package google

import (
	"fmt"
	"reflect"
	"strings"

	"github.com/hashicorp/errwrap"
	"github.com/hashicorp/terraform-plugin-sdk/helper/customdiff"
	"github.com/hashicorp/terraform-plugin-sdk/helper/resource"
	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
	"github.com/hashicorp/terraform-plugin-sdk/helper/validation"

	computeBeta "google.golang.org/api/compute/v0.beta"
)

var (
	schedulingInstTemplateKeys = []string{
		"scheduling.0.on_host_maintenance",
		"scheduling.0.automatic_restart",
		"scheduling.0.preemptible",
		"scheduling.0.node_affinities",
	}

	shieldedInstanceTemplateConfigKeys = []string{
		"shielded_instance_config.0.enable_secure_boot",
		"shielded_instance_config.0.enable_vtpm",
		"shielded_instance_config.0.enable_integrity_monitoring",
	}
)

func resourceComputeInstanceTemplate() *schema.Resource {
	return &schema.Resource{
		Create: resourceComputeInstanceTemplateCreate,
		Read:   resourceComputeInstanceTemplateRead,
		Delete: resourceComputeInstanceTemplateDelete,
		Importer: &schema.ResourceImporter{
			State: resourceComputeInstanceTemplateImportState,
		},
		SchemaVersion: 1,
		CustomizeDiff: customdiff.All(
			resourceComputeInstanceTemplateSourceImageCustomizeDiff,
			resourceComputeInstanceTemplateScratchDiskCustomizeDiff,
			resourceComputeInstanceTemplateBootDiskCustomizeDiff,
		),
		MigrateState: resourceComputeInstanceTemplateMigrateState,

		// A compute instance template is more or less a subset of a compute
		// instance. Please attempt to maintain consistency with the
		// resource_compute_instance schema when updating this one.
		Schema: map[string]*schema.Schema{
			"name": {
				Type:          schema.TypeString,
				Optional:      true,
				Computed:      true,
				ForceNew:      true,
				ConflictsWith: []string{"name_prefix"},
				ValidateFunc:  validateGCPName,
			},

			"name_prefix": {
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
				ValidateFunc: func(v interface{}, k string) (ws []string, errors []error) {
					// https://cloud.google.com/compute/docs/reference/latest/instanceTemplates#resource
					// uuid is 26 characters, limit the prefix to 37.
					value := v.(string)
					if len(value) > 37 {
						errors = append(errors, fmt.Errorf(
							"%q cannot be longer than 37 characters, name is limited to 63", k))
					}
					return
				},
			},

			"disk": {
				Type:     schema.TypeList,
				Required: true,
				ForceNew: true,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"auto_delete": {
							Type:     schema.TypeBool,
							Optional: true,
							Default:  true,
							ForceNew: true,
						},

						"boot": {
							Type:     schema.TypeBool,
							Optional: true,
							ForceNew: true,
							Computed: true,
						},

						"device_name": {
							Type:     schema.TypeString,
							Optional: true,
							Computed: true,
							ForceNew: true,
						},

						"disk_name": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
						},

						"disk_size_gb": {
							Type:     schema.TypeInt,
							Optional: true,
							ForceNew: true,
						},

						"disk_type": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
							Computed: true,
						},

						"labels": {
							Type:     schema.TypeMap,
							Optional: true,
							ForceNew: true,
							Elem: &schema.Schema{
								Type: schema.TypeString,
							},
						},

						"source_image": {
							Type:     schema.TypeString,
							Optional: true,
							Computed: true,
						},

						"interface": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
							Computed: true,
						},

						"mode": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
							Computed: true,
						},

						"source": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
						},

						"type": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
							Computed: true,
						},

						"disk_encryption_key": {
							Type:     schema.TypeList,
							Optional: true,
							ForceNew: true,
							MaxItems: 1,
							Elem: &schema.Resource{
								Schema: map[string]*schema.Schema{
									"kms_key_self_link": {
										Type:             schema.TypeString,
										Required:         true,
										ForceNew:         true,
										DiffSuppressFunc: compareSelfLinkRelativePaths,
									},
								},
							},
						},
					},
				},
			},

			"machine_type": {
				Type:     schema.TypeString,
				Required: true,
				ForceNew: true,
			},

			"can_ip_forward": {
				Type:     schema.TypeBool,
				Optional: true,
				Default:  false,
				ForceNew: true,
			},

			"description": {
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
			},

			"enable_display": {
				Type:     schema.TypeBool,
				Optional: true,
				ForceNew: true,
			},

			"instance_description": {
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
			},

