// +build windows

package drop

import (
	"errors"
	"unsafe"

	"golang.org/x/text/encoding/unicode"
	"opslag.de/schobers/geom"
)

/*
#include <Windows.h>
#include <stdint.h>

void SetDragAndDropHook(void* window);
*/
import "C"

var handler Dropper = nil
var drops map[uint32]droppedFiles = map[uint32]droppedFiles{}

type droppedFiles struct {
	X, Y  int
	Files []string
}

//export droppedFilesPosition
func droppedFilesPosition(id C.uint32_t, x, y C.INT) {
	files := drops[uint32(id)]
	files.X = int(x)
	files.Y = int(y)
	drops[uint32(id)] = files
}

//export droppedFilesFile
func droppedFilesFile(id C.uint32_t, filePath *C.wchar_t, filePathLength C.UINT) {
	files := drops[uint32(id)]
	pathBytes := C.GoBytes(unsafe.Pointer(filePath), C.int(filePathLength)*C.sizeof_wchar_t)
	decoder := unicode.UTF16(unicode.LittleEndian, unicode.UseBOM).NewDecoder()
	path, err := decoder.Bytes(pathBytes)
	if err != nil {
		return
	}
	files.Files = append(files.Files, string(path))
	drops[uint32(id)] = files
}

//export droppedFilesDrop
func droppedFilesDrop(id C.uint32_t) {
	h := handler
	if h == nil {
		return
	}
	drop, ok := drops[uint32(id)]
	if !ok {
		return
	}
	h.FilesDropped(geom.Pt(drop.X, drop.Y).ToF32(), drop.Files)
}

func Register(dropper Dropper) error {
	if handler != nil {
		return errors.New(`can only register single dropper`)
	}
	handler = dropper
	C.SetDragAndDropHook(unsafe.Pointer(dropper.WindowHandle()))
	return nil
}