projection

type GlobalStoreConsumer struct {
	Projector    Projector
	DataStore    persistence.DataStore
	MessageStore messagestore.GloballyOrderedStore
	Offsets      OffsetStore
	Logger       twelf.Logger
	// contains filtered or unexported fields
}

type MessageHandler struct {
	Projector Projector
}

type OffsetStore interface {
	// LoadOffset returns the offset at which a consumer should resume
	// reading from the stream.
	//
	// pk is the projector's persistence key.
	LoadOffset(
		ctx context.Context,
		ds persistence.DataStore,
		pk string,
	) (uint64, error)

	// IncrementOffset increments the offset at which a consumer should resume
	// reading from the stream by one.
	//
	// pk is the projector's persitence key. c is the offset that is currently
	// stored, as returned by LoadOffset(). If c is not the offset that is
	// currently stored, the increment fails and a non-nil error is returned.
	IncrementOffset(
		ctx context.Context,
		tx persistence.Tx,
		pk string,
		c uint64,
	) error
}

type Projector interface {
	// PersistenceKey returns a unique name for the projector.
	//
	// The persistence key is used to relate persisted data with the projector
	// implementation that owns it. Persistence keys should not be changed once
	// a projection has been started.
	PersistenceKey() string

	// MessageTypes returns the set of messages that the projector intends
	// to handle.
	//
	// The return value should be constant as it may be cached.
	MessageTypes() ax.MessageTypeSet

	// ApplyMessage invokes application-defined logic that updates the
	// application state to reflect the occurrence of a message.
	//
	// It may panic if env.Message is not one of the types described by
	// MessageTypes().
	ApplyMessage(ctx context.Context, mctx ax.MessageContext) error
}