Stirling 2.0 (#3928)

# Description of Changes

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File context for managing files between tools and views
Optimisation for large files
Updated Split to work with new file system and match Matts stepped
design closer

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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: Anthony Stirling <[email protected]>

frontend/src/utils/thumbnailUtils.ts

@@ -1,5 +1,19 @@
 import { getDocument } from "pdfjs-dist";
 
+/**
+ * Calculate thumbnail scale based on file size
+ * Smaller files get higher quality, larger files get lower quality
+ */
+export function calculateScaleFromFileSize(fileSize: number): number {
+  const MB = 1024 * 1024;
+  
+  if (fileSize < 1 * MB) return 0.6;      // < 1MB: High quality
+  if (fileSize < 5 * MB) return 0.4;      // 1-5MB: Medium-high quality  
+  if (fileSize < 15 * MB) return 0.3;     // 5-15MB: Medium quality
+  if (fileSize < 30 * MB) return 0.2;     // 15-30MB: Low-medium quality
+  return 0.15;                            // 30MB+: Low quality
+}
+
 /**
  * Generate thumbnail for a PDF file during upload
  * Returns base64 data URL or undefined if generation fails
@@ -14,6 +28,10 @@ export async function generateThumbnailForFile(file: File): Promise<string | und
   try {
     console.log('Generating thumbnail for', file.name);
     
+    // Calculate quality scale based on file size
+    const scale = calculateScaleFromFileSize(file.size);
+    console.log(`Using scale ${scale} for ${file.name} (${(file.size / 1024 / 1024).toFixed(1)}MB)`);
+    
     // Only read first 2MB for thumbnail generation to save memory
     const chunkSize = 2 * 1024 * 1024; // 2MB
     const chunk = file.slice(0, Math.min(chunkSize, file.size));
@@ -26,7 +44,7 @@ export async function generateThumbnailForFile(file: File): Promise<string | und
     }).promise;
     
     const page = await pdf.getPage(1);
-    const viewport = page.getViewport({ scale: 0.2 }); // Smaller scale for memory efficiency
+    const viewport = page.getViewport({ scale }); // Dynamic scale based on file size
     const canvas = document.createElement("canvas");
     canvas.width = viewport.width;
     canvas.height = viewport.height;
@@ -45,7 +63,45 @@ export async function generateThumbnailForFile(file: File): Promise<string | und
     
     return thumbnail;
   } catch (error) {
-    console.warn('Failed to generate thumbnail for', file.name, error);
+    if (error instanceof Error) {
+      if (error.name === 'InvalidPDFException') {
+        console.warn(`PDF structure issue for ${file.name} - using fallback thumbnail`);
+        // Return a placeholder or try with full file instead of chunk
+        try {
+          const fullArrayBuffer = await file.arrayBuffer();
+          const pdf = await getDocument({ 
+            data: fullArrayBuffer,
+            disableAutoFetch: true,
+            disableStream: true,
+            verbosity: 0 // Reduce PDF.js warnings
+          }).promise;
+          
+          const page = await pdf.getPage(1);
+          const viewport = page.getViewport({ scale });
+          const canvas = document.createElement("canvas");
+          canvas.width = viewport.width;
+          canvas.height = viewport.height;
+          const context = canvas.getContext("2d");
+          
+          if (!context) {
+            throw new Error('Could not get canvas context');
+          }
+          
+          await page.render({ canvasContext: context, viewport }).promise;
+          const thumbnail = canvas.toDataURL();
+          
+          pdf.destroy();
+          return thumbnail;
+        } catch (fallbackError) {
+          console.warn('Fallback thumbnail generation also failed for', file.name, fallbackError);
+          return undefined;
+        }
+      } else {
+        console.warn('Failed to generate thumbnail for', file.name, error);
+        return undefined;
+      }
+    }
+    console.warn('Unknown error generating thumbnail for', file.name, error);
     return undefined;
   }
 }