#pragma once

#include "types.h"
#include "util/atomic.hpp"
#include "util/shared_cptr.hpp"

#include <string>
#include <memory>
#include <string_view>

#include "mutex.h"
#include "cond.h"
#include "lockless.h"

// Report error and call std::abort(), defined in main.cpp
[[noreturn]] void report_fatal_error(const std::string&);

// Hardware core layout
enum class native_core_arrangement : u32
{
	undefined,
	generic,
	intel_ht,
	amd_ccx
};

enum class thread_class : u32
{
	general,
	rsx,
	spu,
	ppu
};

enum class thread_state : u32
{
	created,  // Initial state
	aborting, // The thread has been joined in the destructor or explicitly aborted
	errored, // Set after the emergency_exit call
	finished  // Final state, always set at the end of thread execution
};

template <class Context>
class named_thread;

template <typename T>
struct result_storage
{
	static_assert(std::is_default_constructible_v<T> && noexcept(T()));

	alignas(T) std::byte data[sizeof(T)];

	static constexpr bool empty = false;

	using type = T;

	T* get()
	{
		return reinterpret_cast<T*>(&data);
	}

	const T* get() const
	{
		return reinterpret_cast<const T*>(&data);
	}

	void destroy() noexcept
	{
		get()->~T();
	}
};

template <>
struct result_storage<void>
{
	static constexpr bool empty = true;

	using type = void;
};

template <class Context, typename... Args>
using result_storage_t = result_storage<std::invoke_result_t<Context, Args...>>;

template <typename T, typename = void>
struct thread_thread_name : std::bool_constant<false> {};

template <typename T>
struct thread_thread_name<T, std::void_t<decltype(named_thread<T>::thread_name)>> : std::bool_constant<true> {};

// Thread base class
class thread_base
{
	// Native thread entry point function type
#ifdef _WIN32
	using native_entry = uint(__stdcall*)(void* arg);
#else
	using native_entry = void*(*)(void* arg);
#endif

	// Thread handle (platform-specific)
	atomic_t<std::uintptr_t> m_thread{0};

	// Thread playtoy, that shouldn't be used
	atomic_t<u32> m_signal{0};

	// Thread state
	atomic_t<thread_state> m_state = thread_state::created;

	// Thread state notification info
	atomic_t<const void*> m_state_notifier{nullptr};

	// Thread name
	stx::atomic_cptr<std::string> m_tname;

	//
	atomic_t<u64> m_cycles = 0;

	// Start thread
	void start(native_entry);

	// Called at the thread start
	void initialize(void (*error_cb)(), bool(*wait_cb)(const void*));

	// May be called in destructor
	void notify_abort() noexcept;

	// Called at the thread end, returns true if needs destruction
	bool finalize(thread_state result) noexcept;

	// Cleanup after possibly deleting the thread instance
	static void finalize() noexcept;

	friend class thread_ctrl;

	template <class Context>
	friend class named_thread;

protected:
	thread_base(std::string_view name);

	~thread_base();

public:
	// Get CPU cycles since last time this function was called. First call returns 0.
	u64 get_cycles();

	// Wait for the thread (it does NOT change thread state, and can be called from multiple threads)
	bool join() const;

	// Notify the thread
	void notify();
};

// Collection of global function for current thread
class thread_ctrl final
{
	// Current thread
	static thread_local thread_base* g_tls_this_thread;

	// Error handling details
	static thread_local void(*g_tls_error_callback)();

	// Target cpu core layout
	static atomic_t<native_core_arrangement> g_native_core_layout;

	// Internal waiting function, may throw. Infinite value is -1.
	static void _wait_for(u64 usec, bool alert);

	friend class thread_base;

	// Optimized get_name() for logging
	static std::string get_name_cached();

public:
	// Get current thread name
	static std::string get_name()
	{
		return *g_tls_this_thread->m_tname.load();
	}

	// Get thread name
	template <typename T>
	static std::string get_name(const named_thread<T>& thread)
	{
		return *static_cast<const thread_base&>(thread).m_tname.load();
	}

	// Set current thread name (not recommended)
	static void set_name(std::string_view name)
	{
		g_tls_this_thread->m_tname.store(stx::shared_cptr<std::string>::make(name));
	}

	// Set thread name (not recommended)
	template <typename T>
	static void set_name(named_thread<T>& thread, std::string_view name)
	{
		static_cast<thread_base&>(thread).m_tname.store(stx::shared_cptr<std::string>::make(name));
	}

	template <typename T>
	static u64 get_cycles(named_thread<T>& thread)
	{
		return static_cast<thread_base&>(thread).get_cycles();
	}

	template <typename T>
	static void notify(named_thread<T>& thread)
	{
		static_cast<thread_base&>(thread).notify();
	}

	// Read current state
	static inline thread_state state()
	{
		return g_tls_this_thread->m_state;
	}

	// Wait once with timeout. May spuriously return false.
	static inline void wait_for(u64 usec, bool alert = true)
	{
		_wait_for(usec, alert);
	}

	// Wait.
	static inline void wait()
	{
		_wait_for(-1, true);
	}

	// Exit.
	[[noreturn]] static void emergency_exit(std::string_view reason);

	// Get current thread (may be nullptr)
	static thread_base* get_current()
	{
		return g_tls_this_thread;
	}

	// Detect layout
	static void detect_cpu_layout();

	// Returns a core affinity mask. Set whether to generate the high priority set or not
	static u64 get_affinity_mask(thread_class group);

	// Sets the native thread priority
	static void set_native_priority(int priority);

	// Sets the preferred affinity mask for this thread
	static void set_thread_affinity_mask(u64 mask);
};

