document.addEventListener('DOMContentLoaded', () => {
    const pdfInput = document.getElementById('pdf-input');
    const processBtn = document.getElementById('process-btn');
    const downloadBtn = document.getElementById('download-btn');
    const previewContainer = document.getElementById('preview-container');
    const downloadContainer = document.getElementById('download-container');
    const preview = document.getElementById('preview');
    const reverseOrderCheckbox = document.getElementById('reverse-order');
    const addPageNumbersCheckbox = document.getElementById('add-page-numbers');

    let processedPdfBytes = null;

    pdfInput.addEventListener('change', handleFileSelect);
    processBtn.addEventListener('click', processPDF);
    downloadBtn.addEventListener('click', downloadPDF);

    async function handleFileSelect(event) {
        const file = event.target.files[0];
        if (!file) return;

        previewContainer.classList.remove('hidden');
        preview.innerHTML = '<p class="text-gray-500 text-center">Loading preview...</p>';

        try {
            const arrayBuffer = await file.arrayBuffer();
            const pdfDoc = await PDFLib.PDFDocument.load(arrayBuffer);
            const firstPage = pdfDoc.getPages()[0];
            
            // Create a simple preview
            const { width, height } = firstPage.getSize();
            preview.innerHTML = `
                <div class="text-center">
                    <p class="text-gray-700 mb-2"><strong>Original PDF Info</strong></p>
                    <p class="text-gray-600">Pages: ${pdfDoc.getPageCount()}</p>
                    <p class="text-gray-600">Dimensions: ${width.toFixed(0)} × ${height.toFixed(0)}</p>
                    <p class="text-gray-600">Orientation: ${width > height ? 'Landscape' : 'Portrait'}</p>
                </div>
            `;
        } catch (error) {
            preview.innerHTML = '<p class="text-red-500 text-center">Error loading PDF. Please try another file.</p>';
            console.error('Error loading PDF:', error);
        }
    }

    async function processPDF() {
        const file = pdfInput.files[0];
        if (!file) {
            alert('Please select a PDF file first');
            return;
        }

        processBtn.disabled = true;
        processBtn.innerHTML = '<i data-feather="loader" class="animate-spin mr-2"></i> Processing...';
        feather.replace();

        try {
            const arrayBuffer = await file.arrayBuffer();
            const originalPdfDoc = await PDFLib.PDFDocument.load(arrayBuffer);
            const newPdfDoc = await PDFLib.PDFDocument.create();
            
            const originalPages = originalPdfDoc.getPages();
            const pageCount = originalPages.length;
            const reverseOrder = reverseOrderCheckbox.checked;
            const addPageNumbers = addPageNumbersCheckbox.checked;

            // Process pages in pairs
            for (let i = 0; i < pageCount; i += 2) {
                const page1Index = reverseOrder ? pageCount - 1 - i : i;
                const page2Index = reverseOrder ? pageCount - 2 - i : i + 1;
                
                const page1 = originalPages[page1Index];
                const page2 = page2Index < pageCount ? originalPages[page2Index] : null;

                // Create a new landscape page (double width)
                const { width: pw, height: ph } = page1.getSize();
                const newPage = newPdfDoc.addPage([pw * 2, ph]);
                
                // Embed the first page
                const embeddedPage1 = await newPdfDoc.embedPage(page1);
                newPage.drawPage(embeddedPage1, {
                    x: 0,
                    y: 0,
                    width: pw,
                    height: ph,
                });

                // Embed the second page if it exists
                if (page2) {
                    const embeddedPage2 = await newPdfDoc.embedPage(page2);
                    newPage.drawPage(embeddedPage2, {
                        x: pw,
                        y: 0,
                        width: pw,
                        height: ph,
                    });
                }

                // Add page numbers if enabled
                if (addPageNumbers) {
                    const pageNumText = `Page ${page1Index + 1}${page2 ? `-${page2Index + 1}` : ''}`;
                    newPage.drawText(pageNumText, {
                        x: 10,
                        y: 10,
                        size: 12,
                        color: PDFLib.rgb(0.5, 0.5, 0.5),
                    });
                }
            }

            // Save the processed PDF
            processedPdfBytes = await newPdfDoc.save();
            
            // Update UI
            preview.innerHTML = `
                <div class="text-center">
                    <p class="text-green-600 mb-2"><strong>Processing Complete!</strong></p>
                    <p class="text-gray-700">Original pages: ${pageCount}</p>
                    <p class="text-gray-700">New pages: ${Math.ceil(pageCount / 2)}</p>
                </div>
            `;
            downloadContainer.classList.remove('hidden');
        } catch (error) {
            console.error('Error processing PDF:', error);
            preview.innerHTML = '<p class="text-red-500 text-center">Error processing PDF. Please try again.</p>';
        } finally {
            processBtn.disabled = false;
            processBtn.innerHTML = '<i data-feather="repeat" class="mr-2"></i> Process PDF';
            feather.replace();
        }
    }

    function downloadPDF() {
        if (!processedPdfBytes) return;
        
        const fileName = pdfInput.files[0].name.replace('.pdf', '') + '_processed.pdf';
        download(processedPdfBytes, fileName, 'application/pdf');
    }
});