			"metadata": {
				Type:     schema.TypeMap,
				Optional: true,
				ForceNew: true,
			},

			"metadata_startup_script": {
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
			},

			"metadata_fingerprint": {
				Type:     schema.TypeString,
				Computed: true,
			},

			"network_interface": {
				Type:     schema.TypeList,
				Optional: true,
				ForceNew: true,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"network": {
							Type:             schema.TypeString,
							Optional:         true,
							ForceNew:         true,
							Computed:         true,
							DiffSuppressFunc: compareSelfLinkOrResourceName,
						},

						"network_ip": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
						},

						"subnetwork": {
							Type:             schema.TypeString,
							Optional:         true,
							ForceNew:         true,
							Computed:         true,
							DiffSuppressFunc: compareSelfLinkOrResourceName,
						},

						"subnetwork_project": {
							Type:     schema.TypeString,
							Optional: true,
							ForceNew: true,
							Computed: true,
						},

						"access_config": {
							Type:     schema.TypeList,
							Optional: true,
							ForceNew: true,
							Elem: &schema.Resource{
								Schema: map[string]*schema.Schema{
									"nat_ip": {
										Type:     schema.TypeString,
										Optional: true,
										ForceNew: true,
										Computed: true,
									},
									"network_tier": {
										Type:         schema.TypeString,
										Optional:     true,
										Computed:     true,
										ValidateFunc: validation.StringInSlice([]string{"PREMIUM", "STANDARD"}, false),
									},
								},
							},
						},

						"alias_ip_range": {
							Type:     schema.TypeList,
							Optional: true,
							ForceNew: true,
							Elem: &schema.Resource{
								Schema: map[string]*schema.Schema{
									"ip_cidr_range": {
										Type:             schema.TypeString,
										Required:         true,
										ForceNew:         true,
										DiffSuppressFunc: ipCidrRangeDiffSuppress,
									},
									"subnetwork_range_name": {
										Type:     schema.TypeString,
										Optional: true,
										ForceNew: true,
									},
								},
							},
						},
					},
				},
			},

			"project": {
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
				Computed: true,
			},

			"region": {
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
				Computed: true,
			},

			"scheduling": {
				Type:     schema.TypeList,
				Optional: true,
				Computed: true,
				ForceNew: true,
				MaxItems: 1,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"preemptible": {
							Type:         schema.TypeBool,
							Optional:     true,
							AtLeastOneOf: schedulingInstTemplateKeys,
							Default:      false,
							ForceNew:     true,
						},

						"automatic_restart": {
							Type:         schema.TypeBool,
							Optional:     true,
							AtLeastOneOf: schedulingInstTemplateKeys,
							Default:      true,
							ForceNew:     true,
						},

						"on_host_maintenance": {
							Type:         schema.TypeString,
							Optional:     true,
							Computed:     true,
							AtLeastOneOf: schedulingInstTemplateKeys,
							ForceNew:     true,
						},

						"node_affinities": {
							Type:             schema.TypeSet,
							Optional:         true,
							AtLeastOneOf:     schedulingInstTemplateKeys,
							ForceNew:         true,
							Elem:             instanceSchedulingNodeAffinitiesElemSchema(),
							DiffSuppressFunc: emptyOrDefaultStringSuppress(""),
						},
					},
				},
			},

			"self_link": {
				Type:     schema.TypeString,
				Computed: true,
			},

			"service_account": {
				Type:     schema.TypeList,
				MaxItems: 1,
				Optional: true,
				ForceNew: true,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"email": {
							Type:     schema.TypeString,
							Optional: true,
							Computed: true,
							ForceNew: true,
						},

						"scopes": {
							Type:     schema.TypeSet,
							Required: true,
							ForceNew: true,
							Elem: &schema.Schema{
								Type: schema.TypeString,
								StateFunc: func(v interface{}) string {
									return canonicalizeServiceScope(v.(string))
								},
							},
							Set: stringScopeHashcode,
						},
					},
				},
			},

			"shielded_instance_config": {
				Type:     schema.TypeList,
				MaxItems: 1,
				Optional: true,
				ForceNew: true,
				// Since this block is used by the API based on which
				// image being used, the field needs to be marked as Computed.
				Computed:         true,
				DiffSuppressFunc: emptyOrDefaultStringSuppress(""),
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"enable_secure_boot": {
							Type:         schema.TypeBool,
							Optional:     true,
							AtLeastOneOf: shieldedInstanceTemplateConfigKeys,
							Default:      false,
							ForceNew:     true,
						},

						"enable_vtpm": {
							Type:         schema.TypeBool,
							Optional:     true,
							AtLeastOneOf: shieldedInstanceTemplateConfigKeys,
							Default:      true,
							ForceNew:     true,
						},

