private async Task <ICommandResult> ExecuteAsyncInternal(ICommandContext context, CancellationToken cancellationToken = default)
{
if (!this._started)
{
throw new InvalidOperationException($"This {this.GetType().Name} is not started yet");
}
using (CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, this._cts.Token))
{
IEnumerable <KeyValuePair <ICommandInstanceDescriptor, ICommandInstance> > commandsCopy;
// copying might not be the fastest thing to do, but it'll ensure that commands won't be changed out of the lock
// locking only copying to prevent hangs if user is not careful with their commands, while still preventing race conditions with StartAsync
await this._lock.WaitAsync(cts.Token).ConfigureAwait(false);
try
{
// order commands by priority
// try to get from concrete Descriptor if possible, as it should be precached and avoid additional reflection and thus faster
commandsCopy = this._commands.OrderByDescending(kvp => (kvp.Key is CommandInstanceDescriptor cid) ? cid.Priority : kvp.Key.GetPriority());
}
finally
{
this._lock.Release();
}
using (IServiceScope serviceScope = this._services.CreateScope())
{
// Because scope won't have fallback services, and commands might need them, combine scope with fallback services
// TODO: think of a nicer way to solve fallback services problem - I don't like it as it is now
IServiceProvider services = serviceScope.ServiceProvider;
if (!object.ReferenceEquals(services, this._fallbackServices))
{
services = CombinedServiceProvider.Combine(serviceScope.ServiceProvider, this._fallbackServices);
}
foreach (KeyValuePair <ICommandInstanceDescriptor, ICommandInstance> commandKvp in commandsCopy)
{
ICommandInstanceDescriptor command = commandKvp.Key;
ICommandInstance instance = commandKvp.Value;
using (this._log.BeginCommandScope(context, command.GetHandlerType().Name, command.Method.Name))
{
ICommandsHandlerProviderResult handlerResult = null;
try
{
cts.Token.ThrowIfCancellationRequested();
// check if the command should run at all - if not, skip
ICommandResult matchResult = await instance.CheckMatchAsync(context, services, cts.Token).ConfigureAwait(false);
if (!matchResult.IsSuccess)
{
continue;
}
// initialize handler
this._log?.LogTrace("Initializing handler handler {Handler} for command {Name}", command.GetHandlerType().Name, command.Method.Name);
handlerResult = this._handlerProvider.GetCommandHandler(command, services);
if (handlerResult?.HandlerInstance == null)
{
this._log?.LogError("Retrieving handler {Handler} for command {Name} has failed, command execution aborting", command.GetHandlerType().Name, command.Method.Name);
return(CommandExecutionResult.FromException(new ArgumentNullException(nameof(ICommandsHandlerProviderResult.HandlerInstance),
$"Retrieving handler {command.GetHandlerType().Name} for command {command.Method.Name} has failed, command execution aborting")));
}
this._log?.LogTrace("Executing command {Name} from handler {Handler}", command.Method.Name, command.GetHandlerType().Name);
// execute the command
ICommandResult executeResult = await instance.ExecuteAsync(context, services, matchResult, handlerResult.HandlerInstance, cts.Token).ConfigureAwait(false);
if (executeResult.Exception != null)
{
this._log?.LogError(executeResult.Exception, "Exception when executing command {Name} from handler {Handler}", command.Method.Name, command.GetHandlerType().Name);
return(executeResult);
}
if (executeResult is IMessagesCommandResult messagesResult && messagesResult.Messages?.Any() == true)
{
this._log?.LogTrace("Sending command results messages as a command response");
await context.ReplyTextAsync(string.Join("\n", messagesResult.Messages), cts.Token).ConfigureAwait(false);
}
return(executeResult);
}
// special error case: operation canceled
// operation canceled is normal, so it shouldn't be logged as error
catch (OperationCanceledException ex)
{
this._log?.LogWarning("Execution of command {Name} from handler {Handler} was cancelled", command.Method.Name, command.GetHandlerType().Name);
return(CommandExecutionResult.FromException(ex));
}
// special error case: responding when silenced
// bots almost always respond to a command - but if they're silenced, an exception will be thrown
// this is normal - so it shouldn't be logged as error. Warning max
catch (MessageSendingException ex) when
(this.LogSilencedException(ex, context, "Unhandled Exception when executing command {Name} from handler {Handler} - likely due to being silenced or spam filtered", command.Method.Name, command.GetHandlerType().Name))
{
return(CommandExecutionResult.FromException(ex));
}
// normal error case
catch (Exception ex) when(ex.LogAsError(_log, "Unhandled Exception when executing command {Name} from handler {Handler}", command.Method.Name, command.GetHandlerType().Name))
