#include <mutex>
#include <atomic>
#include <thread>

#include "Common/System/NativeApp.h"
#include "Common/System/System.h"
#include "Common/System/Request.h"
#include "Common/Data/Text/I18n.h"
#include "Common/Input/InputState.h"
#include "Common/Data/Encoding/Utf8.h"
#include "Common/Log.h"
#include "Common/StringUtils.h"
#include "Common/GraphicsContext.h"
#include "Common/Thread/ThreadUtil.h"

#include "Windows/EmuThread.h"
#include "Windows/W32Util/Misc.h"
#include "Windows/MainWindow.h"
#include "Core/Reporting.h"
#include "Core/Core.h"
#include "Core/System.h"
#include "Core/Config.h"
#include "Core/ConfigValues.h"

#if PPSSPP_API(ANY_GL)
#include "Windows/GPU/WindowsGLContext.h"
#endif
#include "Windows/GPU/WindowsVulkanContext.h"
#include "Windows/GPU/D3D11Context.h"

enum class EmuThreadState {
	DISABLED,
	START_REQUESTED,
	RUNNING,
	QUIT_REQUESTED,
	STOPPED,
};

static std::thread emuThread;
static std::atomic<EmuThreadState> g_emuThreadState(EmuThreadState::DISABLED);

static std::thread mainThread;
static std::string g_error_message;
static bool g_inLoop;

class GraphicsContext;
static GraphicsContext *g_graphicsContext;

void MainThreadFunc();

void MainThread_Start() {
	mainThread = std::thread([]() {
		MainThreadFunc();
	});
}

void MainThread_Stop() {
	// Already stopped?
	UpdateUIState(UISTATE_EXIT);
	_dbg_assert_(mainThread.joinable());
	mainThread.join();
}

bool MainThread_Ready() {
	if (g_inLoop) {
		_dbg_assert_(mainThread.joinable());
	}
	return g_inLoop;
}

static void EmuThreadFunc(GraphicsContext *graphicsContext) {
	SetCurrentThreadName("EmuThread");

	// There's no real requirement that NativeInit happen on this thread.
	// We just call the update/render loop here.
	g_emuThreadState = EmuThreadState::RUNNING;

	NativeInitGraphics(graphicsContext);

	while (g_emuThreadState != EmuThreadState::QUIT_REQUESTED) {
		// We're here again, so the game quit.  Restart Run() which controls the UI.
		// This way they can load a new game.
		if (!Core_IsActive()) {
			UpdateUIState(UISTATE_MENU);
		}

		Core_StateProcessed();
		NativeFrame(graphicsContext);

		if (GetUIState() == UISTATE_EXIT) {
			g_emuThreadState = EmuThreadState::QUIT_REQUESTED;
		}
	}

	g_emuThreadState = EmuThreadState::STOPPED;

	NativeShutdownGraphics();
}

static void EmuThreadStart(GraphicsContext *graphicsContext) {
	g_emuThreadState = EmuThreadState::START_REQUESTED;
	emuThread = std::thread(&EmuThreadFunc, graphicsContext);
}

static void EmuThreadStop() {
	const EmuThreadState state = g_emuThreadState;
	if (state != EmuThreadState::QUIT_REQUESTED &&
		state != EmuThreadState::STOPPED) {
		g_emuThreadState = EmuThreadState::QUIT_REQUESTED;
	}
}

static void EmuThreadJoin() {
	emuThread.join();
	INFO_LOG(Log::System, "EmuThreadJoin - joined");
}

bool CreateGraphicsBackend(std::string *error_message, GraphicsContext **ctx) {
	WindowsGraphicsContext *graphicsContext = nullptr;
	switch (g_Config.iGPUBackend) {
#if PPSSPP_API(ANY_GL)
	case (int)GPUBackend::OPENGL:
		graphicsContext = new WindowsGLContext();
		break;
#endif
	case (int)GPUBackend::DIRECT3D11:
		graphicsContext = new D3D11Context();
		break;
	case (int)GPUBackend::VULKAN:
		graphicsContext = new WindowsVulkanContext();
		break;
	default:
		return false;
	}

	if (graphicsContext->Init(MainWindow::GetHInstance(), MainWindow::GetHWND(), error_message)) {
		*ctx = graphicsContext;
		return true;
	} else {
		delete graphicsContext;
		*ctx = nullptr;
		return false;
	}
}

void MainThreadFunc() {
	const bool useEmuThread = g_Config.iGPUBackend == (int)GPUBackend::OPENGL;

	SetCurrentThreadName(useEmuThread ? "RenderThread" : "EmuThread");

	System_SetWindowTitle("");

	const bool performingRestart = NativeIsRestarting();

	if (g_Config.sFailedGPUBackends.find("ALL") != std::string::npos) {
		Reporting::ReportMessage("Graphics init error: %s", "ALL");

		auto err = GetI18NCategory(I18NCat::ERRORS);
		const char *defaultErrorAll = "PPSSPP failed to startup with any graphics backend. Try upgrading your graphics and other drivers.";
		std::string_view genericError = err->T("GenericAllStartupError", defaultErrorAll);
		std::wstring title = ConvertUTF8ToWString(err->T("GenericGraphicsError", "Graphics Error"));
		MessageBox(0, ConvertUTF8ToWString(genericError).c_str(), title.c_str(), MB_OK);

