// Copyright Epic Games, Inc. All Rights Reserved.

#include "EventLoop/EventLoop.h"
#include "Templates/SharedPointer.h"

#include "TestHarness.h"

namespace UE::EventLoop
{
	struct FMockTimerHandleTraits
	{
		static constexpr const TCHAR* Name = TEXT("MockTimerHandle");
	};

	struct FEventLoopMockTraits
	{
		static FORCEINLINE uint32 GetCurrentThreadId()
		{
			return CurrentThreadId;
		}

		static FORCEINLINE FTimespan GetCurrentTime()
		{
			return CurrentTime;
		}

		static FORCEINLINE bool IsEventLoopThread(uint32 EventLoopThreadId)
		{
			return EventLoopThreadId == GetCurrentThreadId();
		}

		static FORCEINLINE bool IsInitialized(uint32 EventLoopThreadId)
		{
			return (EventLoopThreadId != 0);
		}

		static FORCEINLINE void CheckInitialized(uint32 EventLoopThreadId)
		{
			bCheckInitializedTriggered = (EventLoopThreadId == 0);
		}

		static FORCEINLINE void CheckNotInitialized(uint32 EventLoopThreadId)
		{
			bCheckNotInitializedTriggered = (EventLoopThreadId != 0);
		}

		static FORCEINLINE void CheckIsEventLoopThread(uint32 EventLoopThreadId)
		{
			bCheckIsEventLoopThreadTriggered = !IsEventLoopThread(EventLoopThreadId);
		}

		static FORCEINLINE bool IsShutdownRequested(bool bInShutdownRequested)
		{
			return bShutdownRequested || bInShutdownRequested;
		}

		struct FTimerManagerTraits : public FTimerManagerTraitsBase
		{
			static void CheckIsManagerThread(bool bIsManagerThread)
			{
				bCheckIsManagerThreadTriggered = !bIsManagerThread;
			}

			using FTimerHeapAllocatorType = TInlineAllocator<32>;
			using FTimerRepeatAllocatorType = TInlineAllocator<32>;

			struct FStorageTraits
			{
				static uint32 GetCurrentThreadId()
				{
					return CurrentThreadId;
				}

				static bool IsManagerThread(uint32 ManagerThreadId)
				{
					return ManagerThreadId == GetCurrentThreadId();
				}

				static void CheckNotInitialized(uint32 ManagerThreadId)
				{
					bCheckNotInitializedTriggered = (ManagerThreadId != 0);
				}

				static void CheckIsManagerThread(uint32 ManagerThreadId)
				{
					bCheckIsManagerThreadTriggered = !IsManagerThread(ManagerThreadId);
				}

				static constexpr bool bStorageAccessThreadChecksEnabled = true;
				using InternalHandleArryAllocatorType = TInlineAllocator<32>;
				using FExternalHandle = FTimerHandle;

				static void ResetTestConditions()
				{
					CurrentThreadId = 1;
					bCheckNotInitializedTriggered = false;
					bCheckIsManagerThreadTriggered = false;
				}

				static uint32 CurrentThreadId;
				static bool bCheckNotInitializedTriggered;
				static bool bCheckIsManagerThreadTriggered;
			};

			static void ResetTestConditions()
			{
				FStorageTraits::ResetTestConditions();
				bCheckIsManagerThreadTriggered = false;
			}

			static bool bCheckIsManagerThreadTriggered;
		};

		static void ResetTestConditions()
		{
			FTimerManagerTraits::ResetTestConditions();
			CurrentThreadId = 1;
			CurrentTime = FTimespan::Zero();
			bCheckInitializedTriggered = false;
			bCheckNotInitializedTriggered = false;
			bCheckIsEventLoopThreadTriggered = false;
			bShutdownRequested = false;
		}

		static uint32 CurrentThreadId;
		static FTimespan CurrentTime;
		static bool bCheckInitializedTriggered;
		static bool bCheckNotInitializedTriggered;
		static bool bCheckIsEventLoopThreadTriggered;
		static bool bShutdownRequested;
	};

