Move stateless functions to dedicated source file

snapshot2/state.go

@@ -0,0 +1,44 @@
+package snapshot2
+
+import (
+	"fmt"
+	"path/filepath"
+	"sort"
+)
+
+// ResolveSnapshots resolves a snapshot ID into its constituent DB file and WAL files. At a minimum,
+// a DB file is returned. If the snapshot is incremental, associated WAL files are also returned. The
+// order in the slice is the order in which the WAL files should be applied to the DB file.
+func ResolveSnapshots(rootDir string, snapshotID string) (dbfile string, walFiles []string, err error) {
+	snapshots, err := getSnapshots(rootDir)
+	if err != nil {
+		return "", nil, err
+	}
+
+	// Walk from newest to oldest.
+	snapshotMetas := snapMetaSlice(snapshots)
+	sort.Sort(sort.Reverse(snapshotMetas))
+
+	found := false
+	for _, snapMeta := range snapshots {
+		if snapMeta.ID != snapshotID && !found {
+			continue
+		}
+		found = true
+
+		if snapMeta.Type == SnapshotMetaTypeFull {
+			// Full DB file so, we're done.
+			return filepath.Join(rootDir, snapMeta.ID, dbfileName), walFiles, nil
+		}
+		// Must be incremental. We need to prepend the WAL file name to the list and
+		// keep walking backwards
+		walFile := filepath.Join(rootDir, snapMeta.ID, walfileName)
+		walFiles = append([]string{walFile}, walFiles...)
+		continue
+	}
+
+	if found {
+		return "", nil, fmt.Errorf("no full snapshot found in chain for snapshot ID %s", snapshotID)
+	}
+	return "", nil, ErrSnapshotNotFound
+}