{
return(CommandExecutionResult.FromException(ex));
}
finally
{
// if handler is allocated, not persistent and disposable, let's dispose it
if (handlerResult?.Descriptor?.Attribute?.IsPersistent != true && handlerResult?.HandlerInstance is IDisposable disposableHandler)
{
try { disposableHandler?.Dispose(); } catch { }
}
}
}
}
}
return(CommandExecutionResult.Failure);
}
}
/// <summary>Gets command's pre-execute checks.</summary> /// <param name="descriptor">Command descriptor.</param> /// <returns>Enumerable on all pre-execute checks on the command's method and handler type.</returns> public static IEnumerable <CommandRequirementAttribute> GetRequirements(this ICommandInstanceDescriptor descriptor) => descriptor.Method.GetCustomAttributes <CommandRequirementAttribute>(true) .Union(descriptor.GetHandlerType().GetCustomAttributes <CommandRequirementAttribute>(true));
/// <summary>Checks if the command is overriding default case sensitivity.</summary> /// <remarks>See <see cref="CaseSensitivityAttribute"/> for more information about command case senstivity.</remarks> /// <returns>True/false if command is overriding case sensitivity - true to be case sensitive, false to be case insensitive; null if not overriding.</returns> public static bool?GetCaseSensitivityOverride(this ICommandInstanceDescriptor descriptor) => descriptor.Method.GetCustomAttribute <CaseSensitivityAttribute>(true)?.CaseSensitive ?? descriptor.GetHandlerType().GetCustomAttribute <CaseSensitivityAttribute>(true)?.CaseSensitive;
/// <summary>Gets command's prefix requirement override.</summary> /// <param name="descriptor">Command descriptor.</param> /// <returns>Prefix requirement value.</returns> public static PrefixRequirement?GetPrefixRequirementOverride(this ICommandInstanceDescriptor descriptor) => descriptor.Method.GetCustomAttribute <PrefixAttribute>(true)?.PrefixRequirementOverride ?? descriptor.GetHandlerType().GetCustomAttribute <PrefixAttribute>(true)?.PrefixRequirementOverride;
/// <inheritdoc/>
public ICommandsHandlerProviderResult GetCommandHandler(ICommandInstanceDescriptor descriptor, IServiceProvider services)
{
Type handlerType = descriptor.GetHandlerType();
CommandHandlerDescriptor handlerDescriptor = null;
lock (_lock)
{
// check if persistent
if (_persistentHandlers.TryGetValue(handlerType, out CommandsHandlerProviderResult handler))
{
return(handler);
}
// keep resolved services to avoid recreating them in case of multiple constructors
IDictionary <Type, object> resolvedServices = new Dictionary <Type, object>();
// if no persistent handler was found, we need to create a new one - check if constructor is known yet
if (!_knownConstructors.TryGetValue(handlerType, out ConstructorInfo handlerConstructor))
{
// if descriptor not cached, create new one
// start with grabbing all constructors
IEnumerable <ConstructorInfo> allConstructors = handlerType
.GetConstructors(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
// check if any of the constructors are specifically designated to be used by Commands System
IEnumerable <ConstructorInfo> selectedConstructors = allConstructors
.Select(ctor => (constructor: ctor, attribute: ctor.GetCustomAttribute <CommandsHandlerConstructorAttribute>(false)))
.Where(ctor => ctor.attribute != null)
.OrderByDescending(ctor => ctor.attribute.Priority)
.ThenByDescending(ctor => ctor.constructor.GetParameters().Length)
.Select(ctor => ctor.constructor);
// if no explicitly-attributed constructor found, grab all that are public
if (!selectedConstructors.Any())
{
selectedConstructors = allConstructors
.Where(ctor => ctor.IsPublic)
.OrderByDescending(ctor => ctor.GetParameters().Length);
}
// try to resolve dependencies for each constructor. First one that can be resolved wins
foreach (ConstructorInfo ctor in selectedConstructors)
{
if (TryCreateHandlerDescriptor(ctor, services, out handlerDescriptor, ref resolvedServices))
{
// cache found descriptor
_knownConstructors.Add(handlerType, ctor);
handlerConstructor = ctor;
break;
}
}
// throw if we didn't find any constructor we can resolve
if (handlerDescriptor == null)
{
throw new InvalidOperationException($"Cannot create descriptor for type {handlerType.FullName} - none of the constructors can have its dependencies resolved");
}
}
// if constructor is already known, just create a descriptor
else
{
TryCreateHandlerDescriptor(handlerConstructor, services, out handlerDescriptor, ref resolvedServices);
}
// now that we have a descriptor, let's create an instance
handler = new CommandsHandlerProviderResult(handlerDescriptor, handlerDescriptor.CreateInstance());
// if it's a persistent instance, store it
if (handlerDescriptor.IsPersistent())
{
_persistentHandlers.Add(handlerType, handler);
}
// finally, return the fresh handler
return(handler);
}
}