A PocketFlow cookbook example that extracts structured data from PDF invoices using GPT-4o vision, then validates the math (line items, tax, and totals).

• PDF Vision Extraction: Converts invoice PDFs to images and uses GPT-4o vision to extract structured fields
• Math Validation: Verifies line item amounts, subtotal, tax calculations, and grand total
• Sample Invoice Generator: Includes a helper script to create a realistic test invoice PDF

1. Install dependencies:

   pip install -r requirements.txt

2. Set your OpenAI API key:

   export OPENAI_API_KEY="your-api-key-here"

   Quick check to make sure your API key works:

   python utils.py

3. Generate a sample invoice PDF:

   python create_invoice.py

4. Run the invoice processor:

   python main.py

   Or specify a custom PDF path:

   python main.py --path=my_invoice.pdf

flowchart LR
    extract[ExtractFields] --> validate[Validate]

1. ExtractFields: Converts the PDF to an image using PyMuPDF, sends it to GPT-4o vision, and extracts structured invoice data (vendor, customer, line items, tax, total) as YAML
2. Validate: Checks the math -- verifies each line item (qty x unit_price = amount), subtotal (sum of amounts), tax (subtotal x rate), and grand total (subtotal + tax)

• main.py: Entry point with CLI argument parsing
• flow.py: Defines the invoice processing flow
• nodes.py: ExtractFields and Validate node implementations
• utils.py: OpenAI GPT-4o and vision API wrappers
• create_invoice.py: Generates a sample invoice PDF for testing
• requirements.txt: Python dependencies

🧾 PocketFlow Invoice Processor

📄 Processing: invoice.pdf

🔍 Converting PDF to image...
🤔 Extracting invoice fields with GPT-4o vision...
  Extracted fields:
    Invoice #: INV-2024-0042
    Vendor: Acme Corp
    Customer: Widget Industries LLC
    Line items: 4
      - Web Development Services: 40 x $150.00 = $6000.00
      - UI/UX Design: 20 x $125.00 = $2500.00
      - Project Management: 10 x $100.00 = $1000.00
      - Quality Assurance Testing: 15 x $95.00 = $1425.00
    Subtotal: $10925.00
    Tax: $928.62
    Total: $11853.62
🔍 Validating invoice math...
  Validation passed ✅

=== Summary ===
  Invoice #: INV-2024-0042
  Total: $11853.62
  Status: PASSED ✅