// Copyright 2017, OpenCensus 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 stackdriver is an example program that collects data for
// video size. Collected data is exported to
// Stackdriver Monitoring.
package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"contrib.go.opencensus.io/exporter/stackdriver"
	"contrib.go.opencensus.io/exporter/stackdriver/monitoredresource"
	"go.opencensus.io/stats"
	"go.opencensus.io/stats/view"
)

// Create measures. The program will record measures for the size of
// processed videos and the nubmer of videos marked as spam.
var videoSize = stats.Int64("my.org/measure/video_size", "size of processed videos", stats.UnitBytes)

func main() {
	ctx := context.Background()

	// Collected view data will be reported to Stackdriver Monitoring API
	// via the Stackdriver exporter.
	//
	// In order to use the Stackdriver exporter, enable Stackdriver Monitoring API
	// at https://console.cloud.google.com/apis/dashboard.
	//
	// Once API is enabled, you can use Google Application Default Credentials
	// to setup the authorization.
	// See https://developers.google.com/identity/protocols/application-default-credentials
	// for more details.
	exporter, err := stackdriver.NewExporter(stackdriver.Options{
		ProjectID:         "your-project-id", // Google Cloud Console project ID for stackdriver.
		MonitoredResource: monitoredresource.Autodetect(),
	})
	if err != nil {
		log.Fatal(err)
	}
	view.RegisterExporter(exporter)

	// Set reporting period to report data at every second.
	view.SetReportingPeriod(1 * time.Second)

	// Create view to see the processed video size cumulatively.
	// Subscribe will allow view data to be exported.
	// Once no longer need, you can unsubscribe from the view.
	if err := view.Register(&view.View{
		Name:        "my.org/views/video_size_cum",
		Description: "processed video size over time",
		Measure:     videoSize,
		Aggregation: view.Distribution(0, 1<<16, 1<<32),
	}); err != nil {
		log.Fatalf("Cannot subscribe to the view: %v", err)
	}

	processVideo(ctx)

	// Wait for a duration longer than reporting duration to ensure the stats
	// library reports the collected data.
	fmt.Println("Wait longer than the reporting duration...")
	time.Sleep(1 * time.Minute)
}

func processVideo(ctx context.Context) {
	// Do some processing and record stats.
	stats.Record(ctx, videoSize.M(25648))
}