						"enable_integrity_monitoring": {
							Type:         schema.TypeBool,
							Optional:     true,
							AtLeastOneOf: shieldedInstanceTemplateConfigKeys,
							Default:      true,
							ForceNew:     true,
						},
					},
				},
			},

			"guest_accelerator": {
				Type:     schema.TypeList,
				Optional: true,
				ForceNew: true,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"count": {
							Type:     schema.TypeInt,
							Required: true,
							ForceNew: true,
						},
						"type": {
							Type:             schema.TypeString,
							Required:         true,
							ForceNew:         true,
							DiffSuppressFunc: compareSelfLinkOrResourceName,
						},
					},
				},
			},

			"min_cpu_platform": {
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
			},

			"tags": {
				Type:     schema.TypeSet,
				Optional: true,
				ForceNew: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
				Set:      schema.HashString,
			},

			"tags_fingerprint": {
				Type:     schema.TypeString,
				Computed: true,
			},

			"labels": {
				Type:     schema.TypeMap,
				Optional: true,
				ForceNew: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
				Set:      schema.HashString,
			},
		},
	}
}

func resourceComputeInstanceTemplateSourceImageCustomizeDiff(diff *schema.ResourceDiff, meta interface{}) error {
	config := meta.(*Config)

	numDisks := diff.Get("disk.#").(int)
	for i := 0; i < numDisks; i++ {
		key := fmt.Sprintf("disk.%d.source_image", i)
		if diff.HasChange(key) {
			var err error
			old, new := diff.GetChange(key)
			if old == "" || new == "" {
				// no sense in resolving empty strings
				err = diff.ForceNew(key)
				if err != nil {
					return err
				}
				continue
			}
			// project must be retrieved once we know there is a diff to resolve, otherwise it will
			// attempt to retrieve project during `plan` before all calculated fields are ready
			// see https://github.com/terraform-providers/terraform-provider-google/issues/2878
			project, err := getProjectFromDiff(diff, config)
			if err != nil {
				return err
			}
			oldResolved, err := resolveImage(config, project, old.(string))
			if err != nil {
				return err
			}
			oldResolved, err = resolveImageRefToRelativeURI(project, oldResolved)
			if err != nil {
				return err
			}
			newResolved, err := resolveImage(config, project, new.(string))
			if err != nil {
				return err
			}
			newResolved, err = resolveImageRefToRelativeURI(project, newResolved)
			if err != nil {
				return err
			}
			if oldResolved != newResolved {
				err = diff.ForceNew(key)
				if err != nil {
					return err
				}
				continue
			}
			err = diff.Clear(key)
			if err != nil {
				return err
			}
		}
	}
	return nil
}

func resourceComputeInstanceTemplateScratchDiskCustomizeDiff(diff *schema.ResourceDiff, meta interface{}) error {
	// separate func to allow unit testing
	return resourceComputeInstanceTemplateScratchDiskCustomizeDiffFunc(diff)
}

func resourceComputeInstanceTemplateScratchDiskCustomizeDiffFunc(diff TerraformResourceDiff) error {
	numDisks := diff.Get("disk.#").(int)
	for i := 0; i < numDisks; i++ {
		// misspelled on purpose, type is a special symbol
		typee := diff.Get(fmt.Sprintf("disk.%d.type", i)).(string)
		diskType := diff.Get(fmt.Sprintf("disk.%d.disk_type", i)).(string)
		if typee == "SCRATCH" && diskType != "local-ssd" {
			return fmt.Errorf("SCRATCH disks must have a disk_type of local-ssd. disk %d has disk_type %s", i, diskType)
		}

		if diskType == "local-ssd" && typee != "SCRATCH" {
			return fmt.Errorf("disks with a disk_type of local-ssd must be SCRATCH disks. disk %d is a %s disk", i, typee)
		}

		diskSize := diff.Get(fmt.Sprintf("disk.%d.disk_size_gb", i)).(int)
		if typee == "SCRATCH" && diskSize != 375 {
			return fmt.Errorf("SCRATCH disks must be exactly 375GB, disk %d is %d", i, diskSize)
		}
	}

	return nil
}

func resourceComputeInstanceTemplateBootDiskCustomizeDiff(diff *schema.ResourceDiff, meta interface{}) error {
	numDisks := diff.Get("disk.#").(int)
	// No disk except the first can be the boot disk
	for i := 1; i < numDisks; i++ {
		key := fmt.Sprintf("disk.%d.boot", i)
		if v, ok := diff.GetOk(key); ok {
			if v.(bool) {
				return fmt.Errorf("Only the first disk specified in instance_template can be the boot disk. %s was true", key)
			}
		}
	}
	return nil
}

func buildDisks(d *schema.ResourceData, config *Config) ([]*computeBeta.AttachedDisk, error) {
	project, err := getProject(d, config)
	if err != nil {
		return nil, err
	}

	disksCount := d.Get("disk.#").(int)

	disks := make([]*computeBeta.AttachedDisk, 0, disksCount)
	for i := 0; i < disksCount; i++ {
		prefix := fmt.Sprintf("disk.%d", i)

