/**
 * Web Uploader - Frontend Application
 * Handles file uploads with drag-and-drop, progress tracking, and image previews.
 */

const IMAGE_EXTENSIONS = /\.(jpg|jpeg|png|gif|webp|bmp|svg)$/i;
const PROGRESS_INTERVAL_MS = 100;
const PROGRESS_INCREMENT = 5;
const MODAL_TRANSITION_MS = 300;
const COPY_FEEDBACK_MS = 2000;

const elements = {
    dropZone: document.getElementById('dropZone'),
    fileInput: document.getElementById('fileInput'),
    browseBtn: document.getElementById('browseBtn'),
    progressContainer: document.getElementById('progressContainer'),
    progressBar: document.getElementById('progressBar'),
    fileName: document.getElementById('fileName'),
    uploadStatus: document.getElementById('uploadStatus'),
    statusMessage: document.getElementById('statusMessage'),
    resultsContainer: document.getElementById('resultsContainer'),
    modal: document.getElementById('imageModal'),
    modalImage: document.getElementById('modalImage'),
    closeModal: document.querySelector('.close-modal'),
    tabBtns: document.querySelectorAll('.tab-btn'),
    tabContents: document.querySelectorAll('.tab-content'),
    expirationSelect: document.getElementById('expiration'),
    historyList: document.getElementById('historyList'),
    clearHistoryBtn: document.getElementById('clearHistoryBtn'),
    toastContainer: document.getElementById('toastContainer'),
    confirmModal: document.getElementById('confirmModal'),
    cancelConfirmBtn: document.getElementById('cancelConfirmBtn'),
    confirmDeleteBtn: document.getElementById('confirmDeleteBtn')
};

function preventDefaults(e) {
    e.preventDefault();
    e.stopPropagation();
}

function highlight() {
    elements.dropZone.classList.add('dragover');
}

function unhighlight() {
    elements.dropZone.classList.remove('dragover');
}

function handleDrop(e) {
    const files = e.dataTransfer.files;
    handleFiles(files);
}

function initDragAndDrop() {
    const dragEvents = ['dragenter', 'dragover', 'dragleave', 'drop'];

    dragEvents.forEach(eventName => {
        elements.dropZone.addEventListener(eventName, preventDefaults, false);
        document.body.addEventListener(eventName, preventDefaults, false);
    });

    ['dragenter', 'dragover'].forEach(eventName => {
        elements.dropZone.addEventListener(eventName, highlight, false);
    });

    ['dragleave', 'drop'].forEach(eventName => {
        elements.dropZone.addEventListener(eventName, unhighlight, false);
    });

    elements.dropZone.addEventListener('drop', handleDrop, false);
}

function initFileInput() {
    elements.browseBtn.addEventListener('click', () => {
        elements.fileInput.click();
    });

    elements.fileInput.addEventListener('change', function () {
        handleFiles(this.files);
    });
    
    // Init History
    renderHistory();
    elements.clearHistoryBtn.addEventListener('click', showConfirmModal);
    initConfirmModal();
}

function handleFiles(files) {
    if (files.length > 0) {
        uploadFiles(files);
    }
}

function resetUploadUI() {
    elements.progressContainer.hidden = false;
    elements.statusMessage.hidden = true;
    elements.resultsContainer.hidden = true;
    elements.resultsContainer.innerHTML = '';
    elements.progressBar.style.width = '0%';
}

function createProgressSimulator() {
    let progress = 0;

    return setInterval(() => {
        progress += PROGRESS_INCREMENT;
        if (progress > 90) return;
        elements.progressBar.style.width = `${progress}%`;
    }, PROGRESS_INTERVAL_MS);
}

async function uploadFiles(files) {
    resetUploadUI();

    const fileLabel = files.length > 1
        ? `${files.length} files selected`
        : files[0].name;
    elements.fileName.textContent = fileLabel;
    elements.uploadStatus.textContent = 'Uploading...';

    const progressInterval = createProgressSimulator();

    const formData = new FormData();
    Array.from(files).forEach(file => {
        formData.append('files', file);
    });
    
