eventsourcing

type Aggregate interface {
	CommandHandler

	// Type is the type of the aggregate that the event can be applied to.
	Type() AggregateType
	// ID is the id of the aggregate that the event should be applied to.
	ID() uuid.UUID
	// Version is the version of the aggregate.
	Version() uint64
	// SetDeleted sets the deleted flag of the aggregate to true
	SetDeleted(bool)
	// Deleted indicates whether the aggregate resource has been deleted
	Deleted() bool
	// UncommittedEvents returns outstanding events that need to persisted. They are cleared on reading them.
	UncommittedEvents() []Event
	// ApplyEvent applies an Event on the aggregate.
	ApplyEvent(Event) error
	// IncrementVersion increments the version of the Aggregate.
	IncrementVersion()
	// Exists returns if the version of the aggregate is >0
	Exists() bool
	// contains filtered or unexported methods
}

type AggregateRegistry interface {
	RegisterAggregate(func() Aggregate)
	CreateAggregate(AggregateType) (Aggregate, error)
}

type AggregateStore interface {
	// Get returns the most recent version of all aggregate of a given type.
	All(context.Context, AggregateType) ([]Aggregate, error)

	// Get returns the most recent version of an aggregate.
	Get(context.Context, AggregateType, uuid.UUID) (Aggregate, error)

	// Update stores all in-flight events for an aggregate.
	Update(context.Context, Aggregate) error
}

type AggregateType string

type BaseAggregate struct {
	// contains filtered or unexported fields
}

type BaseCommand struct {
	// contains filtered or unexported fields
}

type Command interface {
	// AggregateID returns the ID of the aggregate that the command should be
	// handled by.
	AggregateID() uuid.UUID

	// AggregateType returns the type of the aggregate that the command can be
	// handled by.
	AggregateType() AggregateType

	// CommandType returns the type of the command.
	CommandType() CommandType

	// SetData sets type specific additional data.
	SetData(*anypb.Any) error
}

type CommandHandler interface {
	// HandleCommand handles a command.
	HandleCommand(context.Context, Command) (*CommandReply, error)
}

type CommandHandlerMiddleware func(CommandHandler) CommandHandler

type CommandRegistry interface {
	CommandHandler
	RegisterCommand(func(uuid.UUID) Command)
	CreateCommand(id uuid.UUID, commandType CommandType, data *anypb.Any) (Command, error)
	GetRegisteredCommandTypes() []CommandType
	SetHandler(handler CommandHandler, commandType CommandType)
}

type CommandReply struct {
	Id      uuid.UUID
	Version uint64
}

type CommandType string

type Event interface {
	// EventType is the type of the event.
	EventType() EventType
	// Timestamp of when the event was created.
	Timestamp() time.Time
	// AggregateType is the type of the aggregate that the event can be applied to.
	AggregateType() AggregateType
	// AggregateID is the id of the aggregate that the event should be applied to.
	AggregateID() uuid.UUID
	// AggregateVersion is the version of the aggregate.
	AggregateVersion() uint64
	// Event type specific event data.
	Data() EventData
	// Metadata is app-specific metadata originating user etc. when this event has been stored.
	Metadata() map[string]string
	// A string representation of the event.
	String() string
}

type EventBusConnector interface {
	// Close closes the underlying connections
	Close() error
}

type EventBusConsumer interface {
	EventBusConnector
	// Matcher returns a new implementation specific matcher.
	Matcher() EventMatcher
	// AddHandler adds a handler for events matching one of the given EventMatcher.
	AddHandler(context.Context, EventHandler, ...EventMatcher) error
	// AddWorker behave similar to AddHandler but distributes events among the handlers with the same
	// work queue name according to the competing consumers pattern.
	AddWorker(context.Context, EventHandler, string, ...EventMatcher) error
}

type EventBusPublisher interface {
	EventBusConnector
	// PublishEvent publishes the event on the bus.
	PublishEvent(context.Context, Event) error
}

type EventData []byte

type EventHandler interface {
	// HandleEvent handles an event.
	HandleEvent(context.Context, Event) error
}

type EventHandlerMiddleware func(EventHandler) EventHandler

type EventMatcher interface {
	// Any matches any event.
	Any() EventMatcher
	// MatchEventType matches a specific event type.
	MatchEventType(eventType EventType) EventMatcher
	// MatchAggregate matches a specific aggregate type.
	MatchAggregateType(aggregateType AggregateType) EventMatcher
}

type EventStore interface {
	// Open connects to the bus
	Open(context.Context) error

	// Save appends all events in the event stream to the store.
	Save(context.Context, []Event) error

	// Load loads all events for the query from the store.
	Load(context.Context, *StoreQuery) (EventStreamReceiver, error)

	// LoadOr loads all events by combining the queries with the logical OR from the store.
	LoadOr(context.Context, []*StoreQuery) (EventStreamReceiver, error)

	// Close closes the underlying connections
	Close() error
}

type EventStream interface {
	EventStreamSender
	EventStreamReceiver
}

type EventStreamReceiver interface {
	Receive() (Event, error)
}

type EventStreamSender interface {
	Send(Event)
	Error(error)
	Done()
}

type EventType string

type MetadataManager interface {
	// GetContext returns a new context enriched with the metadata of this manager.
	GetContext() context.Context

	// GetMetadata returns the metadata of this manager.
	GetMetadata() map[string]string

	// SetMetadata sets the metadata of this manager.
	SetMetadata(map[string]string) MetadataManager

	// Get returns the information stored for the key.
	Get(string) (string, bool)
	GetObject(string, interface{}) error

	// Set stores information for the key.
	Set(string, string) MetadataManager
	SetObject(string, interface{}) error
}

type Projection interface {
	// ID returns the ID of the Projection.
	ID() uuid.UUID
	// Version returns the version of the aggregate this Projection is based upon.
	Version() uint64
	// IncrementVersion increments the Version of the Projection.
	IncrementVersion()
}

type Projector[T Projection] interface {
	// NewProjection creates a new Projection of the type the Projector projects.
	NewProjection(uuid.UUID) T

	// Project updates the state of the projection according to the given event.
	Project(context.Context, Event, T) (T, error)
}

type Reactor interface {
	// HandleEvent handles a given event send 0..* Events through the given channel in reaction or an error.
	// Attention: The reactor is responsible for closing the channel if no further events will be send to that channel.
	HandleEvent(ctx context.Context, event Event, events chan<- Event) error
}

type Repository[T Projection] interface {
	// ById returns a projection for an ID.
	ById(context.Context, uuid.UUID) (T, error)

	// All returns all projections in the repository.
	All(context.Context) ([]T, error)

	// Upsert saves a projection in the storage or replaces an existing one.
	Upsert(context.Context, T) error

	// RegisterObserver registers the given observer with the registry
	RegisterObserver(RepositoryObserver[T])

	// DeregisterObserver unregisters the given observer with the registry
	DeregisterObserver(RepositoryObserver[T])
}

type RepositoryObserver[T Projection] interface {
	// Notify is called by the repository when an projection has been updated
	Notify(context.Context, T)
}

type Role string

type Scope string

type StoreQuery struct {
	// Filter events by aggregate id
	AggregateId *uuid.UUID
	// Filter events for a specific aggregate type
	AggregateType *AggregateType
	// Filter events with a Version >= MinVersion
	MinVersion *uint64
	// Filter events with a Version <= MaxVersion
	MaxVersion *uint64
	// Filter events with a Timestamp >= MinTimestamp
	MinTimestamp *time.Time
	// Filter events with a Timestamp <= MaxTimestamp
	MaxTimestamp *time.Time
}