// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package rpc

import (
	"context"
	"encoding/json"
	"net"
	"sync"
	"testing"
	"time"
)

type NotificationTestService struct {
	mu           sync.Mutex
	unsubscribed bool

	gotHangSubscriptionReq  chan struct{}
	unblockHangSubscription chan struct{}
}

func (s *NotificationTestService) Echo(i int) int {
	return i
}

func (s *NotificationTestService) wasUnsubCallbackCalled() bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.unsubscribed
}

func (s *NotificationTestService) Unsubscribe(subid string) {
	s.mu.Lock()
	s.unsubscribed = true
	s.mu.Unlock()
}

func (s *NotificationTestService) SomeSubscription(ctx context.Context, n, val int) (*Subscription, error) {
	notifier, supported := NotifierFromContext(ctx)
	if !supported {
		return nil, ErrNotificationsUnsupported
	}

	// by explicitly creating an subscription we make sure that the subscription id is send back to the client
	// before the first subscription.Notify is called. Otherwise the events might be send before the response
	// for the eth_subscribe method.
	subscription := notifier.CreateSubscription()

	go func() {
		// test expects n events, if we begin sending event immediately some events
		// will probably be dropped since the subscription ID might not be send to
		// the client.
		time.Sleep(5 * time.Second)
		for i := 0; i < n; i++ {
			if err := notifier.Notify(subscription.ID, val+i); err != nil {
				return
			}
		}

		select {
		case <-notifier.Closed():
			s.mu.Lock()
			s.unsubscribed = true
			s.mu.Unlock()
		case <-subscription.Err():
			s.mu.Lock()
			s.unsubscribed = true
			s.mu.Unlock()
		}
	}()

	return subscription, nil
}

// HangSubscription blocks on s.unblockHangSubscription before
// sending anything.
func (s *NotificationTestService) HangSubscription(ctx context.Context, val int) (*Subscription, error) {
	notifier, supported := NotifierFromContext(ctx)
	if !supported {
		return nil, ErrNotificationsUnsupported
	}

	s.gotHangSubscriptionReq <- struct{}{}
	<-s.unblockHangSubscription
	subscription := notifier.CreateSubscription()

	go func() {
		notifier.Notify(subscription.ID, val)
	}()
	return subscription, nil
}

func TestNotifications(t *testing.T) {
	server := NewServer()
	service := &NotificationTestService{}

	if err := server.RegisterName("eth", service); err != nil {
		t.Fatalf("unable to register test service %v", err)
	}

	clientConn, serverConn := net.Pipe()

	go server.ServeCodec(NewJSONCodec(serverConn), OptionMethodInvocation|OptionSubscriptions)

	out := json.NewEncoder(clientConn)
	in := json.NewDecoder(clientConn)

	n := 5
	val := 12345
	request := map[string]interface{}{
		"id":      1,
		"method":  "eth_subscribe",
		"version": "2.0",
		"params":  []interface{}{"someSubscription", n, val},
	}

	// create subscription
	if err := out.Encode(request); err != nil {
		t.Fatal(err)
	}

	var subid string
	response := jsonSuccessResponse{Result: subid}
	if err := in.Decode(&response); err != nil {
		t.Fatal(err)
	}

	var ok bool
	if _, ok = response.Result.(string); !ok {
		t.Fatalf("expected subscription id, got %T", response.Result)
	}

	for i := 0; i < n; i++ {
		var notification jsonNotification
		if err := in.Decode(&notification); err != nil {
			t.Fatalf("%v", err)
		}

		if int(notification.Params.Result.(float64)) != val+i {
			t.Fatalf("expected %d, got %d", val+i, notification.Params.Result)
		}
	}

	clientConn.Close() // causes notification unsubscribe callback to be called
	time.Sleep(1 * time.Second)

	if !service.wasUnsubCallbackCalled() {
		t.Error("unsubscribe callback not called after closing connection")
	}
}