rpc_test.go

package jsonrpc

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http/httptest"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/gorilla/websocket"
	logging "github.com/ipfs/go-log/v2"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func init() {
	if err := logging.SetLogLevel("rpc", "DEBUG"); err != nil {
		panic(err)
	}
}

type SimpleServerHandler struct {
	n int
}

type TestType struct {
	S string
	I int
}

type TestOut struct {
	TestType
	Ok bool
}

func (h *SimpleServerHandler) Add(in int) error {
	if in == -3546 {
		return errors.New("test")
	}

	h.n += in

	return nil
}

func (h *SimpleServerHandler) AddGet(in int) int {
	h.n += in
	return h.n
}

func (h *SimpleServerHandler) StringMatch(t TestType, i2 int64) (out TestOut, err error) {
	if strconv.FormatInt(i2, 10) == t.S {
		out.Ok = true
	}
	if i2 != int64(t.I) {
		return TestOut{}, errors.New(":(")
	}
	out.I = t.I
	out.S = t.S
	return
}

func TestReconnection(t *testing.T) {
	var rpcClient struct {
		Add func(int) error
	}

	rpcHandler := SimpleServerHandler{}

	rpcServer := NewServer()
	rpcServer.Register("SimpleServerHandler", &rpcHandler)

	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	// capture connection attempts for this duration
	captureDuration := 3 * time.Second

	// run the test until the timer expires
	timer := time.NewTimer(captureDuration)

	// record the number of connection attempts during this test
	connectionAttempts := 1

	closer, err := NewMergeClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", []interface{}{&rpcClient}, nil, func(c *Config) {
		c.proxyConnFactory = func(f func() (*websocket.Conn, error)) func() (*websocket.Conn, error) {
			return func() (*websocket.Conn, error) {
				defer func() {
					connectionAttempts++
				}()

				if connectionAttempts > 1 {
					return nil, errors.New("simulates a failed reconnect attempt")
				}

				c, err := f()
				if err != nil {
					return nil, err
				}

				// closing the connection here triggers the reconnect logic
				_ = c.Close()

				return c, nil
			}
		}
	})
	require.NoError(t, err)
	defer closer()

	// let the JSON-RPC library attempt to reconnect until the timer runs out
	<-timer.C

	// do some math
	attemptsPerSecond := int64(connectionAttempts) / int64(captureDuration/time.Second)

	assert.Less(t, attemptsPerSecond, int64(50))
}

func (h *SimpleServerHandler) ErrChanSub(ctx context.Context) (<-chan int, error) {
	return nil, errors.New("expect to return an error")
}

func TestRPC(t *testing.T) {
	// setup server

	serverHandler := &SimpleServerHandler{}

	rpcServer := NewServer()
	rpcServer.Register("SimpleServerHandler", serverHandler)

	// httptest stuff
	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()
	// setup client

	var client struct {
		Add         func(int) error
		AddGet      func(int) int
		StringMatch func(t TestType, i2 int64) (out TestOut, err error)
		ErrChanSub  func(context.Context) (<-chan int, error)
	}
	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &client, nil)
	require.NoError(t, err)
	defer closer()

	// Add(int) error

	require.NoError(t, client.Add(2))
	require.Equal(t, 2, serverHandler.n)

	err = client.Add(-3546)
	require.EqualError(t, err, "test")

	// AddGet(int) int

	n := client.AddGet(3)
	require.Equal(t, 5, n)
	require.Equal(t, 5, serverHandler.n)

	// StringMatch

	o, err := client.StringMatch(TestType{S: "0"}, 0)
	require.NoError(t, err)
	require.Equal(t, "0", o.S)
	require.Equal(t, 0, o.I)

	_, err = client.StringMatch(TestType{S: "5"}, 5)
	require.EqualError(t, err, ":(")

	o, err = client.StringMatch(TestType{S: "8", I: 8}, 8)
	require.NoError(t, err)
	require.Equal(t, "8", o.S)
	require.Equal(t, 8, o.I)

	// ErrChanSub
	ctx := context.TODO()
	_, err = client.ErrChanSub(ctx)
	if err == nil {
		t.Fatal("expect an err return, but got nil")
	}

	// Invalid client handlers

	var noret struct {
		Add func(int)
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &noret, nil)
	require.NoError(t, err)

	// this one should actually work
	noret.Add(4)
	require.Equal(t, 9, serverHandler.n)
	closer()

	var noparam struct {
		Add func()
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &noparam, nil)
	require.NoError(t, err)

