package tunnel

import (
	"context"
	"io"
	"net"
	"net/http"
	"sync"
	"time"

	"gitlab.com/wpetit/goweb/logger"

	"forge.cadoles.com/wpetit/go-tunnel/control"
	"github.com/pkg/errors"
	"github.com/xtaci/kcp-go/v5"
	"github.com/xtaci/smux"
)

type Client struct {
	conf            *ClientConfig
	conn            *kcp.UDPSession
	sess            *smux.Session
	control         *control.Control
	http            *http.Client
	openStreamMutex sync.Mutex
}

func (c *Client) Connect(ctx context.Context) error {
	conn, err := kcp.DialWithOptions(
		c.conf.ServerAddress, c.conf.BlockCrypt,
		c.conf.DataShards, c.conf.ParityShards,
	)
	if err != nil {
		return errors.WithStack(err)
	}

	if c.conf.ConfigureConn != nil {
		if err := c.conf.ConfigureConn(conn); err != nil {
			return errors.WithStack(err)
		}
	}

	config := smux.DefaultConfig()
	config.Version = 2
	config.KeepAliveInterval = 10 * time.Second
	config.KeepAliveTimeout = 2 * config.KeepAliveInterval

	sess, err := smux.Client(conn, config)
	if err != nil {
		return errors.WithStack(err)
	}

	control := control.New()
	if err := control.Init(ctx, sess, false); err != nil {
		return errors.WithStack(err)
	}

	logger.Debug(ctx, "sending auth request")

	success, err := control.AuthRequest(c.conf.Credentials)
	if err != nil {
		return errors.WithStack(err)
	}

	if !success {
		defer c.Close()
		return errors.WithStack(ErrAuthFailed)
	}

	c.control = control
	c.conn = conn
	c.sess = sess

	return nil
}

func (c *Client) Listen(ctx context.Context) error {
	logger.Debug(ctx, "listening for messages")

	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	err := c.control.Listen(ctx, control.Handlers{
		control.TypeProxyRequest: c.handleProxyRequest,
	})

	if errors.Is(err, io.ErrClosedPipe) {
		logger.Debug(ctx, "client connection closed")

		return errors.WithStack(ErrConnectionClosed)
	}

	return err
}

func (c *Client) Close() error {
	if c.conn == nil {
		return errors.WithStack(ErrNotConnected)
	}

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

	return nil
}

func (c *Client) handleProxyRequest(ctx context.Context, m *control.Message) (*control.Message, error) {
	proxyReqPayload, ok := m.Payload.(*control.ProxyRequestPayload)
	if !ok {
		return nil, errors.WithStack(ErrUnexpectedMessage)
	}

	ctx = logger.With(ctx,
		logger.F("network", proxyReqPayload.Network),
		logger.F("address", proxyReqPayload.Address),
	)

	logger.Debug(ctx, "handling proxy request")

	out, err := net.Dial(proxyReqPayload.Network, proxyReqPayload.Address)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	go c.handleProxyStream(ctx, out)

	return nil, nil
}

func (c *Client) handleProxyStream(ctx context.Context, out net.Conn) {
	c.openStreamMutex.Lock()

	in, err := c.sess.OpenStream()
	if err != nil {
		c.openStreamMutex.Unlock()
		logger.Error(ctx, "error while accepting proxy stream", logger.E(err))

		return
	}

	c.openStreamMutex.Unlock()

	streamCopy := func(dst io.Writer, src io.ReadCloser) {
		if _, err := Copy(dst, src); err != nil {
			if errors.Is(err, smux.ErrInvalidProtocol) {
				logger.Error(ctx, "error while proxying", logger.E(errors.WithStack(err)))
			}
		}

		logger.Debug(ctx, "closing proxy stream")

		in.Close()
		out.Close()
	}

	go streamCopy(in, out)
	streamCopy(out, in)
}

func NewClient(funcs ...ClientConfigFunc) *Client {
	conf := DefaultClientConfig()

	for _, fn := range funcs {
		fn(conf)
	}

	return &Client{
		conf: conf,
		http: &http.Client{},
	}
}