todos.every(todo => todo.completed);
+    const filtered = todos.filter(todo => todo.completed !== newCompleted);
+    const idsToUpdate = filtered.map(todo => todo.id);
+
+    setUpdatingIds(prev => [...prev, ...idsToUpdate]);
+
+    try {
+      const promises = filtered.map(todo => {
+        return client.patch<Todo>(`/todos/${todo.id}`, {
+          completed: newCompleted,
+        });
+      });
+
+      const updatedTodos = await Promise.all<Todo>(promises);
+
+      setTodos(prevTodos =>
+        prevTodos.map(todo => {
+          const updated = updatedTodos.find(
+            (u: { id: number }) => u.id === todo.id,
+          );
+
+          return updated || todo;
+        }),
+      );
+    } catch {
+      setError('Unable to toggle all todos');
+    } finally {
+      setUpdatingIds(prev => prev.filter(id => !idsToUpdate.includes(id)));
+    }
+  };
+
+  const clearCompleted = async () => {
+    const completedTodos = todos.filter(t => t.completed);
+
+    if (completedTodos.length === 0) {
+      return;
+    }
+
+    const ids = completedTodos.map(t => t.id);
+
+    setUpdatingIds(ids);
+
+    const successIds: number[] = [];
+    let hasError = false;
+
+    await Promise.allSettled(
+      ids.map(async id => {
+        try {
+          await client.delete(`/todos/${id}`);
+          successIds.push(id);
+        } catch {
+          hasError = true;
+        }
+      }),
+    );
+
+    setTodos(prev => prev.filter(t => !successIds.includes(t.id)));
+    setUpdatingIds([]);
+
+    if (!hasError) {
+      newTodoRef.current?.focus();
+    } else {
+      setError('Unable to delete a todo');
+    }
+  };
+
+  const allCompleted = todos.length > 0 && todos.every(todo => todo.completed);
+
   if (!USER_ID) {
     return <UserWarning />;
   }
 
