'wdcli backup': Rework backup process

This commit reworks the backup process to dynamically find the list of
components.

internal/component/triplestore/backup.go

@@ -0,0 +1,58 @@
+package triplestore
+
+import (
+	"encoding/json"
+	"io/fs"
+	"os"
+	"path/filepath"
+
+	"github.com/tkw1536/goprogram/stream"
+)
+
+func (ts *Triplestore) BackupName() string { return "triplestore" }
+
+// Backup makes a backup of all Triplestore repositories databases into the path dest.
+func (ts *Triplestore) Backup(io stream.IOStream, dest string) error {
+
+	// list all the repositories
+	repos, err := ts.listRepositories()
+	if err != nil {
+		return err
+	}
+
+	// create the base directory, todo: outsource this
+	if err := os.Mkdir(dest, fs.ModeDir); err != nil {
+		return err
+	}
+
+	// iterate over all the repositories
+	for _, repo := range repos {
+		if rErr := (func(repo Repository) error {
+			name := filepath.Join(dest, repo.ID+".nq")
+
+			// todo: outsource this
+			dest, err := os.Create(name)
+			if err != nil {
+				return err
+			}
+			defer dest.Close()
+
+			_, err = ts.Snapshot(dest, repo.ID)
+			return err
+		}(repo)); err == nil && rErr != nil {
+			err = rErr
+		}
+	}
+	return err
+}
+
+func (ts Triplestore) listRepositories() (repos []Repository, err error) {
+	res, err := ts.OpenRaw("GET", "/rest/repositories", nil, "", "application/json")
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+
+	err = json.NewDecoder(res.Body).Decode(&repos)
+	return
+}