package etcdserver

import (
	"github.com/coreos/etcd/raft/raftpb"
	"github.com/coreos/etcd/snap"
	"github.com/coreos/etcd/wal"
)

type Storage interface {
	// Save function saves ents and state to the underlying stable storage.
	// Save MUST block until st and ents are on stable storage.
	Save(st raftpb.HardState, ents []raftpb.Entry) error
	// SaveSnap function saves snapshot to the underlying stable storage.
	SaveSnap(snap raftpb.Snapshot) error

	// TODO: WAL should be able to control cut itself. After implement self-controlled cut,
	// remove it in this interface.
	// Cut cuts out a new wal file for saving new state and entries.
	Cut() error
	// Close closes the Storage and performs finalization.
	Close() error
}

type storage struct {
	*wal.WAL
	*snap.Snapshotter
}

func NewStorage(w *wal.WAL, s *snap.Snapshotter) Storage {
	return &storage{w, s}
}

// SaveSnap saves the snapshot to disk and release the locked
// wal files since they will not be used.
func (st *storage) SaveSnap(snap raftpb.Snapshot) error {
	err := st.Snapshotter.SaveSnap(snap)
	if err != nil {
		return err
	}
	err = st.WAL.ReleaseLockTo(snap.Metadata.Index)
	if err != nil {
		return err
	}
	return nil
}