#pragma once

#include "Utilities/mutex.h"
#include "Utilities/sema.h"

#include "Emu/CPU/CPUThread.h"
#include "Emu/Cell/ErrorCodes.h"
#include "Emu/Cell/timers.hpp"
#include "Emu/IdManager.h"
#include "Emu/IPC.h"
#include "Emu/system_config.h"

#include <deque>
#include <thread>

// attr_protocol (waiting scheduling policy)
enum lv2_protocol : u8
{
	SYS_SYNC_FIFO                = 0x1, // First In, First Out Order
	SYS_SYNC_PRIORITY            = 0x2, // Priority Order
	SYS_SYNC_PRIORITY_INHERIT    = 0x3, // Basic Priority Inheritance Protocol
	SYS_SYNC_RETRY               = 0x4, // Not selected while unlocking
};

enum : u32
{
	SYS_SYNC_ATTR_PROTOCOL_MASK  = 0xf,
};

// attr_recursive (recursive locks policy)
enum
{
	SYS_SYNC_RECURSIVE           = 0x10,
	SYS_SYNC_NOT_RECURSIVE       = 0x20,
	SYS_SYNC_ATTR_RECURSIVE_MASK = 0xf0,
};

// attr_pshared (sharing among processes policy)
enum
{
	SYS_SYNC_PROCESS_SHARED      = 0x100,
	SYS_SYNC_NOT_PROCESS_SHARED  = 0x200,
	SYS_SYNC_ATTR_PSHARED_MASK   = 0xf00,
};

// attr_flags (creation policy)
enum
{
	SYS_SYNC_NEWLY_CREATED       = 0x1, // Create new object, fails if specified IPC key exists
	SYS_SYNC_NOT_CREATE          = 0x2, // Reference existing object, fails if IPC key not found
	SYS_SYNC_NOT_CARE            = 0x3, // Reference existing object, create new one if IPC key not found
	SYS_SYNC_ATTR_FLAGS_MASK     = 0xf,
};

// attr_adaptive
enum
{
	SYS_SYNC_ADAPTIVE            = 0x1000,
	SYS_SYNC_NOT_ADAPTIVE        = 0x2000,
	SYS_SYNC_ATTR_ADAPTIVE_MASK  = 0xf000,
};

enum ppu_thread_status : u32;

// Base class for some kernel objects (shared set of 8192 objects).
struct lv2_obj
{
	static const u32 id_step = 0x100;
	static const u32 id_count = 8192;
	static constexpr std::pair<u32, u32> id_invl_range = {0, 8};

private:
	enum thread_cmd : s32
	{
		yield_cmd = smin,
		enqueue_cmd,
	};

	// Function executed under IDM mutex, error will make the object creation fail and the error will be returned
	CellError on_id_create()
	{
		exists++;
		return {};
	}

public:
	SAVESTATE_INIT_POS(4); // Dependency on PPUs

	// Existence validation (workaround for shared-ptr ref-counting)
	atomic_t<u32> exists = 0;

	template <typename Ptr>
	static bool check(Ptr&& ptr)
	{
		return ptr && ptr->exists;
	}

	static std::string name64(u64 name_u64)
	{
		const auto ptr = reinterpret_cast<const char*>(&name_u64);

		// NTS string, ignore invalid/newline characters
		// Example: "lv2\n\0tx" will be printed as "lv2"
		std::string str{ptr, std::find(ptr, ptr + 7, '\0')};
		str.erase(std::remove_if(str.begin(), str.end(), [](uchar c){ return !std::isprint(c); }), str.end());

		return str;
	}

	// Find and remove the object from the deque container
	template <typename T, typename E>
	static T unqueue(std::deque<T>& queue, E object)
	{
		for (auto found = queue.cbegin(), end = queue.cend(); found != end; found++)
		{
			if (*found == object)
			{
				queue.erase(found);
				return static_cast<T>(object);
			}
		}

		return {};
	}

	template <typename E, typename T>
	static T* schedule(std::deque<T*>& queue, u32 protocol)
	{
		if (queue.empty())
		{
			return nullptr;
		}

		if (protocol == SYS_SYNC_FIFO)
		{
			const auto res = queue.front();

			if (res->state.none_of(cpu_flag::again))
				queue.pop_front();

			return res;
		}

		s32 prio = 3071;
		auto it = queue.cbegin();

		for (auto found = it, end = queue.cend(); found != end; found++)
		{
			const s32 _prio = static_cast<E*>(*found)->prio;

			if (_prio < prio)
			{
				it = found;
				prio = _prio;
			}
		}

		const auto res = *it;

		if (res->state.none_of(cpu_flag::again))
			queue.erase(it);

		return res;
	}

private:
	// Remove the current thread from the scheduling queue, register timeout
	static void sleep_unlocked(cpu_thread&, u64 timeout, bool notify_later);