		// Build the disk
		var disk computeBeta.AttachedDisk
		disk.Type = "PERSISTENT"
		disk.Mode = "READ_WRITE"
		disk.Interface = "SCSI"
		disk.Boot = i == 0
		disk.AutoDelete = d.Get(prefix + ".auto_delete").(bool)

		if v, ok := d.GetOk(prefix + ".boot"); ok {
			disk.Boot = v.(bool)
		}

		if v, ok := d.GetOk(prefix + ".device_name"); ok {
			disk.DeviceName = v.(string)
		}

		if _, ok := d.GetOk(prefix + ".disk_encryption_key"); ok {
			disk.DiskEncryptionKey = &computeBeta.CustomerEncryptionKey{}
			if v, ok := d.GetOk(prefix + ".disk_encryption_key.0.kms_key_self_link"); ok {
				disk.DiskEncryptionKey.KmsKeyName = v.(string)
			}
		}

		if v, ok := d.GetOk(prefix + ".source"); ok {
			disk.Source = v.(string)
			conflicts := []string{"disk_size_gb", "disk_name", "disk_type", "source_image", "labels"}
			for _, conflict := range conflicts {
				if _, ok := d.GetOk(prefix + "." + conflict); ok {
					return nil, fmt.Errorf("Cannot use `source` with any of the fields in %s", conflicts)
				}
			}
		} else {
			disk.InitializeParams = &computeBeta.AttachedDiskInitializeParams{}

			if v, ok := d.GetOk(prefix + ".disk_name"); ok {
				disk.InitializeParams.DiskName = v.(string)
			}
			if v, ok := d.GetOk(prefix + ".disk_size_gb"); ok {
				disk.InitializeParams.DiskSizeGb = int64(v.(int))
			}
			disk.InitializeParams.DiskType = "pd-standard"
			if v, ok := d.GetOk(prefix + ".disk_type"); ok {
				disk.InitializeParams.DiskType = v.(string)
			}

			if v, ok := d.GetOk(prefix + ".source_image"); ok {
				imageName := v.(string)
				imageUrl, err := resolveImage(config, project, imageName)
				if err != nil {
					return nil, fmt.Errorf(
						"Error resolving image name '%s': %s",
						imageName, err)
				}
				disk.InitializeParams.SourceImage = imageUrl
			}

			disk.InitializeParams.Labels = expandStringMap(d, prefix+".labels")
		}

		if v, ok := d.GetOk(prefix + ".interface"); ok {
			disk.Interface = v.(string)
		}

		if v, ok := d.GetOk(prefix + ".mode"); ok {
			disk.Mode = v.(string)
		}

		if v, ok := d.GetOk(prefix + ".type"); ok {
			disk.Type = v.(string)
		}

		disks = append(disks, &disk)
	}

	return disks, nil
}

// We don't share this code with compute instances because instances want a
// partial URL, but instance templates want the bare accelerator name (despite
// the docs saying otherwise).
//
// Using a partial URL on an instance template results in:
// Invalid value for field 'resource.properties.guestAccelerators[0].acceleratorType':
// 'zones/us-east1-b/acceleratorTypes/nvidia-tesla-k80'.
// Accelerator type 'zones/us-east1-b/acceleratorTypes/nvidia-tesla-k80'
// must be a valid resource name (not an url).
func expandInstanceTemplateGuestAccelerators(d TerraformResourceData, config *Config) []*computeBeta.AcceleratorConfig {
	configs, ok := d.GetOk("guest_accelerator")
	if !ok {
		return nil
	}
	accels := configs.([]interface{})
	guestAccelerators := make([]*computeBeta.AcceleratorConfig, 0, len(accels))
	for _, raw := range accels {
		data := raw.(map[string]interface{})
		if data["count"].(int) == 0 {
			continue
		}
		guestAccelerators = append(guestAccelerators, &computeBeta.AcceleratorConfig{
			AcceleratorCount: int64(data["count"].(int)),
			// We can't use ParseAcceleratorFieldValue here because an instance
			// template does not have a zone we can use.
			AcceleratorType: data["type"].(string),
		})
	}

