using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using Microsoft.AspNet.CoreServices;
using Microsoft.Owin;

namespace Microsoft.AspNet.Mvc
{
    public class ControllerActionInvoker : IActionInvoker
    {
        private readonly RequestContext _requestContext;
        private readonly ControllerBasedActionDescriptor _descriptor;
        private readonly IActionResultFactory _actionResultFactory;
        private readonly IServiceProvider _serviceProvider;

        public ControllerActionInvoker(RequestContext requestContext,
                                       ControllerBasedActionDescriptor descriptor, 
                                       IActionResultFactory actionResultFactory, 
                                       IServiceProvider serviceProvider)
        {
            _requestContext = requestContext;
            _descriptor = descriptor;
            _actionResultFactory = actionResultFactory;
            _serviceProvider = serviceProvider;
        }

        public Task InvokeActionAsync()
        {
            var factory = _serviceProvider.GetService<IControllerFactory>();
            object controller = factory.CreateController(_requestContext.HttpContext, _descriptor.ControllerName);

            if (controller == null)
            {
                throw new InvalidOperationException(String.Format("Couldn't find controller '{0}'.", _descriptor.ControllerName));
            }

            Initialize(controller);

            var method = controller.GetType().GetMethod(_descriptor.ActionName, BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase);

            if (method == null)
            {
                throw new InvalidOperationException(String.Format("Could not find action method '{0}'", _descriptor.ActionName));
            }

            object actionReturnValue = method.Invoke(controller, null);

            // If it's not already an IActionResult then call into the factory
            var actionResult = actionReturnValue as IActionResult ?? _actionResultFactory.CreateActionResult(actionReturnValue);

            return actionResult.ExecuteResultAsync(_requestContext);
        }

        private void Initialize(object controller)
        {
            var controllerType = controller.GetType();

            foreach (var prop in controllerType.GetProperties())
            {
                if (prop.Name == "Context")
                {
                    if (prop.PropertyType == typeof(IOwinContext))
                    {
                        prop.SetValue(controller, _requestContext.HttpContext);
                    }
                    else if (prop.PropertyType == typeof(IDictionary<string, object>))
                    {
                        prop.SetValue(controller, _requestContext.HttpContext.Environment);
                    }
                }
            }

            var method = controllerType.GetMethod("Initialize");

            if (method == null)
            {
                return;
            }

            var args = method.GetParameters()
                             .Select(p => _serviceProvider.GetService(p.ParameterType)).ToArray();

            method.Invoke(controller, args);
        }
    }
}