	// Schedule the thread
	static bool awake_unlocked(cpu_thread*, bool notify_later = false, s32 prio = enqueue_cmd);

public:
	static constexpr u64 max_timeout = u64{umax} / 1000;

	static void sleep(cpu_thread& cpu, const u64 timeout = 0, bool notify_later = false);

	static bool awake(cpu_thread* const thread, bool notify_later = false, s32 prio = enqueue_cmd);

	// Returns true on successful context switch, false otherwise
	static bool yield(cpu_thread& thread);

	static void set_priority(cpu_thread& thread, s32 prio)
	{
		ensure(prio + 512u < 3712);
		awake(&thread, false, prio);
	}

	static inline void awake_all(bool notify_later = false)
	{
		awake({}, notify_later);
		g_to_awake.clear();
	}

	static ppu_thread_status ppu_state(ppu_thread* ppu, bool lock_idm = true, bool lock_lv2 = true);

	static inline void append(cpu_thread* const thread)
	{
		g_to_awake.emplace_back(thread);
	}

	// Serialization related
	static void set_future_sleep(cpu_thread* cpu);
	static bool is_scheduler_ready();

	static void cleanup();

	template <typename T>
	static inline u64 get_key(const T& attr)
	{
		return (attr.pshared == SYS_SYNC_PROCESS_SHARED ? +attr.ipc_key : 0);
	}

	template <typename T, typename F>
	static error_code create(u32 pshared, u64 ipc_key, s32 flags, F&& make, bool key_not_zero = true)
	{
		switch (pshared)
		{
		case SYS_SYNC_PROCESS_SHARED:
		{
			if (key_not_zero && ipc_key == 0)
			{
				return CELL_EINVAL;
			}

			switch (flags)
			{
			case SYS_SYNC_NEWLY_CREATED:
			case SYS_SYNC_NOT_CARE:
			case SYS_SYNC_NOT_CREATE:
			{
				break;
			}
			default: return CELL_EINVAL;
			}

			break;
		}
		case SYS_SYNC_NOT_PROCESS_SHARED:
		{
			break;
		}
		default: return CELL_EINVAL;
		}

		// EAGAIN for IDM IDs shortage
		CellError error = CELL_EAGAIN;

		if (!idm::import<lv2_obj, T>([&]() -> std::shared_ptr<T>
		{
			std::shared_ptr<T> result = make();

			auto finalize_construct = [&]() -> std::shared_ptr<T>
			{
				if ((error = result->on_id_create()))
				{
					result.reset();
				}

				return std::move(result);
			};

			if (pshared != SYS_SYNC_PROCESS_SHARED)
			{
				// Creation of unique (non-shared) object handle
				return finalize_construct();
			}

			auto& ipc_container = g_fxo->get<ipc_manager<T, u64>>();

			if (flags == SYS_SYNC_NOT_CREATE)
			{
				result = ipc_container.get(ipc_key);

				if (!result)
				{
					error = CELL_ESRCH;
					return result;
				}

				// Run on_id_create() on existing object
				return finalize_construct();
			}

			bool added = false;
			std::tie(added, result) = ipc_container.add(ipc_key, finalize_construct, flags != SYS_SYNC_NEWLY_CREATED);

			if (!added)
			{
				if (flags == SYS_SYNC_NEWLY_CREATED)
				{
					// Object already exists but flags does not allow it
					error = CELL_EEXIST;

					// We specified we do not want to peek pointer's value, result must be empty
					AUDIT(!result);
					return result;
				}