	uint32 FEventLoopMockTraits::CurrentThreadId = 1;
	FTimespan FEventLoopMockTraits::CurrentTime = FTimespan::Zero();
	bool FEventLoopMockTraits::bCheckInitializedTriggered = false;
	bool FEventLoopMockTraits::bCheckNotInitializedTriggered = false;
	bool FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered = false;
	bool FEventLoopMockTraits::bShutdownRequested = false;
	bool FEventLoopMockTraits::FTimerManagerTraits::bCheckIsManagerThreadTriggered = false;
	uint32 FEventLoopMockTraits::FTimerManagerTraits::FStorageTraits::CurrentThreadId = 1;
	bool FEventLoopMockTraits::FTimerManagerTraits::FStorageTraits::bCheckNotInitializedTriggered = false;
	bool FEventLoopMockTraits::FTimerManagerTraits::FStorageTraits::bCheckIsManagerThreadTriggered = false;

	class FIOAccessMock final : public FNoncopyable
	{
	public:
		// Nothing needed for now.
	};

	class FIOManagerMock final : public IIOManager
	{
	public:
		using FIOAccess = FIOAccessMock;

		struct FParams
		{
		};

		FIOManagerMock(IEventLoop&, FParams&&)
		{
		}

		virtual ~FIOManagerMock() = default;

		virtual bool Init() override
		{
			bHasInitialized = true;
			return bInitReturnValue;
		}

		virtual void Shutdown() override
		{
			bHasShutdown = true;
		}

		virtual void Notify() override
		{
			bHasNotified = true;
		}

		virtual void Poll(FTimespan WaitTime) override
		{
			CHECK(bHasNotified == bExpectedNotify);
			CHECK(WaitTime == ExpectedWaitTime);
		}

		FIOAccess& GetIOAccess()
		{
			return IOAccess;
		}

		static void ResetTestConditions()
		{
			bHasInitialized = false;
			bInitReturnValue = true;
			bHasNotified = false;
			bExpectedNotify = false;
			bHasShutdown = false;
			ExpectedWaitTime = FTimespan::Zero();
		}

		static bool bHasInitialized;
		static bool bInitReturnValue;
		static bool bHasNotified;
		static bool bExpectedNotify;
		static bool bHasShutdown;
		static FTimespan ExpectedWaitTime;

		FIOAccess IOAccess;
	};

	bool FIOManagerMock::bHasInitialized = false;
	bool FIOManagerMock::bInitReturnValue = true;
	bool FIOManagerMock::bHasNotified = false;
	bool FIOManagerMock::bExpectedNotify = false;
	bool FIOManagerMock::bHasShutdown = false;
	FTimespan FIOManagerMock::ExpectedWaitTime = FTimespan::Zero();

	TEST_CASE("EventLoop", "[Online][EventLoop][Smoke]")
	{
		TEventLoop<FIOManagerMock, FEventLoopMockTraits> EventLoop;
		FIOManagerMock::ResetTestConditions();
		FEventLoopMockTraits::ResetTestConditions();

		const FTimespan InfiniteWait(std::numeric_limits<int64>::max());
		const uint32 EventLoopThreadId = 1;
		FEventLoopMockTraits::CurrentThreadId = EventLoopThreadId;
		FEventLoopMockTraits::FTimerManagerTraits::FStorageTraits::CurrentThreadId = EventLoopThreadId;

		SECTION("Single init call")
		{
			EventLoop.Init();
			CHECK(!FEventLoopMockTraits::bCheckNotInitializedTriggered);
		}

		SECTION("Double init call")
		{
			EventLoop.Init();
			EventLoop.Init();
			CHECK(FEventLoopMockTraits::bCheckNotInitializedTriggered);
		}

		SECTION("Call Run before Init")
		{
			FEventLoopMockTraits::bShutdownRequested = true;
			FIOManagerMock::ExpectedWaitTime = InfiniteWait;

			EventLoop.Run();
			CHECK(FEventLoopMockTraits::bCheckInitializedTriggered);
		}

		SECTION("Call RunOnce before Init")
		{
			FEventLoopMockTraits::bShutdownRequested = true;

			EventLoop.RunOnce(FTimespan::Zero());
			CHECK(FEventLoopMockTraits::bCheckInitializedTriggered);
		}

		SECTION("Call RequestShutdown before Init")
		{
			EventLoop.RequestShutdown();

			// Request shutdown is allowed to be called before init.
			CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);

