From 12ed50c4c79ca635371c1b9e014c871bac9b5615 Mon Sep 17 00:00:00 2001
From: Anastasia <nastyapugach24@gmail.com>
Date: Tue, 24 Feb 2026 16:58:58 +0100
Subject: [PATCH 1/2] task

---
 src/App.tsx                          | 227 +++++++++++++++++++++++++--
 src/api/todos.ts                     |  24 +++
 src/components/ErrorNotification.tsx |  26 +++
 src/components/Footer.tsx            |  71 +++++++++
 src/components/Header.tsx            |  55 +++++++
 src/components/TodoItem.tsx          | 143 +++++++++++++++++
 src/components/TodoList.tsx          |  45 ++++++
 src/types/ErrorMessage.ts            |   7 +
 src/types/FilterStatus.ts            |   5 +
 src/types/Todo.ts                    |   6 +
 src/utils/fetchClient.ts             |  45 ++++++
 11 files changed, 640 insertions(+), 14 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/ErrorMessage.ts
 create mode 100644 src/types/FilterStatus.ts
 create mode 100644 src/types/Todo.ts
 create mode 100644 src/utils/fetchClient.ts

diff --git a/src/App.tsx b/src/App.tsx
index 81e011f432..94f5b565dd 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,26 +1,225 @@
 /* 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, { useState, useEffect } from 'react';
 import { UserWarning } from './UserWarning';
+import * as todoService from './api/todos';
+import { Todo } from './types/Todo';
+import { FilterStatus } from './types/FilterStatus';
+import { ErrorMessage } from './types/ErrorMessage';
 
-const USER_ID = 0;
+import { ErrorNotification } from './components/ErrorNotification';
+
+import { Header } from './components/Header';
+import { TodoList } from './components/TodoList';
+import { Footer } from './components/Footer';
 
 export const App: React.FC = () => {
-  if (!USER_ID) {
+  const [todos, setTodos] = useState<Todo[]>([]);
+  const [errorMessage, setErrorMessage] = useState('');
+  const [filter, setFilter] = useState<FilterStatus>(FilterStatus.All);
+  const [newTodoTitle, setNewTodoTitle] = useState('');
+  const [tempTodo, setTempTodo] = useState<Todo | null>(null);
+  const [isLoading, setIsLoading] = useState(false);
+  const [loadingIds, setLoadingIds] = useState<number[]>([]);
+
+  const todoFieldRef = React.useRef<HTMLInputElement>(null);
+
+  const activeTodosCount = todos.filter(todo => !todo.completed).length;
+
+  const showError = (message: string) => {
+    setErrorMessage(message);
+    setTimeout(() => setErrorMessage(''), 3000);
+  };
+
+  useEffect(() => {
+    const loadTodos = async () => {
+      setErrorMessage('');
+
+      try {
+        const data = await todoService.getTodos();
+
+        setTodos(data);
+      } catch {
+        showError(ErrorMessage.Load);
+      }
+    };
+
+    loadTodos();
+    todoFieldRef.current?.focus();
+  }, []);
+
+  useEffect(() => {
+    if (!isLoading) {
+      todoFieldRef.current?.focus();
+    }
+  }, [isLoading, todos.length]);
+
+  const visibleTodos = todos.filter(todo => {
+    if (filter === FilterStatus.Active) {
+      return !todo.completed;
+    }
+
+    if (filter === FilterStatus.Completed) {
+      return todo.completed;
+    }
+
+    return true;
+  });
+
+  if (!todoService.USER_ID) {
     return <UserWarning />;
   }
 