   return (
-    <section className="section container">
-      <p className="title is-4">
-        Copy all you need from the prev task:
-        <br />
-        <a href="https://github.com/mate-academy/react_todo-app-add-and-delete#react-todo-app-add-and-delete">
-          React Todo App - Add and Delete
-        </a>
-      </p>
-
-      <p className="subtitle">Styles are already copied</p>
-    </section>
+    <div className="todoapp">
+      <h1 className="todoapp__title">todos</h1>
+
+      <div className="todoapp__content">
+        <Header
+          newTitle={newTitle}
+          setNewTitle={setNewTitle}
+          onSubmit={handleSubmit}
+          isLoading={loading}
+          inputRef={newTodoRef}
+          todosLength={todos.length}
+          allCompleted={allCompleted}
+          onToggleAll={toggleAll}
+        />
+
+        {(loading || todos.length > 0) && (
+          <>
+            <TodoList
+              todos={todos}
+              filter={filter}
+              tempTodo={tempTodo}
+              updatingIds={updatingIds}
+              onToggle={toggleTodo}
+              onDelete={deleteTodo}
+              isLoading={loading}
+              editingId={editingId}
+              onEdit={setEditingId}
+              onUpdate={updateTodo}
+            />
+
+            <Footer
+              activeCount={todos.filter(t => !t.completed).length}
+              filter={filter}
+              setFilter={setFilter}
+              hasCompleted={todos.some(t => t.completed)}
+              onClearCompleted={clearCompleted}
+            />
+          </>
+        )}
+      </div>
+
+      <ErrorNotification error={error} onClose={() => setError('')} />
+    </div>
   );
 };
diff --git a/src/api/todos.ts b/src/api/todos.ts
new file mode 100644
index 0000000000..7b5c4eda5f
--- /dev/null
+++ b/src/api/todos.ts
@@ -0,0 +1,8 @@
+import { Todo } from '../types/Todo';
+import { client } from '../utils/fetchClient';
+
+export const USER_ID = 3995;
+
+export const getTodos = async (): Promise<Todo[]> => {
+  return client.get<Todo[]>(`/todos?userId=${USER_ID}`);
+};
diff --git a/src/components/ErrorNotification.tsx b/src/components/ErrorNotification.tsx
new file mode 100644
index 0000000000..fefceb5c04
--- /dev/null
+++ b/src/components/ErrorNotification.tsx
@@ -0,0 +1,32 @@
+import React from 'react';
+import classNames from 'classnames';
+
+type ErrorNotificationProps = {
+  error: string;
+  onClose: () => void;
+};
+
+export const ErrorNotification: React.FC<ErrorNotificationProps> = ({
+  error,
+  onClose,
+}) => {
+  return (
+    <div
+      data-cy="ErrorNotification"
+      className={classNames(
+        'notification is-danger is-light has-text-weight-normal',
+        { hidden: !error },
+      )}
+    >
+      <button
+        data-cy="HideErrorButton"
+        type="button"
+        className="delete"
+        onClick={onClose}
+      />
+      {error}
+    </div>
+  );
+};
+
+export default ErrorNotification;
diff --git a/src/components/Footer.tsx b/src/components/Footer.tsx
new file mode 100644
index 0000000000..0db676c0df
--- /dev/null
+++ b/src/components/Footer.tsx
@@ -0,0 +1,69 @@
+import React from 'react';
+import classNames from 'classnames';
+
+type FooterProps = {
+  activeCount: number;
+  filter: 'all' | 'active' | 'completed';
+  setFilter: (filter: 'all' | 'active' | 'completed') => void;
+  hasCompleted: boolean;
+  onClearCompleted: () => void;
+};
+
+export const Footer: React.FC<FooterProps> = ({
+  activeCount,
+  filter,
+  setFilter,
+  hasCompleted,
+  onClearCompleted,
+}) => {
+  return (
+    <footer className="todoapp__footer" data-cy="Footer">
+      <span className="todo-count" data-cy="TodosCounter">
+        {activeCount} items left
+      </span>
+
+      <nav className="filter" data-cy="Filter">
+        <a
+          href="#/"
+          className={classNames('filter__link', { selected: filter === 'all' })}
+          data-cy="FilterLinkAll"
+          onClick={() => setFilter('all')}
+        >
+          All
+        </a>
+        <a
+          href="#/active"
+          className={classNames('filter__link', {
+            selected: filter === 'active',
+          })}
+          data-cy="FilterLinkActive"
+          onClick={() => setFilter('active')}
+        >
+          Active
+        </a>
+        <a
+          href="#/completed"
+          className={classNames('filter__link', {
+            selected: filter === 'completed',
+          })}
+          data-cy="FilterLinkCompleted"