			// Check that loop is shutdown when run after calling init.
			CHECK(EventLoop.Init());

			FIOManagerMock::bExpectedNotify = true;
			FIOManagerMock::ExpectedWaitTime = InfiniteWait;
			CHECK(!EventLoop.RunOnce(InfiniteWait));
		}

		SECTION("Call SetTimer before Init")
		{
			bool bTimerRan = false;
			FTimerHandle Handle = EventLoop.SetTimer([&bTimerRan](){ bTimerRan = true; }, FTimespan::FromSeconds(1));
			CHECK(Handle.IsValid());

			// Request shutdown is allowed to be called before init.
			CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);

			// Check that timer is run when run after calling init.
			CHECK(EventLoop.Init());

			// The first run schedules the timer. It will not wait because it has been interrupted.
			FIOManagerMock::bExpectedNotify = true;
			FIOManagerMock::ExpectedWaitTime = InfiniteWait;
			CHECK(EventLoop.RunOnce(InfiniteWait));

			// The second run will run until the timer duration and fire the timer.
			FIOManagerMock::bHasNotified = false;
			FIOManagerMock::bExpectedNotify = false;
			FIOManagerMock::ExpectedWaitTime = FTimespan::FromSeconds(1);
			FEventLoopMockTraits::CurrentTime = FTimespan::FromSeconds(1);
			CHECK(EventLoop.RunOnce(InfiniteWait));
			CHECK(bTimerRan);
		}

		SECTION("Call ClearTimer before Init")
		{
			bool bTimerRan = false;
			FTimerHandle Handle = EventLoop.SetTimer([&bTimerRan](){ bTimerRan = true; }, FTimespan::FromSeconds(1));
			CHECK(Handle.IsValid());

			EventLoop.ClearTimer(Handle);

			// Request shutdown is allowed to be called before init.
			CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);

			// Check that timer is not run when run after calling init.
			CHECK(EventLoop.Init());

			// The first run schedules the timer. It will not wait because it has been interrupted.
			FIOManagerMock::bExpectedNotify = true;
			FIOManagerMock::ExpectedWaitTime = InfiniteWait;
			CHECK(EventLoop.RunOnce(InfiniteWait));

			// The second run would have fired the timer, but it is no longer expected to be present.
			FIOManagerMock::bHasNotified = false;
			FIOManagerMock::bExpectedNotify = false;
			FIOManagerMock::ExpectedWaitTime = InfiniteWait;
			FEventLoopMockTraits::CurrentTime = FTimespan::FromSeconds(1);
			CHECK(EventLoop.RunOnce(InfiniteWait));
			CHECK(!bTimerRan);
		}

		SECTION("Call PostAsyncTask before Init")
		{
			bool bTaskTriggered = false;
			EventLoop.PostAsyncTask([&bTaskTriggered](){ bTaskTriggered = true; });

			// PostAsyncTask is allowed to be called before init.
			CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);

			// Check that task is run when run after calling init.
			CHECK(EventLoop.Init());

			// Loop is expected to have been interrupted due to scheduling a task.
			FIOManagerMock::bExpectedNotify = true;
			FIOManagerMock::ExpectedWaitTime = InfiniteWait;
			CHECK(EventLoop.RunOnce(InfiniteWait));
			CHECK(bTaskTriggered);
		}

		SECTION("Initialized")
		{
			EventLoop.Init();

			SECTION("Call Run")
			{
				FEventLoopMockTraits::bShutdownRequested = true;
				FIOManagerMock::ExpectedWaitTime = InfiniteWait;

				EventLoop.Run();

				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
			}

			SECTION("Call RunOnce - no shutdown")
			{
				FIOManagerMock::ExpectedWaitTime = FTimespan::FromSeconds(1);

				bool bContinueRunning = EventLoop.RunOnce(FIOManagerMock::ExpectedWaitTime);
				CHECK(bContinueRunning == true);

				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
			}

			SECTION("Call RunOnce - shutdown")
			{
				FEventLoopMockTraits::bShutdownRequested = true;
				FIOManagerMock::ExpectedWaitTime = FTimespan::FromSeconds(1);

				bool bContinueRunning = EventLoop.RunOnce(FIOManagerMock::ExpectedWaitTime);
				CHECK(bContinueRunning == false);