// Derived from the callable object Context, possibly a lambda
template <class Context>
class named_thread final : public Context, result_storage_t<Context>, thread_base
{
	using result = result_storage_t<Context>;
	using thread = thread_base;

	// Type-erased thread entry point
#ifdef _WIN32
	static inline uint __stdcall entry_point(void* arg)
#else
	static inline void* entry_point(void* arg)
#endif
	{
		const auto _this = static_cast<named_thread*>(static_cast<thread*>(arg));

		// Perform self-cleanup if necessary
		if (_this->entry_point())
		{
			delete _this;
		}

		thread::finalize();
		return 0;
	}

	bool entry_point()
	{
		auto tls_error_cb = []()
		{
			if constexpr (!result::empty)
			{
				// Construct using default constructor in the case of failure
				new (static_cast<result*>(static_cast<named_thread*>(thread_ctrl::get_current()))->get()) typename result::type();
			}
		};

		thread::initialize(tls_error_cb, [](const void* data)
		{
			const auto _this = thread_ctrl::get_current();

			if (_this->m_state >= thread_state::aborting)
			{
				return false;
			}

			_this->m_state_notifier.release(data);

			if (!data)
			{
				return true;
			}

			if (_this->m_state >= thread_state::aborting)
			{
				_this->m_state_notifier.release(nullptr);
				return false;
			}

			return true;
		});

		if constexpr (result::empty)
		{
			// No result
			Context::operator()();
		}
		else
		{
			// Construct the result using placement new (copy elision should happen)
			new (result::get()) typename result::type(Context::operator()());
		}

		return thread::finalize(thread_state::finished);
	}

	friend class thread_ctrl;

public:
	// Default constructor
	template <bool Valid = std::is_default_constructible_v<Context> && thread_thread_name<Context>(), typename = std::enable_if_t<Valid>>
	named_thread()
		: Context()
		, thread(Context::thread_name)
	{
		thread::start(&named_thread::entry_point);
	}

	// Normal forwarding constructor
	template <typename... Args, typename = std::enable_if_t<std::is_constructible_v<Context, Args&&...>>>
	named_thread(std::string_view name, Args&&... args)
		: Context(std::forward<Args>(args)...)
		, thread(name)
	{
		thread::start(&named_thread::entry_point);
	}

	// Lambda constructor, also the implicit deduction guide candidate
	named_thread(std::string_view name, Context&& f)
		: Context(std::forward<Context>(f))
		, thread(name)
	{
		thread::start(&named_thread::entry_point);
	}

	named_thread(const named_thread&) = delete;

	named_thread& operator=(const named_thread&) = delete;

	// Wait for the completion and access result (if not void)
	[[nodiscard]] decltype(auto) operator()()
	{
		thread::join();

		if constexpr (!result::empty)
		{
			return *result::get();
		}
	}

	// Wait for the completion and access result (if not void)
	[[nodiscard]] decltype(auto) operator()() const
	{
		thread::join();

		if constexpr (!result::empty)
		{
			return *result::get();
		}
	}

	// Access thread state
	operator thread_state() const
	{
		return thread::m_state.load();
	}

	// Try to abort by assigning thread_state::aborting (UB if assigning different state)
	named_thread& operator=(thread_state s)
	{
		ASSUME(s == thread_state::aborting);

		if (s == thread_state::aborting && thread::m_state.compare_and_swap_test(thread_state::created, s))
		{
			if (s == thread_state::aborting)
			{
				thread::notify_abort();
			}
		}

		return *this;
	}

	// Context type doesn't need virtual destructor
	~named_thread()
	{
		// Assign aborting state forcefully
		operator=(thread_state::aborting);
		thread::join();

		if constexpr (!result::empty)
		{
			result::destroy();
		}
	}
};

// Group of named threads, similar to named_thread
template <class Context>
class named_thread_group final
{
	using Thread = named_thread<Context>;

	const u32 m_count;

	Thread* m_threads;

public:
	// Lambda constructor, also the implicit deduction guide candidate
	named_thread_group(std::string_view name, u32 count, const Context& f)
		: m_count(count)
		, m_threads(nullptr)
	{
		if (count == 0)
		{
			return;
		}

		m_threads = static_cast<Thread*>(::operator new(sizeof(Thread) * m_count, std::align_val_t{alignof(Thread)}));

		// Create all threads
		for (u32 i = 0; i < m_count; i++)
		{
			new (static_cast<void*>(m_threads + i)) Thread(std::string(name) + std::to_string(i + 1), f);
		}
	}

	named_thread_group(const named_thread_group&) = delete;

	named_thread_group& operator=(const named_thread_group&) = delete;

	// Wait for completion
	bool join() const
	{
		bool result = true;

		for (u32 i = 0; i < m_count; i++)
		{
			std::as_const(*std::launder(m_threads + i))();

			if (std::as_const(*std::launder(m_threads + i)) != thread_state::finished)
				result = false;
		}

		return result;
	}

	// Join and access specific thread
	auto operator[](u32 index) const
	{
		return std::as_const(*std::launder(m_threads + index))();
	}

	// Join and access specific thread
	auto operator[](u32 index)
	{
		return (*std::launder(m_threads + index))();
	}

	// Dumb iterator
	auto begin()
	{
		return std::launder(m_threads);
	}

	// Dumb iterator
	auto end()
	{
		return m_threads + m_count;
	}

	u32 size() const
	{
		return m_count;
	}

	~named_thread_group()
	{
		// Destroy all threads (it should join them)
		for (u32 i = 0; i < m_count; i++)
		{
			std::launder(m_threads + i)->~Thread();
		}

		::operator delete(static_cast<void*>(m_threads), std::align_val_t{alignof(Thread)});
	}
};