package tunnel

import (
	"io"

	"github.com/pkg/errors"
	"github.com/xtaci/kcp-go/v5"
)

const bufSize = 4096

// From https://github.com/xtaci/kcptun/blob/master/generic/copy.go
// Copyright https://github.com/xtaci
func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
	// If the reader has a WriteTo method, use it to do the copy.
	// Avoids an allocation and a copy.
	if wt, ok := src.(io.WriterTo); ok {
		return wt.WriteTo(dst)
	}
	// Similarly, if the writer has a ReadFrom method, use it to do the copy.
	if rt, ok := dst.(io.ReaderFrom); ok {
		return rt.ReadFrom(src)
	}

	// fallback to standard io.CopyBuffer
	buf := make([]byte, bufSize)
	return io.CopyBuffer(dst, src, buf)
}

func createBlockCrypt(algorithm string, pass []byte) (kcp.BlockCrypt, error) {
	switch algorithm {
	case "sm4":
		return kcp.NewSM4BlockCrypt(pass[:16])
	case "tea":
		return kcp.NewTEABlockCrypt(pass[:16])
	case "xor":
		return kcp.NewSimpleXORBlockCrypt(pass)
	case "none":
		return kcp.NewNoneBlockCrypt(pass)
	case "aes-128":
		return kcp.NewAESBlockCrypt(pass[:16])
	case "aes-192":
		return kcp.NewAESBlockCrypt(pass[:24])
	case "blowfish":
		return kcp.NewBlowfishBlockCrypt(pass)
	case "twofish":
		return kcp.NewTwofishBlockCrypt(pass)
	case "cast5":
		return kcp.NewCast5BlockCrypt(pass[:16])
	case "3des":
		return kcp.NewTripleDESBlockCrypt(pass[:24])
	case "xtea":
		return kcp.NewXTEABlockCrypt(pass[:16])
	case "salsa20":
		return kcp.NewSalsa20BlockCrypt(pass)
	default:
		return nil, errors.Errorf("unknown algorithm '%s'", algorithm)
	}
}