// Copyright 2020, OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Command zipkin is an example program that creates spans
// and uploads to openzipkin collector.
package main

import (
	"context"
	"log"
	"os"
	"time"

	"go.opentelemetry.io/otel/api/global"

	"go.opentelemetry.io/otel/exporters/trace/zipkin"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

var logger = log.New(os.Stderr, "zipkin-example", log.Ldate|log.Ltime|log.Llongfile)

// initTracer creates a new trace provider instance and registers it as global trace provider.
func initTracer() {
	// Create Zipkin Exporter
	exporter, err := zipkin.NewExporter(
		"http://localhost:9411/api/v2/spans",
		zipkin.WithLogger(logger),
	)
	if err != nil {
		log.Fatal(err)
	}

	// For demoing purposes, always sample. In a production application, you should
	// configure this to a trace.ProbabilitySampler set at the desired
	// probability.
	tp, err := sdktrace.NewProvider(
		sdktrace.WithConfig(sdktrace.Config{DefaultSampler: sdktrace.AlwaysSample()}),
		sdktrace.WithBatcher(exporter,
			sdktrace.WithScheduleDelayMillis(5),
			sdktrace.WithMaxExportBatchSize(10),
		),
	)
	if err != nil {
		log.Fatal(err)
	}
	global.SetTraceProvider(tp)
}

func main() {
	initTracer()

	ctx := context.Background()

	tr := global.TraceProvider().Tracer("component-main")
	ctx, span := tr.Start(ctx, "foo")
	<-time.After(6 * time.Millisecond)
	bar(ctx)
	<-time.After(6 * time.Millisecond)
	span.End()
	<-time.After(24 * time.Millisecond)
}

func bar(ctx context.Context) {
	tr := global.TraceProvider().Tracer("component-bar")
	_, span := tr.Start(ctx, "bar")
	<-time.After(6 * time.Millisecond)
	span.End()
}