using System.Collections.Generic;
using Moq;
using NUnit.Framework;
using Robust.Shared.GameObjects;
using Robust.Shared.Reflection;
using Robust.UnitTesting.Server;

namespace Robust.UnitTesting.Shared.GameObjects
{
    internal sealed partial class EntityEventBusTests
    {
        [Test]
        public void SubscribeCompEvent()
        {
            var (bus, sim, entUid, compInstance) = EntFactory();
            var compFactory = sim.Resolve<IComponentFactory>();

            // Subscribe
            int calledCount = 0;
            bus.SubscribeLocalEvent<MetaDataComponent, TestEvent>(HandleTestEvent);
            bus.LockSubscriptions();

            // add a component to the system
            bus.OnEntityAdded(entUid);

            var reg = compFactory.GetRegistration(CompIdx.Index<MetaDataComponent>());
            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(compInstance, entUid), reg));

            // Raise
            var evntArgs = new TestEvent(5);
            bus.RaiseLocalEvent(entUid, evntArgs, true);

            // Assert
            Assert.That(calledCount, Is.EqualTo(1));
            void HandleTestEvent(EntityUid uid, MetaDataComponent component, TestEvent args)
            {
                calledCount++;
                Assert.That(uid, Is.EqualTo(entUid));
                Assert.That(component, Is.EqualTo(compInstance));
                Assert.That(args.TestNumber, Is.EqualTo(5));
            }

        }

        [Test]
        public void UnsubscribeCompEvent()
        {
            var (bus, sim, entUid, compInstance) = EntFactory();
            var compFactory = sim.Resolve<IComponentFactory>();

            // Subscribe
            int calledCount = 0;
            bus.SubscribeLocalEvent<MetaDataComponent, TestEvent>(HandleTestEvent);
            bus.UnsubscribeLocalEvent<MetaDataComponent, TestEvent>();
            bus.LockSubscriptions();

            // add a component to the system
            bus.OnEntityAdded(entUid);

            var reg = compFactory.GetRegistration(CompIdx.Index<MetaDataComponent>());
            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(compInstance, entUid), reg));

            // Raise
            var evntArgs = new TestEvent(5);
            bus.RaiseLocalEvent(entUid, evntArgs, true);

            // Assert
            Assert.That(calledCount, Is.EqualTo(0));
            void HandleTestEvent(EntityUid uid, MetaDataComponent component, TestEvent args)
            {
                calledCount++;
            }
        }

        [Test]
        public void SubscribeCompLifeEvent()
        {
            var (bus, sim, entUid, compInstance) = EntFactory();
            var entMan = sim.Resolve<EntityManager>();
            var fact = sim.Resolve<IComponentFactory>();

            // Subscribe
            int calledCount = 0;
            bus.SubscribeLocalEvent<MetaDataComponent, ComponentInit>(HandleTestEvent);
            bus.LockSubscriptions();

            // Raise
            bus.RaiseComponentEvent(entUid, compInstance, new ComponentInit());

            // Assert
            Assert.That(calledCount, Is.EqualTo(1));
            void HandleTestEvent(EntityUid uid, MetaDataComponent component, ComponentInit args)
            {
                calledCount++;
                Assert.That(uid, Is.EqualTo(entUid));
                Assert.That(component, Is.EqualTo(compInstance));
            }
        }

        [Test]
        public void CompEventOrdered()
        {
            var sim = RobustServerSimulation
                .NewSimulation()
                .RegisterComponents(f =>
                {
                    f.RegisterClass<OrderAComponent>();
                    f.RegisterClass<OrderBComponent>();
                    f.RegisterClass<OrderCComponent>();
                })
                .InitializeInstance();

            var entMan = sim.Resolve<EntityManager>();
            var entUid = entMan.Spawn();
            var instA = entMan.AddComponent<OrderAComponent>(entUid);
            var instB = entMan.AddComponent<OrderBComponent>(entUid);
            var instC = entMan.AddComponent<OrderCComponent>(entUid);
            var bus = entMan.EventBusInternal;
            bus.ClearSubscriptions();

            var fact = sim.Resolve<IComponentFactory>();

            // Subscribe
            var a = false;
            var b = false;
            var c = false;

            void HandlerA(EntityUid uid, Component comp, TestEvent ev)
            {
                Assert.That(b, Is.False, "A should run before B");
                Assert.That(c, Is.False, "A should run before C");

                a = true;
            }

            void HandlerB(EntityUid uid, Component comp, TestEvent ev)
            {
                Assert.That(c, Is.True, "B should run after C");
                b = true;
            }

            void HandlerC(EntityUid uid, Component comp, TestEvent ev) => c = true;

            bus.SubscribeLocalEvent<OrderAComponent, TestEvent>(HandlerA, typeof(OrderAComponent), before: new []{typeof(OrderBComponent), typeof(OrderCComponent)});
            bus.SubscribeLocalEvent<OrderBComponent, TestEvent>(HandlerB, typeof(OrderBComponent), after: new []{typeof(OrderCComponent)});
            bus.SubscribeLocalEvent<OrderCComponent, TestEvent>(HandlerC, typeof(OrderCComponent));
            bus.LockSubscriptions();

