package googlecompute

import (
	"fmt"
	"net/http"
	"time"

	"code.google.com/p/goauth2/oauth"
	"code.google.com/p/goauth2/oauth/jwt"
	"code.google.com/p/google-api-go-client/compute/v1beta16"
	"github.com/mitchellh/packer/packer"
)

// driverGCE is a Driver implementation that actually talks to GCE.
// Create an instance using NewDriverGCE.
type driverGCE struct {
	projectId string
	service   *compute.Service
	ui        packer.Ui
}

const DriverScopes string = "https://www.googleapis.com/auth/compute " +
	"https://www.googleapis.com/auth/devstorage.full_control"

func NewDriverGCE(ui packer.Ui, projectId string, c *clientSecrets, key []byte) (Driver, error) {
	jwtTok := jwt.NewToken(c.Web.ClientEmail, DriverScopes, key)
	jwtTok.ClaimSet.Aud = c.Web.TokenURI
	token, err := jwtTok.Assert(new(http.Client))
	if err != nil {
		return nil, err
	}

	transport := &oauth.Transport{
		Config: &oauth.Config{
			ClientId: c.Web.ClientId,
			Scope:    DriverScopes,
			TokenURL: c.Web.TokenURI,
			AuthURL:  c.Web.AuthURI,
		},
		Token: token,
	}

	service, err := compute.New(transport.Client())
	if err != nil {
		return nil, err
	}

	return &driverGCE{
		projectId: projectId,
		service:   service,
		ui:        ui,
	}, nil
}

func (d *driverGCE) RunInstance(c *InstanceConfig) (<-chan error, error) {
	// Get the zone
	d.ui.Message(fmt.Sprintf("Loading zone: %s", c.Zone))
	zone, err := d.service.Zones.Get(d.projectId, c.Zone).Do()
	if err != nil {
		return nil, err
	}

	// Get the image
	d.ui.Message(fmt.Sprintf("Loading image: %s", c.Image))
	image, err := d.getImage(c.Image)
	if err != nil {
		return nil, err
	}

	// Get the machine type
	d.ui.Message(fmt.Sprintf("Loading machine type: %s", c.MachineType))
	machineType, err := d.service.MachineTypes.Get(
		d.projectId, zone.Name, c.MachineType).Do()
	if err != nil {
		return nil, err
	}
	// TODO(mitchellh): deprecation warnings

	// Get the network
	d.ui.Message(fmt.Sprintf("Loading network: %s", c.Network))
	network, err := d.service.Networks.Get(d.projectId, c.Network).Do()
	if err != nil {
		return nil, err
	}

	// Build up the metadata
	metadata := make([]*compute.MetadataItems, len(c.Metadata))
	for k, v := range c.Metadata {
		metadata = append(metadata, &compute.MetadataItems{
			Key:   k,
			Value: v,
		})
	}

	// Create the instance information
	instance := compute.Instance{
		Description: c.Description,
		Image:       image.SelfLink,
		MachineType: machineType.SelfLink,
		Metadata: &compute.Metadata{
			Items: metadata,
		},
		Name: c.Name,
		NetworkInterfaces: []*compute.NetworkInterface{
			&compute.NetworkInterface{
				AccessConfigs: []*compute.AccessConfig{
					&compute.AccessConfig{
						Name: "AccessConfig created by Packer",
						Type: "ONE_TO_ONE_NAT",
					},
				},
				Network: network.SelfLink,
			},
		},
		ServiceAccounts: []*compute.ServiceAccount{
			&compute.ServiceAccount{
				Email: "default",
				Scopes: []string{
					"https://www.googleapis.com/auth/userinfo.email",
					"https://www.googleapis.com/auth/compute",
					"https://www.googleapis.com/auth/devstorage.full_control",
				},
			},
		},
		Tags: &compute.Tags{
			Items: c.Tags,
		},
	}

	d.ui.Message("Requesting instance creation...")
	op, err := d.service.Instances.Insert(d.projectId, zone.Name, &instance).Do()
	if err != nil {
		return nil, err
	}

	errCh := make(chan error, 1)
	go waitForState(errCh, "DONE", d.refreshZoneOp(op))
	return errCh, nil
}

func (d *driverGCE) getImage(name string) (image *compute.Image, err error) {
	projects := []string{d.projectId, "debian-cloud", "centos-cloud"}
	for _, project := range projects {
		image, err = d.service.Images.Get(project, name).Do()
		if err == nil && image != nil && image.SelfLink != "" {
			return
		}
		image = nil
	}

	if err == nil {
		err = fmt.Errorf("Image could not be found: %s", name)
	}

	return
}

func (d *driverGCE) refreshZoneOp(op *compute.Operation) stateRefreshFunc {
	return func() (string, error) {
		newOp, err := d.service.ZoneOperations.Get(d.projectId, op.Zone, op.Name).Do()
		if err != nil {
			return "", err
		}

		// If the op is done, check for errors
		err = nil
		if newOp.Status == "DONE" {
			if newOp.Error != nil {
				for _, e := range newOp.Error.Errors {
					err = packer.MultiErrorAppend(err, fmt.Errorf(e.Message))
				}
			}
		}

		return newOp.Status, err
	}
}

// stateRefreshFunc is used to refresh the state of a thing and is
// used in conjunction with waitForState.
type stateRefreshFunc func() (string, error)

// waitForState will spin in a loop forever waiting for state to
// reach a certain target.
func waitForState(errCh chan<- error, target string, refresh stateRefreshFunc) {
	for {
		state, err := refresh()
		if err != nil {
			errCh <- err
			return
		}
		if state == target {
			errCh <- nil
			return
		}

		time.Sleep(2 * time.Second)
	}
}