libgofunc/printer.go

package libgofunc

import (
	/*
		#include <stdint.h>
	*/
	"C"
	_ "image/png"
	"os"
	"strings"

	"bufio"
	"log"
	"net"

	"time"

	"github.com/kenshaw/escpos"
)
import (
	"errors"
)

//export PrintImg
func PrintImg(printer *C.char, imagePath *C.char) *C.char {
	goPrinter := C.GoString(printer)
	goImagePath := C.GoString(imagePath)
	// printer := "tcp:192.168.100.151:9100"
	// printer := "usb:/dev/usb/lp1"
	var w *bufio.ReadWriter
	if strings.HasPrefix(goPrinter, "tcp:") {
		location := strings.TrimLeft(goPrinter, "tcp:")
		conn, err := net.Dial("tcp", location)
		if err != nil {
			log.Println("error dialing:", err.Error())
			return NewErr(err)
		}
		defer conn.Close()
		w = bufio.NewReadWriter(bufio.NewReader(conn), bufio.NewWriter(conn))
	} else if strings.HasPrefix(goPrinter, "usb:") {
		location := strings.TrimLeft(goPrinter, "usb:")
		f, err := os.OpenFile(location, os.O_RDWR, os.ModeDevice)
		if err != nil {
			log.Println("error OpenFile usb:", err.Error())
			return NewErr(err)
		}
		defer f.Close()
		w = bufio.NewReadWriter(bufio.NewReader(f), bufio.NewWriter(f))
		// } else if strings.HasPrefix(goPrinter, "int:") {
		// 	ctx := gousb.NewContext()
		// 	// location := strings.TrimLeft(goPrinter, "int:")
		// 	targetBus := 1
		// 	targetAddr := 5
		// 	devs, err := ctx.OpenDevices(func(desc *gousb.DeviceDesc) bool {
		// 		return int(desc.Bus) == targetBus && int(desc.Address) == targetAddr
		// 	})
		// 	if err != nil || len(devs) == 0 {
		// 		log.Fatal("Could not find or open the device")
		// 	}
		// 	dev := devs[0]
		// 	defer dev.Close()
		// 	dev.SetAutoDetach(true)

		// 	// 2. Claim the default interface (usually 0 for printers)
		// 	// Note: This may require detaching the kernel driver on Linux
		// 	intf, done, err := dev.DefaultInterface()
		// 	if err != nil {
		// 		log.Fatalf("Failed to claim interface: %v", err)
		// 	}
		// 	defer done()

		// 	// 3. Open the Bulk Output Endpoint (usually endpoint #1 or #2)
		// 	// You may need to inspect desc.Endpoints to find the correct Bulk Out ID
		// 	out, err = intf.OutEndpoint(1)
		// 	if err != nil {
		// 		log.Fatalf("Failed to open OUT endpoint: %v", err)
		// 	}
		// 	// w = bufio.NewReadWriter(bufio.NewReader(outPort), bufio.NewWriter(f))
		// 	rw := &USBReadWriter{out: out}
		// 	reader := bufio.NewReader(rw)
		// 	writer := bufio.NewWriter(rw)
		// 	w = bufio.NewReadWriter(reader, writer)
	} else {
		return NewErr(errors.New("invalid printer"))
	}
	prt := escpos.New(w)

	prt.Init()
	prt.SetSmooth(1)
	prt.SetAlign("left")

	imgBytes, err := imgData(goImagePath)
	if err != nil {
		return NewErr(err)
	}
	err = WriteChunk(w, prt, imgBytes)
	if err != nil {
		return NewErr(err)
	}
	time.Sleep(500 * time.Millisecond)
	w.Flush()

	prt.WriteRaw([]byte{0x1B, 0x64, 0x03})
	prt.Cut()
	prt.End()
	w.Flush()
	time.Sleep(1 * time.Second)
	return NewOk(nil)
}

func Print(printer, imagePath string) string {
	result := PrintImg(C.CString(printer), C.CString(imagePath))
	r := C.GoString(result)
	return r
}

// WriteChunk breaks the large byte array into smaller chunks
func WriteChunk(w *bufio.ReadWriter, prt *escpos.Escpos, data []byte) error {
	chunkSize := 1024 // 1 KB chunks work best for network printers
	for i := 0; i < len(data); i += chunkSize {
		end := min(i+chunkSize, len(data))

		_, err := prt.WriteRaw(data[i:end])
		if err != nil {
			log.Println("Error writing image chunk:", err)
			return err
		}
		if err := w.Flush(); err != nil {
			log.Println("Error flushing buffer:", err)
			return err
		}
		// Give the printer's network chip a microsecond to breathe
		time.Sleep(5 * time.Millisecond)
	}
	return nil
}