added utility to write artifact file

drone/artifact.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2019, the Drone Plugins project authors.
+// Please see the AUTHORS file for details. All rights reserved.
+// Use of this source code is governed by an Apache 2.0 license that can be
+// found in the LICENSE file.
+
+package drone
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"os"
+	"path/filepath"
+)
+
+// RegistryType is the type of registry
+type RegistryType string
+
+// Registries const
+const (
+	Docker RegistryType = "Docker"
+	ECR    RegistryType = "ECR"
+	GCR    RegistryType = "GCR"
+	ACR    RegistryType = "ACR"
+)
+
+const (
+	dockerArtifactV1 string = "docker/v1"
+)
+
+type (
+	// Image stores the image data
+	Image struct {
+		Image  string `json:"image"`
+		Digest string `json:"digest"`
+	}
+	// Data stores the registry data
+	Data struct {
+		RegistryType RegistryType `json:"registryType"`
+		RegistryURL  string       `json:"registryUrl"`
+		Images       []Image      `json:"images"`
+	}
+	// DockerArtifact is the current artifact
+	DockerArtifact struct {
+		Kind string `json:"kind"`
+		Data Data   `json:"data"`
+	}
+)
+
+// WritePluginArtifactFile writes the docker artifact data to the provided artifact file
+func WritePluginArtifactFile(registryType RegistryType, artifactFilePath, registryURL, imageName, digest string, tags []string) error {
+	var images []Image
+	for _, tag := range tags {
+		images = append(images, Image{
+			Image:  fmt.Sprintf("%s:%s", imageName, tag),
+			Digest: digest,
+		})
+	}
+	data := Data{
+		RegistryType: registryType,
+		RegistryURL:  registryURL,
+		Images:       images,
+	}
+
+	dockerArtifact := DockerArtifact{
+		Kind: dockerArtifactV1,
+		Data: data,
+	}
+
+	b, err := json.MarshalIndent(dockerArtifact, "", "\t")
+	if err != nil {
+		return fmt.Errorf("failed with err %s to marshal output %+v", err, dockerArtifact)
+	}
+
+	dir := filepath.Dir(artifactFilePath)
+	err = os.MkdirAll(dir, 0644)
+	if err != nil {
+		return fmt.Errorf("failed with err %s to create %s directory for artifact file", err, dir)
+	}
+
+	err = os.WriteFile(artifactFilePath, b, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to write artifact to artifact file %s", artifactFilePath)
+	}
+	return nil
+}