spsays-bff/internal/service/notification_service.go

// Package service — NotificationService is the single seam every
// user-facing event flows through ("the notification plugin"). Today it
// does two things per event:
//
//  1. Persists a row in `notifications` (so an in-app notification center
//     and, later, websocket + push delivery can read the same history).
//  2. Sends an email to the recipient via the shared mailer.
//
// Everything here is fire-and-forget from the caller's perspective: a
// follow request must succeed even if the email bounces or the insert
// fails, so Notify* never returns an error — failures are logged. When
// websocket/push land they hook in right here alongside the email send.
package service

import (
	"bytes"
	"context"
	"html/template"
	"strings"

	"github.com/prabhupadasays/spsays-bff/internal/model"
	"github.com/prabhupadasays/spsays-bff/internal/repository"
	"github.com/prabhupadasays/spsays-bff/pkg/mailer"
	"go.uber.org/zap"
)

// Notification kinds — short machine strings stored in notifications.kind.
const (
	NotifFollowRequest  = "follow_request"
	NotifFollowAccepted = "follow_accepted"
)

type NotificationService struct {
	notifs      *repository.NotificationRepo
	users       *repository.UserRepo
	mail        mailer.Mailer
	logger      *zap.Logger
	frontendURL string
}

func NewNotificationService(notifs *repository.NotificationRepo, users *repository.UserRepo, mail mailer.Mailer, logger *zap.Logger, frontendURL string) *NotificationService {
	return &NotificationService{
		notifs:      notifs,
		users:       users,
		mail:        mail,
		logger:      logger,
		frontendURL: strings.TrimRight(frontendURL, "/"),
	}
}

// List returns the caller's notifications, newest first.
func (s *NotificationService) List(ctx context.Context, userID string, limit, offset int) ([]model.Notification, error) {
	if limit <= 0 || limit > 100 {
		limit = 30
	}
	if offset < 0 {
		offset = 0
	}
	return s.notifs.ListByUser(ctx, userID, limit, offset)
}

// UnreadCount returns the caller's unread notification count (for the bell
// badge).
func (s *NotificationService) UnreadCount(ctx context.Context, userID string) (int, error) {
	return s.notifs.CountUnread(ctx, userID)
}

// MarkAllRead marks all of the caller's notifications read.
func (s *NotificationService) MarkAllRead(ctx context.Context, userID string) error {
	return s.notifs.MarkAllRead(ctx, userID)
}

// NotifyFollowRequest tells `recipientID` that `actorID` asked to follow
// them. Persists the row and emails the recipient (if they have an email
// on file).
func (s *NotificationService) NotifyFollowRequest(ctx context.Context, recipientID, actorID string) {
	s.dispatch(ctx, recipientID, actorID, NotifFollowRequest,
		"%s requested to follow you — Prabhupāda Says")
}

// NotifyFollowAccepted tells `recipientID` that `actorID` accepted their
// follow request (i.e. the recipient can now see actor's activity).
func (s *NotificationService) NotifyFollowAccepted(ctx context.Context, recipientID, actorID string) {
	s.dispatch(ctx, recipientID, actorID, NotifFollowAccepted,
		"%s accepted your follow request — Prabhupāda Says")
}

// dispatch persists the notification and sends the matching email. All
// failures are logged, never propagated.
func (s *NotificationService) dispatch(ctx context.Context, recipientID, actorID, kind, subjectFmt string) {
	actor := actorID
	if _, err := s.notifs.Create(ctx, recipientID, &actor, kind); err != nil {
		s.logger.Warn("persist notification failed",
			zap.String("recipient", recipientID), zap.String("kind", kind), zap.Error(err))
		// Persistence failed, but still try to email — the email is the
		// only delivery channel that exists today.
	}

	recipient, err := s.users.FindByID(ctx, recipientID)
	if err != nil {
		s.logger.Warn("notification recipient lookup failed", zap.String("recipient", recipientID), zap.Error(err))
		return
	}
	if recipient.Email == nil || strings.TrimSpace(*recipient.Email) == "" {
		// No email on file (OAuth-only account that never added one) —
		// the persisted row is the notification; nothing to send.
		return
	}
	actorUser, err := s.users.FindByID(ctx, actorID)
	if err != nil {
		s.logger.Warn("notification actor lookup failed", zap.String("actor", actorID), zap.Error(err))
		return
	}

