package wal

import (
	"github.com/milvus-io/milvus/pkg/streaming/util/message"
	"github.com/milvus-io/milvus/pkg/streaming/util/options"
	"github.com/milvus-io/milvus/pkg/streaming/util/types"
)

type MessageFilter = func(message.ImmutableMessage) bool

// ReadOption is the option for reading records from the wal.
type ReadOption struct {
	DeliverPolicy options.DeliverPolicy
	MessageFilter MessageFilter
}

// Scanner is the interface for reading records from the wal.
type Scanner interface {
	// Chan returns the channel of message.
	Chan() <-chan message.ImmutableMessage

	// Channel returns the channel assignment info of the wal.
	Channel() types.PChannelInfo

	// Error returns the error of scanner failed.
	// Will block until scanner is closed or Chan is dry out.
	Error() error

	// Done returns a channel which will be closed when scanner is finished or closed.
	Done() <-chan struct{}

	// Close the scanner, release the underlying resources.
	// Return the error same with `Error`
	Close() error
}