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Ricardo.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace RicardoDeSilva
{
    namespace Contracts
    {
        public enum ScheduleGeneratorType { Daily, Hourly /*,  Add others */ };

        public class DeliveryDetails
        {
            public string Id { get; protected set; }
            public string Description { get; protected set; }
            public DateTime? DeliverStartingFrom { get; protected set; }
            public ScheduleGeneratorType ScheduleGenerator { get; protected set; }
        }
    }

    namespace Modules
    {
        using Contracts;

        public interface IGenerateSchedules
        {
            IEnumerable<DateTime> StartingFrom(DateTime startDate);
        }

        public static class ScheduleModule
        {

            public static IGenerateSchedules GetGenerator(ScheduleGeneratorType @type)
            {
                switch (@type)
                {
                    case (ScheduleGeneratorType.Daily):     return new DailyScheduleGenerator();
                    case (ScheduleGeneratorType.Hourly):    return new HourlyScheduleGenerator();
                    default:                                return UnknownScheduleGenerator;
                }
            }

            class HourlyScheduleGenerator : IGenerateSchedules
            {
                IEnumerable<DateTime> IGenerateSchedules.StartingFrom(DateTime startDate)
                {
                    var currentDate = startDate;
                    while (true)
                    {
                        // this will probably be way more complicated
                        if (currentDate.TimeOfDay.TotalHours >= 8.5 &&
                           currentDate.TimeOfDay.TotalHours < 17)
                        {
                            yield return currentDate;
                        }
                        currentDate += TimeSpan.FromHours(1);
                    }
                }
            }

            class DailyScheduleGenerator : IGenerateSchedules
            {
                IEnumerable<DateTime> IGenerateSchedules.StartingFrom(DateTime startDate)
                {
                    var currentDate = startDate;
                    while (true)
                    {
                        // this will probably be way more complicated
                        if (currentDate.DayOfWeek != DayOfWeek.Saturday &&
                            currentDate.DayOfWeek != DayOfWeek.Sunday)
                        {
                            yield return currentDate;
                        }
                        currentDate += TimeSpan.FromDays(1);
                    }
                }
            }

            class NopScheduleGeneratorClass : IGenerateSchedules
            {
                IEnumerable<DateTime> IGenerateSchedules.StartingFrom(DateTime startDate)
                {
                    throw new NotImplementedException();
                }
            }

            public static IGenerateSchedules UnknownScheduleGenerator = new NopScheduleGeneratorClass();
        }
    }

    namespace Domain
    {
        using Contracts;
        using Modules;

        public class Delivery
        {
            void ProvisionDelivery(DeliveryDetails deliveryDetails)
            {
                var generateSchedule = ScheduleModule.GetGenerator(deliveryDetails.ScheduleGenerator);

                Guard.Against(generateSchedule == ScheduleModule.UnknownScheduleGenerator, "Unknown schedule generator");

                // a later starting date might be picked for whatever reason (f.e. not in stock etc)
                var earliestDate = deliveryDetails.DeliverStartingFrom.HasValue ? deliveryDetails.DeliverStartingFrom.Value : DateTime.Now;

                // here other dates might be picked (f.e. national holiday)
                var scheduledDate = generateSchedule.StartingFrom(earliestDate).First();

                // everything is ok, persist
                this.DeliveryWasProvisioned(deliveryDetails.Id, deliveryDetails.Description, scheduledDate);
            }

            private void DeliveryWasProvisioned(string Id, string Description, DateTime scheduledDate)
            {
                // TODO
                throw new NotImplementedException();
            }
        }
    }



    public static class Guard
    {
        public static void Against(bool condition, string message)
        {
            if (condition)
            {
                throw new InvalidOperationException(message);
            }
        }

        public static void That(bool condition, string message)
        {
            Guard.Against(!condition, message);
        }
    }
}