+          onClick={() => setFilter('completed')}
+        >
+          Completed
+        </a>
+      </nav>
+
+      <button
+        type="button"
+        className="todoapp__clear-completed"
+        data-cy="ClearCompletedButton"
+        disabled={!hasCompleted}
+        onClick={onClearCompleted}
+      >
+        Clear completed
+      </button>
+    </footer>
+  );
+};
+
+export default Footer;
diff --git a/src/components/Header.tsx b/src/components/Header.tsx
new file mode 100644
index 0000000000..ebbac9dcfb
--- /dev/null
+++ b/src/components/Header.tsx
@@ -0,0 +1,55 @@
+import React from 'react';
+import classNames from 'classnames';
+
+type HeaderProps = {
+  newTitle: string;
+  setNewTitle: (value: string) => void;
+  onSubmit: (e: React.FormEvent) => void;
+  isLoading: boolean;
+  inputRef: React.RefObject<HTMLInputElement>;
+  todosLength: number;
+  allCompleted: boolean;
+  onToggleAll: () => void;
+};
+
+export const Header: React.FC<HeaderProps> = ({
+  newTitle,
+  setNewTitle,
+  onSubmit,
+  isLoading,
+  inputRef,
+  todosLength,
+  allCompleted,
+  onToggleAll,
+}) => {
+  return (
+    <header className="todoapp__header">
+      {todosLength > 0 && (
+        <button
+          type="button"
+          className={classNames('todoapp__toggle-all', {
+            active: allCompleted,
+          })}
+          data-cy="ToggleAllButton"
+          onClick={onToggleAll}
+        />
+      )}
+
+      <form onSubmit={onSubmit}>
+        <input
+          ref={inputRef}
+          id="new-todo-input"
+          data-cy="NewTodoField"
+          type="text"
+          className="todoapp__new-todo"
+          placeholder="What needs to be done?"
+          value={newTitle}
+          onChange={e => setNewTitle(e.target.value)}
+          disabled={isLoading}
+        />
+      </form>
+    </header>
+  );
+};
+
+export default Header;
diff --git a/src/components/TodoItem.tsx b/src/components/TodoItem.tsx
new file mode 100644
index 0000000000..131a433793
--- /dev/null
+++ b/src/components/TodoItem.tsx
@@ -0,0 +1,123 @@
+/* eslint-disable jsx-a11y/label-has-associated-control */
+import React from 'react';
+import classNames from 'classnames';
+import { Todo } from '../types/Todo';
+
+type TodoItemProps = {
+  todo: Todo;
+  isUpdating: boolean;
+  isEditing: boolean;
+  onEdit: (id: number | null) => void;
+  onUpdate: (title: string) => void;
+  onToggle: () => void;
+  onDelete: () => void;
+};
+
+export const TodoItem: React.FC<TodoItemProps> = ({
+  todo,
+  isUpdating,
+  isEditing,
+  onEdit,
+  onUpdate,
+  onToggle,
+  onDelete,
+}) => {
+  const [newTitle, setNewTitle] = React.useState(todo.title);
+  const handleSubmit = (event?: React.FormEvent) => {
+    event?.preventDefault();
+
+    if (isUpdating) {
+      return;
+    }
+
+    const trimmedTitle = newTitle.trim();
+
+    if (trimmedTitle === todo.title) {
+      onEdit(null);
+
+      return;
+    }
+
+    if (!trimmedTitle) {
+      onDelete();
+
+      return;
+    }
+
+    onUpdate(trimmedTitle);
+  };
+
+  return (
+    <div
+      data-cy="Todo"
+      className={classNames('todo', {
+        completed: todo.completed,
+        editing: isEditing,
+      })}
+    >
+      <label className="todo__status-label" htmlFor={`todo-status-${todo.id}`}>
+        <input
+          id={`todo-status-${todo.id}`}
+          type="checkbox"
+          className="todo__status"
+          checked={todo.completed}
+          onChange={onToggle}
+          data-cy="TodoStatus"
+        />
+      </label>
+
+      {!isEditing ? (
+        <span
+          data-cy="TodoTitle"
+          className="todo__title"
+          onDoubleClick={() => onEdit(todo.id)}
+        >
+          {todo.title}
+        </span>
+      ) : (
+        <input
+          data-cy="TodoTitleField"
+          type="text"
+          className="todo__edit"
+          value={newTitle}
+          onChange={e => setNewTitle(e.target.value)}
+          autoFocus
+          disabled={isUpdating}
+          onBlur={handleSubmit}
+          onKeyUp={e => {
+            if (e.key === 'Enter') {
+              handleSubmit();
+            }
+
+            if (e.key === 'Escape') {
+              setNewTitle(todo.title);
+              onEdit(null);
+            }
+          }}
+        />
+      )}
+
+      {!isEditing && (
+        <button
+          type="button"
+          className="todo__remove"
+          data-cy="TodoDelete"
+          onClick={onDelete}
+          disabled={isUpdating}
+        >
+          ×
+        </button>
+      )}