	body, err := s.render(kind, recipient, actorUser)
	if err != nil {
		s.logger.Warn("render notification email failed", zap.String("kind", kind), zap.Error(err))
		return
	}
	subject := strings.Replace(subjectFmt, "%s", actorDisplay(actorUser), 1)
	if err := s.mail.Send(strings.TrimSpace(*recipient.Email), subject, body); err != nil {
		s.logger.Warn("notification email send failed",
			zap.String("to", *recipient.Email), zap.String("kind", kind), zap.Error(err))
	}
}

func (s *NotificationService) render(kind string, recipient, actor *model.User) (string, error) {
	data := map[string]any{
		"RecipientName": recipient.Name,
		"ActorName":     actorDisplay(actor),
		"ActorHandle":   actor.Handle,
		"ProfileURL":    s.frontendURL + "/u/" + actor.Handle,
	}
	var tpl *template.Template
	switch kind {
	case NotifFollowRequest:
		tpl = followRequestEmailTpl
	case NotifFollowAccepted:
		tpl = followAcceptedEmailTpl
	default:
		tpl = followRequestEmailTpl
	}
	var buf bytes.Buffer
	if err := tpl.Execute(&buf, data); err != nil {
		return "", err
	}
	return buf.String(), nil
}

// actorDisplay prefers the display name, falling back to @handle.
func actorDisplay(u *model.User) string {
	if n := strings.TrimSpace(u.Name); n != "" {
		return n
	}
	return "@" + u.Handle
}

// Vaishnava-styled, 17px base to match the feedback emails. Both quote
// the actor and link to their profile (where the recipient can accept a
// pending request).
var followRequestEmailTpl = template.Must(template.New("followRequest").Parse(`<div style="font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;color:#2a2118;max-width:560px;margin:0 auto;font-size:17px;line-height:1.7">
  <p style="font-size:18px;color:#9a6b2f;letter-spacing:0.04em;margin-bottom:1em">Hare Kṛṣṇa{{if .RecipientName}}, {{.RecipientName}}{{end}} 🙏</p>

  <p><strong>{{.ActorName}}</strong> (<a href="{{.ProfileURL}}" style="color:#9a6b2f;font-weight:600">@{{.ActorHandle}}</a>)
  has requested to follow you on Prabhupāda Says.</p>

  <p>You can review and accept or decline the request from their profile:</p>

  <p style="margin:1.25em 0">
    <a href="{{.ProfileURL}}" style="display:inline-block;background:#9a6b2f;color:#fff;text-decoration:none;padding:0.6em 1.3em;border-radius:8px;font-weight:600">View request</a>
  </p>

  <p style="margin-top:1.5em">Your servants,<br>
  <strong>The Prabhupāda Says team</strong></p>
</div>`))

var followAcceptedEmailTpl = template.Must(template.New("followAccepted").Parse(`<div style="font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;color:#2a2118;max-width:560px;margin:0 auto;font-size:17px;line-height:1.7">
  <p style="font-size:18px;color:#9a6b2f;letter-spacing:0.04em;margin-bottom:1em">Hare Kṛṣṇa{{if .RecipientName}}, {{.RecipientName}}{{end}} 🙏</p>

  <p><strong>{{.ActorName}}</strong> (<a href="{{.ProfileURL}}" style="color:#9a6b2f;font-weight:600">@{{.ActorHandle}}</a>)
  has accepted your follow request. You're now following them on Prabhupāda Says.</p>

  <p style="margin:1.25em 0">
    <a href="{{.ProfileURL}}" style="display:inline-block;background:#9a6b2f;color:#fff;text-decoration:none;padding:0.6em 1.3em;border-radius:8px;font-weight:600">Visit profile</a>
  </p>

  <p style="margin-top:1.5em">Your servants,<br>
  <strong>The Prabhupāda Says team</strong></p>
</div>`))