	return guestAccelerators
}

func resourceComputeInstanceTemplateCreate(d *schema.ResourceData, meta interface{}) error {
	config := meta.(*Config)

	project, err := getProject(d, config)
	if err != nil {
		return err
	}

	disks, err := buildDisks(d, config)
	if err != nil {
		return err
	}

	metadata, err := resourceInstanceMetadata(d)
	if err != nil {
		return err
	}

	networks, err := expandNetworkInterfaces(d, config)
	if err != nil {
		return err
	}

	scheduling, err := expandResourceComputeInstanceTemplateScheduling(d, config)
	if err != nil {
		return err
	}

	instanceProperties := &computeBeta.InstanceProperties{
		CanIpForward:      d.Get("can_ip_forward").(bool),
		Description:       d.Get("instance_description").(string),
		GuestAccelerators: expandInstanceTemplateGuestAccelerators(d, config),
		MachineType:       d.Get("machine_type").(string),
		MinCpuPlatform:    d.Get("min_cpu_platform").(string),
		Disks:             disks,
		Metadata:          metadata,
		NetworkInterfaces: networks,
		Scheduling:        scheduling,
		ServiceAccounts:   expandServiceAccounts(d.Get("service_account").([]interface{})),
		Tags:              resourceInstanceTags(d),
		ShieldedVmConfig:  expandShieldedVmConfigs(d),
		DisplayDevice:     expandDisplayDevice(d),
	}

	if _, ok := d.GetOk("labels"); ok {
		instanceProperties.Labels = expandLabels(d)
	}

	var itName string
	if v, ok := d.GetOk("name"); ok {
		itName = v.(string)
	} else if v, ok := d.GetOk("name_prefix"); ok {
		itName = resource.PrefixedUniqueId(v.(string))
	} else {
		itName = resource.UniqueId()
	}
	instanceTemplate := &computeBeta.InstanceTemplate{
		Description: d.Get("description").(string),
		Properties:  instanceProperties,
		Name:        itName,
	}

	op, err := config.clientComputeBeta.InstanceTemplates.Insert(project, instanceTemplate).Do()
	if err != nil {
		return fmt.Errorf("Error creating instance template: %s", err)
	}

	// Store the ID now
	d.SetId(fmt.Sprintf("projects/%s/global/instanceTemplates/%s", project, instanceTemplate.Name))

	err = computeOperationWait(config, op, project, "Creating Instance Template")
	if err != nil {
		return err
	}

	return resourceComputeInstanceTemplateRead(d, meta)
}

type diskCharacteristics struct {
	mode        string
	diskType    string
	diskSizeGb  string
	autoDelete  bool
	sourceImage string
}

func diskCharacteristicsFromMap(m map[string]interface{}) diskCharacteristics {
	dc := diskCharacteristics{}
	if v := m["mode"]; v == nil || v.(string) == "" {
		// mode has an apply-time default of READ_WRITE
		dc.mode = "READ_WRITE"
	} else {
		dc.mode = v.(string)
	}

	if v := m["disk_type"]; v != nil {
		dc.diskType = v.(string)
	}

	if v := m["disk_size_gb"]; v != nil {
		// Terraform and GCP return ints as different types (int vs int64), so just
		// use strings to compare for simplicity.
		dc.diskSizeGb = fmt.Sprintf("%v", v)
	}

	if v := m["auto_delete"]; v != nil {
		dc.autoDelete = v.(bool)
	}

	if v := m["source_image"]; v != nil {
		dc.sourceImage = v.(string)
	}
	return dc
}

func flattenDisk(disk *computeBeta.AttachedDisk, defaultProject string) (map[string]interface{}, error) {
	diskMap := make(map[string]interface{})
	if disk.InitializeParams != nil {
		if disk.InitializeParams.SourceImage != "" {
			path, err := resolveImageRefToRelativeURI(defaultProject, disk.InitializeParams.SourceImage)
			if err != nil {
				return nil, errwrap.Wrapf("Error expanding source image input to relative URI: {{err}}", err)
			}
			diskMap["source_image"] = path
		} else {
			diskMap["source_image"] = ""
		}
		diskMap["disk_type"] = disk.InitializeParams.DiskType
		diskMap["disk_name"] = disk.InitializeParams.DiskName
		diskMap["disk_size_gb"] = disk.InitializeParams.DiskSizeGb
		diskMap["labels"] = disk.InitializeParams.Labels
	}