+
+      <div
+        data-cy="TodoLoader"
+        className={classNames('modal overlay', { 'is-active': isUpdating })}
+      >
+        <div className="modal-background has-background-white-ter" />
+        <div className="loader" />
+      </div>
+    </div>
+  );
+};
+
+export default TodoItem;
diff --git a/src/components/TodoList.tsx b/src/components/TodoList.tsx
new file mode 100644
index 0000000000..d9f1c678c9
--- /dev/null
+++ b/src/components/TodoList.tsx
@@ -0,0 +1,86 @@
+/* eslint-disable jsx-a11y/label-has-associated-control */
+import React from 'react';
+import { Todo } from '../types/Todo';
+import TodoItem from './TodoItem';
+
+type TodoListProps = {
+  todos: Todo[];
+  filter: 'all' | 'active' | 'completed';
+  tempTodo: Todo | null;
+  updatingIds: number[];
+  onToggle: (id: number) => void;
+  onDelete: (id: number) => void;
+  isLoading: boolean;
+  editingId: number | null;
+  onEdit: (id: number | null) => void;
+  onUpdate: (id: number, title: string) => void;
+};
+
+export const TodoList: React.FC<TodoListProps> = ({
+  todos,
+  filter,
+  tempTodo,
+  updatingIds,
+  onToggle,
+  onDelete,
+  editingId,
+  onEdit,
+  onUpdate,
+}) => {
+  const visibleTodos = todos.filter(todo => {
+    switch (filter) {
+      case 'active':
+        return !todo.completed;
+      case 'completed':
+        return todo.completed;
+      default:
+        return true;
+    }
+  });
+
+  return (
+    <section className="todoapp__main" data-cy="TodoList">
+      {visibleTodos.map(todo => (
+        <TodoItem
+          key={todo.id}
+          todo={todo}
+          isUpdating={updatingIds.includes(todo.id)}
+          onToggle={() => onToggle(todo.id)}
+          onDelete={() => onDelete(todo.id)}
+          isEditing={todo.id === editingId}
+          onEdit={onEdit}
+          onUpdate={(title: string) => onUpdate(todo.id, title)}
+        />
+      ))}
+
+      {tempTodo && (
+        <div data-cy="Todo" className="todo">
+          <label className="todo__status-label" htmlFor="temp-todo-status">
+            <input
+              id="temp-todo-status"
+              type="checkbox"
+              className="todo__status"
+              checked={false}
+              readOnly
+            />
+          </label>
+
+          <span data-cy="TodoTitle" className="todo__title">
+            {tempTodo.title}
+          </span>
+
+          <button type="button" className="todo__remove" data-cy="TodoDelete">
+            ×
+          </button>
+
+          <div data-cy="TodoLoader" className="modal overlay is-active">
+            <div className="modal-background has-background-white-ter" />
+            <div className="loader" />
+          </div>
+        </div>
+      )}
+    </section>
+  );
+};
+
+export default TodoList;
diff --git a/src/types/Todo.ts b/src/types/Todo.ts
new file mode 100644
index 0000000000..780afae02d
--- /dev/null
+++ b/src/types/Todo.ts
@@ -0,0 +1,6 @@
+export interface Todo {
+  id: number;
+  title: string;
+  completed: boolean;
+  userId: number;
+}
diff --git a/src/utils/fetchClient.ts b/src/utils/fetchClient.ts
new file mode 100644
index 0000000000..708ac4c17b
--- /dev/null
+++ b/src/utils/fetchClient.ts
@@ -0,0 +1,46 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
+const BASE_URL = 'https://mate.academy/students-api';
+
+// returns a promise resolved after a given delay
+function wait(delay: number) {
+  return new Promise(resolve => {
+    setTimeout(resolve, delay);
+  });
+}
+
+// To have autocompletion and avoid mistypes
+type RequestMethod = 'GET' | 'POST' | 'PATCH' | 'DELETE';
+
+function request<T>(
+  url: string,
+  method: RequestMethod = 'GET',
+  data: any = null, // we can send any data to the server
+): Promise<T> {
+  const options: RequestInit = { method };
+
+  if (data) {
+    // We add body and Content-Type only for the requests with data
+    options.body = JSON.stringify(data);
+    options.headers = {
+      'Content-Type': 'application/json; charset=UTF-8',
+    };
+  }
+
+  // DON'T change the delay it is required for tests
+  return wait(100)
+    .then(() => fetch(BASE_URL + url, options))
+    .then(response => {
+      if (!response.ok) {
+        throw new Error();
+      }
+
+      return response.json();
+    });
+}
+
+export const client = {
+  get: <T>(url: string) => request<T>(url),
+  post: <T>(url: string, data: any) => request<T>(url, 'POST', data),
+  patch: <T>(url: string, data: any) => request<T>(url, 'PATCH', data),
+  delete: (url: string) => request(url, 'DELETE'),
+};

