package db0102

import (
	"encoding/binary"
	"errors"
	"io"
)

type Entry struct {
	key []byte
	val []byte
}

func (ent *Entry) Encode() []byte {
	data := make([]byte, 4+4+len(ent.key)+len(ent.val))
	binary.LittleEndian.PutUint32(data[0:4], uint32(len(ent.key)))
	binary.LittleEndian.PutUint32(data[4:8], uint32(len(ent.val)))
	copy(data[8:], ent.key)
	copy(data[8+len(ent.key):], ent.val)
	return data
}

func (ent *Entry) Decode(r io.Reader) error {
	key_len := make([]byte, 4)
	s, err := r.Read(key_len)
	if err != nil {
		return err
	}
	if s != 4 {
		return errors.New("invalid size when reading key length")
	}
	val_len := make([]byte, 4)
	s, err = r.Read(val_len)
	if err != nil {
		return err
	}
	if s != 4 {
		return errors.New("invalid size when reading val length")
	}
	key_data := make([]byte, binary.LittleEndian.Uint32(key_len))
	s, err = r.Read(key_data)
	if err != nil {
		return err
	}
	if s != int(binary.LittleEndian.Uint32(key_len)) {
		return errors.New("invalid size when reading key data")
	}
	val_data := make([]byte, binary.LittleEndian.Uint32(val_len))
	s, err = r.Read(val_data)
	if err != nil {
		return err
	}
	if s != int(binary.LittleEndian.Uint32(val_len)) {
		return errors.New("invalid size when reading val data")
	}
	ent.key = key_data
	ent.val = val_data
	return nil
}

// QzBQWVJJOUhU https://trialofcode.org/