knowfoolery/backend/shared/domain/events/event.go

// Package events provides domain event interfaces and types for the KnowFoolery application.
package events

import (
	"context"
	"time"
)

// Event represents a domain event.
type Event interface {
	// EventType returns the type of the event.
	EventType() EventType
	// OccurredAt returns when the event occurred.
	OccurredAt() time.Time
	// AggregateID returns the ID of the aggregate that produced the event.
	AggregateID() string
	// AggregateType returns the type of the aggregate.
	AggregateType() string
}

// BaseEvent provides a base implementation of the Event interface.
type BaseEvent struct {
	Type      EventType `json:"type"`
	Timestamp time.Time `json:"timestamp"`
	AggrID    string    `json:"aggregate_id"`
	AggrType  string    `json:"aggregate_type"`
}

// EventType returns the type of the event.
func (e *BaseEvent) EventType() EventType {
	return e.Type
}

// OccurredAt returns when the event occurred.
func (e *BaseEvent) OccurredAt() time.Time {
	return e.Timestamp
}

// AggregateID returns the ID of the aggregate that produced the event.
func (e *BaseEvent) AggregateID() string {
	return e.AggrID
}

// AggregateType returns the type of the aggregate.
func (e *BaseEvent) AggregateType() string {
	return e.AggrType
}

// NewBaseEvent creates a new BaseEvent with the given parameters.
func NewBaseEvent(eventType EventType, aggregateID, aggregateType string) BaseEvent {
	return BaseEvent{
		Type:      eventType,
		Timestamp: time.Now(),
		AggrID:    aggregateID,
		AggrType:  aggregateType,
	}
}

// EventHandler handles domain events.
type EventHandler interface {
	// Handle processes the given event.
	Handle(ctx context.Context, event Event) error
	// Handles returns the event types this handler can process.
	Handles() []EventType
}

// EventBus publishes and subscribes to domain events.
type EventBus interface {
	// Publish publishes an event to all subscribers.
	Publish(ctx context.Context, event Event) error
	// Subscribe registers a handler for specific event types.
	Subscribe(handler EventHandler) error
}