document.getElementById('bmi-form').addEventListener('submit', function(e) {
    e.preventDefault();

    const height = document.getElementById('height').value;
    const weight = document.getElementById('weight').value;
    const resultDiv = document.getElementById('result');

    fetch('/calculate', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ height, weight })
    })
    .then(response => response.json())
    .then(data => {
        if (data.error) {
            resultDiv.style.display = 'block';
            resultDiv.style.color = '#cc0000';
            resultDiv.textContent = data.error;
        } else {
            resultDiv.style.display = 'block';
            resultDiv.style.color = '#003366';
            resultDiv.textContent = `Ваш BMI: ${data.bmi}`;
        }
    })
    .catch(() => {
        resultDiv.style.display = 'block';
        resultDiv.textContent = 'Ошибка соединения с сервером.';
        resultDiv.style.color = '#cc0000';
    });
});