DateTimeInputDialog.cs

    [Serializable]
    public class DateTimeInputDialog : IDialog<DateTime>
    {
        /// <summary>
        /// If it is null, we're looking for DateTimeFrom
        /// Else, we're looking for DateTimeTo
        /// </summary>
        private DateTime? inputDateTime;

        private ParkingAreaDetails selectedParkingLocationDetails;

        string selectedDateString, selectedTimeString;

        DateTime selectedDateTime;

        public DateTimeInputDialog(DateTime? inputdt, ParkingAreaDetails selectedPLD)
        {
            inputDateTime = inputdt;
            selectedParkingLocationDetails = selectedPLD;
        }

        public async Task StartAsync(IDialogContext context)
        {
            await PostPromptDateInputMessageAsync(context);
            context.Wait(DateSelected);
        }

        /// <summary>
        /// Parses user's input. If it's "today" or "tomorrow" then we're good to go. Otherwise, it tries to parse the date. If all fail, it asks again for input.
        /// </summary>
        /// <param name="context"></param>
        /// <param name="argument"></param>
        /// <returns></returns>
        public virtual async Task DateSelected(IDialogContext context, IAwaitable<IMessageActivity> argument)
        {
            bool success = false;
            var message = await argument;
            if (message.Text.CompareInput(StringMessages.Today)) //"today" as input
            {
                success = true;
                var date = DateTime.UtcNow.AddHours(selectedParkingLocationDetails.UtcTimeDiff).ToString("dd/MM/yyy");
                selectedDateString = date;
            }
            else if (message.Text.CompareInput(StringMessages.Tomorrow))//"tomorrow" as input
            {
                success = true;
                var date = DateTime.UtcNow.Date.AddDays(1).AddHours(selectedParkingLocationDetails.UtcTimeDiff).ToString("dd/MM/yyy");
                selectedDateString = date;
            }
            else if (Utilities.DateRegex.IsMatch(message.Text))
            {
                var selectedDate = Utilities.ConvertDateTimeStringToDate(message.Text, null);
                if (selectedDate < DateTime.UtcNow.AddHours(selectedParkingLocationDetails.UtcTimeDiff).Date)
                {
                    success = false;
                    await context.PostAsync(StringMessages.SelectedDateLessThanNow);
                }
                else
                {
                    success = true;
                    selectedDateString = message.Text;
                }
            }
            else //no valid input
            {
                success = false;
                await context.PostAsync(StringMessages.WrongInputDate);
            }

            if (success)
            {
                await PostPromptTimeInputMessageAsync(context);
            }
            else
            {

                await PostPromptDateInputMessageAsync(context);
                context.Wait(DateSelected);
            }

        }


        public virtual async Task TimeSelected(IDialogContext context, IAwaitable<IMessageActivity> argument)
        {
            var message = await argument;
            if (Utilities.TimeRegex.IsMatch(message.Text))
            {
                selectedTimeString = message.Text;
                selectedDateTime = Utilities.ConvertDateTimeStringToDate(selectedDateString, selectedTimeString);

                //check if selected date is in the past
                if (selectedDateTime < DateTime.Now)
                {
                    await context.PostAsync(StringMessages.SelectedTimeLessThanNow);
                    context.Wait(TimeSelected);
                }
                //we're checking the "to" date and it's less than "from"
                else if (inputDateTime.HasValue && selectedDateTime < inputDateTime)
                {
                    await context.PostAsync(StringMessages.DepartureDateLessThanArrival);
                    context.Wait(DateSelected);
                }
                else
                {
                    context.Done(selectedDateTime);
                }
            }
            else
            {
                await context.PostAsync(StringMessages.WrongInputTime);
                context.Wait(TimeSelected);
            }
        }

        private async Task PostPromptTimeInputMessageAsync(IDialogContext context)
        {
            string msg = inputDateTime.HasValue ? StringMessages.SelectTimeTo : StringMessages.SelectTimeFrom;
            await context.PostAsync(msg);
            context.Wait(TimeSelected);
        }

        private async Task PostPromptDateInputMessageAsync(IDialogContext context)
        {
            string msg = inputDateTime.HasValue ? StringMessages.SelectDateToList : StringMessages.SelectDateFromList;

            var message = context.MakeMessage();
            message.AttachmentLayout = AttachmentLayoutTypes.List;
            var attachments = new List<Attachment>();

            //we're looking for the arrival date
            if (inputDateTime == null)
            {
                var actions = new List<CardAction>()
                {
                    Utilities.CreateCardAction(StringMessages.Today,StringMessages.Today),
                    Utilities.CreateCardAction(StringMessages.Tomorrow,StringMessages.Tomorrow),
                };

                attachments.Add(Utilities.CreateHeroCardAttachment(msg, StringMessages.UpcomingDates, null, null, actions));
            }
            else //we're looking for the departure date
            //add 3 and 5 days to the arrival date and suggest them to the user
            {
                var after3days = inputDateTime.Value.Date.AddDays(3).ToString("dd/MM/yyyy");
                var after5days = inputDateTime.Value.Date.AddDays(5).ToString("dd/MM/yyyy");

                var actions = new List<CardAction>()
                {
                    Utilities.CreateCardAction(after3days,after3days),
                    Utilities.CreateCardAction(after5days,after5days),
                };

                attachments.Add(Utilities.CreateHeroCardAttachment(msg, StringMessages.UpcomingDatesReturn, null, null, actions));

            }
            message.Attachments = attachments;
            await context.PostAsync(message);
        }
    }