/*
 * This file is part of the Monero P2Pool <https://github.com/SChernykh/p2pool>
 * Copyright (c) 2021 SChernykh <https://github.com/SChernykh>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include "common.h"
#include "uv_util.h"
#include <chrono>
#include <ctime>
#include <fstream>

static constexpr char log_category_prefix[] = "Log ";
static constexpr char log_file_name[] = "p2pool.log";

namespace p2pool {

namespace log {

int GLOBAL_LOG_LEVEL = 5;

static volatile bool stopped = false;
static volatile bool worker_started = false;

#ifdef _WIN32
static const HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
static const HANDLE hStdErr = GetStdHandle(STD_ERROR_HANDLE);
#endif

class Worker
{
public:
	enum params : int
	{
		SLOT_SIZE = 1024,
		BUF_SIZE = SLOT_SIZE * 1024,
	};

	FORCEINLINE Worker()
		: m_writePos(0)
		, m_readPos(0)
	{
		m_logFile.open(log_file_name, std::ios::app | std::ios::binary);

		m_buf.resize(BUF_SIZE);

		// Create default loop here
		uv_default_loop();

		uv_cond_init(&m_cond);
		uv_mutex_init(&m_mutex);
		uv_thread_create(&m_worker, run_wrapper, this);

		do {} while (!worker_started);

#ifdef _WIN32
		DWORD dwConsoleMode;
		if (GetConsoleMode(hStdOut, &dwConsoleMode)) {
			SetConsoleMode(hStdOut, dwConsoleMode | ENABLE_VIRTUAL_TERMINAL_PROCESSING);
		}
#endif

		LOGINFO(0, "started");

		if (!m_logFile.is_open()) {
			LOGERR(0, "failed to open " << log_file_name);
		}
	}

	FORCEINLINE ~Worker()
	{
		stop();
	}

	FORCEINLINE void stop()
	{
		if (stopped) {
			return;
		}

		stopped = true;
		LOGINFO(0, "stopped");
		uv_thread_join(&m_worker);
		uv_cond_destroy(&m_cond);
		uv_mutex_destroy(&m_mutex);
		uv_loop_close(uv_default_loop());

		m_logFile.close();
	}

	FORCEINLINE void write(const char* buf, uint32_t size)
	{
		if (m_writePos.load() - m_readPos > BUF_SIZE - SLOT_SIZE * 16) {
			// Buffer is full, can't log normally
			if (size > 3) {
				fwrite(buf + 3, 1, size - 3, stderr);
			}
			return;
		}

		const uint32_t writePos = m_writePos.fetch_add(SLOT_SIZE);
		char* p = m_buf.data() + (writePos % BUF_SIZE);

		memcpy(p + 1, buf + 1, size - 1);

		std::atomic_thread_fence(std::memory_order_seq_cst);

		// Mark that everything is written into this log slot
		p[0] = buf[0] + 1;

		// Signal the worker thread
		uv_cond_signal(&m_cond);
	}

private:
	static void run_wrapper(void* arg) { reinterpret_cast<Worker*>(arg)->run(); }

	NOINLINE void run()
	{
		worker_started = true;

		do {
			uv_mutex_lock(&m_mutex);
			uv_cond_wait(&m_cond, &m_mutex);
			uv_mutex_unlock(&m_mutex);

			for (uint32_t writePos = m_writePos.load(); m_readPos < writePos; writePos = m_writePos.load()) {
				// We have at least one log slot pending, possibly more than one
				// Process everything in a loop before reading m_writePos again
				do {
					char* p = m_buf.data() + (m_readPos % BUF_SIZE);

					// Wait until everything is written into this log slot
					volatile char& severity = *p;
					while (!severity) {}

					uint32_t size = static_cast<uint8_t>(p[2]);
					size = (size << 8) + static_cast<uint8_t>(p[1]);

					if (size > 3) {
						p += 3;
						size -= 3;

#ifdef _WIN32
						DWORD k;
						WriteConsole((severity == 1) ? hStdOut : hStdErr, p, size, &k, nullptr);
#else
						fwrite(p, 1, size, (severity == 1) ? stdout : stderr);
#endif

						// Reopen the log file if it's been moved (logrotate support)
						if (m_logFile.is_open()) {
							struct stat buf;
							if (stat(log_file_name, &buf) != 0) {
								m_logFile.close();
								m_logFile.open(log_file_name, std::ios::app | std::ios::binary);
							}
						}

						if (m_logFile.is_open()) {
							strip_colors(p, size);

							if (severity == 1) {
								m_logFile.write("NOTICE  ", 8);
							}
							else if (severity == 2) {
								m_logFile.write("WARNING ", 8);
							}
							else if (severity == 3) {
								m_logFile.write("ERROR   ", 8);
							}

							m_logFile.write(p, size);
							m_logFile.flush();
						}
					}

					// Mark this log slot empty
					severity = '\0';

					m_readPos += SLOT_SIZE;
				} while (m_readPos < writePos);
			}
		} while (!stopped);
	}

	static FORCEINLINE void strip_colors(char* buf, uint32_t& size)
	{
		char* p_read = buf;
		char* p_write = buf;
		char* buf_end = buf + size;

		bool is_color = false;

		while (p_read < buf_end) {
			if (!is_color && (*p_read == '\x1b')) {
				is_color = true;
			}

			if (!is_color) {
				*(p_write++) = *p_read;
			}

			if (is_color && (*p_read == 'm')) {
				is_color = false;
			}

			++p_read;
		}

		size = static_cast<uint32_t>(p_write - buf);
	}

	std::vector<char> m_buf;
	std::atomic<uint32_t> m_writePos;
	uint32_t m_readPos;

	uv_cond_t m_cond;
	uv_mutex_t m_mutex;
	uv_thread_t m_worker;

	std::ofstream m_logFile;
};

static Worker worker;

NOINLINE Writer::Writer(Severity severity) : Stream(m_stackBuf)
{
	m_buf[0] = static_cast<char>(severity);
	m_pos = 3;

	using namespace std::chrono;

	const system_clock::time_point now = system_clock::now();
	const time_t t0 = system_clock::to_time_t(now);

	tm t;

#ifdef _WIN32
	localtime_s(&t, &t0);
#else
	localtime_r(&t0, &t);
#endif

	m_numberWidth = 2;
	*this << Cyan() << (t.tm_year + 1900) << '-' << (t.tm_mon + 1) << '-' << t.tm_mday << ' ' << t.tm_hour << ':' << t.tm_min << ':' << t.tm_sec << '.';

	const int32_t mcs = time_point_cast<microseconds>(now).time_since_epoch().count() % 1000000;

	m_numberWidth = 4;
	*this << (mcs / 100) << NoColor() << ' ';
	m_numberWidth = 1;
}

NOINLINE Writer::~Writer()
{
	const uint32_t size = static_cast<uint32_t>(m_pos + 1);
	m_buf[1] = static_cast<uint8_t>(size & 255);
	m_buf[2] = static_cast<uint8_t>(size >> 8);
	m_buf[m_pos] = '\n';
	worker.write(m_buf, size);
}

void reopen()
{
	// This will trigger the worker thread which will then reopen log file if it's been moved
	LOGINFO(0, "reopening " << log_file_name);
}

void stop()
{
	worker.stop();
}

} // namespace log

} // namespace p2pool