package clipboard

import (
	"b612.me/win32api"
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"golang.org/x/image/bmp"
	"image"
	"image/color"
	"image/png"
	"reflect"
	"strings"
	"syscall"
	"unsafe"
)

func fetchClipboardData(uFormat win32api.DWORD, fn func(p unsafe.Pointer, size uint32) ([]byte, error)) ([]byte, error) {
	mem, err := win32api.GetClipboardData(uFormat)
	if err != nil {
		return nil, fmt.Errorf("GetClipboardData failed: %v", err)
	}
	p, err := win32api.GlobalLock(mem)
	if err != nil {
		return nil, fmt.Errorf("GlobalLock failed: %v", err)
	}
	defer win32api.GlobalUnlock(mem)
	size, err := win32api.GlobalSize(mem)
	if err != nil {
		return nil, fmt.Errorf("GlobalSize failed: %v", err)
	}
	if fn == nil {
		return defaultFetchFn(p, uint32(size))
	}
	return fn(p, uint32(size))
}

func defaultFetchFn(p unsafe.Pointer, size uint32) ([]byte, error) {
	var buf []byte
	for i := 0; i < int(size); i++ {
		buf = append(buf, *(*byte)(unsafe.Pointer(uintptr(p) + uintptr(i))))
	}
	return buf, nil
}

func AutoFetcher(uFormat string) ([]byte, error) {
	switch uFormat {
	case "CF_TEXT", "CF_UNICODETEXT":
		return fetchClipboardData(win32api.CF_UNICODETEXT, textFetcher)
	case "HTML Format":
		return fetchClipboardData(win32api.RegisterClipboardFormat("HTML Format"), nil)
	case "CF_HDROP":
		return fetchClipboardData(win32api.CF_HDROP, filedropFetcher)
	case "CF_DIBV5":
		return fetchClipboardData(win32api.CF_DIBV5, cfDIBv5Fetcher)
	case "CF_DIB":
		return fetchClipboardData(win32api.CF_DIB, cfDIBFetcher)
	case "PNG":
		return fetchClipboardData(win32api.RegisterClipboardFormat("PNG"), nil)
	}
	return nil, errors.New("not support uFormat:" + uFormat)
}

func textFetcher(p unsafe.Pointer, size uint32) ([]byte, error) {
	var buf []uint16
	for ptr := unsafe.Pointer(p); *(*uint16)(ptr) != 0; ptr = unsafe.Pointer(uintptr(ptr) + unsafe.Sizeof(*((*uint16)(unsafe.Pointer(p))))) {
		buf = append(buf, *(*uint16)(ptr))
	}
	return []byte(syscall.UTF16ToString(buf)), nil
}

func filedropFetcher(p unsafe.Pointer, size uint32) ([]byte, error) {
	var res []string
	c, err := win32api.DragQueryFile(win32api.HDROP(p), 0xFFFFFFFF, nil, 0)
	if err != nil {
		return nil, err
	}
	count := int(c)

	for i := 0; i < count; i++ {
		c, err = win32api.DragQueryFile(win32api.HDROP(p), win32api.DWORD(i), nil, 0)
		if err != nil {
			return nil, err
		}
		length := int(c)
		buffer := make([]uint16, length+1)

		_, err = win32api.DragQueryFile(win32api.HDROP(p), win32api.DWORD(i),
			&buffer[0], win32api.DWORD(len(buffer)))
		res = append(res, syscall.UTF16ToString(buffer))
	}
	return []byte(strings.Join(res, "|")), nil
}

func cfDIBv5Fetcher(p unsafe.Pointer, size uint32) ([]byte, error) {
	// inspect header information
	info := (*bitmapV5Header)(unsafe.Pointer(p))
	// maybe deal with other formats?
	if info.BitCount != 32 {
		return nil, errors.New("not support image format")
	}

