/*
	This file is part of Warzone 2100.
	Copyright (C) 2010-2020  Warzone 2100 Project

	Warzone 2100 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; either version 2 of the License, or
	(at your option) any later version.

	Warzone 2100 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 Warzone 2100; if not, write to the Free Software
	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
 * @file netqueue.cpp
 *
 * Basic netqueue.
 */
#include "lib/framework/frame.h"
#include "netqueue.h"
#include "netplay.h"

#include <limits>
#include <cstdint>
#include <cstring>

// See comments in netqueue.h.


// Byte n is the final byte, iff it is less than 256-a[n].

// Some possible values of table_uint32_t_a[n], such that the maximum encodable value is 0xFFFFFFFF, satisfying the assertion below:
// ASSERT(0xFFFFFFFF == 255*(1 + a[0]*(1 + a[1]*(1 + a[2]*(1 + a[3]*(1 + a[4]))))), "Maximum encodable value not 0xFFFFFFFF.");

//static const unsigned table_uint32_t_a[5] = {14, 127, 74, 127, 0}, table_uint32_t_m[5] = {1, 14, 1778, 131572, 16709644};  // <242: 1 byte, <2048: 2 bytes, <325644: 3 bytes, <17298432: 4 bytes, <4294967296: 5 bytes
constexpr unsigned table_uint32_t_a[5] = {78, 95, 32, 70, 0}, table_uint32_t_m[5] = {1, 78, 7410, 237120, 16598400};  // <178: 1 byte, <12736: 2 bytes, <1672576: 3 bytes, <45776896: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {78, 95, 71, 31, 0}, table_uint32_t_m[5] = {1, 78, 7410, 526110, 16309410};  // <178: 1 byte, <12736: 2 bytes, <1383586: 3 bytes, <119758336: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 19, 119, 0}, table_uint32_t_m[5] = {1, 104, 7384, 140296, 16695224};  // <152: 1 byte, <19392: 2 bytes, <1769400: 3 bytes, <20989952: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 20, 113, 0}, table_uint32_t_m[5] = {1, 104, 7384, 147680, 16687840};  // <152: 1 byte, <19392: 2 bytes, <1762016: 3 bytes, <22880256: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 24, 94, 0}, table_uint32_t_m[5] = {1, 104, 7384, 177216, 16658304};  // <152: 1 byte, <19392: 2 bytes, <1732480: 3 bytes, <30441472: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 30, 75, 0}, table_uint32_t_m[5] = {1, 104, 7384, 221520, 16614000};  // <152: 1 byte, <19392: 2 bytes, <1688176: 3 bytes, <41783296: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 38, 59, 0}, table_uint32_t_m[5] = {1, 104, 7384, 280592, 16554928};  // <152: 1 byte, <19392: 2 bytes, <1629104: 3 bytes, <56905728: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 40, 56, 0}, table_uint32_t_m[5] = {1, 104, 7384, 295360, 16540160};  // <152: 1 byte, <19392: 2 bytes, <1614336: 3 bytes, <60686336: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 57, 39, 0}, table_uint32_t_m[5] = {1, 104, 7384, 420888, 16414632};  // <152: 1 byte, <19392: 2 bytes, <1488808: 3 bytes, <92821504: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 60, 37, 0}, table_uint32_t_m[5] = {1, 104, 7384, 443040, 16392480};  // <152: 1 byte, <19392: 2 bytes, <1466656: 3 bytes, <98492416: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 76, 29, 0}, table_uint32_t_m[5] = {1, 104, 7384, 561184, 16274336};  // <152: 1 byte, <19392: 2 bytes, <1348512: 3 bytes, <128737280: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 95, 23, 0}, table_uint32_t_m[5] = {1, 104, 7384, 701480, 16134040};  // <152: 1 byte, <19392: 2 bytes, <1208216: 3 bytes, <164653056: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 114, 19, 0}, table_uint32_t_m[5] = {1, 104, 7384, 841776, 15993744};  // <152: 1 byte, <19392: 2 bytes, <1067920: 3 bytes, <200568832: 4 bytes, <4294967296: 5 bytes
//static const unsigned table_uint32_t_a[5] = {104, 71, 120, 18, 0}, table_uint32_t_m[5] = {1, 104, 7384, 886080, 15949440};  // <152: 1 byte, <19392: 2 bytes, <1023616: 3 bytes, <211910656: 4 bytes, <4294967296: 5 bytes

