module;
#include <Windows.h>
module surface.system;
import surface.constants;
import debug.assertions;
import memory.reference;
import surface.requests;
import surface.events;
import logger;
import ecs.registry;
import ecs.entity;
import time;
import std;

namespace lt::surface {

template<class... Ts>
struct overloads: Ts...
{
	using Ts::operator()...;
};

void ensure_component_sanity(const SurfaceComponent &component);

auto CALLBACK native_window_proc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) -> LRESULT;

System::System(memory::Ref<ecs::Registry> registry): m_registry(std::move(registry))
{
	debug::ensure(m_registry, "Failed to initialize surface system: null registry");

	debug::ensure(
	    m_registry->view<SurfaceComponent>().get_size() == 0,
	    "Failed to initialize surface system: registry has surface component(s)"
	);

	m_registry->connect_on_destruct<SurfaceComponent>(
	    [this](ecs::Registry &registry, ecs::EntityId entity) {
		    on_surface_destruct(registry, entity);
	    }
	);

	auto window_class = WNDCLASS {
		.lpfnWndProc = native_window_proc,
		.hInstance = GetModuleHandle(nullptr),
		.lpszClassName = constants::class_name,
	};
	RegisterClass(&window_class);
}

System::~System()
{
	if (!m_registry)
	{
		return;
	}

	try
	{
		// TODO(Light): make registry.remove not invalidate iterators
		auto entities_to_remove = std::vector<ecs::EntityId> {};
		for (auto &[entity, surface] : m_registry->view<SurfaceComponent>())
		{
			entities_to_remove.emplace_back(entity);
		}

		for (auto entity : entities_to_remove)
		{
			m_registry->remove<SurfaceComponent>(entity);
		}

		m_registry->disconnect_on_construct<SurfaceComponent>();
		m_registry->disconnect_on_destruct<SurfaceComponent>();
	}
	catch (const std::exception &exp)
	{
		log::error("Uncaught exception in surface::~System:");
		log::error("\twhat: {}", exp.what());
	}
}

void System::on_register()
{
}

void System::on_unregister()
{
}

void System::create_surface_component(ecs::EntityId entity, SurfaceComponent::CreateInfo info)
try
{
	auto &component = m_registry->add<SurfaceComponent>(entity, info);
	auto &surface = m_registry->get<SurfaceComponent>(entity);
	const auto &resolution = surface.get_resolution();
	const auto &position = surface.get_position();
	ensure_component_sanity(surface);

	surface.m_native_data.window = CreateWindowEx(
	    0,
	    constants::class_name,
	    info.title.data(),
	    WS_OVERLAPPEDWINDOW,
	    CW_USEDEFAULT,
	    CW_USEDEFAULT,
	    CW_USEDEFAULT,
	    CW_USEDEFAULT,
	    nullptr,
	    nullptr,
	    GetModuleHandle(nullptr),
	    nullptr
	);
	debug::ensure(surface.m_native_data.window, "Failed to create Windows surface component");

	ShowWindow(surface.m_native_data.window, SW_NORMAL);