    // Add expiration to formData
    formData.append('expiration', elements.expirationSelect.value);

    try {
        const response = await fetch('/api/upload', {
            method: 'POST',
            body: formData
        });

        clearInterval(progressInterval);
        elements.progressBar.style.width = '100%';

        if (!response.ok) {
            throw new Error('Upload failed');
        }

        const data = await response.json();

        setTimeout(() => {
            elements.uploadStatus.textContent = 'Completed';
            displayResults(data.files);
            saveToHistory(data.files);
            showToast('Files uploaded successfully!', 'success');
        }, 500);

    } catch (error) {
        clearInterval(progressInterval);
        console.error('Upload error:', error);
        elements.uploadStatus.textContent = 'Failed';
        showToast('Upload failed. Please try again.', 'error');
    } finally {
        elements.fileInput.value = '';
    }
}

function isImageFile(filename) {
    return IMAGE_EXTENSIONS.test(filename);
}

function createImagePreview(file) {
    const trigger = document.createElement('div');
    trigger.className = 'preview-link';
    trigger.style.cursor = 'pointer';

    const img = document.createElement('img');
    img.src = file.url;
    img.className = 'result-preview';

    trigger.appendChild(img);
    trigger.onclick = () => openModal(file.url);

    return trigger;
}

function createFileLink(file) {
    const link = document.createElement('a');
    link.href = file.url;
    link.textContent = file.originalName;
    link.className = 'file-link';
    link.target = '_blank';
    return link;
}

function createCopyButton(url) {
    const btn = document.createElement('button');
    btn.className = 'copy-btn';
    btn.textContent = 'Copy';
    btn.setAttribute('aria-label', `Copy link for ${url}`);
    btn.onclick = () => copyToClipboard(url, btn);
    return btn;
}

function displayResults(files) {
    elements.resultsContainer.innerHTML = '';

    files.forEach(file => {
        const item = document.createElement('div');
        item.className = 'result-item';

        if (isImageFile(file.originalName)) {
            item.appendChild(createImagePreview(file));
        }

        const content = document.createElement('div');
        content.className = 'result-content';
        content.appendChild(createFileLink(file));
        content.appendChild(createCopyButton(file.url));

        item.appendChild(content);
        elements.resultsContainer.appendChild(item);
    });

    elements.resultsContainer.hidden = false;
}

async function copyToClipboard(text, btn) {
    try {
        await navigator.clipboard.writeText(text);
        const originalText = btn.textContent;
        btn.textContent = 'Copied!';
        btn.classList.add('copied');
        showToast('Link copied to clipboard!', 'success');

        setTimeout(() => {
            btn.textContent = originalText;
            btn.classList.remove('copied');
        }, COPY_FEEDBACK_MS);
    } catch (err) {
        console.error('Failed to copy:', err);
        showToast('Failed to copy link', 'error');
    }
}

function initTabs() {
    elements.tabBtns.forEach(btn => {
        btn.addEventListener('click', () => {
            const targetTab = btn.dataset.tab;

            elements.tabBtns.forEach(b => b.classList.remove('active'));
            elements.tabContents.forEach(c => c.classList.remove('active'));

            btn.classList.add('active');
            document.getElementById(targetTab).classList.add('active');
        });
    });
}

// History Management
function getHistory() {
    try {
        return JSON.parse(localStorage.getItem('uploadHistory') || '[]');
    } catch {
        return [];
    }
}

function saveToHistory(newFiles) {
    const history = getHistory();
    const updatedHistory = [...newFiles, ...history].slice(0, 50); // Keep last 50
    localStorage.setItem('uploadHistory', JSON.stringify(updatedHistory));
    renderHistory();
}

function showConfirmModal() {
    elements.confirmModal.hidden = false;
    requestAnimationFrame(() => elements.confirmModal.classList.add('show'));
}

function hideConfirmModal() {
    elements.confirmModal.classList.remove('show');
    setTimeout(() => {
        elements.confirmModal.hidden = true;
    }, 300);
}

function initConfirmModal() {
    elements.cancelConfirmBtn.onclick = hideConfirmModal;
    
    elements.confirmDeleteBtn.onclick = () => {
        localStorage.removeItem('uploadHistory');
        renderHistory();
        hideConfirmModal();
        showToast('History cleared', 'success');
    };
    
