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

package service

import (
	"fmt"
	"os"
	"syscall"
	"unsafe"

	"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) {
	paths := []string{
		fmt.Sprintf("\\\\.\\%s", printerName),           // Win32 device
		fmt.Sprintf("\\\\127.0.0.1\\%s", printerName),  // UNC share
	}

	var handle syscall.Handle
	var lastErr error
	for _, path := range paths {
		pathPtr, _ := syscall.UTF16PtrFromString(path)
		handle, lastErr = syscall.CreateFile(pathPtr, syscall.GENERIC_WRITE,
			0, nil, syscall.OPEN_EXISTING, syscall.FILE_ATTRIBUTE_NORMAL, 0)
		if lastErr == nil {
			return &USBPrinter{handle: handle}, nil
		}
	}

	// 所有路径都失败 → 用临时文件 + copy 命令的方式
	return nil, fmt.Errorf("无法打开打印机 %s (\\\\.\\ 和 UNC均失败): %w。"+
		"请到 Windows 控制面板→设备和打印机→右键 %s→打印机属性→共享→勾选'共享这台打印机'并设置共享名",
		printerName, lastErr, printerName)
}

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)
}

// PrintRawFile 备选方案：通过临时文件 + copy 命令打印
func PrintRawFile(printerName string, data []byte) error {
	tmpFile, err := os.CreateTemp("", "ticket_*.bin")
	if err != nil {
		return err
	}
	defer os.Remove(tmpFile.Name())
	if _, err := tmpFile.Write(data); err != nil {
		tmpFile.Close()
		return err
	}
	tmpFile.Close()
	_, _, _ = syscall.NewLazyDLL("kernel32.dll").NewProc("CopyFileW").Call(
		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(tmpFile.Name()))),
		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(fmt.Sprintf("\\\\127.0.0.1\\%s", printerName)))),
		0)
	return nil
}

var _ = os.Stderr // keep os import