				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
			}

			SECTION("Call SetTimer")
			{
				bool bTimerRan = false;
				FIOManagerMock::ExpectedWaitTime = InfiniteWait;
				FIOManagerMock::bExpectedNotify = true;

				EventLoop.SetTimer([&](){ bTimerRan = true; }, FTimespan::FromSeconds(1));
				EventLoop.RunOnce(InfiniteWait);
				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
				CHECK(!bTimerRan);

				FIOManagerMock::ExpectedWaitTime = FTimespan::FromSeconds(1);
				FEventLoopMockTraits::CurrentTime = FTimespan::FromSeconds(1);
				FIOManagerMock::bHasNotified = false;
				FIOManagerMock::bExpectedNotify = false;
				EventLoop.RunOnce(InfiniteWait);
				CHECK(bTimerRan);

				bTimerRan = false;
				FIOManagerMock::ExpectedWaitTime = InfiniteWait;
				FEventLoopMockTraits::CurrentTime = FTimespan::FromSeconds(2);
				FIOManagerMock::bExpectedNotify = false;
				EventLoop.RunOnce(InfiniteWait);
				CHECK(!bTimerRan);
			}

			SECTION("Call SetTimer - repeating")
			{
				bool bTimerRan = false;
				FIOManagerMock::ExpectedWaitTime = InfiniteWait;
				FIOManagerMock::bExpectedNotify = true;
				EventLoop.SetTimer([&](){ bTimerRan = true; }, FTimespan::FromSeconds(1), true);
				EventLoop.RunOnce(InfiniteWait);
				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
				CHECK(!bTimerRan);

				FIOManagerMock::ExpectedWaitTime = FTimespan::FromSeconds(1);
				FEventLoopMockTraits::CurrentTime = FTimespan::FromSeconds(1);
				FIOManagerMock::bHasNotified = false;
				FIOManagerMock::bExpectedNotify = false;
				EventLoop.RunOnce(InfiniteWait);
				CHECK(bTimerRan);

				bTimerRan = false;
				FIOManagerMock::ExpectedWaitTime = FTimespan::FromSeconds(1);
				FEventLoopMockTraits::CurrentTime = FTimespan::FromSeconds(2);
				FIOManagerMock::bExpectedNotify = false;
				EventLoop.RunOnce(InfiniteWait);
				CHECK(bTimerRan);
			}

			SECTION("Call ClearTimer")
			{
				FIOManagerMock::ExpectedWaitTime = InfiniteWait;
				FIOManagerMock::bExpectedNotify = true;

				FTimerHandle Handle;
				EventLoop.ClearTimer(Handle);
				EventLoop.RunOnce(FIOManagerMock::ExpectedWaitTime);

				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
			}

			SECTION("Call PostAsyncTask")
			{
				FIOManagerMock::ExpectedWaitTime = InfiniteWait;
				FIOManagerMock::bExpectedNotify = true;

				bool bTaskRan = false;
				EventLoop.PostAsyncTask([&bTaskRan](){ bTaskRan = true; });
				EventLoop.RunOnce(FIOManagerMock::ExpectedWaitTime);

				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
				CHECK(bTaskRan);
			}

			SECTION("Call RequestShutdown")
			{
				bool bContinueRunning = false;

				FIOManagerMock::ExpectedWaitTime = InfiniteWait;
				FIOManagerMock::bExpectedNotify = true;

				bool bShutdownCompleted = false;
				EventLoop.RequestShutdown([&bShutdownCompleted](){ bShutdownCompleted = true; });
				bContinueRunning = EventLoop.RunOnce(InfiniteWait);

				CHECK(!FEventLoopMockTraits::bCheckInitializedTriggered);
				CHECK(!FEventLoopMockTraits::bCheckIsEventLoopThreadTriggered);
				CHECK(bShutdownCompleted);
				CHECK(!bContinueRunning);

				// Request again after requested.
				bShutdownCompleted = false;
				EventLoop.RequestShutdown([&bShutdownCompleted](){ bShutdownCompleted = true; });
				CHECK(bShutdownCompleted);
				CHECK(!bContinueRunning);

				EventLoop.RunOnce(InfiniteWait);
			}
		}
	}
} // UE::EventLoop