[1ST COMMIT] based on https://github.com/PanJ/promptpay-me/blob/master/generate_payload.go

Author: efairon

qrcode.go

@@ -0,0 +1,120 @@
+package PromptPay
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	qrcode "github.com/skip2/go-qrcode"
+	"github.com/snksoft/crc"
+)
+
+type Payment struct {
+	Amount   float32
+	Country  string
+	Currency string
+	OneTime  bool
+	Account  string
+	Version  string
+}
+
+const ID_PAYLOAD_FORMAT = "00"
+const ID_POI_METHOD = "01"
+const ID_MERCHANT_INFORMATION_BOT = "29"
+const ID_TRANSACTION_CURRENCY = "53"
+const ID_TRANSACTION_AMOUNT = "54"
+const ID_COUNTRY_CODE = "58"
+const ID_CRC = "63"
+
+const PAYLOAD_FORMAT_EMV_QRCPS_MERCHANT_PRESENTED_MODE = "01"
+const POI_METHOD_STATIC = "11"
+const POI_METHOD_DYNAMIC = "12"
+const MERCHANT_INFORMATION_TEMPLATE_ID_GUID = "00"
+const BOT_ID_MERCHANT_PHONE_NUMBER = "01"
+const BOT_ID_MERCHANT_TAX_ID = "02"
+const BOT_ID_MERCHANT_EWALLET_ID = "03"
+const GUID_PROMPTPAY = "A000000677010111"
+const TRANSACTION_CURRENCY_THB = "764"
+const COUNTRY_CODE_TH = "TH"
+
+// NewPayment initialize new payment struct with default values
+func NewPayment() (payment Payment) {
+	payment = Payment{
+		Currency: "THB",
+		Country:  COUNTRY_CODE_TH,
+		Version:  "000201",
+	}
+	return
+}
+
+func f(id string, value string) string {
+	return fmt.Sprintf("%s%02d%s", id, len(value), value)
+}
+
+func serialize(xs []string) string {
+	return strings.Join(xs, "")
+}
+
+func sanitizeTarget(id string) string {
+	regex := regexp.MustCompile(`[^0-9]`)
+	return regex.ReplaceAllString(id, "")
+}
+
+func formatTarget(id string) string {
+	numbers := sanitizeTarget(id)
+	if len(numbers) >= 13 {
+		return numbers
+	}
+	regex := regexp.MustCompile(`^0`)
+	countryCoded := regex.ReplaceAllString(id, "66")
+	return fmt.Sprintf("%013s", countryCoded)
+}
+
+//
+func formatAmount(amount float32) string {
+	return fmt.Sprintf("%.2f", amount)
+}
+
+func formatCrc(crcValue uint64) string {
+	return fmt.Sprintf("%04X", crcValue)
+}
+
+// String returns string of Promptpay QRCode
+func (p Payment) String() string {
+	target := sanitizeTarget(p.Account)
+	var targetType string
+	switch {
+	case len(target) >= 15:
+		targetType = BOT_ID_MERCHANT_EWALLET_ID
+	case len(target) >= 13:
+		targetType = BOT_ID_MERCHANT_TAX_ID
+	default:
+		targetType = BOT_ID_MERCHANT_PHONE_NUMBER
+	}
+
+	var data []string
+	data = append(data, f(ID_PAYLOAD_FORMAT, PAYLOAD_FORMAT_EMV_QRCPS_MERCHANT_PRESENTED_MODE))
+	if p.Amount != 0 {
+		data = append(data, f(ID_POI_METHOD, POI_METHOD_DYNAMIC))
+	} else {
+		data = append(data, f(ID_POI_METHOD, POI_METHOD_STATIC))
+	}
+	merchantInfo := serialize([]string{f(MERCHANT_INFORMATION_TEMPLATE_ID_GUID, GUID_PROMPTPAY), f(targetType, formatTarget(target))})
+	data = append(data, f(ID_MERCHANT_INFORMATION_BOT, merchantInfo))
+	data = append(data, f(ID_COUNTRY_CODE, COUNTRY_CODE_TH))
+	data = append(data, f(ID_TRANSACTION_CURRENCY, TRANSACTION_CURRENCY_THB))
+	data = append(data, f(ID_PAYLOAD_FORMAT, PAYLOAD_FORMAT_EMV_QRCPS_MERCHANT_PRESENTED_MODE))
+	if p.Amount != 0 {
+		data = append(data, f(ID_TRANSACTION_AMOUNT, formatAmount(p.Amount)))
+	}
+
+	dataToCrc := fmt.Sprintf("%s%s%s", serialize(data), ID_CRC, "04")
+	crcValue := crc.CalculateCRC(crc.CCITT, []byte(dataToCrc))
+	data = append(data, f(ID_CRC, formatCrc(crcValue)))
+	return serialize(data)
+}
+
+func (p *Payment) QRCode() (png []byte, err error) {
+	png, err = qrcode.Encode(p.String(), qrcode.High, 512)
+	return
+}