Golang Receipt OCR API for Financial Automation

// 💰 Save hours of development. Get 200 free credits instantly:
// 👉 https://structocr.com/register

package main

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
)

// Define structs for safe JSON unmarshaling
type ApiResponse struct {
	Success bool        `json:"success"`
	Data    ReceiptData `json:"data"`
	Error   string      `json:"error"`
}

type ReceiptData struct {
	Date       string      `json:"date"`
	Currency   string      `json:"currency"`
	Merchant   Merchant    `json:"merchant"`
	Financials Financials  `json:"financials"`
	LineItems  []LineItem  `json:"line_items"`
}

type Merchant struct {
	Name    string `json:"name"`
	Address string `json:"address"`
}

type Financials struct {
	Subtotal    float64 `json:"subtotal"`
	TaxAmount   float64 `json:"tax_amount"`
	TotalAmount float64 `json:"total_amount"`
}

type LineItem struct {
	Description string  `json:"description"`
	Quantity    float64 `json:"quantity"`
	UnitPrice   float64 `json:"unit_price"`
	Amount      float64 `json:"amount"`
}

func main() {
	apiKey := "YOUR_API_KEY" // Replace with your StructOCR API key
	imagePath := "./lunch_receipt.jpg" // Path to your test image

	// 1. Read and base64 encode the image
	imgBytes, err := os.ReadFile(imagePath)
	if err != nil {
		fmt.Println("Error reading file:", err)
		os.Exit(1)
	}
	imgBase64 := base64.StdEncoding.EncodeToString(imgBytes)

	// 2. Prepare JSON payload
	payload := map[string]string{"img": imgBase64}
	payloadBytes, err := json.Marshal(payload)
	if err != nil {
		fmt.Println("Error marshaling payload:", err)
		os.Exit(1)
	}

	// 3. Create HTTP POST request targeting the Receipt endpoint
	req, err := http.NewRequest("POST", "https://api.structocr.com/v1/receipt", bytes.NewBuffer(payloadBytes))
	if err != nil {
		fmt.Println("Error creating request:", err)
		os.Exit(1)
	}

	req.Header.Set("x-api-key", apiKey)
	req.Header.Set("Content-Type", "application/json")

	// 4. Execute the request
	client := &http.Client{}
	res, err := client.Do(req)
	if err != nil {
		fmt.Println("Error executing request:", err)
		os.Exit(1)
	}
	defer res.Body.Close()

	// 5. Parse the structured response
	bodyBytes, _ := io.ReadAll(res.Body)
	var response ApiResponse
	if err := json.Unmarshal(bodyBytes, &response); err != nil {
		fmt.Println("Error decoding JSON response:", err)
		os.Exit(1)
	}

	// 6. Output the parsed data
	if response.Success {
		fmt.Println("✅ Receipt Parsed Successfully!")
		fmt.Printf("Merchant: %s\n", response.Data.Merchant.Name)
		fmt.Printf("Date: %s\n", response.Data.Date)
		fmt.Printf("Total: %.2f %s\n", response.Data.Financials.TotalAmount, response.Data.Currency)
		
		fmt.Println("\n--- Extracted Line Items ---")
		for _, item := range response.Data.LineItems {
			fmt.Printf("- %s (Qty: %.1f) = %.2f\n", item.Description, item.Quantity, item.Amount)
		}
	} else {
		fmt.Println("❌ Extraction Failed:", response.Error)
	}
}