	if disk.DiskEncryptionKey != nil {
		encryption := make([]map[string]interface{}, 1)
		encryption[0] = make(map[string]interface{})
		encryption[0]["kms_key_self_link"] = disk.DiskEncryptionKey.KmsKeyName
		diskMap["disk_encryption_key"] = encryption
	}

	diskMap["auto_delete"] = disk.AutoDelete
	diskMap["boot"] = disk.Boot
	diskMap["device_name"] = disk.DeviceName
	diskMap["interface"] = disk.Interface
	diskMap["source"] = ConvertSelfLinkToV1(disk.Source)
	diskMap["mode"] = disk.Mode
	diskMap["type"] = disk.Type

	return diskMap, nil
}

func reorderDisks(configDisks []interface{}, apiDisks []map[string]interface{}) []map[string]interface{} {
	if len(apiDisks) != len(configDisks) {
		// There are different numbers of disks in state and returned from the API, so it's not
		// worth trying to reorder them since it'll be a diff anyway.
		return apiDisks
	}

	result := make([]map[string]interface{}, len(apiDisks))

	/*
		Disks aren't necessarily returned from the API in the same order they were sent, so gather
		information about the ones in state that we can use to map it back. We can't do this by
		just looping over all of the disks, because you could end up matching things in the wrong
		order. For example, if the config disks contain the following disks:
		disk 1: auto delete = false, size = 10
		disk 2: auto delete = false, size = 10, device name = "disk 2"
		disk 3: type = scratch
		And the disks returned from the API are:
		disk a: auto delete = false, size = 10, device name = "disk 2"
		disk b: auto delete = false, size = 10, device name = "disk 1"
		disk c: type = scratch
		Then disk a will match disk 1, disk b won't match any disk, and c will match 3, making the
		final order a, c, b, which is wrong. To get disk a to match disk 2, we have to go in order
		of fields most specifically able to identify a disk to least.
	*/
	disksByDeviceName := map[string]int{}
	scratchDisksByInterface := map[string][]int{}
	attachedDisksBySource := map[string]int{}
	attachedDisksByDiskName := map[string]int{}
	attachedDisksByCharacteristics := []int{}

	for i, d := range configDisks {
		if i == 0 {
			// boot disk
			continue
		}
		disk := d.(map[string]interface{})
		if v := disk["device_name"]; v.(string) != "" {
			disksByDeviceName[v.(string)] = i
		} else if v := disk["type"]; v.(string) == "SCRATCH" {
			iface := disk["interface"].(string)
			if iface == "" {
				// apply-time default
				iface = "SCSI"
			}
			scratchDisksByInterface[iface] = append(scratchDisksByInterface[iface], i)
		} else if v := disk["source"]; v.(string) != "" {
			attachedDisksBySource[v.(string)] = i
		} else if v := disk["disk_name"]; v.(string) != "" {
			attachedDisksByDiskName[v.(string)] = i
		} else {
			attachedDisksByCharacteristics = append(attachedDisksByCharacteristics, i)
		}
	}

	// Align the disks, going from the most specific criteria to the least.
	for _, apiDisk := range apiDisks {
		// 1. This resource only works if the boot disk is the first one (which should be fixed
		//	  separately), so put the boot disk first.
		if apiDisk["boot"].(bool) {
			result[0] = apiDisk

			// 2. All disks have a unique device name
		} else if i, ok := disksByDeviceName[apiDisk["device_name"].(string)]; ok {
			result[i] = apiDisk

			// 3. Scratch disks are all the same except device name and interface, so match them by
			//    interface.
		} else if apiDisk["type"].(string) == "SCRATCH" {
			iface := apiDisk["interface"].(string)
			indexes := scratchDisksByInterface[iface]
			if len(indexes) > 0 {
				result[indexes[0]] = apiDisk
				scratchDisksByInterface[iface] = indexes[1:]
			} else {
				result = append(result, apiDisk)
			}

			// 4. Each attached disk will have a different source, so match by that.
		} else if i, ok := attachedDisksBySource[apiDisk["source"].(string)]; ok {
			result[i] = apiDisk

			// 5. If a disk was created for this resource via initializeParams, it will have a
			//    unique name.
		} else if v, ok := apiDisk["disk_name"]; ok && attachedDisksByDiskName[v.(string)] != 0 {
			result[attachedDisksByDiskName[v.(string)]] = apiDisk

