feat: Implement Recurrer interface methods for Postgres service

sync/service/postgres.go

@@ -157,6 +157,58 @@ func (p *Postgres) migrate(wanted []string) error {
 	return nil
 }
 
+func (p *Postgres) RecursBefore(date time.Time) ([]item.Item, error) {
+	query := `
+		SELECT id, kind, updated, deleted, body, recurrer, recur_next
+		FROM items
+		WHERE recur_next <= $1 AND recurrer IS NOT NULL`
+
+	rows, err := p.db.Query(query, date)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrPostgresFailure, err)
+	}
+	defer rows.Close()
+
+	result := make([]item.Item, 0)
+	for rows.Next() {
+		var item item.Item
+		if err := rows.Scan(&item.ID, &item.Kind, &item.Updated, &item.Deleted, &item.Body, &item.Recurrer, &item.RecurNext); err != nil {
+			return nil, fmt.Errorf("%w: %v", ErrPostgresFailure, err)
+		}
+		result = append(result, item)
+	}
+
+	return result, nil
+}
+
+func (p *Postgres) RecursNext(id string, date time.Time) error {
+	var item item.Item
+	err := p.db.QueryRow(`
+		SELECT id, kind, updated, deleted, body, recurrer, recur_next
+		FROM items
+		WHERE id = $1`, id).Scan(&item.ID, &item.Kind, &item.Updated, &item.Deleted, &item.Body, &item.Recurrer, &item.RecurNext)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return ErrNotFound
+		}
+		return fmt.Errorf("%w: %v", ErrPostgresFailure, err)
+	}
+
+	if item.Recurrer == nil {
+		return ErrNotARecurrer
+	}
+
+	_, err = p.db.Exec(`
+		UPDATE items 
+		SET recur_next = $1
+		WHERE id = $2`, date, id)
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrPostgresFailure, err)
+	}
+
+	return nil
+}
+
 func compareMigrations(wanted, existing []string) ([]string, error) {
 	var needed []string
 	if len(wanted) < len(existing) {