package flashpart

import "encoding/binary"

type FlashPartHeader struct {
	MediaID byte
	Byte1   byte
	Byte2   byte
	Byte3   byte

	TotalSize   uint32
	RawSize     uint32 // total - 32
	VersionText string // 16byte

	raw []byte
}

func ParseFlashPartHeader(data []byte) (fph *FlashPartHeader) {
	if len(data) != 32 {
		panic("flash part header len != 32")
	}
	fph = &FlashPartHeader{
		MediaID: data[0],
		Byte1:   data[1],
		Byte2:   data[2],
		Byte3:   data[3],

		TotalSize:   binary.LittleEndian.Uint32(data[4:8]),
		VersionText: string(data[16:]),

		raw: data,
	}
	fph.RawSize = fph.TotalSize - 32

	// copyright string in header space
	if fph.MediaID == 67 && fph.Byte1 == 111 && fph.Byte2 == 112 && fph.Byte3 == 121 {
		fph.VersionText = string(data[:])
		fph.TotalSize = 0
		fph.RawSize = 0
	}
	return fph
}

func (fph *FlashPartHeader) AdjustRawSize(size uint32) {
	fph.RawSize = size
	fph.AdjustTotalSize(size + 32)
}
func (fph *FlashPartHeader) AdjustTotalSize(size uint32) {
	fph.TotalSize = size
	totalSizeBytes := make([]byte, 4)
	binary.LittleEndian.PutUint32(totalSizeBytes, fph.TotalSize)
	// TODO: shitty copy
	for i, b := range totalSizeBytes {
		fph.raw[4+i] = b
	}
}
func (fph *FlashPartHeader) AdjustName(name string) {
	// truncate if too long
	if len(name) > 16 {
		name = name[:16]
	}

	for i := 16; i < 32; i++ { // copy version string
		charIndex := i - 16
		if charIndex > len(name)-1 {
			fph.raw[i] = 0x20
		} else {
			fph.raw[i] = name[charIndex]
		}
	}
	fph.VersionText = string(fph.raw[16:])
}
func (fph *FlashPartHeader) GetBytes() []byte {
	return fph.raw
}