main.go

package main

import (
	"fmt"
	"golang.org/x/sys/windows"
	"log"
	"math/rand"
	"os"
	"os/exec"
	"strings"
	"syscall"
	"unsafe"

	"github.com/restartfu/portmypack/portmypack"
	"github.com/restartfu/portmypack/portmypack/java"
)

func main() {
	path, ok := getFileSelectionPath()
	if !ok {
		log.Fatalln("please select a valid zip archive")
	}
	javapack, err := java.NewResourcePack(path)
	if err != nil {
		log.Fatalln(err)
	}

	out := fmt.Sprintf("%s\\portmypack-%d.mcpack", os.TempDir(), rand.Int63())
	portmypack.PortJavaEditionPack(javapack, out)

	cmd := exec.Command("cmd", "/c", out)
	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
	err = cmd.Run()
	if err != nil {
		log.Fatalln(err)
	}
}

var (
	// https://docs.microsoft.com/en-us/windows/win32/api/commdlg/
	_Dialog32 = windows.NewLazySystemDLL("comdlg32.dll")

	_GetOpenFileName = _Dialog32.NewProc("GetOpenFileNameW")

	// https://docs.microsoft.com/en-us/windows/win32/api/commdlg/ns-commdlg-openfilenamew
	_FlagFileMustExist   = uint32(0x00001000)
	_FlagForceShowHidden = uint32(0x10000000)
	_FlagDisableLinks    = uint32(0x00100000)

	_FilePathLength       = uint32(65535)
	_OpenFileStructLength = uint32(unsafe.Sizeof(_OpenFileName{}))
)

type (
	// _OpenFileName is defined at https://docs.microsoft.com/pt-br/windows/win32/api/commdlg/ns-commdlg-openfilenamew
	_OpenFileName struct {
		StructSize      uint32
		Owner           uintptr
		Instance        uintptr
		Filter          *uint16
		CustomFilter    *uint16
		MaxCustomFilter uint32
		FilterIndex     uint32
		File            *uint16
		MaxFile         uint32
		FileTitle       *uint16
		MaxFileTitle    uint32
		InitialDir      *uint16
		Title           *uint16
		Flags           uint32
		FileOffset      uint16
		FileExtension   uint16
		DefExt          *uint16
		CustData        uintptr
		FnHook          uintptr
		TemplateName    *uint16
		PvReserved      uintptr
		DwReserved      uint32
		FlagsEx         uint32
	}
)

func getFileSelectionPath() (string, bool) {
	pathUTF16 := make([]uint16, _FilePathLength)

	open := _OpenFileName{
		File:       &pathUTF16[0],
		MaxFile:    _FilePathLength,
		Filter:     buildFilter([]string{"zip"}),
		Flags:      _FlagFileMustExist | _FlagForceShowHidden | _FlagDisableLinks,
		StructSize: _OpenFileStructLength,
	}

	if r, _, _ := _GetOpenFileName.Call(uintptr(unsafe.Pointer(&open))); r == 0 {
		return "", false
	}

	path := windows.UTF16ToString(pathUTF16)
	if len(path) == 0 {
		return "", false
	}

	return path, true
}

func buildFilter(extensions []string) *uint16 {
	if len(extensions) <= 0 {
		return nil
	}

	for k, v := range extensions {
		// Extension must have `*` wildcard, so `.jpg` must be `*.jpg`.
		if !strings.HasPrefix(v, "*") {
			extensions[k] = "*" + v
		}
	}
	e := strings.ToUpper(strings.Join(extensions, ";"))

	// That is a "string-pair", Windows have a Title and the Filter, for instance it could be:
	// Images\0*.JPG;*.PNG\0\0
	// Where `\0` means NULL
	f := windows.StringToUTF16(e + " " + e) // Use the filter as title so it appear `*.JPG;*.PNG` for the user.
	f[len(e)] = 0                           // Replace the " " (space) with NULL.
	f = append(f, uint16(0))                // Adding another NULL, because we need two.
	return &f[0]
}