//go:build windows

package filedialog

import (
	"path/filepath"
	"strings"
	"syscall"
	"unsafe"

	"golang.org/x/sys/windows"
)

var (
	comdlg32           = windows.NewLazySystemDLL("comdlg32.dll")
	procGetOpenFileName = comdlg32.NewProc("GetOpenFileNameW")
	procGetSaveFileName = comdlg32.NewProc("GetSaveFileNameW")
)

const (
	ofnExplorer        = 0x00080000
	ofnFileMustExist   = 0x00001000
	ofnPathMustExist   = 0x00000800
	ofnOverwritePrompt = 0x00000002
	ofnHideReadOnly    = 0x00000004
	maxPath            = 32768
)

type openFileNameW struct {
	LStructSize       uint32
	HwndOwner         windows.HWND
	HInstance         windows.Handle
	LpstrFilter       *uint16
	LpstrCustomFilter *uint16
	NMaxCustFilter    uint32
	NFilterIndex      uint32
	LpstrFile         *uint16
	NMaxFile          uint32
	LpstrFileTitle    *uint16
	NMaxFileTitle     uint32
	LpstrInitialDir   *uint16
	LpstrTitle        *uint16
	Flags             uint32
	NFileOffset       uint16
	NFileExtension    uint16
	LpstrDefExt       *uint16
	LCustData         uintptr
	LpfnHook          uintptr
	LpTemplateName    *uint16
	PvReserved        unsafe.Pointer
	DwReserved        uint32
	FlagsEx           uint32
}

func jsonFilter() *uint16 {
	// Double-null terminated pairs: label\0pattern\0label\0pattern\0\0
	s := "JSON (*.json)\x00*.json\x00All files\x00*.*\x00"
	return &utf16FromString(s)[0]
}

func utf16FromString(s string) []uint16 {
	u, err := syscall.UTF16FromString(s)
	if err != nil {
		return []uint16{0}
	}
	return u
}

func ensureJSONExt(path string) string {
	if strings.EqualFold(filepath.Ext(path), ".json") {
		return path
	}
	return path + ".json"
}

// SaveJSON shows a Save As dialog for a .json file.
func SaveJSON(title, defaultName string) (string, error) {
	if title == "" {
		title = "Сохранить список серверов"
	}
	if defaultName == "" {
		defaultName = "navis-servers.json"
	}
	buf := make([]uint16, maxPath)
	copy(buf, utf16FromString(defaultName))

	filter := jsonFilter()
	titlePtr, _ := syscall.UTF16PtrFromString(title)
	defExt, _ := syscall.UTF16PtrFromString("json")

	ofn := openFileNameW{
		LStructSize:  uint32(unsafe.Sizeof(openFileNameW{})),
		LpstrFilter:  filter,
		NFilterIndex: 1,
		LpstrFile:    &buf[0],
		NMaxFile:     uint32(len(buf)),
		LpstrTitle:   titlePtr,
		Flags:        ofnExplorer | ofnPathMustExist | ofnOverwritePrompt | ofnHideReadOnly,
		LpstrDefExt:  defExt,
	}
	r, _, _ := procGetSaveFileName.Call(uintptr(unsafe.Pointer(&ofn)))
	if r == 0 {
		return "", ErrCanceled
	}
	path := windows.UTF16ToString(buf)
	if path == "" {
		return "", ErrCanceled
	}
	return ensureJSONExt(path), nil
}

// OpenJSON shows an Open dialog for a .json file.
func OpenJSON(title string) (string, error) {
	if title == "" {
		title = "Загрузить список серверов"
	}
	buf := make([]uint16, maxPath)
	filter := jsonFilter()
	titlePtr, _ := syscall.UTF16PtrFromString(title)

	ofn := openFileNameW{
		LStructSize:  uint32(unsafe.Sizeof(openFileNameW{})),
		LpstrFilter:  filter,
		NFilterIndex: 1,
		LpstrFile:    &buf[0],
		NMaxFile:     uint32(len(buf)),
		LpstrTitle:   titlePtr,
		Flags:        ofnExplorer | ofnFileMustExist | ofnPathMustExist | ofnHideReadOnly,
	}
	r, _, _ := procGetOpenFileName.Call(uintptr(unsafe.Pointer(&ofn)))
	if r == 0 {
		return "", ErrCanceled
	}
	path := windows.UTF16ToString(buf)
	if path == "" {
		return "", ErrCanceled
	}
	return path, nil
}