	// shouldn't panic
	noparam.Add()
	closer()

	var erronly struct {
		AddGet func() (int, error)
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &erronly, nil)
	require.NoError(t, err)

	_, err = erronly.AddGet()
	if err == nil || err.Error() != "RPC error (-32602): wrong param count (method 'SimpleServerHandler.AddGet'): 0 != 1" {
		t.Error("wrong error:", err)
	}
	closer()

	var wrongtype struct {
		Add func(string) error
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &wrongtype, nil)
	require.NoError(t, err)

	err = wrongtype.Add("not an int")
	if err == nil || !strings.Contains(err.Error(), "RPC error (-32700):") || !strings.Contains(err.Error(), "json: cannot unmarshal string into Go value of type int") {
		t.Error("wrong error:", err)
	}
	closer()

	var notfound struct {
		NotThere func(string) error
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &notfound, nil)
	require.NoError(t, err)

	err = notfound.NotThere("hello?")
	if err == nil || err.Error() != "RPC error (-32601): method 'SimpleServerHandler.NotThere' not found" {
		t.Error("wrong error:", err)
	}
	closer()
}

func TestRPCHttpClient(t *testing.T) {
	// setup server

	serverHandler := &SimpleServerHandler{}

	rpcServer := NewServer()
	rpcServer.Register("SimpleServerHandler", serverHandler)

	// httptest stuff
	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()
	// setup client

	var client struct {
		Add         func(int) error
		AddGet      func(int) int
		StringMatch func(t TestType, i2 int64) (out TestOut, err error)
	}
	closer, err := NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &client, nil)
	require.NoError(t, err)
	defer closer()

	// Add(int) error

	require.NoError(t, client.Add(2))
	require.Equal(t, 2, serverHandler.n)

	err = client.Add(-3546)
	require.EqualError(t, err, "test")

	// AddGet(int) int

	n := client.AddGet(3)
	require.Equal(t, 5, n)
	require.Equal(t, 5, serverHandler.n)

	// StringMatch

	o, err := client.StringMatch(TestType{S: "0"}, 0)
	require.NoError(t, err)
	require.Equal(t, "0", o.S)
	require.Equal(t, 0, o.I)

	_, err = client.StringMatch(TestType{S: "5"}, 5)
	require.EqualError(t, err, ":(")

	o, err = client.StringMatch(TestType{S: "8", I: 8}, 8)
	require.NoError(t, err)
	require.Equal(t, "8", o.S)
	require.Equal(t, 8, o.I)

	// Invalid client handlers

	var noret struct {
		Add func(int)
	}
	closer, err = NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &noret, nil)
	require.NoError(t, err)

	// this one should actually work
	noret.Add(4)
	require.Equal(t, 9, serverHandler.n)
	closer()

	var noparam struct {
		Add func()
	}
	closer, err = NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &noparam, nil)
	require.NoError(t, err)

	// shouldn't panic
	noparam.Add()
	closer()

	var erronly struct {
		AddGet func() (int, error)
	}
	closer, err = NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &erronly, nil)
	require.NoError(t, err)

	_, err = erronly.AddGet()
	if err == nil || err.Error() != "RPC error (-32602): wrong param count (method 'SimpleServerHandler.AddGet'): 0 != 1" {
		t.Error("wrong error:", err)
	}
	closer()

	var wrongtype struct {
		Add func(string) error
	}
	closer, err = NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &wrongtype, nil)
	require.NoError(t, err)

	err = wrongtype.Add("not an int")
	if err == nil || !strings.Contains(err.Error(), "RPC error (-32700):") || !strings.Contains(err.Error(), "json: cannot unmarshal string into Go value of type int") {
		t.Error("wrong error:", err)
	}
	closer()

	var notfound struct {
		NotThere func(string) error
	}
	closer, err = NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "SimpleServerHandler", &notfound, nil)
	require.NoError(t, err)

	err = notfound.NotThere("hello?")
	if err == nil || err.Error() != "RPC error (-32601): method 'SimpleServerHandler.NotThere' not found" {
		t.Error("wrong error:", err)
	}
	closer()
}

type CtxHandler struct {
	lk sync.Mutex

	cancelled bool
	i         int
}

func (h *CtxHandler) Test(ctx context.Context) {
	h.lk.Lock()
	defer h.lk.Unlock()
	timeout := time.After(300 * time.Millisecond)
	h.i++

	select {
	case <-timeout:
	case <-ctx.Done():
		h.cancelled = true
	}
}

func TestCtx(t *testing.T) {
	// setup server

	serverHandler := &CtxHandler{}

	rpcServer := NewServer()
	rpcServer.Register("CtxHandler", serverHandler)

