document.addEventListener('DOMContentLoaded', () => {
    // 1. Initialization
    const modeSelector = document.getElementById('mode-selector');
    const qrContainer = document.getElementById('qr-container');
    const downloadBtn = document.getElementById('btn-download');
    
    // Forms
    const forms = {
        text: document.getElementById('form-text'),
        wifi: document.getElementById('form-wifi'),
        email: document.getElementById('form-email')
    };

    // Inputs collection for event binding
    const allInputs = document.querySelectorAll('input, textarea, select');

    // Initialize QR Library
    // Using CorrectLevel.H (High) as requested
    let qrcode = new QRCode(qrContainer, {
        width: 256,
        height: 256,
        colorDark : "#000000",
        colorLight : "#ffffff",
        correctLevel : QRCode.CorrectLevel.H
    });

    // 2. State & Logic
    let currentMode = 'text';
    let debounceTimer;

    // Switch Input Forms
    function switchMode(newMode) {
        currentMode = newMode;
        
        // Hide all forms
        Object.values(forms).forEach(form => form.classList.remove('active'));
        
        // Show selected form
        forms[newMode].classList.add('active');

        // Trigger update immediately
        updateQR();
    }

    // String Builders
    function getDataString() {
        if (currentMode === 'text') {
            return document.getElementById('inp-text').value;
        } 
        
        else if (currentMode === 'wifi') {
            const ssid = document.getElementById('inp-wifi-ssid').value;
            const pass = document.getElementById('inp-wifi-pass').value;
            const type = document.getElementById('inp-wifi-type').value;
            
            if (!ssid) return ''; // SSID is minimum requirement
            
            // Format: WIFI:S:MyNetwork;T:WPA;P:mypassword;;
            // Note: Special characters in SSID/Pass should ideally be escaped, 
            // but standard readers handle raw strings well usually. 
            // Adding escape for semicolons/colons is safer practice:
            const cleanSSID = ssid.replace(/([\\;,:])/g, '\\$1');
            const cleanPass = pass.replace(/([\\;,:])/g, '\\$1');
            
            return `WIFI:S:${cleanSSID};T:${type};P:${cleanPass};;`;
        } 
        
        else if (currentMode === 'email') {
            const to = document.getElementById('inp-email-to').value;
            const sub = document.getElementById('inp-email-sub').value;
            const body = document.getElementById('inp-email-body').value;
            
            if (!to) return '';
            
            return `mailto:${to}?subject=${encodeURIComponent(sub)}&body=${encodeURIComponent(body)}`;
        }
        
        return '';
    }

    // QR Update Logic
    function updateQR() {
        const data = getDataString();
        
        if (!data || data.trim() === '') {
            qrcode.clear(); // Clear the code
            downloadBtn.disabled = true;
            return;
        }

        downloadBtn.disabled = false;

        // Visual Stability: Fade opacity slightly during update logic if desired,
        // but qrcode.makeCode is instantaneous on small data. 
        // We ensure high performance by not recreating the object.
        qrcode.makeCode(data); 
    }

    // Debounce Function
    function handleInput() {
        clearTimeout(debounceTimer);
        debounceTimer = setTimeout(() => {
            updateQR();
        }, 300); // 300ms delay
    }

    // 3. Event Listeners
    
    // Mode Switching
    modeSelector.addEventListener('change', (e) => switchMode(e.target.value));

    // Input Detection (Auto-Update)
    allInputs.forEach(input => {
        // Skip mode selector as it has its own handler
        if(input.id !== 'mode-selector') {
            input.addEventListener('input', handleInput);
        }
    });

    // Download Logic
    downloadBtn.addEventListener('click', () => {
        // Find the image generated by qrcode.js
        const img = qrContainer.querySelector('img');
        
        if (img && img.src) {
            const link = document.createElement('a');
            link.href = img.src;
            link.download = `qrcode-${currentMode}-${Date.now()}.png`;
            document.body.appendChild(link);
            link.click();
            document.body.removeChild(link);
        }
    });

    // Initial run
    switchMode('text');
});