feat(catalog): implement entities get-by-uid command

catalog/client_entities_getbyid.go

@@ -0,0 +1,45 @@
+package catalog
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+)
+
+// GetEntityByUIDRequest is the request to the [Client.GetEntityByUID] method.
+type GetEntityByUIDRequest struct {
+	// UID of the entity to get.
+	UID string
+}
+
+// GetEntityByUID gets an entity by its kind, namespace and name.
+//
+// See: https://backstage.io/docs/features/software-catalog/software-catalog-api/#get-entitiesby-uiduid
+func (c *Client) GetEntityByUID(ctx context.Context, request *GetEntityByUIDRequest) (*Entity, error) {
+	const pathTemplate = "/api/catalog/entities/by-uid/%s"
+	path := fmt.Sprintf(
+		pathTemplate,
+		url.PathEscape(request.UID),
+	)
+	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

@@ -107,6 +107,7 @@ func newEntitiesCommand() *cobra.Command {
 	cmd.Use = "entities"
 	cmd.Short = "Read entities from the Backstage catalog"
 	cmd.AddCommand(newEntitiesListCommand())
+	cmd.AddCommand(newEntitiesGetByUIDCommand())
 	cmd.AddCommand(newEntitiesGetByNameCommand())
 	return cmd
 }
@@ -174,6 +175,29 @@ func newEntitiesGetByNameCommand() *cobra.Command {
 	return cmd
 }
 
+func newEntitiesGetByUIDCommand() *cobra.Command {
+	cmd := newCommand()
+	cmd.Use = "get-by-uid"
+	cmd.Short = "Get an entity by its UID"
+	uid := cmd.Flags().String("uid", "", "UID of the entity to get")
+	_ = cmd.MarkFlagRequired("uid")
+	cmd.RunE = func(cmd *cobra.Command, args []string) error {
+		client, err := newCatalogClient()
+		if err != nil {
+			return err
+		}
+		entity, err := client.GetEntityByUID(cmd.Context(), &catalog.GetEntityByUIDRequest{
+			UID: *uid,
+		})
+		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)