	// httptest stuff
	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	// setup client

	var client struct {
		Test func(ctx context.Context)
	}
	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "CtxHandler", &client, nil)
	require.NoError(t, err)

	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
	defer cancel()

	client.Test(ctx)
	serverHandler.lk.Lock()

	if !serverHandler.cancelled {
		t.Error("expected cancellation on the server side")
	}

	serverHandler.cancelled = false

	serverHandler.lk.Unlock()
	closer()

	var noCtxClient struct {
		Test func()
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "CtxHandler", &noCtxClient, nil)
	if err != nil {
		t.Fatal(err)
	}

	noCtxClient.Test()

	serverHandler.lk.Lock()

	if serverHandler.cancelled || serverHandler.i != 2 {
		t.Error("wrong serverHandler state")
	}

	serverHandler.lk.Unlock()
	closer()
}

func TestCtxHttp(t *testing.T) {
	// setup server

	serverHandler := &CtxHandler{}

	rpcServer := NewServer()
	rpcServer.Register("CtxHandler", serverHandler)

	// httptest stuff
	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	// setup client

	var client struct {
		Test func(ctx context.Context)
	}
	closer, err := NewClient(context.Background(), "http://"+testServ.Listener.Addr().String(), "CtxHandler", &client, nil)
	require.NoError(t, err)

	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
	defer cancel()

	client.Test(ctx)
	serverHandler.lk.Lock()

	if !serverHandler.cancelled {
		t.Error("expected cancellation on the server side")
	}

	serverHandler.cancelled = false

	serverHandler.lk.Unlock()
	closer()

	var noCtxClient struct {
		Test func()
	}
	closer, err = NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "CtxHandler", &noCtxClient, nil)
	if err != nil {
		t.Fatal(err)
	}

	noCtxClient.Test()

	serverHandler.lk.Lock()

	if serverHandler.cancelled || serverHandler.i != 2 {
		t.Error("wrong serverHandler state")
	}

	serverHandler.lk.Unlock()
	closer()
}

type UnUnmarshalable int

func (*UnUnmarshalable) UnmarshalJSON([]byte) error {
	return errors.New("nope")
}

type UnUnmarshalableHandler struct{}

func (*UnUnmarshalableHandler) GetUnUnmarshalableStuff() (UnUnmarshalable, error) {
	return UnUnmarshalable(5), nil
}

func TestUnmarshalableResult(t *testing.T) {
	var client struct {
		GetUnUnmarshalableStuff func() (UnUnmarshalable, error)
	}

	rpcServer := NewServer()
	rpcServer.Register("Handler", &UnUnmarshalableHandler{})

	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "Handler", &client, nil)
	require.NoError(t, err)
	defer closer()

	_, err = client.GetUnUnmarshalableStuff()
	require.EqualError(t, err, "RPC client error: unmarshaling result: nope")
}

type ChanHandler struct {
	wait    chan struct{}
	ctxdone <-chan struct{}
}

func (h *ChanHandler) Sub(ctx context.Context, i int, eq int) (<-chan int, error) {
	out := make(chan int)
	h.ctxdone = ctx.Done()

	wait := h.wait

	log.Warnf("SERVER SUB!")
	go func() {
		defer close(out)
		var n int

		for {
			select {
			case <-ctx.Done():
				fmt.Println("ctxdone1", i, eq)
				return
			case <-wait:
				fmt.Println("CONSUMED WAIT: ", i)
			}

			n += i

			if n == eq {
				fmt.Println("eq")
				return
			}

			select {
			case <-ctx.Done():
				fmt.Println("ctxdone2")
				return
			case out <- n:
			}
		}
	}()

	return out, nil
}

func TestChan(t *testing.T) {
	var client struct {
		Sub func(context.Context, int, int) (<-chan int, error)
	}

	serverHandler := &ChanHandler{
		wait: make(chan struct{}, 5),
	}

	rpcServer := NewServer()
	rpcServer.Register("ChanHandler", serverHandler)

	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "ChanHandler", &client, nil)
	require.NoError(t, err)

	defer closer()

	serverHandler.wait <- struct{}{}

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

	// sub

	sub, err := client.Sub(ctx, 2, -1)
	require.NoError(t, err)

	// recv one

	require.Equal(t, 2, <-sub)

	// recv many (order)

	serverHandler.wait <- struct{}{}
	serverHandler.wait <- struct{}{}
	serverHandler.wait <- struct{}{}

	require.Equal(t, 4, <-sub)
	require.Equal(t, 6, <-sub)
	require.Equal(t, 8, <-sub)