+  const handleFormSubmit = async (event: React.FormEvent) => {
+    event.preventDefault();
+
+    setErrorMessage('');
+
+    const trimmedTodoTitle = newTodoTitle.trim();
+
+    if (!trimmedTodoTitle) {
+      showError(ErrorMessage.Title);
+
+      return;
+    }
+
+    setIsLoading(true);
+
+    const newTempTodo = {
+      id: 0,
+      userId: todoService.USER_ID,
+      title: trimmedTodoTitle,
+      completed: false,
+    };
+
+    setTempTodo(newTempTodo);
+
+    try {
+      const newTodo = await todoService.createTodo(trimmedTodoTitle);
+
+      setTodos(prev => [...prev, newTodo]);
+      setNewTodoTitle('');
+    } catch {
+      showError(ErrorMessage.Add);
+    } finally {
+      setIsLoading(false);
+      setTempTodo(null);
+    }
+  };
+
+  const onDeleteTodo = async (todoId: number) => {
+    setErrorMessage('');
+
+    setLoadingIds(prev => [...prev, todoId]);
+
+    try {
+      await todoService.deleteTodo(todoId);
+      setTodos(prev => prev.filter(todo => todo.id !== todoId));
+    } catch {
+      showError('Unable to delete a todo');
+    } finally {
+      setLoadingIds(prev => prev.filter(id => id !== todoId));
+    }
+  };
+
+  const onToggleTodo = async (todo: Todo) => {
+    setErrorMessage('');
+    setLoadingIds(prev => [...prev, todo.id]);
+
+    try {
+      const updatedTodo = await todoService.updateTodo(todo.id, {
+        completed: !todo.completed,
+      });
+
+      setTodos(prev => prev.map(t => (t.id === todo.id ? updatedTodo : t)));
+    } catch {
+      showError('Unable to update a todo');
+    } finally {
+      setLoadingIds(prev => prev.filter(id => id !== todo.id));
+    }
+  };
+
+  const onUpdateTodo = async (todoToUpdate: Todo, newTitle: string) => {
+    setErrorMessage('');
+    setLoadingIds(prev => [...prev, todoToUpdate.id]);
+
+    try {
+      const updatedTodo = await todoService.updateTodo(todoToUpdate.id, {
+        title: newTitle,
+      });
+
+      setTodos(prev =>
+        prev.map(t => (t.id === todoToUpdate.id ? updatedTodo : t)),
+      );
+    } catch (error) {
+      showError(ErrorMessage.Update);
+      throw error;
+    } finally {
+      setLoadingIds(prev => prev.filter(id => id !== todoToUpdate.id));
+    }
+  };
+
+  const clearCompleted = () => {
+    const completedTodos = todos.filter(t => t.completed);
+
+    completedTodos.forEach(todo => {
+      onDeleteTodo(todo.id);
+    });
+  };
+
+  const onToggleAll = () => {
+    const areAllCompleted = todos.every(todo => todo.completed);
+    const todosToUpdate = todos.filter(
+      todo => todo.completed === areAllCompleted,
+    );
+
+    todosToUpdate.forEach(todo => onToggleTodo(todo));
+  };
+
   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
+          ref={todoFieldRef}
+          title={newTodoTitle}
+          onTitleChange={setNewTodoTitle}
+          onSubmit={handleFormSubmit}
+          isToggleAllActive={
+            todos.length > 0 && todos.every(todo => todo.completed)
+          }
+          isLoading={isLoading}
+          onToggleAll={onToggleAll}
+          hasTodos={todos.length > 0}
+        />
+
+        {(todos.length > 0 || tempTodo) && (
+          <>
+            <TodoList
+              todos={visibleTodos}
+              loadingIds={loadingIds}
+              tempTodo={tempTodo}
+              onDeleteTodo={onDeleteTodo}
+              onToggleTodo={onToggleTodo}
+              onUpdateTodo={onUpdateTodo}
+            />
+            <Footer
+              activeTodosCount={activeTodosCount}
+              filter={filter}
+              setFilter={setFilter}
+              hasCompleted={todos.some(todo => todo.completed)}
+              onClearCompleted={clearCompleted}
+            />
+          </>
+        )}
+      </div>
+
+      <ErrorNotification
+        message={errorMessage}
