function calculateGCD(a, b) {
    a = Math.abs(a);
    b = Math.abs(b);
    
    while (b !== 0) {
        let temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}



function reduceFraction(numerator, denominator) {
    
    if (denominator === 0) {
        return { error: "Знаменатель не может быть нулем!" };
    }
    
    
    if (numerator === 0) {
        return { numerator: 0, denominator: 1 };
    }
    
    
    const gcd = calculateGCD(numerator, denominator);
    
    
    let newNum = numerator / gcd;
    let newDen = denominator / gcd;
    
    
    if (newDen < 0) {
        newNum = -newNum;
        newDen = -newDen;
    }
    
    return { numerator: newNum, denominator: newDen };
}



function addFractions(num1, den1, num2, den2) {
    
    const resultNum = num1 * den2 + num2 * den1;
    const resultDen = den1 * den2;
    return reduceFraction(resultNum, resultDen);
}



function subtractFractions(num1, den1, num2, den2) {
    
    const resultNum = num1 * den2 - num2 * den1;
    const resultDen = den1 * den2;
    return reduceFraction(resultNum, resultDen);
}



function multiplyFractions(num1, den1, num2, den2) {
    
    const resultNum = num1 * num2;
    const resultDen = den1 * den2;
    return reduceFraction(resultNum, resultDen);
}



function divideFractions(num1, den1, num2, den2) {
    
    
    if (num2 === 0) {
        return { error: "Нельзя делить на ноль!" };
    }
    const resultNum = num1 * den2;
    const resultDen = den1 * num2;
    return reduceFraction(resultNum, resultDen);
}



function displayResult(result) {
    const resultDisplay = document.getElementById('result-display');
    const resultNum = document.getElementById('result-num');
    const resultDen = document.getElementById('result-den');
    const resultText = document.getElementById('result-text');
    const errorMessage = document.getElementById('error-message');
    const placeholder = document.getElementById('placeholder-text');
    
    
    resultDisplay.classList.add('hidden');
    resultText.classList.add('hidden');
    errorMessage.classList.add('hidden');
    placeholder.classList.add('hidden');
    
    
    if (result.error) {
        errorMessage.textContent = result.error;
        errorMessage.classList.remove('hidden');
        return;
    }
    
    
    resultNum.textContent = result.numerator;
    resultDen.textContent = result.denominator;
    resultDisplay.classList.remove('hidden');
    
    
    resultText.textContent = `Ответ: ${result.numerator}/${result.denominator}`;
    resultText.classList.remove('hidden');
}



function getInputValues() {
    const num1 = parseInt(document.getElementById('num1').value) || 0;
    const den1 = parseInt(document.getElementById('den1').value) || 1;
    const num2 = parseInt(document.getElementById('num2').value) || 0;
    const den2 = parseInt(document.getElementById('den2').value) || 1;
    
    
    if (den1 === 0 || den2 === 0) {
        return { error: "Знаменатель дроби не может быть равен нулю!" };
    }
    
    return { num1, den1, num2, den2 };
}



function performOperation(operation) {
    
    const inputs = getInputValues();
    
    
    if (inputs.error) {
        displayResult({ error: inputs.error });
        return;
    }
    
    let result;
    
    
    switch(operation) {
        case 'add':
            result = addFractions(inputs.num1, inputs.den1, inputs.num2, inputs.den2);
            break;
        case 'subtract':
            result = subtractFractions(inputs.num1, inputs.den1, inputs.num2, inputs.den2);
            break;
        case 'multiply':
            result = multiplyFractions(inputs.num1, inputs.den1, inputs.num2, inputs.den2);
            break;
        case 'divide':
            result = divideFractions(inputs.num1, inputs.den1, inputs.num2, inputs.den2);
            break;
        default:
            result = { error: "Неизвестная операция" };
    }
    
    
    displayResult(result);
}


document.addEventListener('DOMContentLoaded', function() {
    const inputs = document.querySelectorAll('.fraction-input');
    inputs.forEach(input => {
        input.addEventListener('keypress', function(e) {
            if (e.key === 'Enter') {
                
                performOperation('add');
            }
        });
    });
});