package link

import (
	"encoding/hex"

	"github.com/sirupsen/logrus"

	"github.com/fumiama/WireGold/config"
	"github.com/fumiama/WireGold/internal/algo"
	"github.com/fumiama/WireGold/internal/file"
)

func (l *Link) randkeyidx() uint8 {
	if l.keys[1] == nil {
		return 0
	}
	return algo.RandKeyIndex()
}

// decode by aead and put b into pool
func (l *Link) decode(teatype uint8, additional uint16, b []byte) (db []byte, err error) {
	if len(b) == 0 || teatype >= 32 {
		return
	}
	if l.keys[0] == nil {
		if config.ShowDebugLog {
			n := len(b)
			endl := "."
			if n > 64 {
				n = 64
				endl = "..."
			}
			logrus.Debugln(file.Header(), "copy plain text", hex.EncodeToString(b[:n]), endl)
		}
		db = make([]byte, len(b))
		copy(db, b)
		return
	}
	aead := l.keys[teatype]
	if aead == nil {
		panic("unexpected empty aead")
	}
	return algo.DecodeAEAD(aead, additional, b)
}

// xorenc 按 8 字节, 以初始 m.mask 循环异或编码 data
func (m *Me) xorenc(data []byte, seq uint32) []byte {
	return algo.EncodeXOR(data, m.mask, seq)
}

// xordec 按 8 字节, 以初始 m.mask 循环异或解码 data
func (m *Me) xordec(data []byte) (uint32, []byte) {
	return algo.DecodeXOR(data, m.mask)
}