+        onClose={() => setErrorMessage('')}
+      />
+    </div>
   );
 };
diff --git a/src/api/todos.ts b/src/api/todos.ts
new file mode 100644
index 0000000000..e982fa4541
--- /dev/null
+++ b/src/api/todos.ts
@@ -0,0 +1,24 @@
+import { Todo } from '../types/Todo';
+import { client } from '../utils/fetchClient';
+
+export const USER_ID = 4002;
+
+export const getTodos = () => {
+  return client.get<Todo[]>(`/todos?userId=${USER_ID}`);
+};
+
+export const createTodo = (title: string) => {
+  return client.post<Todo>('/todos', {
+    title,
+    userId: USER_ID,
+    completed: false,
+  });
+};
+
+export const deleteTodo = (todoId: number) => {
+  return client.delete(`/todos/${todoId}`);
+};
+
+export const updateTodo = (todoId: number, data: Partial<Todo>) => {
+  return client.patch<Todo>(`/todos/${todoId}`, data);
+};
diff --git a/src/components/ErrorNotification.tsx b/src/components/ErrorNotification.tsx
new file mode 100644
index 0000000000..1a5a9279b3
--- /dev/null
+++ b/src/components/ErrorNotification.tsx
@@ -0,0 +1,26 @@
+import React from 'react';
+import cn from 'classnames';
+
+type Props = {
+  message: string;
+  onClose: () => void;
+};
+
+export const ErrorNotification: React.FC<Props> = ({ message, onClose }) => {
+  return (
+    <div
+      data-cy="ErrorNotification"
+      className={cn('notification is-danger is-light has-text-weight-normal', {
+        hidden: !message,
+      })}
+    >
+      <button
+        data-cy="HideErrorButton"
+        type="button"
+        className="delete"
+        onClick={onClose}
+      />
+      {message}
+    </div>
+  );
+};
diff --git a/src/components/Footer.tsx b/src/components/Footer.tsx
new file mode 100644
index 0000000000..f5222a0f24
--- /dev/null
+++ b/src/components/Footer.tsx
@@ -0,0 +1,71 @@
+import React from 'react';
+import cn from 'classnames';
+import { FilterStatus } from '../types/FilterStatus';
+
+type Props = {
+  activeTodosCount: number;
+  filter: FilterStatus;
+  setFilter: (status: FilterStatus) => void;
+  hasCompleted: boolean;
+  onClearCompleted: () => void;
+};
+
+const filterLinks = [
+  { status: FilterStatus.All, label: 'All', href: '#/', cy: 'FilterLinkAll' },
+
+  {
+    status: FilterStatus.Active,
+    label: 'Active',
+    href: '#/active',
+    cy: 'FilterLinkActive',
+  },
+  {
+    status: FilterStatus.Completed,
+    label: 'Completed',
+    href: '#/completed',
+    cy: 'FilterLinkCompleted',
+  },
+];
+
+export const Footer: React.FC<Props> = ({
+  activeTodosCount,
+  filter,
+  setFilter,
+  hasCompleted,
+  onClearCompleted,
+}) => {
+  return (
+    <footer className="todoapp__footer" data-cy="Footer">
+      <span className="todo-count" data-cy="TodosCounter">
+        {activeTodosCount} items left
+      </span>
+
+      {/* Active link should have the 'selected' class */}
+      <nav className="filter" data-cy="Filter">
+        {filterLinks.map(({ status, label, href, cy }) => (
+          <a
+            key={status}
+            href={href}
+            className={cn('filter__link', {
+              selected: filter === status,
+            })}
+            onClick={() => setFilter(status)}
+            data-cy={cy}
+          >
+            {label}
+          </a>
+        ))}
+      </nav>
+
+      <button
+        type="button"
+        className="todoapp__clear-completed"
+        data-cy="ClearCompletedButton"
+        onClick={onClearCompleted}
+        disabled={!hasCompleted}
+      >
+        Clear completed
+      </button>
+    </footer>
+  );
+};
diff --git a/src/components/Header.tsx b/src/components/Header.tsx
new file mode 100644
index 0000000000..d13e889bc2
--- /dev/null
+++ b/src/components/Header.tsx
@@ -0,0 +1,55 @@
+import React, { forwardRef } from 'react';
+import cn from 'classnames';
+
