document.addEventListener('DOMContentLoaded', () => {
    fetchFiles();

    document.getElementById('upload-form').addEventListener('submit', handleFileUpload);
    document.getElementById('file-input').addEventListener('change', updateUploadList);

    document.getElementById('select-all').addEventListener('click', handleSelectAll);
    document.getElementById('batch-delete').addEventListener('click', handleBatchDelete);
    document.getElementById('batch-download').addEventListener('click', handleBatchDownload);
    document.getElementById('batch-preview').addEventListener('click', handleBatchPreview);
});

function fetchFiles() {
    fetch('/files')
        .then(response => response.json())
        .then(files => {
            const fileList = document.getElementById('file-list');
            fileList.innerHTML = '';
            files.forEach(file => {
                const li = document.createElement('li');
                
                const checkbox = document.createElement('input');
                checkbox.type = 'checkbox';
                checkbox.value = file.name;
                checkbox.dataset.path = `/uploads/${file.name}`;
                const extension = file.name.split('.').pop().toLowerCase();
                checkbox.dataset.fileType = extension;

                const fileInfo = document.createElement('span');
                fileInfo.className = 'file-info';
                fileInfo.textContent = `${file.name} (Size: ${file.size} bytes, Date: ${new Date(file.date).toLocaleString()})`;

                li.appendChild(checkbox);
                li.appendChild(fileInfo);
                fileList.appendChild(li);
            });
        })
        .catch(error => {
            console.error('Error fetching file list:', error);
        });
}

function updateUploadList(event) {
    const fileInput = event.target;
    const uploadList = document.getElementById('upload-list');
    uploadList.innerHTML = '';
    
    if (fileInput.files.length === 0) return;

    for (const file of fileInput.files) {
        const li = document.createElement('li');
        li.className = 'upload-item';
        li.innerHTML = `
            <span>${file.name} (Size: ${Math.round(file.size / 1024)} KB)</span>
            <div id="progress-${file.name.replace(/[^a-zA-Z0-9]/g, '-')}" class="progress-bar">
                <div class="progress-bar-fill" style="width: 0;"></div>
            </div>
        `;
        uploadList.appendChild(li);
    }
}

function handleFileUpload(event) {
    event.preventDefault();

    const form = event.target;
    const formData = new FormData(form);
    const fileInput = document.getElementById('file-input');
    
    if (fileInput.files.length === 0) {
        alert('Please select files to upload.');
        return;
    }

    const xhr = new XMLHttpRequest();
    
    xhr.upload.addEventListener('progress', (e) => {
        if (e.lengthComputable) {
            const percentComplete = (e.loaded / e.total) * 100;
            const progressBars = document.querySelectorAll('.progress-bar-fill');
            
            progressBars.forEach(bar => {
                bar.style.width = percentComplete.toFixed(2) + '%';
            });
        }
    }, false);

    xhr.addEventListener('load', () => {
        if (xhr.status === 200) {
            alert(xhr.responseText);
            form.reset();
            document.getElementById('upload-list').innerHTML = '';
            fetchFiles();
        } else {
            alert('File upload failed! Server responded with status ' + xhr.status);
        }
    });

    xhr.addEventListener('error', () => {
        console.error('Error uploading file:', xhr.statusText);
        alert('File upload failed!');
    });
    
    xhr.open('POST', '/upload');
    xhr.send(formData);
}

function getSelectedFiles() {
    const selectedCheckboxes = document.querySelectorAll('#file-list input[type="checkbox"]:checked');
    return Array.from(selectedCheckboxes).map(checkbox => ({
        name: checkbox.value,
        path: checkbox.dataset.path,
        type: checkbox.dataset.fileType
    }));
}

function handleSelectAll() {
    const checkboxes = document.querySelectorAll('#file-list input[type="checkbox"]');
    const allChecked = Array.from(checkboxes).every(cb => cb.checked);
    
    checkboxes.forEach(cb => {
        cb.checked = !allChecked;
    });
}

function handleBatchDelete() {
    const filesToDelete = getSelectedFiles();
    if (filesToDelete.length === 0) {
        alert('No files selected for deletion.');
        return;
    }

    if (!confirm(`Are you sure you want to delete ${filesToDelete.length} file(s)?`)) {
        return;
    }

    const deletePromises = filesToDelete.map(file => 
        fetch(`/delete/${file.name}`, { method: 'DELETE' })
            .then(response => {
                if (response.ok) {
                    return { name: file.name, status: 'Success' };
                } else {
                    return { name: file.name, status: 'Failed' };
                }
            })
    );