			// 6. If no unique keys exist on this disk, then use a combination of its remaining
			//    characteristics to see whether it matches exactly.
		} else {
			found := false
			for arrayIndex, i := range attachedDisksByCharacteristics {
				configDisk := configDisks[i].(map[string]interface{})
				stateDc := diskCharacteristicsFromMap(configDisk)
				readDc := diskCharacteristicsFromMap(apiDisk)
				if reflect.DeepEqual(stateDc, readDc) {
					result[i] = apiDisk
					attachedDisksByCharacteristics = append(attachedDisksByCharacteristics[:arrayIndex], attachedDisksByCharacteristics[arrayIndex+1:]...)
					found = true
					break
				}
			}
			if !found {
				result = append(result, apiDisk)
			}
		}
	}

	// Remove nils from map in case there were disks that could not be matched
	ds := []map[string]interface{}{}
	for _, d := range result {
		if d != nil {
			ds = append(ds, d)
		}
	}
	return ds
}

func flattenDisks(disks []*computeBeta.AttachedDisk, d *schema.ResourceData, defaultProject string) ([]map[string]interface{}, error) {
	apiDisks := make([]map[string]interface{}, len(disks))

	for i, disk := range disks {
		d, err := flattenDisk(disk, defaultProject)
		if err != nil {
			return nil, err
		}
		apiDisks[i] = d
	}

	return reorderDisks(d.Get("disk").([]interface{}), apiDisks), nil
}

func resourceComputeInstanceTemplateRead(d *schema.ResourceData, meta interface{}) error {
	config := meta.(*Config)
	project, err := getProject(d, config)
	if err != nil {
		return err
	}

	splits := strings.Split(d.Id(), "/")
	instanceTemplate, err := config.clientComputeBeta.InstanceTemplates.Get(project, splits[len(splits)-1]).Do()
	if err != nil {
		return handleNotFoundError(err, d, fmt.Sprintf("Instance Template %q", d.Get("name").(string)))
	}

	// Set the metadata fingerprint if there is one.
	if instanceTemplate.Properties.Metadata != nil {
		if err = d.Set("metadata_fingerprint", instanceTemplate.Properties.Metadata.Fingerprint); err != nil {
			return fmt.Errorf("Error setting metadata_fingerprint: %s", err)
		}

		md := instanceTemplate.Properties.Metadata

		_md := flattenMetadataBeta(md)

		if script, scriptExists := d.GetOk("metadata_startup_script"); scriptExists {
			if err = d.Set("metadata_startup_script", script); err != nil {
				return fmt.Errorf("Error setting metadata_startup_script: %s", err)
			}
			delete(_md, "startup-script")
		}
		if err = d.Set("metadata", _md); err != nil {
			return fmt.Errorf("Error setting metadata: %s", err)
		}
	}

	// Set the tags fingerprint if there is one.
	if instanceTemplate.Properties.Tags != nil {
		if err = d.Set("tags_fingerprint", instanceTemplate.Properties.Tags.Fingerprint); err != nil {
			return fmt.Errorf("Error setting tags_fingerprint: %s", err)
		}
	} else {
		d.Set("tags_fingerprint", "")
	}
	if instanceTemplate.Properties.Labels != nil {
		d.Set("labels", instanceTemplate.Properties.Labels)
	}
	if err = d.Set("self_link", instanceTemplate.SelfLink); err != nil {
		return fmt.Errorf("Error setting self_link: %s", err)
	}
	if err = d.Set("name", instanceTemplate.Name); err != nil {
		return fmt.Errorf("Error setting name: %s", err)
	}
	if instanceTemplate.Properties.Disks != nil {
		disks, err := flattenDisks(instanceTemplate.Properties.Disks, d, project)
		if err != nil {
			return fmt.Errorf("error flattening disks: %s", err)
		}
		if err = d.Set("disk", disks); err != nil {
			return fmt.Errorf("Error setting disk: %s", err)
		}
	}
	if err = d.Set("description", instanceTemplate.Description); err != nil {
		return fmt.Errorf("Error setting description: %s", err)
	}
	if err = d.Set("machine_type", instanceTemplate.Properties.MachineType); err != nil {
		return fmt.Errorf("Error setting machine_type: %s", err)
	}
	if err = d.Set("min_cpu_platform", instanceTemplate.Properties.MinCpuPlatform); err != nil {
		return fmt.Errorf("Error setting min_cpu_platform: %s", err)
	}

	if err = d.Set("can_ip_forward", instanceTemplate.Properties.CanIpForward); err != nil {
		return fmt.Errorf("Error setting can_ip_forward: %s", err)
	}