//static const unsigned table_uint32_t_m[5] = {1, a[0], a[0]*a[1], a[0]*a[1]*a[2], a[0]*a[1]*a[2]*a[3]};

static_assert(0xFFFFFFFF == 255*(1 + table_uint32_t_a[0]*(1 + table_uint32_t_a[1]*(1 + table_uint32_t_a[2]*(1 + table_uint32_t_a[3]*(1 + table_uint32_t_a[4]))))), "Maximum encodable value not 0xFFFFFFFF.");

unsigned encodedlength_uint32_t(uint32_t v)
{
	for (unsigned n = 0;; ++n)
	{
		const unsigned a = table_uint32_t_a[n];
		const unsigned m = table_uint32_t_m[n];
		const unsigned possibleValues = (256 - a) * m; // Number of values which encode to n + 1 bytes.
		if (v < possibleValues)
		{
			return n + 1;
		}
		v -= possibleValues;
	}
}

bool encode_uint32_t(uint8_t &b, uint32_t &v, unsigned n)
{
	const unsigned a = table_uint32_t_a[n];

	bool isLastByte = v < 256 - a;
	if (isLastByte)
	{
		b = v;
	}
	else
	{
		v -= 256 - a;
		b = 255 - v % a;
		v /= a;
	}
	return !isLastByte;
}

bool decode_uint32_t(uint8_t b, uint32_t &v, unsigned n)
{
	const unsigned a = table_uint32_t_a[n];
	const unsigned m = table_uint32_t_m[n];

	bool isLastByte = b < 256 - a;
	if (isLastByte)
	{
		v += b * m;
	}
	else
	{
		v += (256 - a + 255 - b) * m;
	}
	return !isLastByte;
}

NetMessage::NetMessage(NetMsgDataVector&& data)
	: data_(std::move(data))
{}

uint8_t NetMessage::type() const
{
	ASSERT_OR_RETURN(0, !data_.empty(), "Invalid message data");
	return data_[0];
}

const NetMsgDataVector& NetMessage::rawData() const
{
	return data_;
}

const uint8_t* NetMessage::payload() const
{
	ASSERT_OR_RETURN(nullptr, !data_.empty() && data_.size() >= HEADER_LENGTH, "Invalid message data");
	return &data_[HEADER_LENGTH];
}

size_t NetMessage::payloadSize() const
{
	ASSERT_OR_RETURN(0, data_.size() >= HEADER_LENGTH, "Invalid message data");
	return data_.size() - HEADER_LENGTH;
}

optional<NetMessage> NetMessage::tryFromRawData(const uint8_t* buffer, size_t bufferLen)
{
	if (bufferLen < NetMessage::HEADER_LENGTH) { return nullopt; }

	uint8_t type = buffer[0];
	uint16_t len = 0;
	// Load payload length from uint16_t (network byte order) starting at the second byte of the data buffer.
	wz_ntohs_load_unaligned(len, &buffer[1]);

	if (bufferLen - HEADER_LENGTH < len)
	{
		return nullopt;  // Don't have a whole message ready yet.
	}

	NetMessageBuilder msg(type, len);
	msg.append(&buffer[HEADER_LENGTH], len);
	return optional<NetMessage>{msg.build()};
}

void NetMessage::rawDataAppendToVector(std::vector<uint8_t>& output) const
{
	const size_t oldLen = output.size();
	output.resize(output.size() + data_.size());
	std::memcpy(&output[oldLen], data_.data(), data_.size());
}

NetMessageBuilder::NetMessageBuilder(uint8_t type, size_t reservedCapacity /* = 16 */)
	: data_(MsgDataAllocator(defaultMemoryPool()))
{
	data_.reserve(reservedCapacity + NetMessage::HEADER_LENGTH);
	data_.resize(NetMessage::HEADER_LENGTH);
	data_[0] = type;
}

NetMessageBuilder::NetMessageBuilder(NetMsgDataVector&& rawData)
	: data_(std::move(rawData))
{}

NetQueue::NetQueue()
	: canGetMessagesForNet(true)
	, canGetMessages(true)
	, messages(MsgAllocator(defaultMemoryPool()))
	, pendingGameTimeUpdateMessages(0)
	, bCurrentMessageWasDecrypted(false)
{
	dataPos = messages.end();
	messagePos = messages.end();
}

void NetQueue::writeRawData(const uint8_t *netData, size_t netLen)
{
	size_t used = 0;
	std::vector<uint8_t> &buffer = incompleteReceivedMessageData;  // Short alias.

