async function submitAuthForm(endpoint, email, password, errorElement) {
    errorElement.hidden = true;
    errorElement.textContent = '';

    const response = await fetch(endpoint, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        credentials: 'same-origin',
        body: JSON.stringify({ email, password }),
    });

    if (response.ok) {
        window.location.href = '/home';
        return;
    }

    let message = 'Something went wrong';
    try {
        const body = await response.json();
        if (body.error) {
            message = body.error;
        }
    } catch (parseError) {
        // fall through to generic message
    }
    errorElement.textContent = message;
    errorElement.hidden = false;
}

async function logout() {
    await fetch('/api/auth/logout', {
        method: 'POST',
        credentials: 'same-origin',
    });
    window.location.href = '/login';
}

document.addEventListener('DOMContentLoaded', () => {
    const loginForm = document.getElementById('login-form');
    if (loginForm !== null) {
        const errorElement = document.getElementById('login-error');
        loginForm.addEventListener('submit', async (submitEvent) => {
            submitEvent.preventDefault();
            const email = document.getElementById('email').value;
            const password = document.getElementById('password').value;
            await submitAuthForm(
                '/api/auth/login',
                email,
                password,
                errorElement,
            );
        });
    }

    const registerForm = document.getElementById('register-form');
    if (registerForm !== null) {
        const errorElement = document.getElementById('register-error');
        registerForm.addEventListener('submit', async (submitEvent) => {
            submitEvent.preventDefault();
            const email = document.getElementById('email').value;
            const password = document.getElementById('password').value;
            await submitAuthForm(
                '/api/auth/register',
                email,
                password,
                errorElement,
            );
        });
    }

    const logoutButton = document.getElementById('logout');
    if (logoutButton !== null) {
        logoutButton.addEventListener('click', logout);
    }
});