				// Run on_id_create() on existing object
				return finalize_construct();
			}

			return result;
		}))
		{
			return error;
		}

		return CELL_OK;
	}

	template <typename T>
	static void on_id_destroy(T& obj, u64 ipc_key, u64 pshared = -1)
	{
		if (pshared == umax)
		{
			// Default is to check key
			pshared = ipc_key != 0;
		}

		if (obj.exists-- == 1u && pshared)
		{
			g_fxo->get<ipc_manager<T, u64>>().remove(ipc_key);
		}
	}

	template <typename T>
	static std::shared_ptr<T> load(u64 ipc_key, std::shared_ptr<T> make, u64 pshared = -1)
	{
		if (pshared == umax ? ipc_key != 0 : pshared != 0)
		{
			g_fxo->need<ipc_manager<T, u64>>();

			make = g_fxo->get<ipc_manager<T, u64>>().add(ipc_key, [&]()
			{
				return make;
			}, true).second;
		}

		// Ensure no error
		ensure(!make->on_id_create());
		return make;
	}

	template <bool IsUsleep = false, bool Scale = true>
	static bool wait_timeout(u64 usec, cpu_thread* const cpu = {})
	{
		static_assert(u64{umax} / max_timeout >= 100, "max timeout is not valid for scaling");

		if constexpr (Scale)
		{
			// Scale time
			usec = std::min<u64>(usec, u64{umax} / 100) * 100 / g_cfg.core.clocks_scale;
		}

		// Clamp
		usec = std::min<u64>(usec, max_timeout);

		u64 passed = 0;

		const u64 start_time = get_system_time();

		auto wait_for = [cpu](u64 timeout)
		{
			atomic_bs_t<cpu_flag> dummy{};
			auto& state = cpu ? cpu->state : dummy;
			const auto old = +state;

			if (old & cpu_flag::signal)
			{
				return true;
			}

			thread_ctrl::wait_on(state, old, timeout);
			return false;
		};

		while (usec >= passed)
		{
			u64 remaining = usec - passed;
#ifdef __linux__
			// NOTE: Assumption that timer initialization has succeeded
			u64 host_min_quantum = IsUsleep && remaining <= 1000 ? 10 : 50;
#else
			// Host scheduler quantum for windows (worst case)
			// NOTE: On ps3 this function has very high accuracy
			constexpr u64 host_min_quantum = 500;
#endif
			// TODO: Tune for other non windows operating sytems
			bool escape = false;
			if (g_cfg.core.sleep_timers_accuracy < (IsUsleep ? sleep_timers_accuracy_level::_usleep : sleep_timers_accuracy_level::_all_timers))
			{
				escape = wait_for(remaining);
			}
			else
			{
				if (remaining > host_min_quantum)
				{
#ifdef __linux__
					// Do not wait for the last quantum to avoid loss of accuracy
					escape = wait_for(remaining - ((remaining % host_min_quantum) + host_min_quantum));
#else
					// Wait on multiple of min quantum for large durations to avoid overloading low thread cpus
					escape = wait_for(remaining - (remaining % host_min_quantum));
#endif
				}
				else
				{
					// Try yielding. May cause long wake latency but helps weaker CPUs a lot by alleviating resource pressure
					std::this_thread::yield();
				}
			}

			if (auto cpu0 = get_current_cpu_thread(); cpu0 && cpu0->is_stopped())
			{
				return false;
			}

			if (thread_ctrl::state() == thread_state::aborting)
			{
				return false;
			}

			if (escape)
			{
				return false;
			}

			passed = get_system_time() - start_time;
		}

		return true;
	}

	static inline void notify_all()
	{
		for (auto cpu : g_to_notify)
		{
			if (!cpu)
			{
				g_to_notify[0] = nullptr;
				return;
			}

			cpu->state.notify_one(cpu_flag::suspend + cpu_flag::signal);
		}
	}

	struct notify_all_t
	{
		~notify_all_t() noexcept
		{
			lv2_obj::notify_all();
		}
	};

	// Scheduler mutex
	static shared_mutex g_mutex;

private:
	// Pending list of threads to run
	static thread_local std::vector<class cpu_thread*> g_to_awake;

	// Scheduler queue for active PPU threads
	static std::deque<class ppu_thread*> g_ppu;

	// Waiting for the response from
	static std::deque<class cpu_thread*> g_pending;

	// Scheduler queue for timeouts (wait until -> thread)
	static std::deque<std::pair<u64, class cpu_thread*>> g_waiting;

	// Threads which must call lv2_obj::sleep before the scheduler starts
	static std::deque<class cpu_thread*> g_to_sleep;

	// Pending list of threads to notify
	static thread_local std::add_pointer_t<class cpu_thread> g_to_notify[4];

	static void schedule_all(bool notify_later);
};