// HardState contains term, vote and commit.
// Snapshot contains data and snapshot metadata.
func (n *node) saveToStorage(hardState raftpb.HardState,
	entries []raftpb.Entry, snapshot raftpb.Snapshot) {

	if !raft.IsEmptySnap(snapshot) {
		fmt.Printf("saveToStorage snapshot: %v\n", snapshot.String())
		le, err := n.store.LastIndex()
		if err != nil {
			log.Fatalf("While retrieving last index: %v\n", err)
		}
		te, err := n.store.Term(le)
		if err != nil {
			log.Fatalf("While retrieving term: %v\n", err)
		}
		fmt.Printf("%d node Term for le: %v is %v\n", n.id, le, te)
		if snapshot.Metadata.Index <= le {
			fmt.Printf("%d node ignoring snapshot. Last index: %v\n", n.id, le)
			return
		}

		if err := n.store.ApplySnapshot(snapshot); err != nil {
			log.Fatalf("Applying snapshot: %v", err)
		}
	}

	if !raft.IsEmptyHardState(hardState) {
		n.store.SetHardState(hardState)
	}
	n.store.Append(entries)
}

// Read reads the snapshot named by snapname and returns the snapshot.
func Read(snapname string) (*raftpb.Snapshot, error) {
	b, err := ioutil.ReadFile(snapname)
	if err != nil {
		log.Printf("snap: snapshotter cannot read file %v: %v", snapname, err)
		return nil, err
	}

	var serializedSnap snappb.Snapshot
	if err = serializedSnap.Unmarshal(b); err != nil {
		log.Printf("snap: corrupted snapshot file %v: %v", snapname, err)
		return nil, err
	}

	if len(serializedSnap.Data) == 0 || serializedSnap.Crc == 0 {
		log.Printf("snap: unexpected empty snapshot")
		return nil, ErrEmptySnapshot
	}

	crc := crc32.Update(0, crcTable, serializedSnap.Data)
	if crc != serializedSnap.Crc {
		log.Printf("snap: corrupted snapshot file %v: crc mismatch", snapname)
		return nil, ErrCRCMismatch
	}

	var snap raftpb.Snapshot
	if err = snap.Unmarshal(serializedSnap.Data); err != nil {
		log.Printf("snap: corrupted snapshot file %v: %v", snapname, err)
		return nil, err
	}
	return &snap, nil
}

func (s *Snapshotter) Save(snapshot *raftpb.Snapshot) error {
	fname := fmt.Sprintf("%016x-%016x%s", snapshot.Term, snapshot.Index, snapSuffix)
	b, err := snapshot.Marshal()
	if err != nil {
		panic(err)
	}

	crc := crc32.Update(0, crcTable, b)
	snap := snappb.Snapshot{Crc: crc, Data: b}
	d, err := snap.Marshal()
	if err != nil {
		return err
	}
	return ioutil.WriteFile(path.Join(s.dir, fname), d, 0666)
}

// Store stores the snapshot, hardstate and entries for a given RAFT group.
func (w *Wal) Store(gid uint32, s raftpb.Snapshot, h raftpb.HardState, es []raftpb.Entry) error {
	b := w.wals.NewWriteBatch()
	defer b.Destroy()

	if !raft.IsEmptySnap(s) {
		data, err := s.Marshal()
		if err != nil {
			return x.Wrapf(err, "wal.Store: While marshal snapshot")
		}
		b.Put(w.snapshotKey(gid), data)
	}

	if !raft.IsEmptyHardState(h) {
		data, err := h.Marshal()
		if err != nil {
			return x.Wrapf(err, "wal.Store: While marshal hardstate")
		}
		b.Put(w.hardStateKey(gid), data)
	}

	var t, i uint64
	for _, e := range es {
		t, i = e.Term, e.Index
		data, err := e.Marshal()
		if err != nil {
			return x.Wrapf(err, "wal.Store: While marshal entry")
		}
		k := w.entryKey(gid, e.Term, e.Index)
		b.Put(k, data)
	}

	// If we get no entries, then the default value of t and i would be zero. That would
	// end up deleting all the previous valid raft entry logs. This check avoids that.
	if t > 0 || i > 0 {
		// Delete all keys above this index.
		start := w.entryKey(gid, t, i+1)
		prefix := w.prefix(gid)
		itr := w.wals.NewIterator()
		defer itr.Close()

		for itr.Seek(start); itr.ValidForPrefix(prefix); itr.Next() {
			b.Delete(itr.Key().Data())
		}
	}

	err := w.wals.WriteBatch(b)
	return x.Wrapf(err, "wal.Store: While WriteBatch")
}

func loadSnap(dir, name string) (*raftpb.Snapshot, error) {
	var err error
	var b []byte

	fpath := path.Join(dir, name)
	defer func() {
		if err != nil {
			renameBroken(fpath)
		}
	}()

	b, err = ioutil.ReadFile(fpath)
	if err != nil {
		log.Printf("snap: snapshotter cannot read file %v: %v", name, err)
		return nil, err
	}

	var serializedSnap snappb.Snapshot
	if err = serializedSnap.Unmarshal(b); err != nil {
		log.Printf("snap: corrupted snapshot file %v: %v", name, err)
		return nil, err
	}

	if len(serializedSnap.Data) == 0 || serializedSnap.Crc == 0 {
		log.Printf("snap: unexpected empty snapshot")
		return nil, ErrEmptySnapshot
	}

	crc := crc32.Update(0, crcTable, serializedSnap.Data)
	if crc != serializedSnap.Crc {
		log.Printf("snap: corrupted snapshot file %v: crc mismatch", name)
		return nil, ErrCRCMismatch
	}

	var snap raftpb.Snapshot
	if err = snap.Unmarshal(serializedSnap.Data); err != nil {
		log.Printf("snap: corrupted snapshot file %v: %v", name, err)
		return nil, err
	}
	return &snap, nil
}