Add polished answer notifications (#1)

Sends a branded Resend email when a question receives its first answer, records accepted and failed sends, and adds collapsed answer editing with cancel behavior.

Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/web/server.go

@@ -22,6 +22,7 @@ import (
 
 	"plumber/internal/blob"
 	"plumber/internal/geo"
+	"plumber/internal/mail"
 	"plumber/internal/pacific"
 	"plumber/internal/store"
 )
@@ -34,6 +35,7 @@ type Config struct {
 	// TrustedProxies are CIDRs allowed to set X-Forwarded-For (direct peer).
 	TrustedProxies []*net.IPNet
 	Blob           blob.Uploader
+	Mail           mail.Notifier
 }
 
 type Server struct {
@@ -82,6 +84,7 @@ type submitPage struct {
 type authPage struct {
 	page
 	Username string
+	Email    string
 	Error    string
 	Next     string
 }
@@ -98,6 +101,9 @@ func New(st store.Store, sessionStore scs.Store, templateFS fs.FS, staticFS fs.F
 	if cfg.Blob == nil {
 		cfg.Blob = blob.Disabled{}
 	}
+	if cfg.Mail == nil {
+		cfg.Mail = mail.Nop{}
+	}
 	funcMap := template.FuncMap{
 		"voteCtx": func(user *store.User, csrf, view, date string, q store.RankedQuestion) voteCtx {
 			return voteCtx{User: user, CSRF: csrf, View: view, Date: date, Question: q}
@@ -482,6 +488,17 @@ func (s *Server) handleAnswer(w http.ResponseWriter, r *http.Request) {
 	if len(body) > 12000 {
 		body = truncateRunes(body, 12000)
 	}
+	q, err := s.store.GetQuestion(r.Context(), id, u.ID)
+	if err != nil {
+		http.NotFound(w, r)
+		return
+	}
+	_, priorErr := s.store.GetAnswer(r.Context(), id)
+	wasNew := errors.Is(priorErr, sql.ErrNoRows)
+	if priorErr != nil && !wasNew {
+		http.Error(w, "could not load answer", http.StatusInternalServerError)
+		return
+	}
 	ans := &store.Answer{
 		QuestionID: id,
 		AuthorID:   u.ID,
@@ -491,6 +508,9 @@ func (s *Server) handleAnswer(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "could not save answer", http.StatusInternalServerError)
 		return
 	}
+	if wasNew {
+		s.notifyQuestionAnswered(q, body, u.ID)
+	}
 	saved, err := s.store.GetAnswer(r.Context(), id)
 	if err != nil {
 		http.Error(w, "could not load answer", http.StatusInternalServerError)
@@ -503,6 +523,32 @@ func (s *Server) handleAnswer(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/questions/"+url.PathEscape(id), http.StatusSeeOther)
 }
 
+func (s *Server) notifyQuestionAnswered(q *store.RankedQuestion, answerBody, adminID string) {
+	if q == nil || s.cfg.Mail == nil {
+		return
+	}
+	author, err := s.store.UserByID(context.Background(), q.AuthorID)
+	if err != nil || author == nil || author.Email == "" || author.ID == adminID {
+		return
+	}
+	msg := mail.QuestionAnswered{
+		ToEmail:       author.Email,
+		ToName:        author.Name,
+		QuestionID:    q.ID,
+		QuestionTitle: q.Title,
+		AnswerBody:    answerBody,
+	}
+	go func() {
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+		if err := s.cfg.Mail.NotifyQuestionAnswered(ctx, msg); err != nil {
+			log.Printf("notify answer %s: %v", q.ID, err)
+			return
+		}
+		log.Printf("notify answer %s: accepted", q.ID)
+	}()
+}
+
 func (s *Server) handleHide(w http.ResponseWriter, r *http.Request) {
 	if !s.requireCSRF(w, r) {
 		return