Search App

  public class SearchByString<T> : StringSearchPresenter
    {
        #region plumbing

        readonly ISearchEngine<T> _search;
        readonly IQueryFactory<T> _query;
        readonly StringSearchView<T> _view;

        public SearchByString(ISearchEngine<T> search,IQueryFactory<T> query,StringSearchView<T> view)
        {
            _search = search;
            _query = query;
            _view = view;
        }

        public bool AttemptEmptySearchAnyway { get; set; } = true;

        #endregion

        public View View => _view;

        public async void PerformSearch()
        {
            try
            {
                var search = _view.Search;
                if (string.IsNullOrWhiteSpace(search))
                {
                    Say(EMPTY_SEARCH_STRING);

                    if (AttemptEmptySearchAnyway)
                        await UpdateUiWithResults(string.Empty);
                    else
                        ClearSearchResults();

                    return;
                }


                await UpdateUiWithResults(search);
            }
            catch (Exception ex)
            {
               Say(INTERNAL_ERROR,ex);
            }
        }

        public void UpdateAutoComplete()
        {
            var search = _view.Search;
            if (_search.HasSpellcheckSuggestion(search, out var s))
            {
                _view.DidYouMean = s;
                Say(PROBABLE_SPELLING_MISTAKE);
            }
            _view.AutoComplete = String.IsNullOrWhiteSpace(search) ? new List<string>() : _search.AutoComplete(search);
        }

        void ClearSearchResults()
        {
            _view.Results = new List<T>();
        }

        async Task UpdateUiWithResults(string query)
        {
            var results = (await _query.Search(query).Execute()).ToList();
            if (results.Count <= 0)
               Say(NO_RESULTS);
            _view.Results = results;
        }

        #region Utility

        void Say(string message, object context = null) => _view.SendMessage(Message.Say(message, context));


        #endregion
    }