Ground work for page editor

frontend/src/services/pdfExportService.ts

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+import { PDFDocument as PDFLibDocument, degrees, PageSizes } from 'pdf-lib';
+import { PDFDocument, PDFPage } from '../types/pageEditor';
+
+export interface ExportOptions {
+  selectedOnly?: boolean;
+  filename?: string;
+  splitDocuments?: boolean;
+}
+
+export class PDFExportService {
+  /**
+   * Export PDF document with applied operations
+   */
+  async exportPDF(
+    pdfDocument: PDFDocument, 
+    selectedPageIds: string[] = [],
+    options: ExportOptions = {}
+  ): Promise<{ blob: Blob; filename: string } | { blobs: Blob[]; filenames: string[] }> {
+    const { selectedOnly = false, filename, splitDocuments = false } = options;
+    
+    try {
+      // Determine which pages to export
+      const pagesToExport = selectedOnly && selectedPageIds.length > 0
+        ? pdfDocument.pages.filter(page => selectedPageIds.includes(page.id))
+        : pdfDocument.pages;
+
+      if (pagesToExport.length === 0) {
+        throw new Error('No pages to export');
+      }
+
+      // Load original PDF once
+      const originalPDFBytes = await pdfDocument.file.arrayBuffer();
+      const sourceDoc = await PDFLibDocument.load(originalPDFBytes);
+
+      if (splitDocuments) {
+        return await this.createSplitDocuments(sourceDoc, pagesToExport, filename || pdfDocument.name);
+      } else {
+        const blob = await this.createSingleDocument(sourceDoc, pagesToExport);
+        const exportFilename = this.generateFilename(filename || pdfDocument.name, selectedOnly);
+        return { blob, filename: exportFilename };
+      }
+    } catch (error) {
+      console.error('PDF export error:', error);
+      throw new Error(`Failed to export PDF: ${error instanceof Error ? error.message : 'Unknown error'}`);
+    }
+  }
+
+  /**
+   * Create a single PDF document with all operations applied
+   */
+  private async createSingleDocument(
+    sourceDoc: PDFLibDocument,
+    pages: PDFPage[]
+  ): Promise<Blob> {
+    const newDoc = await PDFLibDocument.create();
+
+    for (const page of pages) {
+      // Get the original page from source document
+      const sourcePageIndex = page.pageNumber - 1;
+      
+      if (sourcePageIndex >= 0 && sourcePageIndex < sourceDoc.getPageCount()) {
+        // Copy the page
+        const [copiedPage] = await newDoc.copyPages(sourceDoc, [sourcePageIndex]);
+        
+        // Apply rotation
+        if (page.rotation !== 0) {
+          copiedPage.setRotation(degrees(page.rotation));
+        }
+        
+        newDoc.addPage(copiedPage);
+      }
+    }
+
+    // Set metadata
+    newDoc.setCreator('Stirling PDF');
+    newDoc.setProducer('Stirling PDF');
+    newDoc.setCreationDate(new Date());
+    newDoc.setModificationDate(new Date());
+
+    const pdfBytes = await newDoc.save();
+    return new Blob([pdfBytes], { type: 'application/pdf' });
+  }
+
+  /**
+   * Create multiple PDF documents based on split markers
+   */
+  private async createSplitDocuments(
+    sourceDoc: PDFLibDocument,
+    pages: PDFPage[],
+    baseFilename: string
+  ): Promise<{ blobs: Blob[]; filenames: string[] }> {
+    const splitPoints: number[] = [];
+    const blobs: Blob[] = [];
+    const filenames: string[] = [];
+
+    // Find split points
+    pages.forEach((page, index) => {
+      if (page.splitBefore && index > 0) {
+        splitPoints.push(index);
+      }
+    });
+
+    // Add end point
+    splitPoints.push(pages.length);
+
+    let startIndex = 0;
+    let partNumber = 1;
+
+    for (const endIndex of splitPoints) {
+      const segmentPages = pages.slice(startIndex, endIndex);
+      
+      if (segmentPages.length > 0) {
+        const newDoc = await PDFLibDocument.create();
+        
+        for (const page of segmentPages) {
+          const sourcePageIndex = page.pageNumber - 1;
+          
+          if (sourcePageIndex >= 0 && sourcePageIndex < sourceDoc.getPageCount()) {
+            const [copiedPage] = await newDoc.copyPages(sourceDoc, [sourcePageIndex]);
+            
+            if (page.rotation !== 0) {
+              copiedPage.setRotation(degrees(page.rotation));
