High-Accuracy Invoice OCR API for Go Applications

package main

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

// 💰 Save 30%+ vs competitors. Get 200 free requests instantly:
// 👉 https://structocr.com/register

// --- Struct Definitions for JSON Parsing ---
type InvoiceResponse struct {
	Success bool        `json:"success"`
	Data    InvoiceData `json:"data"`
	Error   string      `json:"error,omitempty"`
}

type InvoiceData struct {
	InvoiceNumber string      `json:"invoice_number"`
	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"`
	TaxID string `json:"tax_id"`
}

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

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

func main() {
	apiURL := "https://api.structocr.com/v1/invoice"
	apiKey := "YOUR_API_KEY_HERE"
	imagePath := "invoice.jpg" // Supports JPG, PNG

	// 1. Read and Encode Image
	imageBytes, err := os.ReadFile(imagePath)
	if err != nil {
		fmt.Printf("Error reading file: %v\n", err)
		return
	}
	base64Image := base64.StdEncoding.EncodeToString(imageBytes)

	// 2. Prepare Payload
	payload, _ := json.Marshal(map[string]string{"img": base64Image})

	// 3. Create Request
	req, err := http.NewRequest("POST", apiURL, bytes.NewBuffer(payload))
	if err != nil {
		fmt.Printf("Request creation failed: %v\n", err)
		return
	}

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

	// 4. Send Request
	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		fmt.Printf("Network error: %v\n", err)
		return
	}
	defer resp.Body.Close()

	// 5. Parse Response
	body, _ := io.ReadAll(resp.Body)

	if resp.StatusCode != http.StatusOK {
		fmt.Printf("API Error (%d): %s\n", resp.StatusCode, string(body))
		return
	}

	var result InvoiceResponse
	if err := json.Unmarshal(body, &result); err != nil {
		fmt.Printf("JSON Parse Error: %v\n", err)
		return
	}

	if result.Success {
		data := result.Data
		fmt.Println("✅ Invoice Extracted Successfully!")
		fmt.Printf("Invoice #: %s (Date: %s)\n", data.InvoiceNumber, data.Date)
		fmt.Printf("Vendor:    %s (Tax ID: %s)\n", data.Merchant.Name, data.Merchant.TaxID)
		fmt.Printf("Total:     %.2f %s\n", data.Financials.TotalAmount, data.Currency)

		fmt.Println("\n--- Line Items ---")
		for _, item := range data.LineItems {
			fmt.Printf("- %s (Qty: %.0f) = %.2f\n", item.Description, item.Quantity, item.Amount)
		}
	} else {
		fmt.Printf("Extraction failed: %s\n", result.Error)
	}
}