snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/basic/6-cqrs-ordered-events/activity.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"sync"
+	"time"
+)
+
+// ActivityEntry represents a single event in the timeline
+type ActivityEntry struct {
+	Timestamp    time.Time
+	SubscriberID string
+	ActivityType string
+	Details      string
+}
+
+// ActivityTimelineReadModel maintains a chronological log of all subscription-related events
+type ActivityTimelineReadModel struct {
+	activities []ActivityEntry
+	lock       sync.RWMutex
+}
+
+func NewActivityTimelineModel() *ActivityTimelineReadModel {
+	return &ActivityTimelineReadModel{
+		activities: make([]ActivityEntry, 0),
+	}
+}
+
+// OnSubscribed handles subscription events
+func (m *ActivityTimelineReadModel) OnSubscribed(ctx context.Context, event *SubscriberSubscribed) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	entry := ActivityEntry{
+		Timestamp:    time.Now(),
+		SubscriberID: event.SubscriberId,
+		ActivityType: "SUBSCRIBED",
+		Details:      fmt.Sprintf("Subscribed with email: %s", event.Email),
+	}
+
+	m.activities = append(m.activities, entry)
+	m.logActivity(entry)
+	return nil
+}
+
+// OnUnsubscribed handles unsubscription events
+func (m *ActivityTimelineReadModel) OnUnsubscribed(ctx context.Context, event *SubscriberUnsubscribed) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	entry := ActivityEntry{
+		Timestamp:    time.Now(),
+		SubscriberID: event.SubscriberId,
+		ActivityType: "UNSUBSCRIBED",
+		Details:      "Subscriber unsubscribed",
+	}
+
+	m.activities = append(m.activities, entry)
+	m.logActivity(entry)
+	return nil
+}
+
+// OnEmailUpdated handles email update events
+func (m *ActivityTimelineReadModel) OnEmailUpdated(ctx context.Context, event *SubscriberEmailUpdated) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	entry := ActivityEntry{
+		Timestamp:    time.Now(),
+		SubscriberID: event.SubscriberId,
+		ActivityType: "EMAIL_UPDATED",
+		Details:      fmt.Sprintf("Email updated to: %s", event.NewEmail),
+	}
+
+	m.activities = append(m.activities, entry)
+	m.logActivity(entry)
+	return nil
+}
+
+func (m *ActivityTimelineReadModel) logActivity(entry ActivityEntry) {
+	slog.Info(
+		"[ACTIVITY]",
+		"activity_type", entry.ActivityType,
+		"subscriber_id", entry.SubscriberID,
+		"details", entry.Details,
+	)
+}