    Promise.all(deletePromises)
        .then(results => {
            const successfulDeletes = results.filter(r => r.status === 'Success');
            const failedDeletes = results.filter(r => r.status === 'Failed');
            
            if (successfulDeletes.length > 0) {
                alert(`Successfully deleted ${successfulDeletes.length} file(s).`);
            }
            if (failedDeletes.length > 0) {
                alert(`Failed to delete ${failedDeletes.length} file(s). Check console for errors.`);
            }
            fetchFiles();
        })
        .catch(error => {
            console.error('Error during batch deletion:', error);
            alert('An error occurred during batch deletion.');
        });
}

function handleBatchDownload() {
    const filesToDownload = getSelectedFiles();
    if (filesToDownload.length === 0) {
        alert('No files selected for download.');
        return;
    }

    filesToDownload.forEach(file => {
        window.location.href = `/download/${file.name}`;
    });
    
    alert(`Initiating download for ${filesToDownload.length} file(s). Check your browser's download manager.`);
}

function handleBatchPreview() {
    const selectedFiles = getSelectedFiles();
    const previewableFiles = selectedFiles.filter(file => 
        file.type === 'txt' || file.type.match(/^(jpg|jpeg|png|gif)$/)
    );

    if (previewableFiles.length === 0) {
        alert('No previewable files (.txt, .jpg, .png, .gif) selected.');
        return;
    }

    showMultiPreview(previewableFiles);
}

function showMultiPreview(files) {
    let currentIndex = 0;
    const previewContainer = document.createElement('div');
    previewContainer.className = 'preview-modal';
    
    const content = document.createElement('div');
    content.className = 'preview-content';
    
    const controls = document.createElement('div');
    controls.className = 'preview-controls';
    
    const prevButton = document.createElement('button');
    prevButton.textContent = 'Previous';
    prevButton.onclick = () => {
        if (currentIndex > 0) {
            currentIndex--;
            updatePreviewContent();
        }
    };

    const nextButton = document.createElement('button');
    nextButton.textContent = 'Next';
    nextButton.onclick = () => {
        if (currentIndex < files.length - 1) {
            currentIndex++;
            updatePreviewContent();
        }
    };
    
    const closeButton = document.createElement('button');
    closeButton.textContent = 'Close Preview';
    closeButton.onclick = () => {
        document.body.removeChild(previewContainer);
    };

    controls.appendChild(prevButton);
    controls.appendChild(closeButton);
    controls.appendChild(nextButton);

    const updatePreviewContent = () => {
        content.innerHTML = '';
        const file = files[currentIndex];
        
        prevButton.disabled = currentIndex === 0;
        nextButton.disabled = currentIndex === files.length - 1;
        
        const counter = document.createElement('p');
        counter.textContent = `File ${currentIndex + 1} of ${files.length}: ${file.name}`;
        content.appendChild(counter);

        if (file.type === 'txt') {
            const textPreview = document.createElement('iframe');
            textPreview.src = file.path;
            textPreview.style.width = '100%';
            textPreview.style.height = '400px';
            content.appendChild(textPreview);
        } else if (file.type.match(/^(jpg|jpeg|png|gif)$/)) {
            const imgPreview = document.createElement('img');
            imgPreview.src = file.path;
            content.appendChild(imgPreview);
        } else {
            content.textContent = `Preview not available for this file type: ${file.name}.`;
        }
    };

    previewContainer.appendChild(controls);
    previewContainer.appendChild(content);
    document.body.appendChild(previewContainer);
    
    updatePreviewContent();
}