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using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using StardewModdingAPI.Events;
using StardewModdingAPI.Internal;
namespace StardewModdingAPI.Framework.Events
{
/// <summary>An event wrapper which intercepts and logs errors in handler code.</summary>
/// <typeparam name="TEventArgs">The event arguments type.</typeparam>
internal class ManagedEvent<TEventArgs> : IManagedEvent
{
/*********
** Fields
*********/
/// <summary>The mod registry with which to identify mods.</summary>
protected readonly ModRegistry ModRegistry;
/// <summary>The underlying event handlers.</summary>
private readonly List<ManagedEventHandler<TEventArgs>> Handlers = new();
/// <summary>A cached snapshot of <see cref="Handlers"/>, or <c>null</c> to rebuild it next raise.</summary>
private ManagedEventHandler<TEventArgs>[]? CachedHandlers = Array.Empty<ManagedEventHandler<TEventArgs>>();
/// <summary>The total number of event handlers registered for this events, regardless of whether they're still registered.</summary>
private int RegistrationIndex;
/// <summary>Whether new handlers were added since the last raise.</summary>
private bool HasNewHandlers;
/*********
** Accessors
*********/
/// <inheritdoc />
public string EventName { get; }
/// <inheritdoc />
public bool IsPerformanceCritical { get; }
/*********
** Public methods
*********/
/// <summary>Construct an instance.</summary>
/// <param name="eventName">A human-readable name for the event.</param>
/// <param name="modRegistry">The mod registry with which to identify mods.</param>
/// <param name="isPerformanceCritical">Whether the event is typically called at least once per second.</param>
public ManagedEvent(string eventName, ModRegistry modRegistry, bool isPerformanceCritical = false)
{
this.EventName = eventName;
this.ModRegistry = modRegistry;
this.IsPerformanceCritical = isPerformanceCritical;
}
/// <summary>Get whether anything is listening to the event.</summary>
public bool HasListeners()
{
return this.Handlers.Count > 0;
}
/// <summary>Add an event handler.</summary>
/// <param name="handler">The event handler.</param>
/// <param name="mod">The mod which added the event handler.</param>
public void Add(EventHandler<TEventArgs> handler, IModMetadata mod)
{
lock (this.Handlers)
{
EventPriority priority = handler.Method.GetCustomAttribute<EventPriorityAttribute>()?.Priority ?? EventPriority.Normal;
var managedHandler = new ManagedEventHandler<TEventArgs>(handler, this.RegistrationIndex++, priority, mod);
this.Handlers.Add(managedHandler);
this.CachedHandlers = null;
this.HasNewHandlers = true;
}
}
/// <summary>Remove an event handler.</summary>
/// <param name="handler">The event handler.</param>
public void Remove(EventHandler<TEventArgs> handler)
{
lock (this.Handlers)
{
// match C# events: if a handler is listed multiple times, remove the last one added
for (int i = this.Handlers.Count - 1; i >= 0; i--)
{
if (this.Handlers[i].Handler != handler)
continue;
this.Handlers.RemoveAt(i);
this.CachedHandlers = null;
break;
}
}
}
/// <summary>Raise the event and notify all handlers.</summary>
/// <param name="args">The event arguments to pass.</param>
/// <param name="match">A lambda which returns true if the event should be raised for the given mod.</param>
public void Raise(TEventArgs args, Func<IModMetadata, bool>? match = null)
{
this.Raise((_, invoke) => invoke(args), match);
}
/// <summary>Raise the event and notify all handlers.</summary>
/// <param name="invoke">Invoke an event handler. This receives the mod which registered the handler, and should invoke the callback with the event arguments to pass it.</param>
/// <param name="match">A lambda which returns true if the event should be raised for the given mod.</param>
public void Raise(Action<IModMetadata, Action<TEventArgs>> invoke, Func<IModMetadata, bool>? match = null)
{
// skip if no handlers
if (this.Handlers.Count == 0)
return;
// update cached data
// (This is debounced here to avoid repeatedly sorting when handlers are added/removed,
// and keeping a separate cached list allows changes during enumeration.)
var handlers = this.CachedHandlers; // iterate local copy in case a mod adds/removes a handler while handling the event, which will set this field to null
if (handlers == null)
{
lock (this.Handlers)
{
if (this.HasNewHandlers && this.Handlers.Any(p => p.Priority != EventPriority.Normal))
this.Handlers.Sort();
this.CachedHandlers = handlers = this.Handlers.ToArray();
this.HasNewHandlers = false;
}
}
// raise event
foreach (ManagedEventHandler<TEventArgs> handler in handlers)
{
if (match != null && !match(handler.SourceMod))
continue;
try
{
invoke(handler.SourceMod, args => handler.Handler.Invoke(null, args));
}
catch (Exception ex)
{
this.LogError(handler, ex);
}
}
}
/*********
** Private methods
*********/
/// <summary>Log an exception from an event handler.</summary>
/// <param name="handler">The event handler instance.</param>
/// <param name="ex">The exception that was raised.</param>
protected void LogError(ManagedEventHandler<TEventArgs> handler, Exception ex)
{
handler.SourceMod.LogAsMod($"This mod failed in the {this.EventName} event. Technical details: \n{ex.GetLogSummary()}", LogLevel.Error);
}
}
}
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