    elements.confirmModal.addEventListener('click', (e) => {
        if (e.target === elements.confirmModal) hideConfirmModal();
    });
}

function renderHistory() {
    const history = getHistory();
    elements.historyList.innerHTML = '';

    if (history.length === 0) {
        elements.historyList.innerHTML = '<p class="empty-state" style="text-align: center; color: var(--text-secondary); padding: 2rem;">No upload history yet.</p>';
        return;
    }

    history.forEach(file => {
        const item = document.createElement('div');
        item.className = 'result-item'; // Reuse result item styling

        if (isImageFile(file.originalName)) {
            // Create small preview
            const trigger = document.createElement('div');
            trigger.className = 'preview-link';
            trigger.style.cursor = 'pointer';
            const img = document.createElement('img');
            img.src = file.url;
            img.className = 'result-preview';
            trigger.appendChild(img);
            trigger.setAttribute('role', 'button');
            trigger.setAttribute('aria-label', `Preview ${file.originalName}`);
            trigger.setAttribute('tabindex', '0');
            trigger.onkeypress = (e) => {
                if (e.key === 'Enter') openModal(file.url);
            };
            trigger.onclick = () => openModal(file.url);
            item.appendChild(trigger);
        }

        const content = document.createElement('div');
        content.className = 'result-content';
        
        // Wrapper for link and expiration info
        const infoWrapper = document.createElement('div');
        infoWrapper.style.flex = '1';
        infoWrapper.style.minWidth = '0';
        infoWrapper.style.display = 'flex';
        infoWrapper.style.flexDirection = 'column';

        infoWrapper.appendChild(createFileLink(file));
        
        if (file.expiresAt) {
            const expirationSpan = document.createElement('span');
            expirationSpan.style.fontSize = '0.75rem';
            expirationSpan.style.color = 'var(--text-muted)';
            expirationSpan.style.marginTop = '4px';
            
            const expDate = new Date(file.expiresAt);
            const now = new Date();
            const isExpired = expDate < now;
            
            if (isExpired) {
                 expirationSpan.textContent = 'Expired';
                 expirationSpan.style.color = 'var(--error-color)';
            } else {
                expirationSpan.textContent = `Expires: ${expDate.toLocaleString()}`;
            }
            
            infoWrapper.appendChild(expirationSpan);
        } else {
             const permanentSpan = document.createElement('span');
             permanentSpan.style.fontSize = '0.75rem';
             permanentSpan.style.color = 'var(--success-color)';
             permanentSpan.style.marginTop = '4px';
             permanentSpan.textContent = 'Permanent';
             infoWrapper.appendChild(permanentSpan);
        }

        content.appendChild(infoWrapper);
        content.appendChild(createCopyButton(file.url));
        item.appendChild(content);
        elements.historyList.appendChild(item);
    });
}

// Toast Notification System
function showToast(message, type = 'info') {
    const toast = document.createElement('div');
    toast.className = `toast ${type}`;
    
    toast.innerHTML = `
        <span class="toast-message">${message}</span>
    `;
    
    elements.toastContainer.appendChild(toast);
    
    // Remove after 3 seconds
    setTimeout(() => {
        toast.classList.add('hiding');
        toast.addEventListener('animationend', () => toast.remove());
    }, 3000);
}

function openModal(src) {
    elements.modal.hidden = false;
    requestAnimationFrame(() => {
        elements.modal.classList.add('show');
    });
    elements.modalImage.src = src;
}

function handleCloseModal() {
    elements.modal.classList.remove('show');
    setTimeout(() => {
        elements.modal.hidden = true;
        elements.modalImage.src = '';
    }, MODAL_TRANSITION_MS);
}

function initModal() {
    elements.closeModal.addEventListener('click', handleCloseModal);

    elements.modal.addEventListener('click', (e) => {
        if (e.target === elements.modal) {
            handleCloseModal();
        }
    });

    document.addEventListener('keydown', (e) => {
        if (e.key === 'Escape' && elements.modal.classList.contains('show')) {
            handleCloseModal();
        }
    });
}

function init() {
    initDragAndDrop();
    initFileInput();
    initTabs();
    initModal();
}

init();