#pragma once

#include "Utilities/types.h"
#include "util/logs.hpp"
#include "Utilities/sysinfo.h"
#include "system_config.h"
#include "IdManager.h"
#include <array>
#include <cmath>

LOG_CHANNEL(perf_log, "PERF");

// TODO: constexpr with the help of bitcast
template <auto Name>
inline const auto perf_name = []
{
	constexpr auto short_name = Name;
	std::array<char, sizeof(Name) + 1> result{};
	std::memcpy(result.data(), &short_name, sizeof(Name));
	return result;
}();

class perf_stat_base
{
	atomic_t<u64> m_log[66]{};

protected:
	// Print accumulated values
	void print(const char* name) noexcept;

	// Accumulate values from a thread
	void push(u64 ns[66]) noexcept;

public:
	perf_stat_base() noexcept = default;

	perf_stat_base(const perf_stat_base&) = delete;

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

	~perf_stat_base() {}
};

// Object that prints event length stats at the end
template <auto ShortName>
class perf_stat final : public perf_stat_base
{
	static inline thread_local struct perf_stat_local
	{
		// Local non-atomic values for increments
		u64 m_log[66]{};

		~perf_stat_local()
		{
			// Update on thread exit
			if (m_log[0])
			{
				if (auto* pfs = g_fxo->get<perf_stat>())
				{
					pfs->perf_stat_base::push(m_log);
				}
			}
		}
	} g_tls_perf_stat;

public:
	~perf_stat()
	{
		perf_stat_base::print(perf_name<ShortName>.data());
	}

	void push(u64 ns) noexcept
	{
		auto& data = g_tls_perf_stat.m_log;
		data[0] += ns != 0;
		data[64 - std::countl_zero(ns)]++;
		data[65] += ns;
	}
};

// Object that prints event length at the end
template <auto ShortName, auto... SubEvents>
class perf_meter
{
	// Initialize array (possibly only 1 element) with timestamp
	u64 m_timestamps[1 + sizeof...(SubEvents)] = {__rdtsc()};

public:
	SAFE_BUFFERS perf_meter() noexcept
	{
		m_timestamps[0] = __rdtsc();
		std::memset(m_timestamps + 1, 0, sizeof(m_timestamps) - sizeof(u64));
	}

	// Copy first timestamp
	template <auto SN, auto... S>
	SAFE_BUFFERS perf_meter(const perf_meter<SN, S...>& r) noexcept
	{
		m_timestamps[0] = r.get();
		std::memset(m_timestamps + 1, 0, sizeof(m_timestamps) - sizeof(u64));
	}

	template <auto SN, auto... S>
	SAFE_BUFFERS perf_meter(perf_meter<SN, S...>&& r) noexcept
	{
		m_timestamps[0] = r.get();
		r.reset();
	}

	// Copy first timestamp
	template <auto SN, auto... S>
	SAFE_BUFFERS perf_meter& operator =(const perf_meter<SN, S...>& r) noexcept
	{
		m_timestamps[0] = r.get();
		return *this;
	}

	template <auto SN, auto... S>
	SAFE_BUFFERS perf_meter& operator =(perf_meter<SN, S...>& r) noexcept
	{
		m_timestamps[0] = r.get();
		r.reset();
		return *this;
	}

	// Push subevent data in array
	template <auto Event, std::size_t Index = 0>
	SAFE_BUFFERS void push() noexcept
	{
		// TODO: should use more efficient search with type comparison, then value comparison, or pattern matching
		if constexpr (std::array<bool, sizeof...(SubEvents)>{(SubEvents == Event)...}[Index])
		{
			// Push actual timestamp into an array
			m_timestamps[Index + 1] = __rdtsc();
		}
		else if constexpr (Index < sizeof...(SubEvents))
		{
			// Proceed search recursively
			push<Event, Index + 1>();
		}
	}

	// Obtain initial timestamp
	u64 get() const noexcept
	{
		return m_timestamps[0];
	}

	// Disable this counter
	SAFE_BUFFERS void reset() noexcept
	{
		m_timestamps[0] = 0;
	}

	SAFE_BUFFERS ~perf_meter()
	{
		// Disabled counter
		if (!m_timestamps[0]) [[unlikely]]
		{
			return;
		}

		if (!g_cfg.core.perf_report) [[likely]]
		{
			return;
		}

		// Event end
		const u64 end_time = __rdtsc();

		// Compute difference in seconds
		const f64 diff = (end_time - m_timestamps[0]) * 1. / utils::get_tsc_freq();

		// Register perf stat in nanoseconds
		g_fxo->get<perf_stat<ShortName>>()->push(static_cast<u64>(diff * 1000'000'000.));

		// Print in microseconds
		if (static_cast<u64>(diff * 1000'000.) >= g_cfg.core.perf_report_threshold)
		{
			perf_log.notice("%s: %.3fµs", perf_name<ShortName>.data(), diff * 1000'000.);
		}

		// TODO: handle push(), currently ignored
	}
};