My solution to the saga homework for https://particular.net/adsd

UdiWorld.cs

namespace UdiWorld
{
    using System;
    using System.Threading.Tasks;
    using NServiceBus;

    public class UserBecamePreferred
    {
        public Guid UserId { get; set; }
    }

    public class UserBecameUnpreferred
    {
        public Guid UserId { get; set; }
    }

    public class UdiCoinsPurchased
    {
        public Guid UserId { get; set; }

        public int Amount { get; set; }
    }

    public class BuyItem
    {
        public Guid UserId { get; set; }

        public Guid ItemId { get; set; }

        public int Price { get; set; }
    }

    public class DecrementOneWeekTotal
    {
        public int Amount { get; set; }
    }

    public class DecrementTwoWeekTotal
    {
        public int Amount { get; set; }
    }

    public class FulfillPurchase
    {
        public Guid UserId { get; set; }

        public Guid ItemId { get; set; }
    }

    public class BalanceInsufficient
    {
        public Guid UserId { get; set; }

        public Guid ItemId { get; set; }
    }

    public class InAppPurchases : Saga<InAppPurchases.State>,
        IAmStartedByMessages<UserBecamePreferred>,
        IAmStartedByMessages<UserBecameUnpreferred>,
        IAmStartedByMessages<UdiCoinsPurchased>,
        IAmStartedByMessages<BuyItem>,
        IHandleTimeouts<DecrementOneWeekTotal>,
        IHandleTimeouts<DecrementTwoWeekTotal>
    {
        public Task Handle(UserBecamePreferred message, IMessageHandlerContext context)
        {
            Data.IsPreferred = true;
            return Task.CompletedTask;
        }

        public Task Handle(UserBecameUnpreferred message, IMessageHandlerContext context)
        {
            Data.IsPreferred = false;
            return Task.CompletedTask;
        }

        public Task Handle(UdiCoinsPurchased message, IMessageHandlerContext context)
        {
            Data.Balance += message.Amount;
            return Task.CompletedTask;
        }

        public async Task Handle(BuyItem message, IMessageHandlerContext context)
        {
            var totalOrderValue = Data.IsPreferred
                ? Data.TwoWeekTotal
                : Data.OneWeekTotal;

            var discount = totalOrderValue > 100
                ? 0.2
                : 0.1;

            var price = (int)(message.Price * (1 - discount));

            if (Data.Balance > price)
            {
                Data.Balance -= price;

                Data.OneWeekTotal += message.Price;
                await RequestTimeout(context, TimeSpan.FromDays(7), new DecrementOneWeekTotal { Amount = message.Price });

                Data.TwoWeekTotal += message.Price;
                await RequestTimeout(context, TimeSpan.FromDays(14), new DecrementTwoWeekTotal { Amount = message.Price });

                await context.Send(new FulfillPurchase { UserId = message.UserId, ItemId = message.ItemId });
            }
            else
            {
                await context.Publish(new BalanceInsufficient { UserId = message.UserId, ItemId = message.ItemId });
            }
        }

        public Task Timeout(DecrementOneWeekTotal state, IMessageHandlerContext context)
        {
            Data.OneWeekTotal -= state.Amount;
            return Task.CompletedTask;
        }

        public Task Timeout(DecrementTwoWeekTotal state, IMessageHandlerContext context)
        {
            Data.TwoWeekTotal -= state.Amount;
            return Task.CompletedTask;
        }

        protected override void ConfigureHowToFindSaga(SagaPropertyMapper<State> mapper)
        {
            mapper.ConfigureMapping<UserBecamePreferred>(m => m.UserId).ToSaga(s => s.UserId);
            mapper.ConfigureMapping<UserBecameUnpreferred>(m => m.UserId).ToSaga(s => s.UserId);
            mapper.ConfigureMapping<UdiCoinsPurchased>(m => m.UserId).ToSaga(s => s.UserId);
            mapper.ConfigureMapping<BuyItem>(m => m.UserId).ToSaga(s => s.UserId);
        }

        public class State : ContainSagaData
        {
            public Guid UserId { get; set; }

            public bool IsPreferred { get; set; }

            public int OneWeekTotal { get; set; }

            public int TwoWeekTotal { get; set; }

            public int Balance { get; set; }
        }
    }
}