processReceipt function

Future<Order> processReceipt(String receiptText, String api, List<String> categories)

Processes a receipt text using the Google Generative AI API and returns the structured Order object.

This function sends the receipt text to the AI model, which extracts items, their quantity, price, subtotal, tax, and total. It also assigns categories to each item based on the provided list.

The AI expects the data in the following JSON format:

{
  "invoice_number": "Invoice Number",
  "date": "Date",
  "payment_method":"Payment Method",
  "items": [
    {
      "name": "Item Name",
      "quantity": Quantity,
      "price": Price,
      "category": "category"
    },
    ...
  ],
  "subtotal": Subtotal,
  "tax": Tax,
  "total": Total
}

If the response does not contain valid JSON or an error occurs during the request, an exception is thrown.

Parameters:

• receiptText: The raw text from the receipt to be processed.
• api: The API key for accessing the Google Generative AI model.
• categories: A list of categories to classify the items.

Returns: A future that resolves to an Order object containing the extracted information.

Throws:

• Exception if there is an error processing the receipt or the API response is invalid.

Implementation

Future<Order> processReceipt(
  String receiptText,
  String api,
  List<String> categories,
) async {
  try {
    final model = GenerativeModel(
      model: 'gemini-1.5-flash-latest',
      apiKey: api,
    );

    final List<String> formattedList = ['unkown'];

    for (String category in categories) {
      formattedList.add(category.toLowerCase());
    }

    String prompt = """
      Extract the invoice number, date, payment method, items, their quantity, price, subtotal, total, and tax from the following receipt:
      $receiptText And give each item a category strictly from this list of categories $categories. If the invoice number, payment method, date, can't be extracted please put the string "UNKNOWN"

      Please return the response in the following JSON format:
      ```json
      {
        "invoice_number": "Invoice Number",
        "date": "Date",
        "payment_method":"PAYMENT METHOD",
        "items": [
          {
            "name": "Item Name",
            "quantity": Quantity,
            "price": Price,
            "category": "category"
          },
          ...
        ],
        "subtotal": Subtotal,
        "tax": Tax,
        "total": Total
      }
      ```""";

    final content = [Content.text(prompt)];
    final response = await model.generateContent(content);

    // Extract the generated text which contains the JSON wrapped in ```json ```
    String generatedText = response.text ?? '';

    // Extract the JSON part from the wrapped ```json ``` text
    String jsonString = extractJsonFromText(generatedText);

    // Convert the response into a JSON structure
    Map<String, dynamic> extractedData = jsonDecode(jsonString);

    Order order = Order.fromJson(extractedData);

    // Return the extracted JSON data
    return order;
  } catch (error) {
    // Handle any errors that may occur during the request
    throw Exception("Error processing receipt: $error");
  }
}