	var data []byte
	sh := (*reflect.SliceHeader)(unsafe.Pointer(&data))
	sh.Data = uintptr(p)
	sh.Cap = int(info.Size + 4*uint32(info.Width)*uint32(info.Height))
	sh.Len = int(info.Size + 4*uint32(info.Width)*uint32(info.Height))
	img := image.NewRGBA(image.Rect(0, 0, int(info.Width), int(info.Height)))
	offset := int(info.Size)
	stride := int(info.Width)
	for y := 0; y < int(info.Height); y++ {
		for x := 0; x < int(info.Width); x++ {
			idx := offset + 4*(y*stride+x)
			xhat := (x + int(info.Width)) % int(info.Width)
			yhat := int(info.Height) - 1 - y
			r := data[idx+2]
			g := data[idx+1]
			b := data[idx+0]
			a := data[idx+3]
			img.SetRGBA(xhat, yhat, color.RGBA{r, g, b, a})
		}
	}
	// always use PNG encoding.
	var buf bytes.Buffer
	err := png.Encode(&buf, img)
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func cfDIBFetcher(p unsafe.Pointer, size uint32) ([]byte, error) {
	// 函数意外报错，待修正
	const (
		fileHeaderLen = 14
		infoHeaderLen = 40
	)
	bmpHeader := (*bitmapHeader)(p)
	dataSize := bmpHeader.SizeImage + fileHeaderLen + infoHeaderLen

	if bmpHeader.SizeImage == 0 && bmpHeader.Compression == 0 {
		iSizeImage := bmpHeader.Height * ((bmpHeader.Width*uint32(bmpHeader.BitCount)/8 + 3) &^ 3)
		dataSize += iSizeImage
	}
	buf := new(bytes.Buffer)
	binary.Write(buf, binary.LittleEndian, uint16('B')|(uint16('M')<<8))
	binary.Write(buf, binary.LittleEndian, uint32(dataSize))
	binary.Write(buf, binary.LittleEndian, uint32(0))
	const sizeof_colorbar = 0
	binary.Write(buf, binary.LittleEndian, uint32(fileHeaderLen+infoHeaderLen+sizeof_colorbar))
	j := 0
	for i := fileHeaderLen; i < int(dataSize); i++ {
		binary.Write(buf, binary.BigEndian, *(*byte)(unsafe.Pointer(uintptr(p) + uintptr(j))))
		j++
	}
	return bmpToPng(buf)
}

func bmpToPng(bmpBuf *bytes.Buffer) (buf []byte, err error) {
	var f bytes.Buffer
	original_image, err := bmp.Decode(bmpBuf)
	if err != nil {
		return nil, err
	}
	err = png.Encode(&f, original_image)
	if err != nil {
		return nil, err
	}
	return f.Bytes(), nil
}

type bitmapV5Header struct {
	Size          uint32
	Width         int32
	Height        int32
	Planes        uint16
	BitCount      uint16
	Compression   uint32
	SizeImage     uint32
	XPelsPerMeter int32
	YPelsPerMeter int32
	ClrUsed       uint32
	ClrImportant  uint32
	RedMask       uint32
	GreenMask     uint32
	BlueMask      uint32
	AlphaMask     uint32
	CSType        uint32
	Endpoints     struct {
		CiexyzRed, CiexyzGreen, CiexyzBlue struct {
			CiexyzX, CiexyzY, CiexyzZ int32 // FXPT2DOT30
		}
	}
	GammaRed    uint32
	GammaGreen  uint32
	GammaBlue   uint32
	Intent      uint32
	ProfileData uint32
	ProfileSize uint32
	Reserved    uint32
}

type bitmapHeader struct {
	Size          uint32
	Width         uint32
	Height        uint32
	PLanes        uint16
	BitCount      uint16
	Compression   uint32
	SizeImage     uint32
	XPelsPerMeter uint32
	YPelsPerMeter uint32
	ClrUsed       uint32
	ClrImportant  uint32
}