text: // Copyright 2017 Google LLC
  //
  // 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.
  
  package main
  
  import (
  	"fmt"
  	"log"
  	"net/http"
  	"os"
  	"strings"
  
  	compute "google.golang.org/api/compute/v1"
  	"google.golang.org/api/googleapi"
  )
  
  func init() {
  	scopes := strings.Join([]string{
  		compute.DevstorageFullControlScope,
  		compute.ComputeScope,
  	}, " ")
  	registerDemo("compute", scopes, computeMain)
  }
  
  func computeMain(client *http.Client, argv []string) {
  	if len(argv) != 2 {
  		fmt.Fprintln(os.Stderr, "Usage: compute project_id instance_name (to start an instance)")
  		return
  	}
  
  	service, err := compute.New(client)
  	if err != nil {
  		log.Fatalf("Unable to create Compute service: %v", err)
  	}
  
  	projectId := argv[0]
  	instanceName := argv[1]
  
  	prefix := "https://www.googleapis.com/compute/v1/projects/" + projectId
  	imageURL := "https://www.googleapis.com/compute/v1/projects/debian-cloud/global/images/debian-7-wheezy-v20140606"
  	zone := "us-central1-a"
  
  	// Show the current images that are available.
  	res, err := service.Images.List(projectId).Do()
  	log.Printf("Got compute.Images.List, err: %#v, %v", res, err)
  
  	instance := &compute.Instance{
  		Name:        instanceName,
  		Description: "compute sample instance",
  		MachineType: prefix + "/zones/" + zone + "/machineTypes/n1-standard-1",
  		Disks: []*compute.AttachedDisk{
  			{
  				AutoDelete: true,
  				Boot:       true,
  				Type:       "PERSISTENT",
  				InitializeParams: &compute.AttachedDiskInitializeParams{
  					DiskName:    "my-root-pd",
  					SourceImage: imageURL,
  				},
  			},
  		},
  		NetworkInterfaces: []*compute.NetworkInterface{
  			&compute.NetworkInterface{
  				AccessConfigs: []*compute.AccessConfig{
  					&compute.AccessConfig{
  						Type: "ONE_TO_ONE_NAT",
  						Name: "External NAT",
  					},
  				},
  				Network: prefix + "/global/networks/default",
  			},
  		},
  		ServiceAccounts: []*compute.ServiceAccount{
  			{
  				Email: "default",
  				Scopes: []string{
  					compute.DevstorageFullControlScope,
  					compute.ComputeScope,
  				},
  			},
  		},
  	}
  
  	op, err := service.Instances.Insert(projectId, zone, instance).Do()
  	log.Printf("Got compute.Operation, err: %#v, %v", op, err)
  	etag := op.Header.Get("Etag")
  	log.Printf("Etag=%v", etag)
  
  	inst, err := service.Instances.Get(projectId, zone, instanceName).IfNoneMatch(etag).Do()
  	log.Printf("Got compute.Instance, err: %#v, %v", inst, err)
  	if googleapi.IsNotModified(err) {
  		log.Printf("Instance not modified since insert.")
  	} else {
  		log.Printf("Instance modified since insert.")
  	}
  }
  