feat: add email notification for post like

internal/repository/social_graph_repo.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"time"
 
 	"github.com/jackc/pgx/v5"
 	"github.com/prabhupadasays/spsays-bff/internal/model"
@@ -347,25 +348,57 @@ func (r *NotificationRepo) ListByUser(ctx context.Context, userID string, limit,
 
 // UpsertLike records (or aggregates) a like notification: one row per
 // (recipient, post). On a repeat like it refreshes the most-recent actor,
-// bumps actor_count, and re-marks the row unread + most-recent. Returns the
-// new actor_count.
-func (r *NotificationRepo) UpsertLike(ctx context.Context, userID, actorID, postID string) (int, error) {
-	var count int
-	err := r.pg.Pool.QueryRow(ctx, `
-		INSERT INTO notifications (user_id, actor_id, kind, post_id, actor_count)
-		VALUES ($1, $2, 'post_like', $3, 1)
+// bumps actor_count, and re-marks the row unread + most-recent.
+//
+// It also throttles the aggregated like *email*: like_email_sent_at is stamped
+// to now() on the first like and again only once `throttle` has elapsed since
+// the last email. Returns the new actor_count and whether an email is due this
+// call (i.e. the stamp was (re)set now) — decided atomically in one statement
+// to avoid double-emailing under concurrent likes.
+func (r *NotificationRepo) UpsertLike(ctx context.Context, userID, actorID, postID string, throttle time.Duration) (count int, emailDue bool, err error) {
+	secs := int(throttle.Seconds())
+	err = r.pg.Pool.QueryRow(ctx, `
+		INSERT INTO notifications (user_id, actor_id, kind, post_id, actor_count, like_email_sent_at)
+		VALUES ($1, $2, 'post_like', $3, 1, now())
 		ON CONFLICT (user_id, post_id) WHERE kind = 'post_like'
 		DO UPDATE SET actor_id    = EXCLUDED.actor_id,
 		              actor_count  = notifications.actor_count + 1,
 		              read_at      = NULL,
-		              created_at   = now()
-		RETURNING actor_count`,
-		userID, actorID, postID,
-	).Scan(&count)
+		              created_at   = now(),
+		              like_email_sent_at = CASE
+		                  WHEN notifications.like_email_sent_at IS NULL
+		                    OR notifications.like_email_sent_at < now() - make_interval(secs => $4)
+		                  THEN now()
+		                  ELSE notifications.like_email_sent_at
+		              END
+		RETURNING actor_count, (like_email_sent_at = now())`,
+		userID, actorID, postID, secs,
+	).Scan(&count, &emailDue)
 	if err != nil {
-		return 0, fmt.Errorf("upsert like notification: %w", err)
+		return 0, false, fmt.Errorf("upsert like notification: %w", err)
 	}
-	return count, nil
+	return count, emailDue, nil
+}
+
+// LikeEmailsEnabled reports whether the user wants aggregated like emails.
+func (r *NotificationRepo) LikeEmailsEnabled(ctx context.Context, userID string) (bool, error) {
+	var enabled bool
+	if err := r.pg.Pool.QueryRow(ctx,
+		`SELECT like_emails_enabled FROM users WHERE id = $1`, userID,
+	).Scan(&enabled); err != nil {
+		return false, fmt.Errorf("get like-email pref: %w", err)
+	}
+	return enabled, nil
+}
+
+// SetLikeEmailsEnabled flips the user's like-email opt-in.
+func (r *NotificationRepo) SetLikeEmailsEnabled(ctx context.Context, userID string, enabled bool) error {
+	if _, err := r.pg.Pool.Exec(ctx,
+		`UPDATE users SET like_emails_enabled = $1 WHERE id = $2`, enabled, userID,
+	); err != nil {
+		return fmt.Errorf("set like-email pref: %w", err)
+	}
+	return nil
 }
 
 // CountUnread returns how many of a recipient's notifications are unread.