Send reply mail from the post event bus.

internal/mail/subscriber.go

@@ -0,0 +1,89 @@
+package mail
+
+import (
+	"context"
+	"log"
+	"strings"
+	"time"
+
+	"plumber/internal/events"
+	"plumber/internal/store"
+)
+
+// Subscribe sends reply emails from PostCreated events. Nop or nil is a no-op.
+func Subscribe(bus *events.Bus, st store.Store, n Notifier) {
+	if bus == nil || st == nil || n == nil {
+		return
+	}
+	if _, disabled := n.(Nop); disabled {
+		return
+	}
+	s := subscriber{store: st, mail: n}
+	bus.Subscribe(s.handle)
+}
+
+type subscriber struct {
+	store store.Store
+	mail  Notifier
+}
+
+func (s subscriber) handle(_ context.Context, ev any) {
+	created, ok := ev.(events.PostCreated)
+	if !ok {
+		return
+	}
+	if strings.TrimSpace(created.ParentID) == "" {
+		return
+	}
+	go s.notifyReply(created.PostEvent)
+}
+
+func (s subscriber) notifyReply(ev events.PostEvent) {
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	parent, err := s.store.GetPost(ctx, ev.ParentID)
+	if err != nil {
+		log.Printf("notify reply %s: load parent: %v", ev.PostID, err)
+		return
+	}
+	root, err := s.store.GetPost(ctx, ev.RootID)
+	if err != nil {
+		log.Printf("notify reply %s: load root: %v", ev.PostID, err)
+		return
+	}
+	author, err := s.store.UserByID(ctx, ev.AuthorID)
+	if err != nil {
+		log.Printf("notify reply %s: load author: %v", ev.PostID, err)
+		return
+	}
+	recipientID := parent.AuthorID
+	if author.Admin() {
+		recipientID = root.AuthorID
+	}
+	if recipientID == author.ID {
+		return
+	}
+	msg := PostReply{
+		RootID:          root.ID,
+		RootTitle:       root.Title,
+		ReplyID:         ev.PostID,
+		ReplyBody:       ev.Body,
+		ReplyAuthorName: author.Name,
+	}
+	recipient, err := s.store.UserByID(ctx, recipientID)
+	if err != nil {
+		log.Printf("notify reply %s: load recipient: %v", msg.ReplyID, err)
+		return
+	}
+	if recipient == nil || strings.TrimSpace(recipient.Email) == "" {
+		return
+	}
+	msg.ToEmail = recipient.Email
+	msg.ToName = recipient.Name
+	if err := s.mail.NotifyPostReply(ctx, msg); err != nil {
+		log.Printf("notify reply %s: %v", msg.ReplyID, err)
+		return
+	}
+	log.Printf("notify reply %s: accepted", msg.ReplyID)
+}