Add automatic invoice parsing to extract purchase items

- Install pdf-parse and tesseract.js for PDF/image processing
- Create /api/admin/parse-invoice endpoint to extract line items from invoices
- Parser extracts quantity and description from invoice text
- Attempts to match extracted items to products in database
- Update PurchaseForm with "Extract items" button
- Pre-fill purchase form with parsed items (user can edit/add more)
- Supports PDF files and image scans (JPG, PNG, etc)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/app/api/admin/parse-invoice/route.ts

@@ -0,0 +1,124 @@
+import { NextResponse } from 'next/server';
+import { isAdminAuthenticated } from '@/lib/adminAuth';
+import { prisma } from '@/lib/prisma';
+import pdfParse from 'pdf-parse';
+import * as Tesseract from 'tesseract.js';
+
+type ExtractedItem = {
+  description: string;
+  quantity: number;
+  productId?: string;
+};
+
+async function extractTextFromPDF(buffer: Buffer): Promise<string> {
+  try {
+    const data = await pdfParse(buffer);
+    return data.text;
+  } catch (err) {
+    throw new Error('Failed to extract text from PDF');
+  }
+}
+
+async function extractTextFromImage(buffer: Buffer): Promise<string> {
+  try {
+    const result = await Tesseract.recognize(buffer, 'eng');
+    return result.data.text;
+  } catch (err) {
+    throw new Error('Failed to OCR image');
+  }
+}
+
+function parseInvoiceText(text: string, products: any[]): ExtractedItem[] {
+  const items: ExtractedItem[] = [];
+  const lines = text.split('\n');
+
+  // Build product search index (lowercase for matching)
+  const productIndex = new Map(products.map((p) => [p.name.toLowerCase(), p.id]));
+
+  for (const line of lines) {
+    const trimmed = line.trim();
+    if (!trimmed || trimmed.length < 5) continue;
+
+    // Look for patterns like: quantity x product or product x quantity
+    // Examples: "10 x T-Shirt", "T-Shirt - 10", "10x hoodies"
+    const matches = trimmed.match(/(\d+)\s*x?\s*(.+?)(?:\s*-\s*£?[\d.]+)?$/i);
+    if (!matches) continue;
+
+    const quantity = parseInt(matches[1], 10);
+    let description = matches[2].trim();
+
+    // Clean up description (remove common noise)
+    description = description.replace(/\s*-\s*\d+\s*$/, ''); // Remove trailing numbers
+    description = description.replace(/£[\d.]+/, '').trim(); // Remove prices
+
+    if (quantity > 0 && description.length > 2) {
+      // Try to match to a product
+      const lowerDesc = description.toLowerCase();
+      let productId: string | undefined;
+
+      for (const [productName, pId] of productIndex) {
+        if (lowerDesc.includes(productName)) {
+          productId = pId;
+          break;
+        }
+      }
+
+      items.push({
+        description,
+        quantity,
+        productId,
+      });
+    }
+  }
+
+  return items;
+}
+
+export async function POST(req: Request) {
+  const isAdmin = await isAdminAuthenticated();
+  if (!isAdmin) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  try {
+    const formData = await req.formData();
+    const file = formData.get('invoice') as File;
+
+    if (!file) {
+      return NextResponse.json({ error: 'No file provided' }, { status: 400 });
+    }
+
+    if (file.size > 8 * 1024 * 1024) {
+      return NextResponse.json({ error: 'File too large (max 8MB)' }, { status: 400 });
+    }
+
+    const buffer = Buffer.from(await file.arrayBuffer());
+    let text = '';
+
+    if (file.type === 'application/pdf') {
+      text = await extractTextFromPDF(buffer);
+    } else if (file.type.startsWith('image/')) {
+      text = await extractTextFromImage(buffer);
+    } else {
+      return NextResponse.json(
+        { error: 'Unsupported file type. Use PDF or image.' },
+        { status: 400 }
+      );
+    }
+
+    // Get all products for matching
+    const products = await prisma.product.findMany({
+      select: { id: true, name: true },
+    });
+
+    const extractedItems = parseInvoiceText(text, products);
+
+    return NextResponse.json({
+      items: extractedItems,
+      rawText: text.substring(0, 500), // First 500 chars for debugging
+    });
+  } catch (err) {
+    const message = err instanceof Error ? err.message : 'Unknown error';
+    return NextResponse.json({ error: message }, { status: 500 });
+  }
+}