	// TODO(Light): refactor "environment" into standalone module
	// NOLINTNEXTLINE(concurrency-mt-unsafe)
	// auto *display_env = std::getenv("DISPLAY");
	// debug::ensure(display_env != nullptr, "DISPLAY env var not found!");
	//
	// auto *display = XOpenDisplay(display_env);
	// debug::ensure(display, "Failed to open XDisplay with DISPLAY: {}", display_env);
	//
	// auto root_window = XDefaultRootWindow(display);
	//
	// auto border_width = 0;
	// auto depth = std::int32_t { CopyFromParent };
	// auto window_class = CopyFromParent;
	// auto *visual = (Visual *)CopyFromParent;
	//
	// auto attribute_value_mask = CWBackPixel | CWEventMask;
	// auto attributes = XSetWindowAttributes {
	// 	.background_pixel = 0xffafe9af,
	// 	.event_mask = all_events_mask,
	// };
	//
	// typedef struct Hints
	// {
	// 	unsigned long flags;
	// 	unsigned long functions;
	// 	unsigned long decorations;
	// 	long inputMode;
	// 	unsigned long status;
	// } Hints;
	//
	// auto main_window = XCreateWindow(
	//     display,
	//     root_window,
	//     position.x,
	//     position.y,
	//     resolution.x,
	//     resolution.y,
	//     border_width,
	//     depth,
	//     window_class,
	//     visual,
	//     attribute_value_mask,
	//     &attributes
	// );
	// surface.m_native_data.display = display;
	// surface.m_native_data.window = main_window;
	//
	// surface.m_native_data.wm_delete_message = XInternAtom(display, "WM_DELETE_WINDOW", False);
	// XSetWMProtocols(display, main_window, &surface.m_native_data.wm_delete_message, 1);
	//
	// // code to remove decoration
	// auto hints = std::array<const unsigned char, 5> { 2, 0, 0, 0, 0 };
	// const auto motif_hints = XInternAtom(display, "_MOTIF_WM_HINTS", False);
	//
	// XChangeProperty(
	//     display,
	//     surface.m_native_data.window,
	//     motif_hints,
	//     motif_hints,
	//     32,
	//     PropModeReplace,
	//     hints.data(),
	//     5
	// );
	//
	// XMapWindow(display, main_window);
	// XStoreName(display, main_window, surface.m_title.c_str());
	// XFlush(display);
	//
	// if (!surface.is_visible())
	// {
	// 	XUnmapWindow(display, main_window);
	// }
}
catch (const std::exception &exp)
{
	log::error("Exception thrown when on_constructing surface component");
	log::error("\tentity: {}", std::uint32_t { entity });
	log::error("\twhat: {}", exp.what());
	m_registry->remove<SurfaceComponent>(entity);
}

void System::on_surface_destruct(ecs::Registry &registry, ecs::EntityId entity)
{
	auto *window = registry.get<SurfaceComponent>(entity).get_native_data().window;
	if (!window)
	{
		log::warn("Surface component destroyed with null window handle");
		return;
	}

	DestroyWindow(window);
}

void System::handle_events(SurfaceComponent &surface)
{
	auto &queue = surface.m_event_queue;
	queue.clear();

	auto message = MSG {};
	while (PeekMessage(&message, 0, {}, {}, PM_REMOVE))
	{
		switch (message.message)
		{
		}

		log::debug("Window message type: {}", std::uint32_t { message.message });
	}

	// auto event = XEvent {};
	// auto &[display, window, wm_delete_message] = surface.m_native_data;
	//
	// XFlush(display);
	// while (XEventsQueued(display, QueuedAlready) != 0)
	// {
	// 	XNextEvent(surface.m_native_data.display, &event);
	//
	// 	switch (event.type)
	// 	{
	// 	case KeyPress:
	// 	{
	// 		queue.emplace_back<KeyPressedEvent>(
	// 		    static_cast<std::uint32_t>(XLookupKeysym(&event.xkey, 0))
	// 		);
	// 		break;
	// 	}
	// 	case KeyRelease:
	// 	{
	// 		queue.emplace_back<KeyReleasedEvent>(
	// 		    static_cast<std::uint32_t>(XLookupKeysym(&event.xkey, 0))
	// 		);
	// 		break;
	// 	}
	// 	case ButtonPress:
	// 	{
	// 		queue.emplace_back<ButtonPressedEvent>(static_cast<int>(event.xbutton.button));
	// 		break;
	// 	}
	// 	case ButtonRelease:
	// 	{
	// 		queue.emplace_back<ButtonReleasedEvent>(static_cast<int>(event.xbutton.button));
	// 		break;
	// 	}
	// 	case FocusIn:
	// 	{
	// 		queue.emplace_back<GainFocusEvent>({});
	// 		break;
	// 	}
	// 	case FocusOut:
	// 	{
	// 		queue.emplace_back<LostFocusEvent>({});
	// 		break;
	// 	}
	// 	case ClientMessage:
	// 	{
	// 		if (event.xclient.data.l[0] == wm_delete_message)
	// 		{
	// 			queue.emplace_back<ClosedEvent>({});
	// 		}
	//
	// 		break;
	// 	}
	// 	case MotionNotify:
	// 	{
	// 		queue.emplace_back<MouseMovedEvent>(MouseMovedEvent {
	// 		    static_cast<float>(event.xmotion.x),
	// 		    static_cast<float>(event.xmotion.y),
	// 		});
	// 		break;
	// 	}
	// 	case ConfigureNotify:
	// 	{
	// 		const auto [prev_width, prev_height] = surface.get_resolution();
	// 		const auto new_width = event.xconfigure.width;
	// 		const auto new_height = event.xconfigure.height;
	// 		if (prev_width != new_width || prev_height != new_height)
	// 		{
	// 			surface.m_resolution.x = new_width;
	// 			surface.m_resolution.y = new_height;
	// 			queue.emplace_back<ResizedEvent>(ResizedEvent {
	// 			    static_cast<std::uint32_t>(new_width),
	// 			    static_cast<std::uint32_t>(new_height),
	// 			});
	// 		}
	//
	// 		const auto [prev_x, prev_y] = surface.get_position();
	// 		const auto new_x = event.xconfigure.x;
	// 		const auto new_y = event.xconfigure.y;
	// 		if (prev_x != new_x || prev_y != new_y)
	// 		{
	// 			surface.m_position.x = new_x;
	// 			surface.m_position.y = new_y;
	// 			queue.emplace_back<MovedEvent>(MovedEvent {
	// 			    new_x,
	// 			    new_y,
	// 			});
	// 		}
	// 		break;
	// 	}
	//
	// 	default: break; /* pass */
	// 	}
	// }
}

