Add initial triplestore rebuild functionality

internal/wisski/ingredient/trb/trb.go

@@ -0,0 +1,91 @@
+package trb
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient"
+	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient/barrel"
+	"github.com/FAU-CDI/wisski-distillery/pkg/logging"
+)
+
+type TRB struct {
+	ingredient.Base
+
+	dependencies struct {
+		Barrel *barrel.Barrel
+	}
+}
+
+func (trb *TRB) DoSomething(ctx context.Context, out io.Writer, allowEmptyRepository bool) (err error) {
+
+	// stop instance, restart when done
+	logging.LogMessage(out, "Shutting down instance")
+	if err := trb.dependencies.Barrel.Stack().Down(ctx, out); err != nil {
+		return err
+	}
+
+	defer func() {
+		logging.LogMessage(out, "Restarting instance")
+		e := trb.dependencies.Barrel.Stack().Up(ctx, out)
+		if err == nil {
+			err = e
+		}
+	}()
+
+	// make the backup
+	logging.LogMessage(out, "Dumping triplestore")
+	path, err := trb.makeBackup(ctx, allowEmptyRepository)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Wrote %q\n", path)
+
+	logging.LogMessage(out, "Purging triplestore")
+	if err := trb.Malt.TS.Purge(ctx, trb.Instance, trb.Domain()); err != nil {
+		return err
+	}
+
+	logging.LogMessage(out, "Provising triplestore")
+	if err := trb.Malt.TS.Provision(ctx, trb.Instance, trb.Domain()); err != nil {
+		return err
+	}
+
+	logging.LogMessage(out, "Loading dump file")
+	content, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer content.Close()
+
+	logging.LogMessage(out, "Restoring triplestore")
+	if err := trb.Malt.TS.RestoreDB(ctx, trb.GraphDBRepository, content); err != nil {
+		return err
+	}
+
+	return
+}
+
+var errBackupEmpty = errors.New("no data contained in backup file (is the repository empty?)")
+
+func (trb *TRB) makeBackup(ctx context.Context, allowEmptyRepository bool) (path string, err error) {
+	f, err := os.CreateTemp("", "")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	count, err := trb.Malt.TS.SnapshotDB(ctx, f, trb.GraphDBRepository)
+	if err != nil {
+		return "", err
+	}
+
+	if count == 0 && !allowEmptyRepository {
+		return "", errBackupEmpty
+	}
+
+	return f.Name(), nil
+}