	// close (through ctx)
	cancel()

	_, ok := <-sub
	require.Equal(t, false, ok)

	// sub (again)

	serverHandler.wait = make(chan struct{}, 5)
	serverHandler.wait <- struct{}{}

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

	log.Warnf("last sub")
	sub, err = client.Sub(ctx, 3, 6)
	require.NoError(t, err)

	log.Warnf("waiting for value now")
	require.Equal(t, 3, <-sub)
	log.Warnf("not equal")

	// close (remote)
	serverHandler.wait <- struct{}{}
	_, ok = <-sub
	require.Equal(t, false, ok)
}

func TestChanClosing(t *testing.T) {
	var client struct {
		Sub func(context.Context, int, int) (<-chan int, error)
	}

	serverHandler := &ChanHandler{
		wait: make(chan struct{}, 5),
	}

	rpcServer := NewServer()
	rpcServer.Register("ChanHandler", serverHandler)

	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "ChanHandler", &client, nil)
	require.NoError(t, err)

	defer closer()

	ctx1, cancel1 := context.WithCancel(context.Background())
	ctx2, cancel2 := context.WithCancel(context.Background())

	// sub

	sub1, err := client.Sub(ctx1, 2, -1)
	require.NoError(t, err)

	sub2, err := client.Sub(ctx2, 3, -1)
	require.NoError(t, err)

	// recv one

	serverHandler.wait <- struct{}{}
	serverHandler.wait <- struct{}{}

	require.Equal(t, 2, <-sub1)
	require.Equal(t, 3, <-sub2)

	cancel1()

	require.Equal(t, 0, <-sub1)
	time.Sleep(time.Millisecond * 50) // make sure the loop has exited (having a shared wait channel makes this annoying)

	serverHandler.wait <- struct{}{}
	require.Equal(t, 6, <-sub2)

	cancel2()
	require.Equal(t, 0, <-sub2)
}

func TestChanServerClose(t *testing.T) {
	var client struct {
		Sub func(context.Context, int, int) (<-chan int, error)
	}

	serverHandler := &ChanHandler{
		wait: make(chan struct{}, 5),
	}

	rpcServer := NewServer()
	rpcServer.Register("ChanHandler", serverHandler)

	tctx, tcancel := context.WithCancel(context.Background())

	testServ := httptest.NewServer(rpcServer)
	testServ.Config.ConnContext = func(ctx context.Context, c net.Conn) context.Context {
		return tctx
	}

	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "ChanHandler", &client, nil)
	require.NoError(t, err)

	defer closer()

	serverHandler.wait <- struct{}{}

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

	// sub

	sub, err := client.Sub(ctx, 2, -1)
	require.NoError(t, err)

	// recv one

	require.Equal(t, 2, <-sub)

	// make sure we're blocked

	select {
	case <-time.After(200 * time.Millisecond):
	case <-sub:
		t.Fatal("didn't expect to get anything from sub")
	}

	// close server

	tcancel()
	testServ.Close()

	_, ok := <-sub
	require.Equal(t, false, ok)
}

func TestServerChanLockClose(t *testing.T) {
	var client struct {
		Sub func(context.Context, int, int) (<-chan int, error)
	}

	serverHandler := &ChanHandler{
		wait: make(chan struct{}),
	}

	rpcServer := NewServer()
	rpcServer.Register("ChanHandler", serverHandler)

	testServ := httptest.NewServer(rpcServer)

	var closeConn func() error

	_, err := NewMergeClient(context.Background(), "ws://"+testServ.Listener.Addr().String(),
		"ChanHandler",
		[]interface{}{&client}, nil,
		func(c *Config) {
			c.proxyConnFactory = func(f func() (*websocket.Conn, error)) func() (*websocket.Conn, error) {
				return func() (*websocket.Conn, error) {
					c, err := f()
					if err != nil {
						return nil, err
					}

					closeConn = c.UnderlyingConn().Close

					return c, nil
				}
			}
		})
	require.NoError(t, err)

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

	// sub

	sub, err := client.Sub(ctx, 2, -1)
	require.NoError(t, err)

