lc_garage/internal/modules/printer/service/serial.go

package service

import (
	"fmt"
	"os"
	"syscall"

	"github.com/tarm/serial"
)

// SerialPrinter 通用打印机接口（串口或 Windows USB）
type Printer interface {
	Write(data []byte) error
	Close() error
}

type SerialPrinter struct {
	Port *serial.Port
}

func NewSerialPrinter(portName string, baudRate int) (*SerialPrinter, error) {
	if baudRate <= 0 {
		baudRate = 9600
	}
	// 非 COM 端口 → 尝试 Windows 打印机路径
	if len(portName) >= 3 && portName[:3] != "COM" {
		return nil, fmt.Errorf("非串口设备，请使用 USB 驱动安装虚拟 COM 口，或连接真实 COM 口")
	}
	c := &serial.Config{Name: portName, Baud: baudRate}
	port, err := serial.OpenPort(c)
	if err != nil {
		return nil, fmt.Errorf("打开串口失败 %s: %w", portName, err)
	}
	return &SerialPrinter{Port: port}, nil
}

func (p *SerialPrinter) Write(data []byte) error {
	_, err := p.Port.Write(data)
	return err
}

func (p *SerialPrinter) Close() error {
	return p.Port.Close()
}

// USBPrinter Windows USB 打印机（原生 API 发送 RAW 数据）
type USBPrinter struct {
	handle syscall.Handle
}

func NewUSBPrinter(printerName string) (*USBPrinter, error) {
	path := fmt.Sprintf("\\\\.\\%s", printerName)
	pathPtr, err := syscall.UTF16PtrFromString(path)
	if err != nil {
		return nil, err
	}
	handle, err := syscall.CreateFile(
		pathPtr,
		syscall.GENERIC_WRITE,
		syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE,
		nil,
		syscall.OPEN_EXISTING,
		syscall.FILE_ATTRIBUTE_NORMAL,
		0,
	)
	if err != nil {
		// 尝试通过 UNC 路径
		uncPath := fmt.Sprintf("\\127.0.0.1\\%s", printerName)
		uncPtr, _ := syscall.UTF16PtrFromString(uncPath)
		handle, err = syscall.CreateFile(uncPtr, syscall.GENERIC_WRITE,
			syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE, nil,
			syscall.OPEN_EXISTING, 0, 0)
		if err != nil {
			return nil, fmt.Errorf("无法打开打印机 %s: %w", printerName, err)
		}
	}
	return &USBPrinter{handle: handle}, nil
}

func (p *USBPrinter) Write(data []byte) error {
	var written uint32
	return syscall.WriteFile(p.handle, data, &written, nil)
}

func (p *USBPrinter) Close() error {
	return syscall.CloseHandle(p.handle)
}

var _ = os.Stderr // keep os import