package rpc

import (
	"context"
	"fmt"
	"net"

	middleware "github.com/grpc-ecosystem/go-grpc-middleware"
	recovery "github.com/grpc-ecosystem/go-grpc-middleware/recovery"
	grpc_opentracing "github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing"
	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
	pb "github.com/prysmaticlabs/prysm/proto/validator/accounts/v2"
	"github.com/prysmaticlabs/prysm/shared/rand"
	"github.com/prysmaticlabs/prysm/shared/traceutil"
	"github.com/prysmaticlabs/prysm/validator/client"
	"github.com/prysmaticlabs/prysm/validator/db"
	"github.com/sirupsen/logrus"
	"go.opencensus.io/plugin/ocgrpc"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/reflection"
)

var log logrus.FieldLogger

func init() {
	log = logrus.WithField("prefix", "rpc")
}

// Config options for the gRPC server.
type Config struct {
	Host             string
	Port             string
	CertFlag         string
	KeyFlag          string
	ValDB            db.Database
	ValidatorService *client.ValidatorService
}

// Server defining a gRPC server for the remote signer API.
type Server struct {
	valDB            db.Database
	ctx              context.Context
	cancel           context.CancelFunc
	host             string
	port             string
	listener         net.Listener
	withCert         string
	withKey          string
	credentialError  error
	grpcServer       *grpc.Server
	jwtKey           []byte
	validatorService *client.ValidatorService
}

// NewServer instantiates a new gRPC server.
func NewServer(ctx context.Context, cfg *Config) *Server {
	ctx, cancel := context.WithCancel(ctx)
	return &Server{
		ctx:              ctx,
		cancel:           cancel,
		host:             cfg.Host,
		port:             cfg.Port,
		withCert:         cfg.CertFlag,
		withKey:          cfg.KeyFlag,
		valDB:            cfg.ValDB,
		validatorService: cfg.ValidatorService,
	}
}

// Start the gRPC server.
func (s *Server) Start() {
	// Setup the gRPC server options and TLS configuration.
	address := fmt.Sprintf("%s:%s", s.host, s.port)
	lis, err := net.Listen("tcp", address)
	if err != nil {
		log.Errorf("Could not listen to port in Start() %s: %v", address, err)
	}
	s.listener = lis

	// Register interceptors for metrics gathering as well as our
	// own, custom JWT unary interceptor.
	opts := []grpc.ServerOption{
		grpc.StatsHandler(&ocgrpc.ServerHandler{}),
		grpc.UnaryInterceptor(middleware.ChainUnaryServer(
			recovery.UnaryServerInterceptor(
				recovery.WithRecoveryHandlerContext(traceutil.RecoveryHandlerFunc),
			),
			grpc_prometheus.UnaryServerInterceptor,
			grpc_opentracing.UnaryServerInterceptor(),
			s.JWTInterceptor(),
		)),
	}
	grpc_prometheus.EnableHandlingTimeHistogram()

	if s.withCert != "" && s.withKey != "" {
		creds, err := credentials.NewServerTLSFromFile(s.withCert, s.withKey)
		if err != nil {
			log.Errorf("Could not load TLS keys: %s", err)
			s.credentialError = err
		}
		opts = append(opts, grpc.Creds(creds))
		log.WithFields(logrus.Fields{
			"crt-path": s.withCert,
			"key-path": s.withKey,
		}).Info("Loaded TLS certificates")
	}
	s.grpcServer = grpc.NewServer(opts...)

	// We create a new, random JWT key upon validator startup.
	r := rand.NewGenerator()
	jwtKey := make([]byte, 32)
	n, err := r.Read(jwtKey)
	if err != nil {
		log.WithError(err).Fatal("Could not initialize validator jwt key")
	}
	if n != len(jwtKey) {
		log.WithError(err).Fatal("Could not create random jwt key for validator")
	}
	s.jwtKey = jwtKey

	// Register services available for the gRPC server.
	reflection.Register(s.grpcServer)
	pb.RegisterAuthServer(s.grpcServer, s)
	pb.RegisterHealthServer(s.grpcServer, s)

	go func() {
		if s.listener != nil {
			if err := s.grpcServer.Serve(s.listener); err != nil {
				log.Errorf("Could not serve: %v", err)
			}
		}
	}()
	log.WithField("address", address).Info("gRPC server listening on address")
}

// Stop the gRPC server.
func (s *Server) Stop() error {
	s.cancel()
	if s.listener != nil {
		s.grpcServer.GracefulStop()
		log.Debug("Initiated graceful stop of server")
	}
	return nil
}

// Status returns nil or credentialError.
func (s *Server) Status() error {
	return s.credentialError
}