package kvstore

import "encoding/binary"

const recHeaderSize = 22

func encodeRecordHeader(rec record, buf []byte) {
	// SeqNum (8)
	// ID (8)
	// DataLen (4)
	// Store (1)
	// CollectionLen (1)

	binary.LittleEndian.PutUint64(buf[:8], rec.SeqNum)
	buf = buf[8:]
	binary.LittleEndian.PutUint64(buf[:8], rec.ID)
	buf = buf[8:]

	if rec.Store {
		binary.LittleEndian.PutUint32(buf[:4], uint32(len(rec.Data)))
		buf[4] = 1
	} else {
		binary.LittleEndian.PutUint32(buf[:4], 0)
		buf[4] = 0
	}
	buf = buf[5:]

	buf[0] = byte(len(rec.Collection))
}

func decodeRecHeader(header []byte) (rec record, colLen, dataLen int) {
	buf := header

	rec.SeqNum = binary.LittleEndian.Uint64(buf[:8])
	buf = buf[8:]
	rec.ID = binary.LittleEndian.Uint64(buf[:8])
	buf = buf[8:]
	dataLen = int(binary.LittleEndian.Uint32(buf[:4]))
	buf = buf[4:]
	rec.Store = buf[0] != 0
	buf = buf[1:]
	colLen = int(buf[0])

	return
}