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EventStore.cs
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EventStore.cs
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namespace IntroductionToEventSourcing.GettingStateFromEvents.Tools;
public class EventStore
{
private readonly Dictionary<Type, List<Action<EventEnvelope>>> handlers = new();
private readonly Dictionary<Guid, List<EventEnvelope>> events = new();
public void Register<TEvent>(Action<EventEnvelope<TEvent>> handler) where TEvent : notnull
{
var eventType = typeof(TEvent);
void WrappedHandler(object @event) => handler((EventEnvelope<TEvent>)@event);
if (handlers.ContainsKey(eventType))
handlers[eventType].Add(WrappedHandler);
else
handlers.Add(eventType, new List<Action<EventEnvelope>> { WrappedHandler });
}
public void Append<TEvent>(Guid streamId, TEvent @event) where TEvent : notnull
{
if (!events.ContainsKey(streamId))
events[streamId] = new List<EventEnvelope>();
var eventEnvelope = new EventEnvelope<TEvent>(@event,
EventMetadata.For(
(ulong)events[streamId].Count + 1,
(ulong)events.Values.Sum(s => s.Count)
)
);
events[streamId].Add(eventEnvelope);
if (!handlers.TryGetValue(eventEnvelope.Data.GetType(), out var eventHandlers)) return;
foreach (var handle in eventHandlers)
{
handle(eventEnvelope);
}
}
}