            // add a component to the system
            bus.OnEntityAdded(entUid);

            var regA = fact.GetRegistration(CompIdx.Index<OrderAComponent>());
            var regB = fact.GetRegistration(CompIdx.Index<OrderBComponent>());
            var regC = fact.GetRegistration(CompIdx.Index<OrderCComponent>());

            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instA, entUid), regA));
            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instB, entUid), regB));
            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instC, entUid), regC));

            // Raise
            var evntArgs = new TestEvent(5);
            bus.RaiseLocalEvent(entUid, evntArgs, true);

            // Assert
            Assert.That(a, Is.True, "A did not fire");
            Assert.That(b, Is.True, "B did not fire");
            Assert.That(c, Is.True, "C did not fire");
        }

        [Test]
        public void CompEventLoop()
        {
            var sim = RobustServerSimulation
                .NewSimulation()
                .RegisterComponents(f =>
                {
                    f.RegisterClass<OrderAComponent>();
                    f.RegisterClass<OrderBComponent>();
                })
                .InitializeInstance();

            var entMan = sim.Resolve<EntityManager>();
            var entUid = entMan.Spawn();
            var instA = entMan.AddComponent<OrderAComponent>(entUid);
            var instB = entMan.AddComponent<OrderBComponent>(entUid);
            var bus = entMan.EventBusInternal;
            bus.ClearSubscriptions();

            var fact = sim.Resolve<IComponentFactory>();
            var regA = fact.GetRegistration(CompIdx.Index<OrderAComponent>());
            var regB = fact.GetRegistration(CompIdx.Index<OrderBComponent>());

            var handlerACount = 0;
            void HandlerA(EntityUid uid, Component comp, TestEvent ev)
            {
                Assert.That(handlerACount, Is.EqualTo(0));
                handlerACount++;

                // add and then remove component B
                bus.OnComponentRemoved(new RemovedComponentEventArgs(new ComponentEventArgs(instB, entUid), false, default!, CompIdx.Index<OrderBComponent>()));
                bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instB, entUid), regB));
            }

            var handlerBCount = 0;
            void HandlerB(EntityUid uid, Component comp, TestEvent ev)
            {
                Assert.That(handlerBCount, Is.EqualTo(0));
                handlerBCount++;

                // add and then remove component A
                bus.OnComponentRemoved(new RemovedComponentEventArgs(new ComponentEventArgs(instA, entUid), false, default!, CompIdx.Index<OrderAComponent>()));
                bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instA, entUid), regA));
            }

            bus.SubscribeLocalEvent<OrderAComponent, TestEvent>(HandlerA, typeof(OrderAComponent));
            bus.SubscribeLocalEvent<OrderBComponent, TestEvent>(HandlerB, typeof(OrderBComponent));
            bus.LockSubscriptions();

            // add a component to the system
            bus.OnEntityAdded(entUid);

            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instA, entUid), regA));
            bus.OnComponentAdded(new AddedComponentEventArgs(new ComponentEventArgs(instB, entUid), regB));

            // Event subscriptions currently use a linked list.
            // Currently expect event subscriptions to be raised in order: handlerB -> handlerA
            // If a component gets removed and added again, it gets moved back to the front of the linked list.
            // I.e., adding and then removing compA changes the linked list order:  handlerA -> handlerB
            //
            // This could in principle cause the event raising code to  enter an infinite loop.
            // Adding and removing a comp in an event handler may seem silly but:
            // - it doesn't have to be the same component if you had a chain of three or more components
            // - some event handlers raise other events and can lead to convoluted chains of interactions that might inadvertently trigger something like this.

            // Raise
            bus.RaiseLocalEvent(entUid, new TestEvent(0));

            // Assert
            Assert.That(handlerACount, Is.LessThanOrEqualTo(1));
            Assert.That(handlerBCount, Is.LessThanOrEqualTo(1));
            Assert.That(handlerACount+handlerBCount, Is.GreaterThan(0));
        }

        private sealed partial class DummyComponent : Component
        {
        }

        private sealed partial class OrderAComponent : Component
        {
        }

        private sealed partial class OrderBComponent : Component
        {
        }

        private sealed partial class OrderCComponent : Component
        {
        }

        private sealed class TestEvent : EntityEventArgs
        {
            public int TestNumber { get; }

            public TestEvent(int testNumber)
            {
                TestNumber = testNumber;
            }
        }
    }
}