+type Props = {
+  title: string;
+  onTitleChange: (value: string) => void;
+  onSubmit: (event: React.FormEvent) => void;
+  isToggleAllActive: boolean;
+  isLoading: boolean;
+  onToggleAll: () => void;
+  hasTodos: boolean;
+};
+
+export const Header = forwardRef<HTMLInputElement, Props>(
+  (
+    {
+      title,
+      onTitleChange,
+      onSubmit,
+      isToggleAllActive,
+      isLoading,
+      onToggleAll,
+      hasTodos,
+    },
+    ref,
+  ) => (
+    <header className="todoapp__header">
+      {hasTodos && (
+        <button
+          type="button"
+          className={cn('todoapp__toggle-all', {
+            active: isToggleAllActive,
+          })}
+          data-cy="ToggleAllButton"
+          onClick={onToggleAll}
+        />
+      )}
+
+      <form onSubmit={onSubmit}>
+        <input
+          ref={ref}
+          value={title}
+          data-cy="NewTodoField"
+          type="text"
+          className="todoapp__new-todo"
+          placeholder="What needs to be done?"
+          onChange={event => onTitleChange(event.target.value)}
+          disabled={isLoading}
+        />
+      </form>
+    </header>
+  ),
+);
+
+Header.displayName = 'Header';
diff --git a/src/components/TodoItem.tsx b/src/components/TodoItem.tsx
new file mode 100644
index 0000000000..c15c66c734
--- /dev/null
+++ b/src/components/TodoItem.tsx
@@ -0,0 +1,143 @@
+/* eslint-disable max-len */
+/* eslint-disable jsx-a11y/label-has-associated-control */
+/* eslint-disable jsx-a11y/control-has-associated-label */
+import React, { useState, useEffect, useRef } from 'react';
+import cn from 'classnames';
+import { Todo } from '../types/Todo';
+
+type Props = {
+  todo: Todo;
+  isLoading: boolean;
+  onDeleteTodo: (todoId: number) => void;
+  onToggleTodo: (todo: Todo) => void;
+  onUpdateTodo: (todo: Todo, newTitle: string) => Promise<void>;
+};
+
+export const TodoItem: React.FC<Props> = ({
+  todo,
+  isLoading,
+  onDeleteTodo,
+  onToggleTodo,
+  onUpdateTodo,
+}) => {
+  const [isEditing, setIsEditing] = useState(false);
+  const [title, setTitle] = useState(todo.title);
+
+  const editFieldRef = useRef<HTMLInputElement>(null);
+
+  useEffect(() => {
+    if (isEditing) {
+      editFieldRef.current?.focus();
+    }
+  }, [isEditing]);
+
+  useEffect(() => {
+    setTitle(todo.title);
+  }, [todo.title]);
+
+  const handleEdit = () => {
+    setIsEditing(true);
+  };
+
+  const handleCancel = () => {
+    setIsEditing(false);
+    setTitle(todo.title);
+  };
+
+  const handleKeyDown = (event: React.KeyboardEvent) => {
+    if (event.key === 'Escape') {
+      handleCancel();
+    }
+
+    if (event.key === 'Enter') {
+      // eslint-disable-next-line @typescript-eslint/no-use-before-define
+      handleSubmit(event);
+    }
+  };
+
+  const handleSubmit = async (event?: React.BaseSyntheticEvent) => {
+    event?.preventDefault();
+
+    if (isLoading) {
+      return;
+    }
+
+    const trimmedTitle = title.trim();
+
+    if (trimmedTitle === todo.title) {
+      setIsEditing(false);
+
+      return;
+    }
+
+    if (!trimmedTitle) {
+      onDeleteTodo(todo.id);
+
+      return;
+    }
+
+    try {
+      await onUpdateTodo(todo, trimmedTitle);
+      setIsEditing(false);
+    } catch (error) {}
+  };
+
+  return (
+    <div data-cy="Todo" className={cn('todo', { completed: todo.completed })}>
+      <label className="todo__status-label">
+        <input
+          data-cy="TodoStatus"
+          type="checkbox"
+          className="todo__status"
+          checked={todo.completed}
+          onChange={() => onToggleTodo(todo)}
+        />
+      </label>
+
+      {isEditing ? (
+        <form onSubmit={handleSubmit}>
+          <input
+            ref={editFieldRef}
+            data-cy="TodoTitleField"
+            type="text"