		// Let's continue (and probably crash) just so they have a way to keep trying.
	}

	System_Notify(SystemNotification::UI);

	std::string error_string;
	bool success = CreateGraphicsBackend(&error_string, &g_graphicsContext);

	if (success) {
		// Main thread is the render thread.
		success = g_graphicsContext->InitFromRenderThread(&error_string);
	}

	if (!success) {
		// Before anything: are we restarting right now?
		if (performingRestart) {
			// Okay, switching graphics didn't work out.  Probably a driver bug - fallback to restart.
			// This happens on NVIDIA when switching OpenGL -> Vulkan.
			g_Config.Save("switch_graphics_failed");
			W32Util::ExitAndRestart();
		}

		auto err = GetI18NCategory(I18NCat::ERRORS);
		Reporting::ReportMessage("Graphics init error: %s", error_string.c_str());

		const char *defaultErrorVulkan = "Failed initializing graphics. Try upgrading your graphics drivers.\n\nWould you like to try switching to OpenGL?\n\nError message:";
		const char *defaultErrorOpenGL = "Failed initializing graphics. Try upgrading your graphics drivers.\n\nWould you like to try switching to DirectX 9?\n\nError message:";
		const char *defaultErrorDirect3D9 = "Failed initializing graphics. Try upgrading your graphics drivers and directx 9 runtime.\n\nWould you like to try switching to OpenGL?\n\nError message:";
		std::string_view genericError;
		GPUBackend nextBackend = GPUBackend::VULKAN;
		switch (g_Config.iGPUBackend) {
		case (int)GPUBackend::VULKAN:
			nextBackend = GPUBackend::OPENGL;
			genericError = err->T("GenericVulkanError", defaultErrorVulkan);
			break;
		case (int)GPUBackend::OPENGL:
		default:
			nextBackend = GPUBackend::DIRECT3D11;
			genericError = err->T("GenericOpenGLError", defaultErrorOpenGL);
			break;
		}
		std::string full_error = StringFromFormat("%.*s\n\n%s", (int)genericError.size(), genericError.data(), error_string.c_str());
		std::wstring title = ConvertUTF8ToWString(err->T("GenericGraphicsError", "Graphics Error"));
		bool yes = IDYES == MessageBox(0, ConvertUTF8ToWString(full_error).c_str(), title.c_str(), MB_ICONERROR | MB_YESNO);
		ERROR_LOG(Log::Boot, "%s", full_error.c_str());

		if (yes) {
			// Change the config to the alternative and restart.
			g_Config.iGPUBackend = (int)nextBackend;
			// Clear this to ensure we try their selection.
			g_Config.sFailedGPUBackends.clear();
			g_Config.Save("save_graphics_fallback");

			W32Util::ExitAndRestart();
		}

		// No safe way out without graphics.
		ExitProcess(1);
	}

	GraphicsContext *graphicsContext = g_graphicsContext;

	if (!useEmuThread) {
		NativeInitGraphics(graphicsContext);
		NativeResized();
	}

	DEBUG_LOG(Log::Boot, "Done.");

	g_inLoop = true;

	if (useEmuThread) {
		EmuThreadStart(graphicsContext);
	}
	graphicsContext->ThreadStart();

	if (useEmuThread) {
		// Again, this thread becomes the render thread.
		while (true) {
			if (equals_any(g_emuThreadState, EmuThreadState::QUIT_REQUESTED, EmuThreadState::STOPPED)) {
				break;
			}
			graphicsContext->ThreadFrame(true);
			if (GetUIState() == UISTATE_EXIT) {
				break;
			}
		}
	} else {
		// Same contents as EmuThread.
		while (GetUIState() != UISTATE_EXIT) {  //  && GetUIState() != UISTATE_EXCEPTION
			// We're here again, so the game quit.  Restart Run() which controls the UI.
			// This way they can load a new game.
			if (!(Core_IsActive() || Core_IsStepping()))
				UpdateUIState(UISTATE_MENU);
			Core_StateProcessed();
			NativeFrame(graphicsContext);
		}
	}
	Core_Stop();
	if (!useEmuThread) {
		// Process the shutdown.  Without this, non-GL delays 800ms on shutdown.
		Core_StateProcessed();
		NativeFrame(graphicsContext);
	}

	g_inLoop = false;

	if (useEmuThread) {
		EmuThreadStop();
		graphicsContext->ThreadFrameUntilCondition([] {
			// Need to keep eating frames to allow the EmuThread to exit correctly.
			return g_emuThreadState == EmuThreadState::STOPPED;
		});
		EmuThreadJoin();
	}

	if (!useEmuThread) {
		NativeShutdownGraphics();
	}

	g_graphicsContext->ThreadEnd();
	g_graphicsContext->ShutdownFromRenderThread();
	g_graphicsContext->Shutdown();

	delete g_graphicsContext;
	g_graphicsContext = nullptr;

	PostMessage(MainWindow::GetHWND(), MainWindow::WM_USER_UPDATE_UI, 0, 0);
}