// +build windows

package dragdrop

import (
	"unsafe"

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

/*
#cgo LDFLAGS: -lole32 -luuid

#include <Windows.h>
#include <oleidl.h>
#include <stdint.h>
#include <stdlib.h>

extern uint32_t RegisterHandler(void* windowHandle);
*/
import "C"

//export clearFiles
func clearFiles(handle uint32) {
	handler := handlers[handle]
	handler.Files = nil
	handlers[handle] = handler
}

//export addFile
func addFile(handle uint32, pathNative *C.wchar_t, pathNativeLength C.UINT) {
	pathBytes := C.GoBytes(unsafe.Pointer(pathNative), C.int(pathNativeLength)*C.sizeof_wchar_t)
	decoder := unicode.UTF16(unicode.LittleEndian, unicode.UseBOM).NewDecoder()
	path, err := decoder.Bytes(pathBytes)
	if err != nil {
		return
	}
	handler := handlers[handle]
	handler.Files = append(handler.Files, string(path))
	handlers[handle] = handler
}

//export onDragEnter
func onDragEnter(handle uint32, x, y C.LONG) {
	invokeHandler(handle, func(target ui.DragDropEventTarget, files []string) {
		target.DragEnter(pos(x, y), files)
	})
}

//export onDragOver
func onDragOver(handle uint32, x, y C.LONG) {
	invokeHandler(handle, func(target ui.DragDropEventTarget, _ []string) {
		target.DragMove(pos(x, y))
	})
}

//export onDragLeave
func onDragLeave(handle uint32) {
	invokeHandler(handle, func(target ui.DragDropEventTarget, _ []string) {
		target.DragLeave()
	})
}

//export onDrop
func onDrop(handle uint32, x, y C.LONG) {
	invokeHandler(handle, func(target ui.DragDropEventTarget, files []string) {
		target.Drop(pos(x, y), files)
	})
}

type handler struct {
	Target ui.DragDropEventTarget
	Files  []string
}

var handlers map[uint32]handler = map[uint32]handler{}

func invokeHandler(handle uint32, invoke func(ui.DragDropEventTarget, []string)) {
	handler := handlers[handle]
	invoke(handler.Target, handler.Files)
}

func pos(x, y C.LONG) geom.PointF32 { return geom.Pt(int(x), int(y)).ToF32() }

type provider struct{}

func (p provider) Register(windowHandle uintptr, target ui.DragDropEventTarget) {
	handle := C.RegisterHandler(unsafe.Pointer(windowHandle))
	handlers[uint32(handle)] = handler{target, nil}
}

func init() {
	ui.DefaultDragDropProvider = provider{}
}