From 6f00e458870ddf929d4caaf6c7497c0adfb3ea9f Mon Sep 17 00:00:00 2001
From: Horoshko Vitaliy <horoshko29@gmail.com>
Date: Mon, 9 Mar 2026 06:16:18 +0200
Subject: [PATCH 2/2] task solution #2

---
 src/App.tsx                 | 20 +++++++-------
 src/components/Footer.tsx   | 52 ++++++++++++++++---------------------
 src/components/TodoItem.tsx | 22 +++++++++-------
 src/components/TodoList.tsx |  7 ++---
 src/types/ErrorMessage.ts   |  8 ++++++
 src/types/Filter.ts         |  5 ++++
 6 files changed, 62 insertions(+), 52 deletions(-)
 create mode 100644 src/types/ErrorMessage.ts
 create mode 100644 src/types/Filter.ts

diff --git a/src/App.tsx b/src/App.tsx
index d4ea2ca7b5..a399fe5bf7 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -10,11 +10,13 @@ import Header from './components/Header';
 import TodoList from './components/TodoList';
 import Footer from './components/Footer';
 import ErrorNotification from './components/ErrorNotification';
+import { ErrorMessage } from './types/ErrorMessage';
+import { Filter } from './types/Filter';
 
 export const App: React.FC = () => {
   const [todos, setTodos] = useState<Todo[]>([]);
   const [error, setError] = useState('');
-  const [filter, setFilter] = useState<'all' | 'active' | 'completed'>('all');
+  const [filter, setFilter] = useState<Filter>(Filter.ALL);
   const [loading, setLoading] = useState(false);
   const [tempTodo, setTempTodo] = useState<Todo | null>(null);
   const [updatingIds, setUpdatingIds] = useState<number[]>([]);
@@ -34,7 +36,7 @@ export const App: React.FC = () => {
       .then(todosFromServer => {
         setTimeout(() => setTodos(todosFromServer), 150);
       })
-      .catch(() => setError('Unable to load todos'))
+      .catch(() => setError(ErrorMessage.LOAD_TODOS))
       .finally(() => setLoading(false));
   }, []);
 
@@ -57,7 +59,7 @@ export const App: React.FC = () => {
     const trimmed = newTitle.trim();
 
     if (!trimmed) {
-      setError('Title should not be empty');
+      setError(ErrorMessage.EMPTY_TITLE);
 
       return;
     }
@@ -84,7 +86,7 @@ export const App: React.FC = () => {
       setNewTitle('');
       newTodoRef.current?.focus();
     } catch {
-      setError('Unable to add a todo');
+      setError(ErrorMessage.ADD_TODO);
       setTempTodo(null);
       newTodoRef.current?.focus();
     } finally {
@@ -100,7 +102,7 @@ export const App: React.FC = () => {
 
       newTodoRef.current?.focus();
     } catch {
-      setError('Unable to delete a todo');
+      setError(ErrorMessage.DELETE_TODO);
     } finally {
       setUpdatingIds(prev => prev.filter(i => i !== id));
     }
@@ -128,7 +130,7 @@ export const App: React.FC = () => {
         }),
       );
     } catch {
-      setError('Unable to update a todo');
+      setError(ErrorMessage.UPDATE_TODO);
     } finally {
       setUpdatingIds(prev => prev.filter(i => i !== id));
     }
@@ -143,7 +145,7 @@ export const App: React.FC = () => {
       setTodos(prev => prev.map(todo => (todo.id === id ? updatedTodo : todo)));
       setEditingId(null);
     } catch {
-      setError('Unable to update a todo');
+      setError(ErrorMessage.UPDATE_TODO);
     } finally {
       setUpdatingIds(prev => prev.filter(i => i !== id));
     }
@@ -175,7 +177,7 @@ export const App: React.FC = () => {
         }),
       );
     } catch {
-      setError('Unable to toggle all todos');
+      setError(ErrorMessage.TOGGLE_ALL);
     } finally {
       setUpdatingIds(prev => prev.filter(id => !idsToUpdate.includes(id)));
     }
@@ -212,7 +214,7 @@ export const App: React.FC = () => {
     if (!hasError) {
       newTodoRef.current?.focus();
     } else {
-      setError('Unable to delete a todo');
+      setError(ErrorMessage.DELETE_TODO);
     }
   };
 
diff --git a/src/components/Footer.tsx b/src/components/Footer.tsx
index 0db676c0df..810374a49e 100644
--- a/src/components/Footer.tsx
+++ b/src/components/Footer.tsx
@@ -1,14 +1,21 @@
 import React from 'react';
 import classNames from 'classnames';
+import { Filter } from '../types/Filter';
 
 type FooterProps = {
   activeCount: number;
-  filter: 'all' | 'active' | 'completed';
-  setFilter: (filter: 'all' | 'active' | 'completed') => void;
+  filter: Filter;
+  setFilter: (filter: Filter) => void;
   hasCompleted: boolean;
   onClearCompleted: () => void;
 };
 
+const filters = [
+  { value: Filter.ALL, label: 'All', href: '#/' },
+  { value: Filter.ACTIVE, label: 'Active', href: '#/active' },
+  { value: Filter.COMPLETED, label: 'Completed', href: '#/completed' },
+];
+
 export const Footer: React.FC<FooterProps> = ({
   activeCount,
   filter,
@@ -23,34 +30,19 @@ export const Footer: React.FC<FooterProps> = ({
       </span>
 
