feat(util/ds2/delayed) add delayed datastore

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

util/datastore2/delayed.go

+package datastore2
+
+import (
+	datastore "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	delay "github.com/jbenet/go-ipfs/util/delay"
+)
+
+func WithDelay(ds datastore.Datastore, delay delay.D) datastore.Datastore {
+	return &delayed{ds: ds, delay: delay}
+}
+
+type delayed struct {
+	ds    datastore.Datastore
+	delay delay.D
+}
+
+func (dds *delayed) Put(key datastore.Key, value interface{}) (err error) {
+	dds.delay.Wait()
+	return dds.ds.Put(key, value)
+}
+
+func (dds *delayed) Get(key datastore.Key) (value interface{}, err error) {
+	dds.delay.Wait()
+	return dds.ds.Get(key)
+}
+
+func (dds *delayed) Has(key datastore.Key) (exists bool, err error) {
+	dds.delay.Wait()
+	return dds.ds.Has(key)
+}
+
+func (dds *delayed) Delete(key datastore.Key) (err error) {
+	dds.delay.Wait()
+	return dds.ds.Delete(key)
+}
+
+func (dds *delayed) KeyList() ([]datastore.Key, error) {
+	dds.delay.Wait()
+	return dds.ds.KeyList()
+}
+
+var _ datastore.Datastore = &delayed{}