feat(catalog): implement entities get-by-name endpoint

catalog/client_entities_getbyname.go

@@ -0,0 +1,51 @@
+package catalog
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+)
+
+// GetEntityByNameRequest is the request to the [Client.GetEntityByName] method.
+type GetEntityByNameRequest struct {
+	// Kind of the entity to get.
+	Kind string
+	// Namespace of the entity to get.
+	Namespace string
+	// Name of the entity to get.
+	Name string
+}
+
+// GetEntityByName gets an entity by its kind, namespace and name.
+//
+// See: https://backstage.io/docs/features/software-catalog/software-catalog-api/#get-entitiesby-namekindnamespacename
+func (c *Client) GetEntityByName(ctx context.Context, request *GetEntityByNameRequest) (*Entity, error) {
+	const pathTemplate = "/api/catalog/entities/by-name/%s/%s/%s"
+	path := fmt.Sprintf(
+		pathTemplate,
+		url.PathEscape(request.Kind),
+		url.PathEscape(request.Namespace),
+		url.PathEscape(request.Name),
+	)
+	var rawEntity json.RawMessage
+	if err := c.get(ctx, path, nil, func(response *http.Response) error {
+		data, err := io.ReadAll(response.Body)
+		if err != nil {
+			return err
+		}
+		rawEntity = data
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+	entity := Entity{
+		Raw: rawEntity,
+	}
+	if err := json.Unmarshal(rawEntity, &entity); err != nil {
+		return nil, err
+	}
+	return &entity, nil
+}

cmd/backstage/main.go

@@ -102,13 +102,23 @@ func newCatalogCommand() *cobra.Command {
 		Use:   "catalog",
 		Short: "Work with the Backstage catalog",
 	}
-	cmd.AddCommand(newListEntitiesCommand())
+	cmd.AddCommand(newEntitiesCommand())
 	return cmd
 }
 
-func newListEntitiesCommand() *cobra.Command {
+func newEntitiesCommand() *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "list-entities",
+		Use:   "entities",
+		Short: "Read entities from the Backstage catalog",
+	}
+	cmd.AddCommand(newEntitiesListCommand())
+	cmd.AddCommand(newEntitiesGetByNameCommand())
+	return cmd
+}
+
+func newEntitiesListCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "list",
 		Short: "List entities in the catalog",
 	}
 	filters := cmd.Flags().StringArray("filter", nil, "select only a subset of all entities")
@@ -142,6 +152,35 @@ func newListEntitiesCommand() *cobra.Command {
 	return cmd
 }
 
+func newEntitiesGetByNameCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "get-by-name",
+		Short: "Get an entity by its kind, namespace and name",
+	}
+	kind := cmd.Flags().String("kind", "", "kind of the entity to get")
+	_ = cmd.MarkFlagRequired("kind")
+	namespace := cmd.Flags().String("namespace", "default", "namespace of the entity to get")
+	name := cmd.Flags().String("name", "", "name of the entity to get")
+	_ = cmd.MarkFlagRequired("name")
+	cmd.RunE = func(cmd *cobra.Command, args []string) error {
+		client, err := newCatalogClient()
+		if err != nil {
+			return err
+		}
+		entity, err := client.GetEntityByName(cmd.Context(), &catalog.GetEntityByNameRequest{
+			Kind:      *kind,
+			Namespace: *namespace,
+			Name:      *name,
+		})
+		if err != nil {
+			return err
+		}
+		printRawJSON(cmd, entity.Raw)
+		return nil
+	}
+	return cmd
+}
+
 func printRawJSON(cmd *cobra.Command, raw json.RawMessage) {
 	var indented bytes.Buffer
 	indented.Grow(len(raw) * 2)