// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

// Opentelemetry_server exemplifies the use of the OpenCensus propagator in an
// OpenTelemetry server.
package main // import "go.opentelemetry.io/otel/bridge/opencensus/examples/grpc/server"

import (
	"context"
	"log"
	"math/rand"
	"net"
	"time"

	pb "go.opencensus.io/examples/grpc/proto"
	"go.opencensus.io/trace"
	"go.opentelemetry.io/otel"
	stdout "go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"google.golang.org/grpc"

	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
	"go.opentelemetry.io/contrib/propagators/opencensus"
)

const address = "localhost:50051"

// server is used to implement helloworld.GreeterServer.
type server struct{}

// SayHello implements helloworld.GreeterServer.
func (*server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	_, span := trace.StartSpan(ctx, "sleep")
	time.Sleep(time.Duration(rand.Float64() * float64(time.Second))) //nolint:gosec // Ignoring G404: Use of weak random number generator (math/rand instead of crypto/rand)
	span.End()
	return &pb.HelloReply{Message: "Hello " + in.Name}, nil
}

func main() {
	lis, err := (&net.ListenConfig{}).Listen(context.Background(), "tcp", address)
	if err != nil {
		log.Fatalf("Failed to listen: %v", err)
	}

	log.Println("Registering OpenTelemetry stdout exporter.")
	otExporter, err := stdout.New(stdout.WithPrettyPrint())
	if err != nil {
		log.Fatal(err)
	}
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(otExporter),
		sdktrace.WithSampler(sdktrace.AlwaysSample()),
	)
	defer func() {
		if err := tp.Shutdown(context.Background()); err != nil {
			log.Printf("Error shutting down tracer provider: %v", err)
		}
	}()
	otel.SetTracerProvider(tp)

	// Set up a new server with the OpenCensus
	// handler to enable tracing.
	log.Println("Starting the GRPC server, and using the OpenCensus binary propagation format.")
	s := grpc.NewServer(
		grpc.StatsHandler(otelgrpc.NewServerHandler(otelgrpc.WithPropagators(opencensus.Binary{}))),
	)
	pb.RegisterGreeterServer(s, &server{})

	if err := s.Serve(lis); err != nil {
		log.Fatalf("Failed to serve: %v", err)
	}
}
