package tunnel

import (
	"crypto/sha1"
	"time"

	"github.com/pkg/errors"
	"github.com/xtaci/kcp-go/v5"
	"github.com/xtaci/smux"
	"golang.org/x/crypto/pbkdf2"
)

type ClientConfig struct {
	ServerAddress         string
	BlockCrypt            kcp.BlockCrypt
	DataShards            int
	ParityShards          int
	Credentials           interface{}
	ConfigureConn         ConfigureConnFunc
	AuthenticationTimeout time.Duration
	ProxyRequestTimeout   time.Duration
	SmuxConfig            *smux.Config
}

// nolint: go-mnd
func DefaultClientConfig() *ClientConfig {
	unencryptedBlock, err := kcp.NewNoneBlockCrypt(nil)
	if err != nil { // should never happen
		panic(errors.WithStack(err))
	}

	smuxConfig := smux.DefaultConfig()
	smuxConfig.Version = 2
	smuxConfig.KeepAliveInterval = 10 * time.Second
	smuxConfig.MaxReceiveBuffer = 4194304
	smuxConfig.MaxStreamBuffer = 2097152

	return &ClientConfig{
		ServerAddress:         "127.0.0.1:36543",
		BlockCrypt:            unencryptedBlock,
		DataShards:            3,
		ParityShards:          10,
		Credentials:           nil,
		ConfigureConn:         DefaultClientConfigureConn,
		AuthenticationTimeout: 30 * time.Second,
		ProxyRequestTimeout:   5 * time.Second,
		SmuxConfig:            smuxConfig,
	}
}

type ClientConfigFunc func(c *ClientConfig)

func WithClientServerAddress(addr string) ClientConfigFunc {
	return func(conf *ClientConfig) {
		conf.ServerAddress = addr
	}
}

func WithClientCredentials(credentials interface{}) ClientConfigFunc {
	return func(conf *ClientConfig) {
		conf.Credentials = credentials
	}
}

func WithClientBlockCrypt(alg string, pass, salt string, iterations, keyLen int) ClientConfigFunc {
	return func(conf *ClientConfig) {
		key := pbkdf2.Key([]byte(pass), []byte(salt), iterations, keyLen, sha1.New)

		block, err := createBlockCrypt(alg, key)
		if err != nil {
			panic(errors.Wrap(err, "could not create block crypt"))
		}

		conf.BlockCrypt = block
	}
}

func WithClientConfigureConn(fn ConfigureConnFunc) ClientConfigFunc {
	return func(conf *ClientConfig) {
		conf.ConfigureConn = fn
	}
}

func WithClientSmuxConfig(c *smux.Config) ClientConfigFunc {
	return func(conf *ClientConfig) {
		conf.SmuxConfig = c
	}
}

// nolint: go-mnd
func DefaultClientConfigureConn(conn *kcp.UDPSession) error {
	// Based on kcptun default configuration, mode 'fast3'
	conn.SetStreamMode(true)
	conn.SetWriteDelay(false)
	conn.SetNoDelay(1, 10, 2, 1)
	conn.SetWindowSize(128, 512)
	conn.SetMtu(1400)
	conn.SetACKNoDelay(true)

	if err := conn.SetReadBuffer(16777217); err != nil {
		return errors.WithStack(err)
	}

	if err := conn.SetWriteBuffer(16777217); err != nil {
		return errors.WithStack(err)
	}

	if err := conn.SetDSCP(46); err != nil {
		return errors.WithStack(err)
	}

	return nil
}