Generalize post reply notifications.

Notify direct parent authors throughout threaded conversations while skipping self-replies, edits, and recipients without email.

internal/web/posts.go

@@ -5,12 +5,15 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"log"
 	"net/http"
 	"net/url"
 	"strings"
+	"time"
 
 	"github.com/go-chi/chi/v5"
 
+	"plumber/internal/mail"
 	"plumber/internal/store"
 )
 
@@ -37,7 +40,7 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 		AuthorID: user.ID,
 		Body:     truncateRunes(body, 12000),
 	}
-	var root *store.Post
+	var parent, root *store.Post
 	if parentID == "" {
 		post.Title = truncateRunes(strings.TrimSpace(r.PostFormValue("title")), 120)
 		post.City = truncateRunes(strings.TrimSpace(r.PostFormValue("city")), 80)
@@ -46,7 +49,7 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 	} else {
-		parent, threadRoot, err := s.postAndRoot(r.Context(), parentID)
+		loadedParent, threadRoot, err := s.postAndRoot(r.Context(), parentID)
 		if err != nil {
 			if errors.Is(err, sql.ErrNoRows) {
 				http.NotFound(w, r)
@@ -63,6 +66,7 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "forbidden", http.StatusForbidden)
 			return
 		}
+		parent = loadedParent
 		post.ParentID = &parent.ID
 		root = threadRoot
 	}
@@ -78,6 +82,9 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 	if root == nil {
 		root = post
 	}
+	if parent != nil {
+		s.notifyPostReply(parent, root, post, user)
+	}
 	http.Redirect(
 		w,
 		r,
@@ -86,6 +93,53 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 	)
 }
 
+// notifyPostReply asynchronously emails the direct parent post's author.
+func (s *Server) notifyPostReply(
+	parent *store.Post,
+	root *store.Post,
+	reply *store.Post,
+	replyAuthor *store.User,
+) {
+	if parent == nil ||
+		root == nil ||
+		reply == nil ||
+		replyAuthor == nil ||
+		s.cfg.Mail == nil ||
+		parent.AuthorID == replyAuthor.ID {
+		return
+	}
+	if _, disabled := s.cfg.Mail.(mail.Nop); disabled {
+		return
+	}
+	msg := mail.PostReply{
+		RootID:          root.ID,
+		RootTitle:       root.Title,
+		ReplyID:         reply.ID,
+		ReplyBody:       reply.Body,
+		ReplyAuthorName: replyAuthor.Name,
+	}
+	recipientID := parent.AuthorID
+	go func() {
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+		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.cfg.Mail.NotifyPostReply(ctx, msg); err != nil {
+			log.Printf("notify reply %s: %v", msg.ReplyID, err)
+			return
+		}
+		log.Printf("notify reply %s: accepted", msg.ReplyID)
+	}()
+}
+
 // handleEditPost updates only a post's body after verifying that the current
 // homeowner owns it or that an admin is editing an admin-authored post.
 func (s *Server) handleEditPost(w http.ResponseWriter, r *http.Request) {