	if err = d.Set("instance_description", instanceTemplate.Properties.Description); err != nil {
		return fmt.Errorf("Error setting instance_description: %s", err)
	}
	if err = d.Set("project", project); err != nil {
		return fmt.Errorf("Error setting project: %s", err)
	}
	if instanceTemplate.Properties.NetworkInterfaces != nil {
		networkInterfaces, region, _, _, err := flattenNetworkInterfaces(d, config, instanceTemplate.Properties.NetworkInterfaces)
		if err != nil {
			return err
		}
		if err = d.Set("network_interface", networkInterfaces); err != nil {
			return fmt.Errorf("Error setting network_interface: %s", err)
		}
		// region is where to look up the subnetwork if there is one attached to the instance template
		if region != "" {
			if err = d.Set("region", region); err != nil {
				return fmt.Errorf("Error setting region: %s", err)
			}
		}
	}
	if instanceTemplate.Properties.Scheduling != nil {
		scheduling := flattenScheduling(instanceTemplate.Properties.Scheduling)
		if err = d.Set("scheduling", scheduling); err != nil {
			return fmt.Errorf("Error setting scheduling: %s", err)
		}
	}
	if instanceTemplate.Properties.Tags != nil {
		if err = d.Set("tags", instanceTemplate.Properties.Tags.Items); err != nil {
			return fmt.Errorf("Error setting tags: %s", err)
		}
	} else {
		if err = d.Set("tags", nil); err != nil {
			return fmt.Errorf("Error setting empty tags: %s", err)
		}
	}
	if instanceTemplate.Properties.ServiceAccounts != nil {
		if err = d.Set("service_account", flattenServiceAccounts(instanceTemplate.Properties.ServiceAccounts)); err != nil {
			return fmt.Errorf("Error setting service_account: %s", err)
		}
	}
	if instanceTemplate.Properties.GuestAccelerators != nil {
		if err = d.Set("guest_accelerator", flattenGuestAccelerators(instanceTemplate.Properties.GuestAccelerators)); err != nil {
			return fmt.Errorf("Error setting guest_accelerator: %s", err)
		}
	}
	if instanceTemplate.Properties.ShieldedVmConfig != nil {
		if err = d.Set("shielded_instance_config", flattenShieldedVmConfig(instanceTemplate.Properties.ShieldedVmConfig)); err != nil {
			return fmt.Errorf("Error setting shielded_instance_config: %s", err)
		}
	}
	if instanceTemplate.Properties.DisplayDevice != nil {
		if err = d.Set("enable_display", flattenEnableDisplay(instanceTemplate.Properties.DisplayDevice)); err != nil {
			return fmt.Errorf("Error setting enable_display: %s", err)
		}
	}
	return nil
}

func resourceComputeInstanceTemplateDelete(d *schema.ResourceData, meta interface{}) error {
	config := meta.(*Config)

	project, err := getProject(d, config)
	if err != nil {
		return err
	}

	splits := strings.Split(d.Id(), "/")
	op, err := config.clientCompute.InstanceTemplates.Delete(
		project, splits[len(splits)-1]).Do()
	if err != nil {
		return fmt.Errorf("Error deleting instance template: %s", err)
	}

	err = computeOperationWait(config, op, project, "Deleting Instance Template")
	if err != nil {
		return err
	}

	d.SetId("")
	return nil
}

// This wraps the general compute instance helper expandScheduling.
// Default value of OnHostMaintenance depends on the value of Preemptible,
// so we can't set a default in schema
func expandResourceComputeInstanceTemplateScheduling(d *schema.ResourceData, meta interface{}) (*computeBeta.Scheduling, error) {
	v, ok := d.GetOk("scheduling")
	if !ok || v == nil {
		// We can't set defaults for lists (e.g. scheduling)
		return &computeBeta.Scheduling{
			OnHostMaintenance: "MIGRATE",
		}, nil
	}

	expanded, err := expandScheduling(v)
	if err != nil {
		return nil, err
	}

	// Make sure we have an appropriate value for OnHostMaintenance if Preemptible
	if expanded.Preemptible && expanded.OnHostMaintenance == "" {
		expanded.OnHostMaintenance = "TERMINATE"
	}
	return expanded, nil
}

func resourceComputeInstanceTemplateImportState(d *schema.ResourceData, meta interface{}) ([]*schema.ResourceData, error) {
	config := meta.(*Config)
	if err := parseImportId([]string{"projects/(?P<project>[^/]+)/global/instanceTemplates/(?P<name>[^/]+)", "(?P<project>[^/]+)/(?P<name>[^/]+)", "(?P<name>[^/]+)"}, d, config); err != nil {
		return nil, err
	}

	// Replace import id for the resource id
	id, err := replaceVars(d, config, "projects/{{project}}/global/instanceTemplates/{{name}}")
	if err != nil {
		return nil, fmt.Errorf("Error constructing id: %s", err)
	}
	d.SetId(id)

	return []*schema.ResourceData{d}, nil
}
