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

// Example using OTLP exporters + collector + third-party backends. For
// information about using the exporter, see:
// https://pkg.go.dev/go.opentelemetry.io/otel/exporters/otlp?tab=doc#example-package-Insecure
package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"os/signal"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/propagation"
	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.41.0"
	"go.opentelemetry.io/otel/trace"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
)

var serviceName = semconv.ServiceNameKey.String("test-service")

// Initialize a gRPC connection to be used by both the tracer and meter
// providers.
func initConn() (*grpc.ClientConn, error) {
	// It connects the OpenTelemetry Collector through local gRPC connection.
	// You may replace `localhost:4317` with your endpoint.
	conn, err := grpc.NewClient(
		"localhost:4317",
		// Note the use of insecure transport here. TLS is recommended in production.
		grpc.WithTransportCredentials(insecure.NewCredentials()),
	)
	if err != nil {
		return nil, fmt.Errorf("failed to create gRPC connection to collector: %w", err)
	}

	return conn, err
}

// Initializes an OTLP exporter, and configures the corresponding trace provider.
func initTracerProvider(ctx context.Context, res *resource.Resource, conn *grpc.ClientConn) (func(context.Context) error, error) {
	// Set up a trace exporter
	traceExporter, err := otlptracegrpc.New(ctx, otlptracegrpc.WithGRPCConn(conn))
	if err != nil {
		return nil, fmt.Errorf("failed to create trace exporter: %w", err)
	}

	// Register the trace exporter with a TracerProvider, using a batch
	// span processor to aggregate spans before export.
	bsp := sdktrace.NewBatchSpanProcessor(traceExporter)
	tracerProvider := sdktrace.NewTracerProvider(
		sdktrace.WithSampler(sdktrace.AlwaysSample()),
		sdktrace.WithResource(res),
		sdktrace.WithSpanProcessor(bsp),
	)
	otel.SetTracerProvider(tracerProvider)

	// Set global propagator to tracecontext (the default is no-op).
	otel.SetTextMapPropagator(propagation.TraceContext{})

	// Shutdown will flush any remaining spans and shut down the exporter.
	return tracerProvider.Shutdown, nil
}

// Initializes an OTLP exporter, and configures the corresponding meter provider.
func initMeterProvider(ctx context.Context, res *resource.Resource, conn *grpc.ClientConn) (func(context.Context) error, error) {
	metricExporter, err := otlpmetricgrpc.New(ctx, otlpmetricgrpc.WithGRPCConn(conn))
	if err != nil {
		return nil, fmt.Errorf("failed to create metrics exporter: %w", err)
	}

	meterProvider := sdkmetric.NewMeterProvider(
		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(metricExporter)),
		sdkmetric.WithResource(res),
	)
	otel.SetMeterProvider(meterProvider)

	return meterProvider.Shutdown, nil
}

func main() {
	log.Printf("Waiting for connection...")

	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
	defer cancel()

	conn, err := initConn()
	if err != nil {
		log.Fatal(err)
	}

	res, err := resource.New(
		ctx,
		resource.WithAttributes(
			// The service name used to display traces in backends
			serviceName,
		),
	)
	if err != nil {
		log.Fatal(err)
	}

	shutdownTracerProvider, err := initTracerProvider(ctx, res, conn)
	if err != nil {
		log.Fatal(err)
	}
	defer func() {
		if err := shutdownTracerProvider(ctx); err != nil {
			log.Fatalf("failed to shutdown TracerProvider: %s", err)
		}
	}()

	shutdownMeterProvider, err := initMeterProvider(ctx, res, conn)
	if err != nil {
		log.Fatal(err)
	}
	defer func() {
		if err := shutdownMeterProvider(ctx); err != nil {
			log.Fatalf("failed to shutdown MeterProvider: %s", err)
		}
	}()

	name := "go.opentelemetry.io/contrib/examples/otel-collector"
	tracer := otel.Tracer(name)
	meter := otel.Meter(name)

	// Attributes represent additional key-value descriptors that can be bound
	// to a metric observer or recorder.
	commonAttrs := []attribute.KeyValue{
		attribute.String("attrA", "chocolate"),
		attribute.String("attrB", "raspberry"),
		attribute.String("attrC", "vanilla"),
	}

	runCount, err := meter.Int64Counter("run", metric.WithDescription("The number of times the iteration ran"))
	if err != nil {
		log.Fatal(err)
	}

	// Work begins
	ctx, span := tracer.Start(
		ctx,
		"CollectorExporter-Example",
		trace.WithAttributes(commonAttrs...),
	)
	defer span.End()
	for i := range 10 {
		_, iSpan := tracer.Start(ctx, fmt.Sprintf("Sample-%d", i))
		runCount.Add(ctx, 1, metric.WithAttributes(commonAttrs...))
		log.Printf("Doing really hard work (%d / 10)\n", i+1)

		<-time.After(time.Second)
		iSpan.End()
	}

	log.Printf("Done!")
}
