// Returns ErrInvalidType if value is not of type []byte.
//
// Note: using sync = false.
// see http://godoc.org/github.com/syndtr/goleveldb/leveldb/opt#WriteOptions
func (d *datastore) Put(key ds.Key, value interface{}) (err error) {
	val, ok := value.([]byte)
	if !ok {
		return ds.ErrInvalidType
	}
	return d.DB.Put(key.Bytes(), val, nil)
}

func (d *datastore) Get(key ds.Key) (value interface{}, err error) {
	val, err := d.DB.Get(key.Bytes(), nil)
	if err != nil {
		if err == leveldb.ErrNotFound {
			return nil, ds.ErrNotFound
		}
		return nil, err
	}
	return val, nil
}

func (d *Datastore) lookup(key ds.Key) (ds.Datastore, ds.Key, ds.Key) {
	d.lk.Lock()
	defer d.lk.Unlock()
	for _, m := range d.mounts {
		if m.Prefix.Equal(key) || m.Prefix.IsAncestorOf(key) {
			s := strings.TrimPrefix(key.String(), m.Prefix.String())
			k := ds.NewKey(s)
			return m.Datastore, m.Prefix, k
		}
	}
	return nil, ds.NewKey("/"), key
}

func (d *datastore) Delete(key ds.Key) (err error) {
	// leveldb Delete will not return an error if the key doesn't
	// exist (see https://github.com/syndtr/goleveldb/issues/109),
	// so check that the key exists first and if not return an
	// error
	exists, err := d.DB.Has(key.Bytes(), nil)
	if !exists {
		return ds.ErrNotFound
	} else if err != nil {
		return err
	}
	return d.DB.Delete(key.Bytes(), nil)
}

func (ds *Datastore) Put(key datastore.Key, value interface{}) error {
	ds.mu.Lock()
	defer ds.mu.Unlock()

	data, ok := value.([]byte)
	if !ok {
		return ErrInvalidType
	}

	ds.client.Append("SET", key.String(), data)
	if ds.ttl != 0 {
		ds.client.Append("EXPIRE", key.String(), ds.ttl.Seconds())
	}
	if err := ds.client.GetReply().Err; err != nil {
		return fmt.Errorf("failed to put value: %s", err)
	}
	if ds.ttl != 0 {
		if err := ds.client.GetReply().Err; err != nil {
			return fmt.Errorf("failed to set expiration: %s", err)
		}
	}
	return nil
}

// PrefixTransform constructs a KeyTransform with a pair of functions that
// add or remove the given prefix key.
//
// Warning: will panic if prefix not found when it should be there. This is
// to avoid insidious data inconsistency errors.
func PrefixTransform(prefix ds.Key) ktds.KeyTransform {
	return &ktds.Pair{

		// Convert adds the prefix
		Convert: func(k ds.Key) ds.Key {
			return prefix.Child(k)
		},

		// Invert removes the prefix. panics if prefix not found.
		Invert: func(k ds.Key) ds.Key {
			if !prefix.IsAncestorOf(k) {
				fmt.Errorf("Expected prefix (%s) in key (%s)", prefix, k)
				panic("expected prefix not found")
			}

			s := strings.TrimPrefix(k.String(), prefix.String())
			return ds.NewKey(s)
		},
	}
}

func (d *datastore) Has(key ds.Key) (exists bool, err error) {
	return d.DB.Has(key.Bytes(), nil)
}

// KeyFilename returns the filename associated with `key`
func (d *Datastore) KeyFilename(key ds.Key) string {
	return filepath.Join(d.path, key.String(), ObjectKeySuffix)
}

func (ds *Datastore) Delete(key datastore.Key) (err error) {
	ds.mu.Lock()
	defer ds.mu.Unlock()
	return ds.client.Cmd("DEL", key.String()).Err
}

func (ds *Datastore) Has(key datastore.Key) (exists bool, err error) {
	ds.mu.Lock()
	defer ds.mu.Unlock()
	return ds.client.Cmd("EXISTS", key.String()).Bool()
}

func (ds *Datastore) Get(key datastore.Key) (value interface{}, err error) {
	ds.mu.Lock()
	defer ds.mu.Unlock()
	return ds.client.Cmd("GET", key.String()).Bytes()
}