	// Insert the data.
	buffer.insert(buffer.end(), netData, netData + netLen);

	// Extract the messages.
	while (buffer.size() - used >= NetMessage::HEADER_LENGTH)
	{
		uint8_t type = buffer[used];
		uint16_t len = 0;
		// Load payload length from uint16_t (network byte order) starting at the second byte of the data buffer.
		wz_ntohs_load_unaligned(len, &buffer[used + 1]);

		if (buffer.size() - used - NetMessage::HEADER_LENGTH < len)
		{
			break;  // Don't have a whole message ready yet.
		}

		NetMessageBuilder msg(type, len);
		msg.append(buffer.data() + used + NetMessage::HEADER_LENGTH, len);
		messages.emplace_front(msg.build());

		if (type == GAME_GAME_TIME)
		{
			++pendingGameTimeUpdateMessages;
		}
		used += NetMessage::HEADER_LENGTH + len;
	}

	// Recycle old data.
	buffer.erase(buffer.begin(), buffer.begin() + used);
}

size_t NetQueue::currentIncompleteDataBuffered() const
{
	return incompleteReceivedMessageData.size();
}

void NetQueue::setWillNeverGetMessagesForNet()
{
	canGetMessagesForNet = false;
}

unsigned NetQueue::numMessagesForNet() const
{
	unsigned count = 0;
	if (canGetMessagesForNet)
	{
		for (List::iterator i = dataPos; i != messages.begin(); --i)
		{
			++count;
		}
	}

	return count;
}

const NetMessage &NetQueue::getMessageForNet() const
{
	ASSERT(canGetMessagesForNet, "Wrong NetQueue type for getMessageForNet.");
	ASSERT(dataPos != messages.begin(), "No message to get!");

	// Return the message.
	return internal_getMessageForNet();
}

void NetQueue::popMessageForNet()
{
	ASSERT(canGetMessagesForNet, "Wrong NetQueue type for popMessageForNet.");
	ASSERT(dataPos != messages.begin(), "No message to pop!");

	if (messagePos != messages.begin() && internal_getMessageForNet().type() == GAME_GAME_TIME)
	{
		if (pendingGameTimeUpdateMessages > 0)
		{
			--pendingGameTimeUpdateMessages;
		}
	}

	// Pop the message.
	--dataPos;

	// Recycle old data.
	popOldMessages();
}

void NetQueue::pushMessage(NetMessage&& message)
{
	if (message.type() == GAME_GAME_TIME)
	{
		++pendingGameTimeUpdateMessages;
	}
	messages.emplace_front(std::move(message));
}

void NetQueue::setWillNeverGetMessages()
{
	canGetMessages = false;
}

bool NetQueue::haveMessage() const
{
	ASSERT(canGetMessages, "Wrong NetQueue type for haveMessage.");
	return messagePos != messages.begin();
}

const NetMessage &NetQueue::getMessage() const
{
	ASSERT(canGetMessages, "Wrong NetQueue type for getMessage.");
	ASSERT(messagePos != messages.begin(), "No message to get!");

	// Return the message.
	return internal_getConstMessage();
}

bool NetQueue::currentMessageWasDecrypted() const
{
	return bCurrentMessageWasDecrypted;
}

bool NetQueue::replaceCurrentWithDecrypted(NetMessage &&decryptedMessage)
{
	ASSERT_OR_RETURN(false, canGetMessages, "Wrong NetQueue type for getMessage.");
	ASSERT_OR_RETURN(false, messagePos != messages.begin(), "No message to get!");

	NetMessage& currentMessage = internal_getMessage();
	ASSERT_OR_RETURN(false, currentMessage.type() == NET_SECURED_NET_MESSAGE, "Current message is not a secured message!");

	currentMessage = std::move(decryptedMessage);
	bCurrentMessageWasDecrypted = true;
	return true;
}

void NetQueue::popMessage()
{
	ASSERT(canGetMessages, "Wrong NetQueue type for popMessage.");
	ASSERT(messagePos != messages.begin(), "No message to pop!");

	if (messagePos != messages.begin() && internal_getConstMessage().type() == GAME_GAME_TIME)
	{
		if (pendingGameTimeUpdateMessages > 0)
		{
			--pendingGameTimeUpdateMessages;
		}
	}

	// Pop the message.
	--messagePos;
	bCurrentMessageWasDecrypted = false;

	// Recycle old data.
	popOldMessages();
}

void NetQueue::popOldMessages()
{
	if (!canGetMessagesForNet)
	{
		dataPos = messages.begin();
	}
	if (!canGetMessages)
	{
		messagePos = messages.begin();
	}

	List::iterator i = messages.end();
	while (i != dataPos && i != messagePos)
	{
		--i;
	}

	if (i == dataPos)
	{
		dataPos = messages.end();  // Old iterator will become invalid.
	}
	if (i == messagePos)
	{
		messagePos = messages.end();  // Old iterator will become invalid.
	}

	messages.erase(i, messages.end());
}