feat(builder/hcloud): allow selecting image based on filters

builder/hcloud/config.go

@@ -25,10 +25,11 @@ type Config struct {
 	Endpoint     string        `mapstructure:"endpoint"`
 	PollInterval time.Duration `mapstructure:"poll_interval"`
 
-	ServerName string `mapstructure:"server_name"`
-	Location   string `mapstructure:"location"`
-	ServerType string `mapstructure:"server_type"`
-	Image      string `mapstructure:"image"`
+	ServerName  string       `mapstructure:"server_name"`
+	Location    string       `mapstructure:"location"`
+	ServerType  string       `mapstructure:"server_type"`
+	Image       string       `mapstructure:"image"`
+	ImageFilter *imageFilter `mapstructure:"image_filter"`
 
 	SnapshotName   string            `mapstructure:"snapshot_name"`
 	SnapshotLabels map[string]string `mapstructure:"snapshot_labels"`
@@ -41,6 +42,11 @@ type Config struct {
 	ctx interpolate.Context
 }
 
+type imageFilter struct {
+	WithSelector []string `mapstructure:"with_selector"`
+	MostRecent   bool     `mapstructure:"most_recent"`
+}
+
 func NewConfig(raws ...interface{}) (*Config, []string, error) {
 	c := new(Config)
 
@@ -108,9 +114,18 @@ func NewConfig(raws ...interface{}) (*Config, []string, error) {
 			errs, errors.New("server type is required"))
 	}
 
-	if c.Image == "" {
+	if c.Image == "" && c.ImageFilter == nil {
 		errs = packer.MultiErrorAppend(
-			errs, errors.New("image is required"))
+			errs, errors.New("image or image_filter is required"))
+	}
+	if c.ImageFilter != nil {
+		if len(c.ImageFilter.WithSelector) == 0 {
+			errs = packer.MultiErrorAppend(
+				errs, errors.New("image_filter.with_selector is required when specifying filter"))
+		} else if c.Image != "" {
+			errs = packer.MultiErrorAppend(
+				errs, errors.New("only one of image or image_filter can be specified"))
+		}
 	}
 
 	if c.UserData != "" && c.UserDataFile != "" {

builder/hcloud/step_create_server.go

@@ -3,8 +3,9 @@ package hcloud
 import (
 	"context"
 	"fmt"
-
 	"io/ioutil"
+	"sort"
+	"strings"
 
 	"github.com/hashicorp/packer/helper/multistep"
 	"github.com/hashicorp/packer/packer"
@@ -50,10 +51,24 @@ func (s *stepCreateServer) Run(ctx context.Context, state multistep.StateBag) mu
 		sshKeys = append(sshKeys, sshKey)
 	}
 
+	var image *hcloud.Image
+	if c.Image != "" {
+		image = &hcloud.Image{Name: c.Image}
+	} else {
+		var err error
+		image, err = getImageWithSelectors(ctx, client, c)
+		if err != nil {
+			ui.Error(err.Error())
+			state.Put("error", err)
+			return multistep.ActionHalt
+		}
+		ui.Message(fmt.Sprintf("Using image %s with ID %d", image.Description, image.ID))
+	}
+
 	serverCreateResult, _, err := client.Server.Create(ctx, hcloud.ServerCreateOpts{
 		Name:       c.ServerName,
 		ServerType: &hcloud.ServerType{Name: c.ServerType},
-		Image:      &hcloud.Image{Name: c.Image},
+		Image:      image,
 		SSHKeys:    sshKeys,
 		Location:   &hcloud.Location{Name: c.Location},
 		UserData:   userData,
@@ -185,3 +200,32 @@ func waitForAction(ctx context.Context, client *hcloud.Client, action *hcloud.Ac
 	}
 	return nil
 }
+
+func getImageWithSelectors(ctx context.Context, client *hcloud.Client, c *Config) (*hcloud.Image, error) {
+	var allImages []*hcloud.Image
+
+	var selector = strings.Join(c.ImageFilter.WithSelector, ",")
+	opts := hcloud.ImageListOpts{
+		ListOpts: hcloud.ListOpts{LabelSelector: selector},
+		Status:   []hcloud.ImageStatus{hcloud.ImageStatusAvailable},
+	}
+
+	allImages, err := client.Image.AllWithOpts(ctx, opts)
+	if err != nil {
+		return nil, err
+	}
+	if len(allImages) == 0 {
+		return nil, fmt.Errorf("no image found for selector %q", selector)
+	}
+	if len(allImages) > 1 {
+		if !c.ImageFilter.MostRecent {
+			return nil, fmt.Errorf("more than one image found for selector %q", selector)
+		}
+
+		sort.Slice(allImages, func(i, j int) bool {
+			return allImages[i].Created.After(allImages[j].Created)
+		})
+	}
+
+	return allImages[0], nil
+}