//
// CommandProcessor.cs
//
// Copyright (c) František Boháček. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
using System;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;
using NosSmooth.Core.Errors;
using Remora.Results;
namespace NosSmooth.Core.Commands;
///
/// Calls for the executing command
/// by using dependency injection.
///
public class CommandProcessor
{
private readonly IServiceProvider _provider;
///
/// Initializes a new instance of the class.
///
/// The dependency injection provider.
public CommandProcessor(IServiceProvider provider)
{
_provider = provider;
}
///
/// Processes the given command, calling its handler or returning error.
///
/// The command to process.
/// The cancellation token for cancelling the operation.
/// A result that may or may not have succeeded.
/// Thrown on critical error.
public Task ProcessCommand(ICommand command, CancellationToken ct = default)
{
var processMethod = GetType().GetMethod
(
nameof(DispatchCommandHandler),
BindingFlags.NonPublic | BindingFlags.Instance
);
if (processMethod is null)
{
throw new InvalidOperationException("Could not find process command generic method in command processor.");
}
var boundProcessMethod = processMethod.MakeGenericMethod(command.GetType());
return (Task)boundProcessMethod.Invoke(this, new object[] { command, ct })!;
}
private Task DispatchCommandHandler(TCommand command, CancellationToken ct = default)
where TCommand : class, ICommand
{
using var scope = _provider.CreateScope();
var commandHandler = scope.ServiceProvider.GetService>();
if (commandHandler is null)
{
return Task.FromResult(Result.FromError(new CommandHandlerNotFound(command.GetType())));
}
return commandHandler.HandleCommand(command, ct);
}
}