+            className="todo__title-field"
+            value={title}
+            onChange={event => setTitle(event.target.value)}
+            onKeyDown={handleKeyDown}
+            onBlur={handleSubmit}
+            autoFocus
+            disabled={isLoading}
+          />
+        </form>
+      ) : (
+        <>
+          <span
+            data-cy="TodoTitle"
+            className="todo__title"
+            onDoubleClick={handleEdit}
+          >
+            {todo.title}
+          </span>
+          <button
+            type="button"
+            className="todo__remove"
+            data-cy="TodoDelete"
+            onClick={() => onDeleteTodo(todo.id)}
+          >
+            ×
+          </button>
+        </>
+      )}
+
+      <div
+        data-cy="TodoLoader"
+        className={cn('modal overlay', {
+          'is-active': isLoading,
+        })}
+      >
+        <div className="modal-background has-background-white-ter" />
+        <div className="loader" />
+      </div>
+    </div>
+  );
+};
diff --git a/src/components/TodoList.tsx b/src/components/TodoList.tsx
new file mode 100644
index 0000000000..71453907f5
--- /dev/null
+++ b/src/components/TodoList.tsx
@@ -0,0 +1,45 @@
+/* eslint-disable jsx-a11y/label-has-associated-control */
+/* eslint-disable jsx-a11y/control-has-associated-label */
+import React from 'react';
+import { Todo } from '../types/Todo';
+import { TodoItem } from './TodoItem';
+
+type Props = {
+  todos: Todo[];
+  loadingIds: number[];
+  tempTodo: Todo | null;
+  onDeleteTodo: (todoId: number) => void;
+  onToggleTodo: (todo: Todo) => void;
+  onUpdateTodo: (todo: Todo, newTitle: string) => Promise<void>;
+};
+
+export const TodoList: React.FC<Props> = ({
+  todos,
+  loadingIds,
+  tempTodo,
+  onDeleteTodo,
+  onToggleTodo,
+  onUpdateTodo,
+}) => (
+  <section className="todoapp__main" data-cy="TodoList">
+    {todos.map(todo => (
+      <TodoItem
+        key={todo.id}
+        todo={todo}
+        isLoading={loadingIds.includes(todo.id)}
+        onDeleteTodo={onDeleteTodo}
+        onToggleTodo={onToggleTodo}
+        onUpdateTodo={onUpdateTodo}
+      />
+    ))}
+    {tempTodo && (
+      <TodoItem
+        todo={tempTodo}
+        isLoading={true}
+        onDeleteTodo={onDeleteTodo}
+        onToggleTodo={onToggleTodo}
+        onUpdateTodo={onUpdateTodo}
+      />
+    )}
+  </section>
+);
diff --git a/src/types/ErrorMessage.ts b/src/types/ErrorMessage.ts
new file mode 100644
index 0000000000..91de57ea7f
--- /dev/null
+++ b/src/types/ErrorMessage.ts
@@ -0,0 +1,7 @@
+export enum ErrorMessage {
+  Load = 'Unable to load todos',
+  Title = 'Title should not be empty',
+  Add = 'Unable to add a todo',
+  Delete = 'Unable to delete a todo',
+  Update = 'Unable to update a todo',
+}
diff --git a/src/types/FilterStatus.ts b/src/types/FilterStatus.ts
new file mode 100644
index 0000000000..13d1a2739c
--- /dev/null
+++ b/src/types/FilterStatus.ts
@@ -0,0 +1,5 @@
+export enum FilterStatus {
+  All = 'all',
+  Active = 'active',
+  Completed = 'completed',
+}
diff --git a/src/types/Todo.ts b/src/types/Todo.ts
new file mode 100644
index 0000000000..3f52a5fdde
--- /dev/null
+++ b/src/types/Todo.ts
@@ -0,0 +1,6 @@
+export interface Todo {
+  id: number;
+  userId: number;
+  title: string;
+  completed: boolean;
+}
diff --git a/src/utils/fetchClient.ts b/src/utils/fetchClient.ts
new file mode 100644
index 0000000000..5620945028
--- /dev/null
+++ b/src/utils/fetchClient.ts
@@ -0,0 +1,45 @@
+/* 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',
+    };
+  }
+
+  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 c34ca94127efe196a3c0d3d2da754b554e6fe65d Mon Sep 17 00:00:00 2001
From: Anastasia <nastyapugach24@gmail.com>
Date: Tue, 24 Feb 2026 19:23:45 +0100
Subject: [PATCH 2/2] changed App and ErrorNotification

