codec

type DDLEventBatchEncoder interface {
	// EncodeCheckpointEvent appends a checkpoint event into the batch.
	// This event will be broadcast to all partitions to signal a global checkpoint.
	EncodeCheckpointEvent(ts uint64) (*common.Message, error)
	// EncodeDDLEvent appends a DDL event into the batch
	EncodeDDLEvent(e *model.DDLEvent) (*common.Message, error)
}

type EncoderGroup interface {
	// Run start the group
	Run(ctx context.Context) error
	// AddEvents add events into the group and encode them by one of the encoders in the group.
	// Note: The caller should make sure all events should belong to the same topic and partition.
	AddEvents(ctx context.Context, key model.TopicPartitionKey, events ...*dmlsink.RowChangeCallbackableEvent) error
	// Output returns a channel produce futures
	Output() <-chan *future
}

type MessageBuilder interface {
	// Build builds the batch and returns the bytes of key and value.
	// Should be called after `AppendRowChangedEvent`
	Build() []*common.Message
}

type MockRowEventEncoder struct{}

type MockRowEventEncoderBuilder struct{}

type RowEventDecoder interface {
	// AddKeyValue add the received key and values to the decoder,
	// should be called before `HasNext`
	// decoder decode the key and value into the event format.
	AddKeyValue(key, value []byte) error

	// HasNext returns
	//     1. the type of the next event
	//     2. a bool if the next event is exist
	//     3. error
	HasNext() (model.MessageType, bool, error)
	// NextResolvedEvent returns the next resolved event if exists
	NextResolvedEvent() (uint64, error)
	// NextRowChangedEvent returns the next row changed event if exists
	NextRowChangedEvent() (*model.RowChangedEvent, error)
	// NextDDLEvent returns the next DDL event if exists
	NextDDLEvent() (*model.DDLEvent, error)
}

type RowEventEncoder interface {
	DDLEventBatchEncoder
	// AppendRowChangedEvent appends a row changed event into the batch or buffer.
	AppendRowChangedEvent(context.Context, string, *model.RowChangedEvent, func()) error
	MessageBuilder
}

type RowEventEncoderBuilder interface {
	Build() RowEventEncoder
	CleanMetrics()
}

type TxnEventEncoder interface {
	// AppendTxnEvent append a txn event into the buffer.
	AppendTxnEvent(*model.SingleTableTxn, func()) error
	MessageBuilder
}

type TxnEventEncoderBuilder interface {
	Build() TxnEventEncoder
}