smartpreview/ts/smartpreview.ts

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

/**
 * Main SmartPreview class for Node.js environment
 * Provides unified API for generating previews from various document formats
 */
export class SmartPreview {
  private pdfProcessor: PdfProcessor | null = null;
  private isInitialized = false;

  /**
   * Create a new SmartPreview instance
   */
  constructor() {
    // Constructor kept minimal following async initialization pattern
  }

  /**
   * Initialize the SmartPreview instance and all processors
   */
  public async init(): Promise<void> {
    if (this.isInitialized) {
      return;
    }

    try {
      // Initialize PDF processor
      this.pdfProcessor = new PdfProcessor();
      await this.pdfProcessor.init();

      this.isInitialized = true;
    } catch (error) {
      await this.cleanup(); // Cleanup on initialization failure
      throw new PreviewError(
        'PROCESSING_FAILED',
        'Failed to initialize SmartPreview',
        error instanceof Error ? error : new Error(String(error))
      );
    }
  }

  /**
   * Generate preview from buffer
   * @param input - Buffer containing the document data
   * @param options - Preview generation options
   * @returns Promise resolving to preview result
   */
  public async generatePreview(input: Buffer, options: IPreviewOptions = {}): Promise<IPreviewResult> {
    if (!this.isInitialized) {
      throw new PreviewError('PROCESSING_FAILED', 'SmartPreview not initialized. Call init() first.');
    }

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

    // Detect format and route to appropriate processor
    const format = await this.detectFormat(input);
    
    switch (format) {
      case 'pdf':
        if (!this.pdfProcessor) {
          throw new PreviewError('PROCESSING_FAILED', 'PDF processor not available');
        }
        return await this.pdfProcessor.processPreview(input, options);
      
      default:
        throw new PreviewError('UNSUPPORTED_FORMAT', `Format '${format}' is not supported`);
    }
  }

  /**
   * Generate preview from file path
   * @param filePath - Path to the document file
   * @param options - Preview generation options
   * @returns Promise resolving to preview result
   */
  public async generatePreviewFromFile(filePath: string, options: IPreviewOptions = {}): Promise<IPreviewResult> {
    if (!plugins.fs.existsSync(filePath)) {
      throw new PreviewError('INVALID_INPUT', `File not found: ${filePath}`);
    }

    try {
      const buffer = await plugins.fs.promises.readFile(filePath);
      return await this.generatePreview(buffer, options);
    } catch (error) {
      if (error instanceof PreviewError) {
        throw error;
      }
      throw new PreviewError(
        'PROCESSING_FAILED',
        `Failed to read file: ${filePath}`,
        error instanceof Error ? error : new Error(String(error))
      );
    }
  }

  /**
   * Save preview to file
   * @param input - Buffer containing the document data
   * @param outputPath - Path where the preview should be saved
   * @param options - Preview generation options
   */
  public async savePreview(input: Buffer, outputPath: string, options: IPreviewOptions = {}): Promise<void> {
    const result = await this.generatePreview(input, options);
    
    try {
      // Ensure output directory exists
      const outputDir = plugins.path.dirname(outputPath);
      await plugins.fs.promises.mkdir(outputDir, { recursive: true });
      
      // Write preview to file
      await plugins.fs.promises.writeFile(outputPath, result.buffer);
    } catch (error) {
      throw new PreviewError(
        'PROCESSING_FAILED',
        `Failed to save preview to: ${outputPath}`,
        error instanceof Error ? error : new Error(String(error))
      );
    }
  }

  /**
   * Get supported input formats
   */
  public getSupportedFormats(): TSupportedInputFormat[] {
    return ['pdf'];
  }

  /**
   * Check if a format is supported
   */
  public isFormatSupported(format: string): format is TSupportedInputFormat {
    return this.getSupportedFormats().includes(format as TSupportedInputFormat);
  }

  /**
   * Clean up resources
   */
  public async cleanup(): Promise<void> {
    if (this.pdfProcessor) {
      await this.pdfProcessor.cleanup();
      this.pdfProcessor = null;
    }
    this.isInitialized = false;
  }

  /**
   * Detect document format from buffer
   * @private
   */
  private async detectFormat(buffer: Buffer): Promise<TSupportedInputFormat> {
    // Check PDF magic bytes
    if (buffer.length >= 4) {
      const header = buffer.subarray(0, 4);
      if (header.equals(Buffer.from('%PDF'))) {
        return 'pdf';
      }
    }

    // Future format detection can be added here
    // Example: JPEG, PNG, TIFF, etc.

    throw new PreviewError('UNSUPPORTED_FORMAT', 'Unable to detect supported format from input');
  }

  /**
   * Static factory method for convenient instantiation
   */
  public static async create(options: IPreviewOptions = {}): Promise<SmartPreview> {
    const instance = new SmartPreview();
    await instance.init();
    return instance;
  }
}