void System::handle_requests(SurfaceComponent &surface)
{
	const auto visitor = overloads {
		[&](const ModifyTitleRequest &request) { modify_title(surface, request); },
		[&](const ModifyResolutionRequest &request) { modify_resolution(surface, request); },
		[&](const ModifyPositionRequest &request) { modify_position(surface, request); },
		[&](const ModifyVisibilityRequest &request) { modify_visiblity(surface, request); },
		[&](const auto &) { log::error("Unknown surface request"); },
	};

	for (const auto &request : surface.peek_requests())
	{
		std::visit(visitor, request);
	}

	surface.m_requests.clear();
}

void System::modify_title(SurfaceComponent &surface, const ModifyTitleRequest &request)
{
	surface.m_title = request.title;

	// const auto &[display, window, _] = surface.get_native_data();
	// XStoreName(display, window, request.title.c_str());
}

void System::modify_resolution(SurfaceComponent &surface, const ModifyResolutionRequest &request)
{
	// surface.m_resolution = request.resolution;

	// auto &[display, window, _] = surface.m_native_data;
	// const auto &[width, height] = request.resolution;
	// // XResizeWindow(display, window, width, height);
	//
	// // get baseline serial number for X requests generated from XResizeWindow
	// auto serial = NextRequest(display);
	//
	// // request a new window size from the X server
	// XResizeWindow(
	//     display,
	//     window,
	//     static_cast<std::uint32_t>(width),
	//     static_cast<std::uint32_t>(height)
	// );
	//
	// // flush output queue and wait for X server to processes the request
	// XSync(display, False);
	// // The documentation for XResizeWindow includes this important note:
	// //
	// //   If the override-redirect flag of the window is False and some
	// //   other client has selected SubstructureRedirectMask on the parent,
	// //   the X server generates a ConfigureRequest event, and no further
	// //   processing is performed.
	// //
	// // What this means, essentially, is that if this window is a top-level
	// // window, then it's the window manager (the "other client") that is
	// // responsible for changing this window's size.  So when we call
	// // XResizeWindow() on a top-level window, then instead of resizing
	// // the window immediately, the X server informs the window manager,
	// // and then the window manager sets our new size (usually it will be
	// // the size we asked for).  We receive a ConfigureNotify event when
	// // our new size has been set.
	// constexpr auto lifespan = std::chrono::milliseconds { 10 };
	// auto timer = time::Timer {};
	// auto event = XEvent {};
	// while (!XCheckIfEvent(
	//            display,
	//            &event,
	//            XEventTypeEquals<ConfigureNotify>,
	//            reinterpret_cast<XPointer>(&window) // NOLINT
	//        )
	//        || event.xconfigure.serial < serial)
	// {
	// 	std::this_thread::sleep_for(std::chrono::microseconds { 100 });
	// 	if (timer.elapsed_time() > lifespan)
	// 	{
	// 		log::error("Timed out waiting for XResizeWindow's event");
	// 		return;
	// 	}
	// }
	// // We don't need to update the component's state and handle the event in this funcion.
	// // Since handle_requests is called before handle_events.
	// // So we just put the event back into the queue and move on.
	// XPutBackEvent(display, &event);
	// XSync(display, False);
	// XFlush(display);
}

