Refactor common boltdb fields to subpackage

Moves label and timestamp bolt functions to subpackage
for use outside the metadata package without importing
metadata package.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

metadata/boltutil/helpers.go

@@ -0,0 +1,111 @@
+package boltutil
+
+import (
+	"time"
+
+	"github.com/boltdb/bolt"
+	"github.com/pkg/errors"
+)
+
+var (
+	bucketKeyLabels    = []byte("labels")
+	bucketKeyCreatedAt = []byte("createdat")
+	bucketKeyUpdatedAt = []byte("updatedat")
+)
+
+// ReadLabels reads the labels key from the bucket
+// Uses the key "labels"
+func ReadLabels(bkt *bolt.Bucket) (map[string]string, error) {
+	lbkt := bkt.Bucket(bucketKeyLabels)
+	if lbkt == nil {
+		return nil, nil
+	}
+	labels := map[string]string{}
+	if err := lbkt.ForEach(func(k, v []byte) error {
+		labels[string(k)] = string(v)
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+	return labels, nil
+}
+
+// WriteLabels will write a new labels bucket to the provided bucket at key
+// bucketKeyLabels, replacing the contents of the bucket with the provided map.
+//
+// The provide map labels will be modified to have the final contents of the
+// bucket. Typically, this removes zero-value entries.
+// Uses the key "labels"
+func WriteLabels(bkt *bolt.Bucket, labels map[string]string) error {
+	// Remove existing labels to keep from merging
+	if lbkt := bkt.Bucket(bucketKeyLabels); lbkt != nil {
+		if err := bkt.DeleteBucket(bucketKeyLabels); err != nil {
+			return err
+		}
+	}
+
+	if len(labels) == 0 {
+		return nil
+	}
+
+	lbkt, err := bkt.CreateBucket(bucketKeyLabels)
+	if err != nil {
+		return err
+	}
+
+	for k, v := range labels {
+		if v == "" {
+			delete(labels, k) // remove since we don't actually set it
+			continue
+		}
+
+		if err := lbkt.Put([]byte(k), []byte(v)); err != nil {
+			return errors.Wrapf(err, "failed to set label %q=%q", k, v)
+		}
+	}
+
+	return nil
+}
+
+// ReadTimestamps reads created and updated timestamps from a bucket.
+// Uses keys "createdat" and "updatedat"
+func ReadTimestamps(bkt *bolt.Bucket, created, updated *time.Time) error {
+	for _, f := range []struct {
+		b []byte
+		t *time.Time
+	}{
+		{bucketKeyCreatedAt, created},
+		{bucketKeyUpdatedAt, updated},
+	} {
+		v := bkt.Get(f.b)
+		if v != nil {
+			if err := f.t.UnmarshalBinary(v); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// WriteTimestamps writes created and updated timestamps to a bucket.
+// Uses keys "createdat" and "updatedat"
+func WriteTimestamps(bkt *bolt.Bucket, created, updated time.Time) error {
+	createdAt, err := created.MarshalBinary()
+	if err != nil {
+		return err
+	}
+	updatedAt, err := updated.MarshalBinary()
+	if err != nil {
+		return err
+	}
+	for _, v := range [][2][]byte{
+		{bucketKeyCreatedAt, createdAt},
+		{bucketKeyUpdatedAt, updatedAt},
+	} {
+		if err := bkt.Put(v[0], v[1]); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}