feat: add feedback resolver

internal/service/feedback_service.go

@@ -92,6 +92,70 @@ func (s *FeedbackService) Submit(ctx context.Context, userID *string, category,
 	return f, nil
 }
 
+// ErrAlreadyResolved is returned by Resolve when the row was already
+// closed (or doesn't exist). The handler maps it to a benign redirect
+// rather than an error — the end state the admin wanted is already true.
+var ErrAlreadyResolved = errors.New("feedback already resolved")
+
+// Resolve marks a feedback row resolved (one-way) and, if a recipient
+// address is known, sends the author a Vaishnava-styled thank-you note.
+//
+// The DB update is the source of truth: MarkResolved's `resolved_at IS
+// NULL` guard guarantees the email fires at most once even under
+// concurrent button presses. The email is fire-and-forget — a send
+// failure logs but doesn't un-resolve the row.
+func (s *FeedbackService) Resolve(ctx context.Context, id string) error {
+	resolved, err := s.repo.MarkResolved(ctx, id)
+	if err != nil {
+		return err
+	}
+	if !resolved {
+		return ErrAlreadyResolved
+	}
+
+	// Re-read with author joins so we know where to send the thank-you.
+	f, err := s.repo.FindByID(ctx, id)
+	if err != nil {
+		// Row IS resolved; we just can't assemble the email. Log and
+		// succeed — the resolve itself stuck.
+		s.logger.Warn("feedback resolved but hydrate failed; skipping thank-you email",
+			zap.String("feedback_id", id), zap.Error(err))
+		return nil
+	}
+
+	to := feedbackReplyTo(f)
+	if to == "" {
+		// No email on file (anonymous submitter who left no contact, or
+		// a since-deleted account). Nothing to send — that's fine.
+		s.logger.Info("feedback resolved; no recipient address, skipping thank-you email",
+			zap.String("feedback_id", id))
+		return nil
+	}
+
+	body, err := renderFeedbackResolvedEmail(f)
+	if err != nil {
+		s.logger.Warn("render feedback-resolved email failed", zap.Error(err))
+		return nil
+	}
+	if err := s.mail.Send(to, "Your feedback has been addressed — Prabhupāda Says", body); err != nil {
+		s.logger.Warn("feedback-resolved email send failed",
+			zap.String("to", to), zap.Error(err))
+	}
+	return nil
+}
+
+// feedbackReplyTo picks the address to thank: the authed submitter's
+// account email if present, else the anonymous contact_email, else "".
+func feedbackReplyTo(f *model.Feedback) string {
+	if f.AuthorEmail != nil && strings.TrimSpace(*f.AuthorEmail) != "" {
+		return strings.TrimSpace(*f.AuthorEmail)
+	}
+	if f.ContactEmail != nil && strings.TrimSpace(*f.ContactEmail) != "" {
+		return strings.TrimSpace(*f.ContactEmail)
+	}
+	return ""
+}
+
 // notifyAdmins fires one HTML email per configured admin. Each
 // failure logs and falls through — the row is persisted so a missed
 // email is annoying but not data-losing.
@@ -165,3 +229,50 @@ func derefOr(p *string, fallback string) string {
 	}
 	return *p
 }
+
+// feedbackResolvedEmailTpl is the author-facing thank-you sent when an
+// admin marks their feedback resolved. Vaishnava-styled — warm,
+// devotional register, addressed to the submitter by name when known.
+var feedbackResolvedEmailTpl = template.Must(template.New("feedbackResolved").Parse(`<div style="font-family:Georgia,'Times New Roman',serif;color:#2a2118;max-width:560px;margin:0 auto;line-height:1.7">
+  <p style="font-size:15px;color:#9a6b2f;letter-spacing:0.04em;margin-bottom:1.25em">Hare Kṛṣṇa{{if .Name}}, {{.Name}}{{end}} 🙏</p>
+
+  <p>Please accept our humble obeisances. All glories to Śrīla Prabhupāda.</p>
+
+  <p>We are writing to let you know that the feedback you kindly shared with
+  us has been <strong>acknowledged and addressed</strong>. The necessary
+  features and fixes you pointed us toward have now been implemented.</p>
+
+  <p>Your observations help us serve Śrīla Prabhupāda's <em>vāṇī</em> more
+  faithfully, and we are sincerely grateful that you took the time to write.
+  Devotee feedback like yours is one of the ways this humble service keeps
+  improving.</p>
+
+  <p>We warmly invite you to continue using
+  <a href="https://prabhupadasays.org" style="color:#9a6b2f;font-weight:600">prabhupadasays.org</a>
+  with even greater enthusiasm — there is always more of Śrīla Prabhupāda's
+  nectar waiting to be relished.</p>
+
+  <p style="margin-top:1.75em">Your servants,<br>
+  <strong>The Prabhupāda Says team</strong></p>
+
+  <hr style="border:none;border-top:1px solid #e8ddc9;margin:2em 0">
+  <p style="font-size:12px;color:#a89878;font-style:italic">
+    “Books are the basis.” — His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda
+  </p>
+</div>`))
+
+func renderFeedbackResolvedEmail(f *model.Feedback) (string, error) {
+	// Prefer the account display name; fall back to no name (the
+	// template drops the comma cleanly when Name is empty).
+	name := ""
+	if f.AuthorName != nil {
+		name = strings.TrimSpace(*f.AuthorName)
+	}
+	var buf bytes.Buffer
+	if err := feedbackResolvedEmailTpl.Execute(&buf, map[string]any{
+		"Name": name,
+	}); err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}