void System::modify_position(SurfaceComponent &surface, const ModifyPositionRequest &request)
{
	// surface.m_position = request.position;

	// auto &[display, window, _] = surface.m_native_data;
	// const auto &[x, y] = request.position;
	//
	// // get baseline serial number for X requests generated from XResizeWindow
	// auto serial = NextRequest(display);
	// XMoveWindow(display, window, static_cast<int>(x), static_cast<int>(y));
	//
	// // flush output queue and wait for X server to processes the request
	// XSync(display, False);
	// constexpr auto lifespan = std::chrono::milliseconds { 10 };
	// auto timer = time::Timer {};
	// auto event = XEvent {};
	// while (!XCheckIfEvent(
	//            display,
	//            &event,
	//            XEventTypeEquals<ConfigureNotify>,
	//            reinterpret_cast<XPointer>(&window) // NOLINT
	//        )
	//        || event.xconfigure.serial < serial)
	// {
	// 	std::this_thread::sleep_for(std::chrono::microseconds { 100 });
	// 	if (timer.elapsed_time() > lifespan)
	// 	{
	// 		log::error("Timed out waiting for XMoveWindow's event");
	// 		return;
	// 	}
	// }
	// // We don't need to update the component's state and handle the event in this funcion.
	// // Since handle_requests is called before handle_events.
	// // So we just put the event back into the queue and move on.
	// XPutBackEvent(display, &event);
	// XSync(display, False);
	// XFlush(display);
}

void System::modify_visiblity(SurfaceComponent &surface, const ModifyVisibilityRequest &request)
{
	// const auto &[display, window, _] = surface.get_native_data();
	// surface.m_visible = request.visible;

	// if (request.visible)
	// {
	// 	XMapWindow(display, window);
	// }
	// else
	// {
	// 	XUnmapWindow(display, window);
	// }
}

void System::tick(app::TickInfo tick)
{
	for (auto &[id, surface] : m_registry->view<SurfaceComponent>())
	{
		handle_requests(surface);
		handle_events(surface);
	}

	const auto now = std::chrono::steady_clock::now();
	m_last_tick_result = app::TickResult {
		.info = tick,
		.duration = now - tick.start_time,
		.end_time = now,
	};
}

void ensure_component_sanity(const SurfaceComponent &component)
{
	auto [width, height] = component.get_resolution();

	debug::ensure(width != 0u, "Received bad values for surface component: width({}) == 0", width);

	debug::ensure(
	    height != 0u,
	    "Received bad values for surface component: height({}) == 0",
	    height
	);

	debug::ensure(
	    width < SurfaceComponent::max_dimension,
	    "Received bad values for surface component: width({}) > max_dimension({})",
	    width,
	    SurfaceComponent::max_dimension
	);

	debug::ensure(
	    height < SurfaceComponent::max_dimension,
	    "Received bad values for surface component: height({}) > max_dimension({})",
	    height,
	    SurfaceComponent::max_dimension
	);

	debug::ensure(
	    component.get_title().size() < SurfaceComponent::max_title_length,
	    "Received bad values for surface component: title.size({}) > max_title_length({})",
	    component.get_title().size(),
	    SurfaceComponent::max_title_length
	);
}

auto CALLBACK native_window_proc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) -> LRESULT
{
	switch (uMsg)
	{
	case WM_DESTROY:
	{
		PostQuitMessage(0);
		return 0;
	}
	}

	return DefWindowProcA(hwnd, uMsg, wParam, lParam);
}

} // namespace lt::surface