// LogStreamAppenderOption configures a LogStreamAppender.
type LogStreamAppenderOption interface {
}

// WithPipelineSize sets request pipeline size. The default pipeline size is
// two. Any value below one will be set to one, and any above eight will be
// limited to eight.
func WithPipelineSize(pipelineSize int) LogStreamAppenderOption {
}

// WithDefaultBatchCallback sets the default callback function. The default callback
// function can be overridden by the argument callback of the AppendBatch
// method.
func WithDefaultCallback(callback AppendBatchCallback) LogStreamAppenderOption {
}

type Varlog interface {
	// NewLogStreamAppender returns a new LogStreamAppender. The argument ctx
	// is used for all lifetimes of the result LogStreamAppender.
	NewLogStreamAppender(ctx context.Context, tpid types.TopicID, lsid types.LogStreamID, opts ...LogStreamAppenderOption) (LogStreamAppender, error)
}

// BatchCallback is a callback function to notify the result of
// AppendBatch.
type BatchCallback func([]varlogpb.LogEntryMeta, error)

// LogStreamAppender is a client only to be able to append to a particular log
// stream.
type LogStreamAppender interface {
	// AppendBatch appends dataBatch to the given log stream asynchronously.
	// Users can call this method without being blocked until the pipeline of
	// the LogStreamAppender is full. If the pipeline of the LogStreamAppender
	// is already full, it may become blocked. However, the process will
	// continue once a response is received from the storage node.
	// On completion of AppendBatch, the argument callback provided by users
	// will be invoked. All callback functions registered to the same
	// LogStreamAppender will be called by the same goroutine sequentially.
	// Therefore, the callback should be lightweight. If heavy work is
	// necessary for the callback, it would be better to use separate worker
	// goroutines.
	// The only error from the AppendBatch is ErrClosed, which is returned when
	// the LogStreamAppender is already closed. It returns nil even if the
	// underlying stream is disconnected and notifies errors via callback.
	AppendBatch(dataBatch [][]byte, callback BatchCallback) error

	// Close closes the LogStreamAppender client. Once the client is closed,
	// calling AppendBatch will fail immediately. If AppendBatch still waits
	// for room of pipeline, Close will be blocked. It also waits for all
	// pending callbacks to be called.
	Close()
}