package main

import (
	"crypto/tls"
	"errors"
	"net"
	"time"

	grpcconfig "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-node/config/grpc"
	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
	metrics "git.frostfs.info/TrueCloudLab/frostfs-observability/metrics/grpc"
	tracing "git.frostfs.info/TrueCloudLab/frostfs-observability/tracing/grpc"
	"go.uber.org/zap"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
)

const maxRecvMsgSize = 256 << 20

func initGRPC(c *cfg) {
	var endpointsToReconnect []string
	var successCount int
	grpcconfig.IterateEndpoints(c.appCfg, func(sc *grpcconfig.Config) {
		serverOpts, ok := getGrpcServerOpts(c, sc)
		if !ok {
			return
		}

		lis, err := net.Listen("tcp", sc.Endpoint())
		if err != nil {
			c.metricsCollector.GrpcServerMetrics().MarkUnhealthy(sc.Endpoint())
			c.log.Error(logs.FrostFSNodeCantListenGRPCEndpoint, zap.Error(err))
			endpointsToReconnect = append(endpointsToReconnect, sc.Endpoint())
			return
		}
		c.metricsCollector.GrpcServerMetrics().MarkHealthy(sc.Endpoint())

		srv := grpc.NewServer(serverOpts...)

		c.onShutdown(func() {
			stopGRPC("FrostFS Public API", srv, c.log)
		})

		c.cfgGRPC.append(sc.Endpoint(), lis, srv)
		successCount++
	})

	if successCount == 0 {
		fatalOnErr(errors.New("could not listen to any gRPC endpoints"))
	}
	c.cfgGRPC.reconnectTimeout = grpcconfig.ReconnectTimeout(c.appCfg)

	for _, endpoint := range endpointsToReconnect {
		scheduleReconnect(endpoint, c)
	}
}

func scheduleReconnect(endpoint string, c *cfg) {
	c.wg.Add(1)
	go func() {
		defer c.wg.Done()

		t := time.NewTicker(c.cfgGRPC.reconnectTimeout)
		for {
			select {
			case <-t.C:
				if tryReconnect(endpoint, c) {
					return
				}
			case <-c.done:
				return
			}
		}
	}()
}

func tryReconnect(endpoint string, c *cfg) bool {
	c.log.Info(logs.FrostFSNodeGRPCReconnecting, zap.String("endpoint", endpoint))

	serverOpts, found := getGRPCEndpointOpts(endpoint, c)
	if !found {
		c.log.Warn(logs.FrostFSNodeGRPCServerConfigNotFound, zap.String("endpoint", endpoint))
		return true
	}

	lis, err := net.Listen("tcp", endpoint)
	if err != nil {
		c.metricsCollector.GrpcServerMetrics().MarkUnhealthy(endpoint)
		c.log.Error(logs.FrostFSNodeCantListenGRPCEndpoint, zap.Error(err))
		c.log.Warn(logs.FrostFSNodeGRPCReconnectFailed, zap.Duration("next_try_in", c.cfgGRPC.reconnectTimeout))
		return false
	}
	c.metricsCollector.GrpcServerMetrics().MarkHealthy(endpoint)

	srv := grpc.NewServer(serverOpts...)

	c.onShutdown(func() {
		stopGRPC("FrostFS Public API", srv, c.log)
	})

	c.cfgGRPC.appendAndHandle(endpoint, lis, srv)

	c.log.Info(logs.FrostFSNodeGRPCReconnectedSuccessfully, zap.String("endpoint", endpoint))
	return true
}

func getGRPCEndpointOpts(endpoint string, c *cfg) (result []grpc.ServerOption, found bool) {
	unlock := c.LockAppConfigShared()
	defer unlock()
	grpcconfig.IterateEndpoints(c.appCfg, func(sc *grpcconfig.Config) {
		if found {
			return
		}
		if sc.Endpoint() != endpoint {
			return
		}
		var ok bool
		result, ok = getGrpcServerOpts(c, sc)
		if !ok {
			return
		}
		found = true
	})
	return
}

func getGrpcServerOpts(c *cfg, sc *grpcconfig.Config) ([]grpc.ServerOption, bool) {
	serverOpts := []grpc.ServerOption{
		grpc.MaxRecvMsgSize(maxRecvMsgSize),
		grpc.ChainUnaryInterceptor(
			metrics.NewUnaryServerInterceptor(),
			tracing.NewUnaryServerInterceptor(),
		),
		grpc.ChainStreamInterceptor(
			metrics.NewStreamServerInterceptor(),
			tracing.NewStreamServerInterceptor(),
		),
	}

	tlsCfg := sc.TLS()

	if tlsCfg != nil {
		cert, err := tls.LoadX509KeyPair(tlsCfg.CertificateFile(), tlsCfg.KeyFile())
		if err != nil {
			c.log.Error(logs.FrostFSNodeCouldNotReadCertificateFromFile, zap.Error(err))
			return nil, false
		}

		var cipherSuites []uint16
		if !tlsCfg.UseInsecureCrypto() {
			// This more or less follows the list in https://wiki.mozilla.org/Security/Server_Side_TLS
			// excluding:
			// 1. TLS 1.3 suites need not be specified here.
			// 2. Suites that use DH key exchange are not implemented by stdlib.
			cipherSuites = []uint16{
				tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
				tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
				tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
				tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
				tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
				tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
			}
		}
		creds := credentials.NewTLS(&tls.Config{
			MinVersion:   tls.VersionTLS12,
			CipherSuites: cipherSuites,
			Certificates: []tls.Certificate{cert},
		})

		serverOpts = append(serverOpts, grpc.Creds(creds))
	}

	return serverOpts, true
}

func serveGRPC(c *cfg) {
	c.cfgGRPC.performAndSave(func(e string, l net.Listener, s *grpc.Server) {
		c.wg.Add(1)

		go func() {
			defer func() {
				c.log.Info(logs.FrostFSNodeStopListeningGRPCEndpoint,
					zap.Stringer("endpoint", l.Addr()),
				)

				c.wg.Done()
			}()

			c.log.Info(logs.FrostFSNodeStartListeningEndpoint,
				zap.String("service", "gRPC"),
				zap.Stringer("endpoint", l.Addr()),
			)

			if err := s.Serve(l); err != nil {
				c.metricsCollector.GrpcServerMetrics().MarkUnhealthy(e)
				c.log.Error(logs.FrostFSNodeGRPCServerError, zap.Error(err))
				c.cfgGRPC.dropConnection(e)
				scheduleReconnect(e, c)
			}
		}()
	})
}

func stopGRPC(name string, s *grpc.Server, l *logger.Logger) {
	l = &logger.Logger{Logger: l.With(zap.String("name", name))}

	l.Info(logs.FrostFSNodeStoppingGRPCServer)

	// GracefulStop() may freeze forever, see #1270
	done := make(chan struct{})
	go func() {
		s.GracefulStop()
		close(done)
	}()

	select {
	case <-done:
	case <-time.After(1 * time.Minute):
		l.Info(logs.FrostFSNodeGRPCCannotShutdownGracefullyForcingStop)
		s.Stop()
	}

	l.Info(logs.FrostFSNodeGRPCServerStoppedSuccessfully)
}