+            }
+            
+            newDoc.addPage(copiedPage);
+          }
+        }
+
+        // Set metadata
+        newDoc.setCreator('Stirling PDF');
+        newDoc.setProducer('Stirling PDF');
+        newDoc.setTitle(`${baseFilename} - Part ${partNumber}`);
+        
+        const pdfBytes = await newDoc.save();
+        const blob = new Blob([pdfBytes], { type: 'application/pdf' });
+        const filename = this.generateSplitFilename(baseFilename, partNumber);
+        
+        blobs.push(blob);
+        filenames.push(filename);
+        partNumber++;
+      }
+      
+      startIndex = endIndex;
+    }
+
+    return { blobs, filenames };
+  }
+
+  /**
+   * Generate appropriate filename for export
+   */
+  private generateFilename(originalName: string, selectedOnly: boolean): string {
+    const baseName = originalName.replace(/\.pdf$/i, '');
+    const suffix = selectedOnly ? '_selected' : '_edited';
+    return `${baseName}${suffix}.pdf`;
+  }
+
+  /**
+   * Generate filename for split documents
+   */
+  private generateSplitFilename(baseName: string, partNumber: number): string {
+    const cleanBaseName = baseName.replace(/\.pdf$/i, '');
+    return `${cleanBaseName}_part_${partNumber}.pdf`;
+  }
+
+  /**
+   * Download a single file
+   */
+  downloadFile(blob: Blob, filename: string): void {
+    const url = URL.createObjectURL(blob);
+    const link = document.createElement('a');
+    link.href = url;
+    link.download = filename;
+    link.style.display = 'none';
+    
+    document.body.appendChild(link);
+    link.click();
+    document.body.removeChild(link);
+    
+    // Clean up the URL after a short delay
+    setTimeout(() => URL.revokeObjectURL(url), 1000);
+  }
+
+  /**
+   * Download multiple files as a ZIP
+   */
+  async downloadAsZip(blobs: Blob[], filenames: string[], zipFilename: string): Promise<void> {
+    // For now, download files individually
+    // TODO: Implement ZIP creation when needed
+    blobs.forEach((blob, index) => {
+      setTimeout(() => {
+        this.downloadFile(blob, filenames[index]);
+      }, index * 500); // Stagger downloads
+    });
+  }
+
+  /**
+   * Validate PDF operations before export
+   */
+  validateExport(pdfDocument: PDFDocument, selectedPageIds: string[], selectedOnly: boolean): string[] {
+    const errors: string[] = [];
+
+    if (selectedOnly && selectedPageIds.length === 0) {
+      errors.push('No pages selected for export');
+    }
+
+    if (pdfDocument.pages.length === 0) {
+      errors.push('No pages available to export');
+    }
+
+    const pagesToExport = selectedOnly 
+      ? pdfDocument.pages.filter(page => selectedPageIds.includes(page.id))
+      : pdfDocument.pages;
+
+    if (pagesToExport.length === 0) {
+      errors.push('No valid pages to export after applying filters');
+    }
+
+    return errors;
+  }
+
+  /**
+   * Get export preview information
+   */
+  getExportInfo(pdfDocument: PDFDocument, selectedPageIds: string[], selectedOnly: boolean): {
+    pageCount: number;
+    splitCount: number;
+    estimatedSize: string;
+  } {
+    const pagesToExport = selectedOnly 
+      ? pdfDocument.pages.filter(page => selectedPageIds.includes(page.id))
+      : pdfDocument.pages;
+
+    const splitCount = pagesToExport.reduce((count, page, index) => {
+      return count + (page.splitBefore && index > 0 ? 1 : 0);
+    }, 1); // At least 1 document
+
+    // Rough size estimation (very approximate)
+    const avgPageSize = pdfDocument.file.size / pdfDocument.totalPages;
+    const estimatedBytes = avgPageSize * pagesToExport.length;
+    const estimatedSize = this.formatFileSize(estimatedBytes);
+
+    return {
+      pageCount: pagesToExport.length,
+      splitCount,
+      estimatedSize
+    };
+  }
+
+  /**
+   * Format file size for display
+   */
+  private formatFileSize(bytes: number): string {
+    if (bytes === 0) return '0 B';
+    const k = 1024;
+    const sizes = ['B', 'KB', 'MB', 'GB'];
+    const i = Math.floor(Math.log(bytes) / Math.log(k));
+    return parseFloat((bytes / Math.pow(k, i)).toFixed(2)) + ' ' + sizes[i];
+  }
+}
+
+// Export singleton instance
+export const pdfExportService = new PDFExportService();