[core] add support for DB indexes (#62)

* fix typo in log message

* update namespace to use prefix __index_ to avoid possible user conflicts

1 files changed, 85 insertions, 0 deletions

diff --git a/system/db/index.go b/system/db/index.go
new file mode 100644
index 0000000..6a2727a
--- /dev/null
+++ b/system/db/index.go
@@ -0,0 +1,85 @@
+package db
+
+import (
+	"bytes"
+	"encoding/json"
+
+	"github.com/boltdb/bolt"
+)
+
+// Index gets the value from the namespace at the key provided
+func Index(namespace, key string) ([]byte, error) {
+	val := &bytes.Buffer{}
+	err := store.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket([]byte(index(namespace)))
+		if b == nil {
+			return nil
+		}
+
+		v := b.Get([]byte(key))
+
+		_, err := val.Write(v)
+		if err != nil {
+			return err
+		}
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return val.Bytes(), nil
+}
+
+// SetIndex sets a key/value pair within the namespace provided and will return
+// an error if it fails
+func SetIndex(namespace, key string, value interface{}) error {
+	return store.Update(func(tx *bolt.Tx) error {
+		b, err := tx.CreateBucketIfNotExists([]byte(index(namespace)))
+		if err != nil {
+			return err
+		}
+
+		val, err := json.Marshal(value)
+		if err != nil {
+			return err
+		}
+
+		return b.Put([]byte(key), val)
+	})
+}
+
+// DeleteIndex removes the key and value from the namespace provided and will
+// return an error if it fails. It will return nil if there was no key/value in
+// the index to delete.
+func DeleteIndex(namespace, key string) error {
+	return store.Update(func(tx *bolt.Tx) error {
+		b := tx.Bucket([]byte(index(namespace)))
+		if b == nil {
+			return nil
+		}
+
+		return b.Delete([]byte(key))
+	})
+}
+
+// DropIndex removes the index and all key/value pairs in the namespace index
+func DropIndex(namespace string) error {
+	return store.Update(func(tx *bolt.Tx) error {
+		err := tx.DeleteBucket([]byte(index(namespace)))
+		if err == bolt.ErrBucketNotFound {
+			return nil
+		}
+
+		if err != nil {
+			return err
+		}
+
+		return nil
+	})
+}
+
+func index(namespace string) string {
+	return "__index_" + namespace
+}