	// recv one

	go func() {
		serverHandler.wait <- struct{}{}
	}()
	require.Equal(t, 2, <-sub)

	for i := 0; i < 100; i++ {
		serverHandler.wait <- struct{}{}
	}

	if err := closeConn(); err != nil {
		t.Fatal(err)
	}

	<-serverHandler.ctxdone
}

type StreamingHandler struct {
}

func (h *StreamingHandler) GetData(ctx context.Context, n int) (<-chan int, error) {
	out := make(chan int)

	go func() {
		defer close(out)

		for i := 0; i < n; i++ {
			out <- i
		}
	}()

	return out, nil
}

func TestChanClientReceiveAll(t *testing.T) {
	var client struct {
		GetData func(context.Context, int) (<-chan int, error)
	}

	serverHandler := &StreamingHandler{}

	rpcServer := NewServer()
	rpcServer.Register("ChanHandler", serverHandler)

	tctx, tcancel := context.WithCancel(context.Background())

	testServ := httptest.NewServer(rpcServer)
	testServ.Config.ConnContext = func(ctx context.Context, c net.Conn) context.Context {
		return tctx
	}

	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "ChanHandler", &client, nil)
	require.NoError(t, err)

	defer closer()

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

	// sub

	sub, err := client.GetData(ctx, 100)
	require.NoError(t, err)

	for i := 0; i < 100; i++ {
		select {
		case v, ok := <-sub:
			if !ok {
				t.Fatal("channel closed", i)
			}

			if v != i {
				t.Fatal("got wrong value", v, i)
			}
		case <-time.After(time.Second):
			t.Fatal("timed out waiting for values")
		}
	}

	tcancel()
	testServ.Close()

}

func TestControlChanDeadlock(t *testing.T) {
	for r := 0; r < 20; r++ {
		testControlChanDeadlock(t)
	}
}

func testControlChanDeadlock(t *testing.T) {
	var client struct {
		Sub func(context.Context, int, int) (<-chan int, error)
	}

	n := 5000

	serverHandler := &ChanHandler{
		wait: make(chan struct{}, n),
	}

	rpcServer := NewServer()
	rpcServer.Register("ChanHandler", serverHandler)

	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	closer, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "ChanHandler", &client, nil)
	require.NoError(t, err)

	defer closer()

	for i := 0; i < n; i++ {
		serverHandler.wait <- struct{}{}
	}

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

	sub, err := client.Sub(ctx, 1, -1)
	require.NoError(t, err)

	done := make(chan struct{})

	go func() {
		defer close(done)
		for i := 0; i < n; i++ {
			if <-sub != i+1 {
				panic("bad!")
				//require.Equal(t, i+1, <-sub)
			}
		}
	}()

	// reset this channel so its not shared between the sub requests...
	serverHandler.wait = make(chan struct{}, n)
	for i := 0; i < n; i++ {
		serverHandler.wait <- struct{}{}
	}

	_, err = client.Sub(ctx, 2, -1)
	require.NoError(t, err)
	<-done
}

type InterfaceHandler struct {
}

func (h *InterfaceHandler) ReadAll(ctx context.Context, r io.Reader) ([]byte, error) {
	return ioutil.ReadAll(r)
}

func TestInterfaceHandler(t *testing.T) {
	var client struct {
		ReadAll func(ctx context.Context, r io.Reader) ([]byte, error)
	}

	serverHandler := &InterfaceHandler{}

	rpcServer := NewServer(WithParamDecoder(new(io.Reader), readerDec))
	rpcServer.Register("InterfaceHandler", serverHandler)

	testServ := httptest.NewServer(rpcServer)
	defer testServ.Close()

	closer, err := NewMergeClient(context.Background(), "ws://"+testServ.Listener.Addr().String(), "InterfaceHandler", []interface{}{&client}, nil, WithParamEncoder(new(io.Reader), readerEnc))
	require.NoError(t, err)

	defer closer()

	read, err := client.ReadAll(context.TODO(), strings.NewReader("pooooootato"))
	require.NoError(t, err)
	require.Equal(t, "pooooootato", string(read), "potatos weren't equal")
}

var (
	readerRegistery   = map[int]io.Reader{}
	readerRegisteryN  = 31
	readerRegisteryLk sync.Mutex
)

func readerEnc(rin reflect.Value) (reflect.Value, error) {
	reader := rin.Interface().(io.Reader)

	readerRegisteryLk.Lock()
	defer readerRegisteryLk.Unlock()

	n := readerRegisteryN
	readerRegisteryN++

	readerRegistery[n] = reader
	return reflect.ValueOf(n), nil
}

func readerDec(ctx context.Context, rin []byte) (reflect.Value, error) {
	var id int
	if err := json.Unmarshal(rin, &id); err != nil {
		return reflect.Value{}, err
	}

	readerRegisteryLk.Lock()
	defer readerRegisteryLk.Unlock()

	return reflect.ValueOf(readerRegistery[id]), nil
}