       <nav className="filter" data-cy="Filter">
-        <a
-          href="#/"
-          className={classNames('filter__link', { selected: filter === 'all' })}
-          data-cy="FilterLinkAll"
-          onClick={() => setFilter('all')}
-        >
-          All
-        </a>
-        <a
-          href="#/active"
-          className={classNames('filter__link', {
-            selected: filter === 'active',
-          })}
-          data-cy="FilterLinkActive"
-          onClick={() => setFilter('active')}
-        >
-          Active
-        </a>
-        <a
-          href="#/completed"
-          className={classNames('filter__link', {
-            selected: filter === 'completed',
-          })}
-          data-cy="FilterLinkCompleted"
-          onClick={() => setFilter('completed')}
-        >
-          Completed
-        </a>
+        {filters.map(item => (
+          <a
+            key={item.value}
+            href={item.href}
+            className={classNames('filter__link', {
+              selected: filter === item.value,
+            })}
+            data-cy={`FilterLink${item.label}`}
+            onClick={() => setFilter(item.value)}
+          >
+            {item.label}
+          </a>
+        ))}
       </nav>
 
       <button
diff --git a/src/components/TodoItem.tsx b/src/components/TodoItem.tsx
index 131a433793..add227f264 100644
--- a/src/components/TodoItem.tsx
+++ b/src/components/TodoItem.tsx
@@ -47,6 +47,17 @@ export const TodoItem: React.FC<TodoItemProps> = ({
     onUpdate(trimmedTitle);
   };
 
+  const handleKeyUp = (e: React.KeyboardEvent<HTMLInputElement>) => {
+    if (e.key === 'Enter') {
+      handleSubmit();
+    }
+
+    if (e.key === 'Escape') {
+      setNewTitle(todo.title);
+      onEdit(null);
+    }
+  };
+
   return (
     <div
       data-cy="Todo"
@@ -84,16 +95,7 @@ export const TodoItem: React.FC<TodoItemProps> = ({
           autoFocus
           disabled={isUpdating}
           onBlur={handleSubmit}
-          onKeyUp={e => {
-            if (e.key === 'Enter') {
-              handleSubmit();
-            }
-
-            if (e.key === 'Escape') {
-              setNewTitle(todo.title);
-              onEdit(null);
-            }
-          }}
+          onKeyUp={handleKeyUp}
         />
       )}
 
diff --git a/src/components/TodoList.tsx b/src/components/TodoList.tsx
index d9f1c678c9..e1a2732df0 100644
--- a/src/components/TodoList.tsx
+++ b/src/components/TodoList.tsx
@@ -2,10 +2,11 @@
 import React from 'react';
 import { Todo } from '../types/Todo';
 import TodoItem from './TodoItem';
+import { Filter } from '../types/Filter';
 
 type TodoListProps = {
   todos: Todo[];
-  filter: 'all' | 'active' | 'completed';
+  filter: Filter;
   tempTodo: Todo | null;
   updatingIds: number[];
   onToggle: (id: number) => void;
@@ -29,9 +30,9 @@ export const TodoList: React.FC<TodoListProps> = ({
 }) => {
   const visibleTodos = todos.filter(todo => {
     switch (filter) {
-      case 'active':
+      case Filter.ACTIVE:
         return !todo.completed;
-      case 'completed':
+      case Filter.COMPLETED:
         return todo.completed;
       default:
         return true;
diff --git a/src/types/ErrorMessage.ts b/src/types/ErrorMessage.ts
new file mode 100644
index 0000000000..414defe058
--- /dev/null
+++ b/src/types/ErrorMessage.ts
@@ -0,0 +1,8 @@
+export enum ErrorMessage {
+  LOAD_TODOS = 'Unable to load todos',
+  ADD_TODO = 'Unable to add a todo',
+  DELETE_TODO = 'Unable to delete a todo',
+  UPDATE_TODO = 'Unable to update a todo',
+  TOGGLE_ALL = 'Unable to toggle all todos',
+  EMPTY_TITLE = 'Title should not be empty',
+}
diff --git a/src/types/Filter.ts b/src/types/Filter.ts
new file mode 100644
index 0000000000..6dad7340f0
--- /dev/null
+++ b/src/types/Filter.ts
@@ -0,0 +1,5 @@
+export enum Filter {
+  ALL = 'all',
+  ACTIVE = 'active',
+  COMPLETED = 'completed',
+}