smartpreview/ts/pdfprocessor.ts

import * as plugins from './plugins.js';
import type { IPdfProcessor, IPreviewOptions, IPreviewResult } from './interfaces.js';
import { PreviewError } from './interfaces.js';

/**
 * PDF processor implementation using @push.rocks/smartpdf
 */
export class PdfProcessor implements IPdfProcessor {
  public readonly inputFormat = 'pdf' as const;
  public readonly outputFormat = 'jpeg' as const;

  private smartPdf: plugins.SmartPdf | null = null;

  /**
   * Initialize the PDF processor
   */
  public async init(): Promise<void> {
    try {
      this.smartPdf = await plugins.SmartPdf.create();
      await this.smartPdf.start();
    } catch (error) {
      throw new PreviewError(
        'PROCESSING_FAILED',
        'Failed to initialize PDF processor',
        error instanceof Error ? error : new Error(String(error))
      );
    }
  }

  /**
   * Clean up resources
   */
  public async cleanup(): Promise<void> {
    if (this.smartPdf) {
      try {
        await this.smartPdf.stop();
        this.smartPdf = null;
      } catch (error) {
        console.warn('Warning: Failed to cleanly stop SmartPdf instance:', error);
      }
    }
  }

  /**
   * Process PDF and generate JPEG preview
   */
  public async processPreview(input: Buffer, options: IPreviewOptions): Promise<IPreviewResult> {
    if (!this.smartPdf) {
      throw new PreviewError('PROCESSING_FAILED', 'PDF processor not initialized');
    }

    if (!input || input.length === 0) {
      throw new PreviewError('INVALID_INPUT', 'Input buffer is empty or invalid');
    }

    try {
      // Validate PDF buffer
      await this.validatePdfBuffer(input);

      // Set default options
      const processOptions = {
        quality: options.quality ?? 80,
        width: options.width ?? 800,
        height: options.height ?? 600,
        page: options.page ?? 1,
        scale: options.scale ?? 1.0,
      };

      // Validate options
      this.validateOptions(processOptions);

      // Generate JPEG from PDF using SmartPdf
      // Note: This is a placeholder implementation
      // TODO: Implement actual PDF to JPEG conversion using the correct SmartPdf API
      
      // For development purposes, create a mock JPEG buffer
      const buffer = Buffer.from('JPEG placeholder - implement PDF to JPEG conversion');
      
      // In a real implementation, this would use SmartPdf to convert PDF to image
      // await this.smartPdf.convertToImage(input, options);
      
      return {
        buffer,
        dimensions: {
          width: processOptions.width,
          height: processOptions.height,
        },
        size: buffer.length,
        mimeType: 'image/jpeg',
      };
    } catch (error) {
      if (error instanceof PreviewError) {
        throw error;
      }

      // Handle specific SmartPdf errors
      if (error instanceof Error) {
        if (error.message.includes('invalid PDF')) {
          throw new PreviewError('PDF_CORRUPTED', 'Invalid or corrupted PDF file', error);
        }
        if (error.message.includes('page not found')) {
          throw new PreviewError('PAGE_NOT_FOUND', `Page ${options.page} not found in PDF`, error);
        }
      }

      throw new PreviewError(
        'PROCESSING_FAILED',
        'Unexpected error during PDF processing',
        error instanceof Error ? error : new Error(String(error))
      );
    }
  }

  /**
   * Validate PDF buffer format
   */
  private async validatePdfBuffer(buffer: Buffer): Promise<void> {
    // Check PDF magic bytes
    const pdfHeader = buffer.subarray(0, 4);
    if (!pdfHeader.equals(Buffer.from('%PDF'))) {
      throw new PreviewError('INVALID_INPUT', 'Input is not a valid PDF file');
    }
  }

  /**
   * Validate processing options
   */
  private validateOptions(options: Required<IPreviewOptions>): void {
    if (options.quality < 1 || options.quality > 100) {
      throw new PreviewError('INVALID_OPTIONS', 'Quality must be between 1 and 100');
    }

    if (options.width <= 0 || options.height <= 0) {
      throw new PreviewError('INVALID_OPTIONS', 'Width and height must be positive numbers');
    }

    if (options.page < 1) {
      throw new PreviewError('INVALID_OPTIONS', 'Page number must be 1 or greater');
    }

    if (options.scale <= 0) {
      throw new PreviewError('INVALID_OPTIONS', 'Scale must be a positive number');
    }
  }
}