package tarodb

import "encoding/binary"

// Entry 磁盘文件保存entry,
// 内存中list保存key索引
// keySize | valueSize | mark | key | value
//    4B  |    4B     |   2B | ... | ...
type Entry struct {
	Key       []byte
	Value     []byte
	KeySize   uint32
	ValueSize uint32
	Mark      uint16
}

const (
	FIXED_ENTRY_HEADER_SIZE = 10
)

func NewEntry(key, value []byte, mark uint16) *Entry {
	return &Entry{
		Key:       key,
		Value:     value,
		KeySize:   uint32(len(key)),
		ValueSize: uint32(len(value)),
		Mark:      mark,
	}
}

func (e *Entry) Encode() ([]byte, error) {
	buf := make([]byte, e.getSize())
	binary.BigEndian.PutUint32(buf[0:4], e.KeySize)
	binary.BigEndian.PutUint32(buf[4:8], e.ValueSize)
	binary.BigEndian.PutUint16(buf[8:10], e.Mark)
	copy(buf[FIXED_ENTRY_HEADER_SIZE:FIXED_ENTRY_HEADER_SIZE+e.KeySize], e.Key)
	copy(buf[FIXED_ENTRY_HEADER_SIZE+e.KeySize:], e.Value)

	return buf, nil
}

func (e *Entry) getSize() int64 {
	return int64(FIXED_ENTRY_HEADER_SIZE + e.KeySize + e.ValueSize)
}