// No update at this point
        private async Task <string> UpsertTag(string tag, List <string> tagList)
        {
            if (tagList.Any(x => x == TagNormaliser.Normalise(tag)))
            {
                return(null);
            }

            return(TagNormaliser.Normalise(tag));
        }
        public async Task <TagsDto> GetTagsByTagNameAndDate(string tag, DateTime date)
        {
            if (tag == null || date == default(DateTime))
            {
                return(null);
            }

            var normalisedTag = TagNormaliser.Normalise(tag);

            var articles = _articlesContext.Articles
                           .Where(x => x.Tags.Any(y => y == normalisedTag) && x.Date.Date == date.Date).ToList();

            if (!articles.Any())
            {
                return(null);
            }

            // rather big linq statement -> select tags lists from each article and flatten
            var relatedTags = articles
                              .SelectMany(x => x.Tags)
                              // Remove present tag
                              .Where(x => x != normalisedTag)
                              // deduplicate
                              .ToHashSet();

            var tagDto = new TagsDto
            {
                Tag = normalisedTag,
                // take a maximum of 10 articles
                Articles = articles.Select(x => x.Id).Take(10).ToArray(),
                // Get total related tags for the day
                Count       = articles.SelectMany(x => x.Tags).Count(),
                RelatedTags = relatedTags.ToArray()
            };

            return(tagDto);
        }