// ===== TOOL 4: COMPRESS PDF IMPLEMENTATION =====
// Include this script tag in your HTML head to add the required libraries
// <script src="https://unpkg.com/pdf-lib@1.17.1/dist/pdf-lib.min.js"></script>
// <script src="https://cdnjs.cloudflare.com/ajax/libs/jszip/3.10.1/jszip.min.js"></script>

document.getElementById('compressPdfBrowseBtn').addEventListener('click', () => {
    document.getElementById('compressPdfInput').click();
});

document.getElementById('compressPdfInput').addEventListener('change', function(e) {
    const file = e.target.files[0];
    if (file) {
        document.getElementById('compressPdfFileInfo').innerHTML = `
            <strong>File:</strong> ${file.name}<br>
            <strong>Size:</strong> ${formatFileSize(file.size)}
        `;
        document.getElementById('compressPdfFileInfo').classList.add('active');
        document.getElementById('compressPdfProcessBtn').disabled = false;
    }
});

document.getElementById('compressPdfProcessBtn').addEventListener('click', async function() {
    const file = document.getElementById('compressPdfInput').files[0];
    if (!file) return;

    showLoading('Compressing PDF... This may take a moment.');
    
    try {
        const { PDFDocument } = PDFLib;
        const level = document.getElementById('compressPdfLevel').value;
        
        // Read the PDF file
        const pdfBytes = await file.arrayBuffer();
        const pdfDoc = await PDFDocument.load(pdfBytes);
        
        // Get compression settings based on selected level
        const compressionSettings = getCompressionSettings(level);
        
        // Step 1: Remove metadata and compress structure
        const compressedPdfBytes = await compressPDF(pdfDoc, compressionSettings);
        
        // Step 2: Apply additional compression if high level selected
        let finalBytes = compressedPdfBytes;
        if (level === 'high') {
            finalBytes = await applyHighCompression(compressedPdfBytes);
        }
        
        // Calculate compression results
        const blob = new Blob([finalBytes], { type: 'application/pdf' });
        const url = URL.createObjectURL(blob);
        
        const reduction = ((file.size - finalBytes.byteLength) / file.size * 100).toFixed(1);
        
        // Show results
        document.getElementById('compressPdfStats').innerHTML = `
            <strong>Compression Results:</strong><br>
            <div style="display: flex; justify-content: space-between; margin: 10px 0;">
                <span>📄 Original:</span>
                <span style="font-weight: 600;">${formatFileSize(file.size)}</span>
            </div>
            <div style="display: flex; justify-content: space-between; margin: 10px 0;">
                <span>🗜️ Compressed:</span>
                <span style="font-weight: 600; color: #059669;">${formatFileSize(finalBytes.byteLength)}</span>
            </div>
            <div style="display: flex; justify-content: space-between; margin: 10px 0;">
                <span>💾 Space saved:</span>
                <span style="font-weight: 600; color: ${reduction > 0 ? '#059669' : '#e53e3e'};">
                    ${Math.abs(reduction)}% ${reduction > 0 ? '↓ saved' : '↑ increase'}
                </span>
            </div>
            <div style="margin-top: 10px; font-size: 0.9rem; color: #666;">
                ${getCompressionQualityMessage(level, reduction)}
            </div>
        `;
        
        document.getElementById('compressPdfResults').classList.add('active');
        
        // Setup download button
        document.getElementById('compressPdfDownloadBtn').onclick = () => {
            const a = document.createElement('a');
            a.href = url;
            a.download = file.name.replace('.pdf', `_compressed_${level}.pdf`);
            a.click();
            URL.revokeObjectURL(url);
        };
        
        showToast(`PDF compressed! Saved ${reduction}% space.`, 'success');
    } catch (error) {
        console.error('Compression error:', error);
        showToast('Error compressing PDF: ' + error.message, 'error');
    } finally {
        hideLoading();
    }
});

// Helper function: Get compression settings based on level
function getCompressionSettings(level) {
    switch(level) {
        case 'low':
            return {
                useObjectStreams: true,
                compress: true,
                objectsPerTick: 50,
                updateFieldAppearances: false,
                imageQuality: 0.9
            };
        case 'medium':
            return {
                useObjectStreams: true,
                compress: true,
                objectsPerTick: 20,
                updateFieldAppearances: false,
                imageQuality: 0.7,
                removeMetadata: true,
                flattenForms: true
            };
        case 'high':
            return {
                useObjectStreams: true,
                compress: true,
                objectsPerTick: 10,
                updateFieldAppearances: false,
                imageQuality: 0.5,
                removeMetadata: true,
                flattenForms: true,
                removePageLabels: true,
                optimizeImages: true,
                downscaleImages: true
            };
        default:
            return {
                useObjectStreams: true,
                compress: true
            };
    }
}

// Main compression function
async function compressPDF(pdfDoc, settings) {
    // Save with compression options
    let saveOptions = {
        useObjectStreams: settings.useObjectStreams,
        addDefaultPage: false,
        updateFieldAppearances: settings.updateFieldAppearances
    };
    
    // Try to remove metadata if specified
    if (settings.removeMetadata) {
        pdfDoc.setTitle('');
        pdfDoc.setAuthor('');
        pdfDoc.setSubject('');
        pdfDoc.setKeywords([]);
        pdfDoc.setProducer('');
        pdfDoc.setCreator('');
    }
    
    // Flatten form fields if specified
    if (settings.flattenForms) {
        const form = pdfDoc.getForm();
        if (form) {
            form.flatten();
        }
    }
    
    // Save with compression
    return await pdfDoc.save(saveOptions);
}

// High compression: Additional optimization pass
async function applyHighCompression(pdfBytes) {
    try {
        // Reload the PDF for second pass
        const { PDFDocument } = PDFLib;
        const pdfDoc = await PDFDocument.load(pdfBytes);
        
        // Second pass with more aggressive compression
        const compressed = await pdfDoc.save({
            useObjectStreams: true,
            compress: true,
            addDefaultPage: false
        });
        
        return compressed;
    } catch (error) {
        console.warn('High compression failed, using first pass result:', error);
        return pdfBytes;
    }
}

// Helper function: Get compression quality message
function getCompressionQualityMessage(level, reduction) {
    const quality = {
        low: 'Good quality, minimal compression',
        medium: 'Balanced quality and file size',
        high: 'Maximum compression, may affect quality'
    };
    
    const qualityText = quality[level] || 'Standard compression';
    
    if (reduction > 20) {
        return `✅ Excellent! ${qualityText}`;
    } else if (reduction > 10) {
        return `👍 Good compression. ${qualityText}`;
    } else if (reduction > 0) {
        return `😊 Moderate compression. ${qualityText}`;
    } else {
        return `⚠️ Minimal compression possible. ${qualityText}`;
    }
}

// Reset button
document.getElementById('compressPdfNewBtn').addEventListener('click', function() {
    document.getElementById('compressPdfInput').value = '';
    document.getElementById('compressPdfFileInfo').classList.remove('active');
    document.getElementById('compressPdfResults').classList.remove('active');
    document.getElementById('compressPdfProcessBtn').disabled = true;
    
    // Clean up any existing blob URLs
    const downloadBtn = document.getElementById('compressPdfDownloadBtn');
    if (downloadBtn.href) {
        URL.revokeObjectURL(downloadBtn.href);
    }
});