---
 src/App.tsx                          | 26 +++++++++++++-------------
 src/components/ErrorNotification.tsx |  3 ++-
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/src/App.tsx b/src/App.tsx
index 94f5b565dd..87ab2f0014 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -16,7 +16,7 @@ import { Footer } from './components/Footer';
 
 export const App: React.FC = () => {
   const [todos, setTodos] = useState<Todo[]>([]);
-  const [errorMessage, setErrorMessage] = useState('');
+  const [errorMessage, setErrorMessage] = useState<ErrorMessage | null>(null);
   const [filter, setFilter] = useState<FilterStatus>(FilterStatus.All);
   const [newTodoTitle, setNewTodoTitle] = useState('');
   const [tempTodo, setTempTodo] = useState<Todo | null>(null);
@@ -27,14 +27,14 @@ export const App: React.FC = () => {
 
   const activeTodosCount = todos.filter(todo => !todo.completed).length;
 
-  const showError = (message: string) => {
+  const showError = (message: ErrorMessage) => {
     setErrorMessage(message);
-    setTimeout(() => setErrorMessage(''), 3000);
+    setTimeout(() => setErrorMessage(null), 3000);
   };
 
   useEffect(() => {
     const loadTodos = async () => {
-      setErrorMessage('');
+      setErrorMessage(null);
 
       try {
         const data = await todoService.getTodos();
@@ -74,7 +74,7 @@ export const App: React.FC = () => {
   const handleFormSubmit = async (event: React.FormEvent) => {
     event.preventDefault();
 
-    setErrorMessage('');
+    setErrorMessage(null);
 
     const trimmedTodoTitle = newTodoTitle.trim();
 
@@ -109,7 +109,7 @@ export const App: React.FC = () => {
   };
 
   const onDeleteTodo = async (todoId: number) => {
-    setErrorMessage('');
+    setErrorMessage(null);
 
     setLoadingIds(prev => [...prev, todoId]);
 
@@ -117,14 +117,14 @@ export const App: React.FC = () => {
       await todoService.deleteTodo(todoId);
       setTodos(prev => prev.filter(todo => todo.id !== todoId));
     } catch {
-      showError('Unable to delete a todo');
+      showError(ErrorMessage.Delete);
     } finally {
       setLoadingIds(prev => prev.filter(id => id !== todoId));
     }
   };
 
   const onToggleTodo = async (todo: Todo) => {
-    setErrorMessage('');
+    setErrorMessage(null);
     setLoadingIds(prev => [...prev, todo.id]);
 
     try {
@@ -134,14 +134,14 @@ export const App: React.FC = () => {
 
       setTodos(prev => prev.map(t => (t.id === todo.id ? updatedTodo : t)));
     } catch {
-      showError('Unable to update a todo');
+      showError(ErrorMessage.Update);
     } finally {
       setLoadingIds(prev => prev.filter(id => id !== todo.id));
     }
   };
 
   const onUpdateTodo = async (todoToUpdate: Todo, newTitle: string) => {
-    setErrorMessage('');
+    setErrorMessage(null);
     setLoadingIds(prev => [...prev, todoToUpdate.id]);
 
     try {
@@ -192,10 +192,10 @@ export const App: React.FC = () => {
           }
           isLoading={isLoading}
           onToggleAll={onToggleAll}
-          hasTodos={todos.length > 0}
+          hasTodos={!!todos.length}
         />
 
-        {(todos.length > 0 || tempTodo) && (
+        {(!!todos.length || tempTodo) && (
           <>
             <TodoList
               todos={visibleTodos}
@@ -218,7 +218,7 @@ export const App: React.FC = () => {
 
       <ErrorNotification
         message={errorMessage}
-        onClose={() => setErrorMessage('')}
+        onClose={() => setErrorMessage(null)}
       />
     </div>
   );
diff --git a/src/components/ErrorNotification.tsx b/src/components/ErrorNotification.tsx
index 1a5a9279b3..79a7fcc0ae 100644
--- a/src/components/ErrorNotification.tsx
+++ b/src/components/ErrorNotification.tsx
@@ -1,8 +1,9 @@
 import React from 'react';
 import cn from 'classnames';
+import { ErrorMessage } from '../types/ErrorMessage';
 
 type Props = {
-  message: string;
+  message: ErrorMessage | null;
   onClose: () => void;
 };