feat(initial): add comprehensive PDF to JPEG preview library with dual-environment support

- Add Node.js implementation using @push.rocks/smartpdf
- Add browser implementation with PDF.js and Web Workers
- Support configurable quality, dimensions, and page selection
- Include comprehensive TypeScript definitions and error handling
- Provide extensive test coverage for both environments
- Add download functionality and browser compatibility checking

ts_web/pdfworker.ts

@@ -0,0 +1,191 @@
+/**
+ * PDF.js worker for processing PDFs in the browser
+ * This file runs in a Web Worker context
+ */
+
+// Import types for worker context
+import type { 
+  IWorkerMessage, 
+  IPdfProcessRequest, 
+  IPdfProcessResponse,
+  TWorkerMessageType
+} from './interfaces.js';
+import { PreviewError } from './interfaces.js';
+
+// PDF.js library (loaded from CDN or bundled)
+declare const pdfjsLib: any;
+
+/**
+ * Worker context interface
+ */
+declare const self: any;
+
+/**
+ * PDF.js configuration
+ */
+const PDFJS_CDN_URL = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js';
+const WORKER_CDN_URL = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';
+
+/**
+ * Worker state
+ */
+let isInitialized = false;
+let pdfjsWorker: any = null;
+
+/**
+ * Initialize PDF.js in worker context
+ */
+async function initializePdfJs(): Promise<void> {
+  if (isInitialized) {
+    return;
+  }
+
+  try {
+    // Load PDF.js library
+    self.importScripts(PDFJS_CDN_URL);
+    
+    if (typeof pdfjsLib === 'undefined') {
+      throw new Error('Failed to load PDF.js library');
+    }
+
+    // Configure PDF.js worker
+    pdfjsLib.GlobalWorkerOptions.workerSrc = WORKER_CDN_URL;
+    
+    isInitialized = true;
+    postMessage({
+      type: 'WORKER_READY',
+      id: 'init',
+      data: { version: pdfjsLib.version }
+    } as IWorkerMessage);
+  } catch (error) {
+    postMessage({
+      type: 'PROCESS_ERROR',
+      id: 'init',
+      error: `Failed to initialize PDF.js: ${error instanceof Error ? error.message : String(error)}`
+    } as IWorkerMessage);
+  }
+}
+
+/**
+ * Process PDF and generate JPEG preview
+ */
+async function processPdf(requestId: string, request: IPdfProcessRequest): Promise<void> {
+  if (!isInitialized) {
+    postMessage({
+      type: 'PROCESS_ERROR',
+      id: requestId,
+      error: 'Worker not initialized'
+    } as IWorkerMessage);
+    return;
+  }
+
+  try {
+    // Load PDF document
+    const loadingTask = pdfjsLib.getDocument({
+      data: request.pdfData,
+      cMapUrl: 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/cmaps/',
+      cMapPacked: true,
+    });
+
+    const pdf = await loadingTask.promise;
+
+    // Validate page number
+    if (request.options.page > pdf.numPages || request.options.page < 1) {
+      throw new Error(`Page ${request.options.page} not found. Document has ${pdf.numPages} pages.`);
+    }
+
+    // Get the specified page
+    const page = await pdf.getPage(request.options.page);
+
+    // Calculate viewport
+    const viewport = page.getViewport({ scale: request.options.scale });
+    
+    // Adjust viewport to fit within max dimensions
+    let { width, height } = viewport;
+    if (request.options.width && width > request.options.width) {
+      const scale = request.options.width / width;
+      width = request.options.width;
+      height = height * scale;
+    }
+    if (request.options.height && height > request.options.height) {
+      const scale = request.options.height / height;
+      height = request.options.height;
+      width = width * scale;
+    }
+
+    const scaledViewport = page.getViewport({ 
+      scale: Math.min(width / viewport.width, height / viewport.height) * request.options.scale 
+    });
+
+    // Create canvas and render page
+    const canvas = new OffscreenCanvas(scaledViewport.width, scaledViewport.height);
+    const context = canvas.getContext('2d');
+
+    if (!context) {
+      throw new Error('Failed to get 2D rendering context');
+    }
+
+    const renderContext = {
+      canvasContext: context,
+      viewport: scaledViewport,
+    };
+
+    await page.render(renderContext).promise;
+
+    // Convert to JPEG
+    const blob = await canvas.convertToBlob({
+      type: 'image/jpeg',
+      quality: request.options.quality / 100,
+    });
+
+    // Convert blob to ArrayBuffer
+    const arrayBuffer = await blob.arrayBuffer();
+
+    // Send response
+    const response: IPdfProcessResponse = {
+      imageData: arrayBuffer,
+      width: scaledViewport.width,
+      height: scaledViewport.height,
+    };
+
+    postMessage({
+      type: 'PROCESS_COMPLETE',
+      id: requestId,
+      data: response
+    } as IWorkerMessage);
+
+  } catch (error) {
+    postMessage({
+      type: 'PROCESS_ERROR',
+      id: requestId,
+      error: error instanceof Error ? error.message : String(error)
+    } as IWorkerMessage);
+  }
+}
+
+/**
+ * Handle worker messages
+ */
+self.addEventListener('message', async (event: MessageEvent<IWorkerMessage>) => {
+  const { type, id, data } = event.data;
+
+  switch (type) {
+    case 'INIT':
+      await initializePdfJs();
+      break;
+
+    case 'PROCESS_PDF':
+      await processPdf(id, data as IPdfProcessRequest);
+      break;
+
+    default:
+      postMessage({
+        type: 'PROCESS_ERROR',
+        id: id || 'unknown',
+        error: `Unknown message type: ${type}`
+      } as IWorkerMessage);
+  }
+});
+
+// Auto-initialize when worker starts
+initializePdfJs();